Support RocksDB transaction. (#565)

librocksdb-sys/build.rs

@@ -98,13 +98,8 @@ fn build_rocksdb() {
         .trim()
         .split('\n')
         .map(str::trim)
-        .collect::<Vec<&'static str>>();
+        // We have a pre-generated a version of build_version.cc in the local directory
-
+        .filter(|file| !matches!(*file, "util/build_version.cc"))
-    // We have a pregenerated a version of build_version.cc in the local directory
-    lib_sources = lib_sources
-        .iter()
-        .cloned()
-        .filter(|&file| file != "util/build_version.cc")
         .collect::<Vec<&'static str>>();
 
     if target.contains("x86_64") {
@@ -143,10 +138,6 @@ fn build_rocksdb() {
         }
     }
 
-    if target.contains("aarch64") {
-        lib_sources.push("util/crc32c_arm64.cc")
-    }
-
     if target.contains("apple-ios") {
         config.define("OS_MACOSX", None);
 
@@ -248,8 +239,7 @@ fn build_rocksdb() {
     }
 
     for file in lib_sources {
-        let file = "rocksdb/".to_string() + file;
+        config.file(&format!("rocksdb/{file}"));
-        config.file(&file);
     }
 
     config.file("build_version.cc");

librocksdb-sys/rocksdb_lib_sources.txt

@@ -145,12 +145,6 @@ options/options.cc
 options/options_helper.cc
 options/options_parser.cc
 port/port_posix.cc
-port/win/env_default.cc
-port/win/env_win.cc
-port/win/io_win.cc
-port/win/port_win.cc
-port/win/win_logger.cc
-port/win/win_thread.cc
 port/stack_trace.cc
 table/adaptive/adaptive_table_factory.cc
 table/block_based/binary_search_index_reader.cc

src/backup.rs

@@ -13,7 +13,7 @@
 // limitations under the License.
 //
 
-use crate::{ffi, ffi_util::to_cpath, Error, DB};
+use crate::{db::DBInner, ffi, ffi_util::to_cpath, Error, DB};
 
 use libc::{c_int, c_uchar};
 use std::path::Path;
@@ -82,7 +82,7 @@ impl BackupEngine {
         unsafe {
             ffi_try!(ffi::rocksdb_backup_engine_create_new_backup_flush(
                 self.inner,
-                db.inner,
+                db.inner.inner(),
                 c_uchar::from(flush_before_backup),
             ));
             Ok(())

src/checkpoint.rs

@@ -17,9 +17,8 @@
 //!
 //! [1]: https://github.com/facebook/rocksdb/wiki/Checkpoints
 
-use crate::{ffi, ffi_util::to_cpath, Error, DB};
+use crate::{db::DBInner, ffi, ffi_util::to_cpath, DBCommon, Error, ThreadMode};
-use std::marker::PhantomData;
+use std::{marker::PhantomData, path::Path};
-use std::path::Path;
 
 /// Undocumented parameter for `ffi::rocksdb_checkpoint_create` function. Zero by default.
 const LOG_SIZE_FOR_FLUSH: u64 = 0_u64;
@@ -36,11 +35,11 @@ impl<'db> Checkpoint<'db> {
     ///
     /// Does not actually produce checkpoints, call `.create_checkpoint()` method to produce
     /// a DB checkpoint.
-    pub fn new(db: &'db DB) -> Result<Self, Error> {
+    pub fn new<T: ThreadMode, I: DBInner>(db: &'db DBCommon<T, I>) -> Result<Self, Error> {
         let checkpoint: *mut ffi::rocksdb_checkpoint_t;
 
         unsafe {
-            checkpoint = ffi_try!(ffi::rocksdb_checkpoint_object_create(db.inner));
+            checkpoint = ffi_try!(ffi::rocksdb_checkpoint_object_create(db.inner.inner()));
         }
 
         if checkpoint.is_null() {

src/db.rs

@@ -67,7 +67,7 @@ pub trait ThreadMode {
 ///
 /// See [`DB`] for more details, including performance implications for each mode
 pub struct SingleThreaded {
-    cfs: BTreeMap<String, ColumnFamily>,
+    pub(crate) cfs: BTreeMap<String, ColumnFamily>,
 }
 
 /// Actual marker type for the marker trait `ThreadMode`, which holds
@@ -76,7 +76,7 @@ pub struct SingleThreaded {
 ///
 /// See [`DB`] for more details, including performance implications for each mode
 pub struct MultiThreaded {
-    cfs: RwLock<BTreeMap<String, Arc<UnboundColumnFamily>>>,
+    pub(crate) cfs: RwLock<BTreeMap<String, Arc<UnboundColumnFamily>>>,
 }
 
 impl ThreadMode for SingleThreaded {
@@ -116,22 +116,36 @@ impl ThreadMode for MultiThreaded {
     }
 }
 
-/// A RocksDB database.
+/// Get underlying `rocksdb_t`.
-///
+pub trait DBInner {
-/// This is previously named [`DB`], which is a type alias now for compatibility.
+    fn inner(&self) -> *mut ffi::rocksdb_t;
+}
+
+/// A helper type to implement some common methods for [`DBWithThreadMode`]
+/// and [`OptimisticTransactionDB`].
 ///
-/// See crate level documentation for a simple usage example.
+/// [`OptimisticTransactionDB`]: crate::OptimisticTransactionDB
-pub struct DBWithThreadMode<T: ThreadMode> {
+pub struct DBCommon<T: ThreadMode, D: DBInner> {
-    pub(crate) inner: *mut ffi::rocksdb_t,
+    pub(crate) inner: D,
     cfs: T, // Column families are held differently depending on thread mode
     path: PathBuf,
     _outlive: Vec<OptionsMustOutliveDB>,
 }
 
-/// Minimal set of DB-related methods, intended to be  generic over
+/// Minimal set of DB-related methods, intended to be generic over
 /// `DBWithThreadMode<T>`. Mainly used internally
 pub trait DBAccess {
-    fn inner(&self) -> *mut ffi::rocksdb_t;
+    unsafe fn create_snapshot(&self) -> *const ffi::rocksdb_snapshot_t;
+
+    unsafe fn release_snapshot(&self, snapshot: *const ffi::rocksdb_snapshot_t);
+
+    unsafe fn create_iterator(&self, readopts: &ReadOptions) -> *mut ffi::rocksdb_iterator_t;
+
+    unsafe fn create_iterator_cf(
+        &self,
+        cf_handle: *mut ffi::rocksdb_column_family_handle_t,
+        readopts: &ReadOptions,
+    ) -> *mut ffi::rocksdb_iterator_t;
 
     fn get_opt<K: AsRef<[u8]>>(
         &self,
@@ -177,22 +191,27 @@ pub trait DBAccess {
         K: AsRef<[u8]>,
         I: IntoIterator<Item = (&'b W, K)>,
         W: AsColumnFamilyRef + 'b;
+}
+
+impl<T: ThreadMode, D: DBInner> DBAccess for DBCommon<T, D> {
+    unsafe fn create_snapshot(&self) -> *const ffi::rocksdb_snapshot_t {
+        ffi::rocksdb_create_snapshot(self.inner.inner())
+    }
 
-    fn batched_multi_get_cf_opt<K, I>(
+    unsafe fn release_snapshot(&self, snapshot: *const ffi::rocksdb_snapshot_t) {
+        ffi::rocksdb_release_snapshot(self.inner.inner(), snapshot);
+    }
+
+    unsafe fn create_iterator(&self, readopts: &ReadOptions) -> *mut ffi::rocksdb_iterator_t {
+        ffi::rocksdb_create_iterator(self.inner.inner(), readopts.inner)
+    }
+
+    unsafe fn create_iterator_cf(
         &self,
-        cf: &impl AsColumnFamilyRef,
+        cf_handle: *mut ffi::rocksdb_column_family_handle_t,
-        keys: I,
-        sorted_input: bool,
         readopts: &ReadOptions,
-    ) -> Vec<Result<Option<DBPinnableSlice>, Error>>
+    ) -> *mut ffi::rocksdb_iterator_t {
-    where
+        ffi::rocksdb_create_iterator_cf(self.inner.inner(), readopts.inner, cf_handle)
-        K: AsRef<[u8]>,
-        I: IntoIterator<Item = K>;
-}
-
-impl<T: ThreadMode> DBAccess for DBWithThreadMode<T> {
-    fn inner(&self) -> *mut ffi::rocksdb_t {
-        self.inner
     }
 
     fn get_opt<K: AsRef<[u8]>>(
@@ -229,53 +248,63 @@ impl<T: ThreadMode> DBAccess for DBWithThreadMode<T> {
         self.get_pinned_cf_opt(cf, key, readopts)
     }
 
-    fn multi_get_opt<K, I>(
+    fn multi_get_opt<K, Iter>(
         &self,
-        keys: I,
+        keys: Iter,
         readopts: &ReadOptions,
     ) -> Vec<Result<Option<Vec<u8>>, Error>>
     where
         K: AsRef<[u8]>,
-        I: IntoIterator<Item = K>,
+        Iter: IntoIterator<Item = K>,
     {
         self.multi_get_opt(keys, readopts)
     }
 
-    fn multi_get_cf_opt<'b, K, I, W>(
+    fn multi_get_cf_opt<'b, K, Iter, W>(
         &self,
-        keys_cf: I,
+        keys_cf: Iter,
         readopts: &ReadOptions,
     ) -> Vec<Result<Option<Vec<u8>>, Error>>
     where
         K: AsRef<[u8]>,
-        I: IntoIterator<Item = (&'b W, K)>,
+        Iter: IntoIterator<Item = (&'b W, K)>,
         W: AsColumnFamilyRef + 'b,
     {
         self.multi_get_cf_opt(keys_cf, readopts)
     }
+}
 
-    fn batched_multi_get_cf_opt<K, I>(
+pub struct DBWithThreadModeInner {
-        &self,
+    inner: *mut ffi::rocksdb_t,
-        cf: &impl AsColumnFamilyRef,
+}
-        keys: I,
+
-        sorted_input: bool,
+impl DBInner for DBWithThreadModeInner {
-        readopts: &ReadOptions,
+    fn inner(&self) -> *mut ffi::rocksdb_t {
-    ) -> Vec<Result<Option<DBPinnableSlice>, Error>>
+        self.inner
-    where
+    }
-        K: AsRef<[u8]>,
+}
-        I: IntoIterator<Item = K>,
+
-    {
+impl Drop for DBWithThreadModeInner {
-        self.batched_multi_get_cf_opt(cf, keys, sorted_input, readopts)
+    fn drop(&mut self) {
+        unsafe {
+            ffi::rocksdb_close(self.inner);
+        }
     }
 }
 
+/// A type alias to RocksDB database.
+///
+/// See crate level documentation for a simple usage example.
+/// See [`DBCommon`] for full list of methods.
+pub type DBWithThreadMode<T> = DBCommon<T, DBWithThreadModeInner>;
+
 /// A type alias to DB instance type with the single-threaded column family
 /// creations/deletions
 ///
 /// # Compatibility and multi-threaded mode
 ///
 /// Previously, [`DB`] was defined as a direct `struct`. Now, it's type-aliased for
-/// compatibility. Use `DBWithThreadMode<MultiThreaded>` for multi-threaded
+/// compatibility. Use `DBCommon<MultiThreaded>` for multi-threaded
 /// column family alternations.
 ///
 /// # Limited performance implication for single-threaded mode
@@ -300,11 +329,11 @@ pub type DB = DBWithThreadMode<MultiThreaded>;
 // Safety note: auto-implementing Send on most db-related types is prevented by the inner FFI
 // pointer. In most cases, however, this pointer is Send-safe because it is never aliased and
 // rocksdb internally does not rely on thread-local information for its user-exposed types.
-unsafe impl<T: ThreadMode + Send> Send for DBWithThreadMode<T> {}
+unsafe impl<T: ThreadMode + Send, I: DBInner> Send for DBCommon<T, I> {}
 
 // Sync is similarly safe for many types because they do not expose interior mutability, and their
 // use within the rocksdb library is generally behind a const reference
-unsafe impl<T: ThreadMode> Sync for DBWithThreadMode<T> {}
+unsafe impl<T: ThreadMode, I: DBInner> Sync for DBCommon<T, I> {}
 
 // Specifies whether open DB for read only.
 enum AccessType<'a> {
@@ -314,6 +343,7 @@ enum AccessType<'a> {
     WithTTL { ttl: Duration },
 }
 
+/// Methods of `DBWithThreadMode`.
 impl<T: ThreadMode> DBWithThreadMode<T> {
     /// Opens a database with default options.
     pub fn open_default<P: AsRef<Path>>(path: P) -> Result<Self, Error> {
@@ -620,7 +650,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         }
 
         Ok(Self {
-            inner: db,
+            inner: DBWithThreadModeInner { inner: db },
             path: path.as_ref().to_path_buf(),
             cfs: T::new_cf_map_internal(cf_map),
             _outlive: outlive,
@@ -720,6 +750,74 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         Ok(db)
     }
 
+    /// Removes the database entries in the range `["from", "to")` using given write options.
+    pub fn delete_range_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        from: K,
+        to: K,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error> {
+        let from = from.as_ref();
+        let to = to.as_ref();
+
+        unsafe {
+            ffi_try!(ffi::rocksdb_delete_range_cf(
+                self.inner.inner(),
+                writeopts.inner,
+                cf.inner(),
+                from.as_ptr() as *const c_char,
+                from.len() as size_t,
+                to.as_ptr() as *const c_char,
+                to.len() as size_t,
+            ));
+            Ok(())
+        }
+    }
+
+    /// Removes the database entries in the range `["from", "to")` using default write options.
+    pub fn delete_range_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        from: K,
+        to: K,
+    ) -> Result<(), Error> {
+        self.delete_range_cf_opt(cf, from, to, &WriteOptions::default())
+    }
+
+    pub fn write_opt(&self, batch: WriteBatch, writeopts: &WriteOptions) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_write(
+                self.inner.inner(),
+                writeopts.inner,
+                batch.inner
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn write(&self, batch: WriteBatch) -> Result<(), Error> {
+        self.write_opt(batch, &WriteOptions::default())
+    }
+
+    pub fn write_without_wal(&self, batch: WriteBatch) -> Result<(), Error> {
+        let mut wo = WriteOptions::new();
+        wo.disable_wal(true);
+        self.write_opt(batch, &wo)
+    }
+}
+
+/// Common methods of `DBWithThreadMode` and `OptimisticTransactionDB`.
+impl<T: ThreadMode, D: DBInner> DBCommon<T, D> {
+    pub(crate) fn new(inner: D, cfs: T, path: PathBuf, outlive: Vec<OptionsMustOutliveDB>) -> Self {
+        Self {
+            inner,
+            cfs,
+            path,
+            _outlive: outlive,
+        }
+    }
+
     pub fn list_cf<P: AsRef<Path>>(opts: &Options, path: P) -> Result<Vec<String>, Error> {
         let cpath = to_cpath(path)?;
         let mut length = 0;
@@ -764,7 +862,10 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     /// the data to disk.
     pub fn flush_wal(&self, sync: bool) -> Result<(), Error> {
         unsafe {
-            ffi_try!(ffi::rocksdb_flush_wal(self.inner, c_uchar::from(sync)));
+            ffi_try!(ffi::rocksdb_flush_wal(
+                self.inner.inner(),
+                c_uchar::from(sync)
+            ));
         }
         Ok(())
     }
@@ -772,7 +873,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     /// Flushes database memtables to SST files on the disk.
     pub fn flush_opt(&self, flushopts: &FlushOptions) -> Result<(), Error> {
         unsafe {
-            ffi_try!(ffi::rocksdb_flush(self.inner, flushopts.inner));
+            ffi_try!(ffi::rocksdb_flush(self.inner.inner(), flushopts.inner));
         }
         Ok(())
     }
@@ -790,7 +891,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     ) -> Result<(), Error> {
         unsafe {
             ffi_try!(ffi::rocksdb_flush_cf(
-                self.inner,
+                self.inner.inner(),
                 flushopts.inner,
                 cf.inner()
             ));
@@ -804,23 +905,6 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         self.flush_cf_opt(cf, &FlushOptions::default())
     }
 
-    pub fn write_opt(&self, batch: WriteBatch, writeopts: &WriteOptions) -> Result<(), Error> {
-        unsafe {
-            ffi_try!(ffi::rocksdb_write(self.inner, writeopts.inner, batch.inner));
-        }
-        Ok(())
-    }
-
-    pub fn write(&self, batch: WriteBatch) -> Result<(), Error> {
-        self.write_opt(batch, &WriteOptions::default())
-    }
-
-    pub fn write_without_wal(&self, batch: WriteBatch) -> Result<(), Error> {
-        let mut wo = WriteOptions::new();
-        wo.disable_wal(true);
-        self.write_opt(batch, &wo)
-    }
-
     /// Return the bytes associated with a key value with read options. If you only intend to use
     /// the vector returned temporarily, consider using [`get_pinned_opt`](#method.get_pinned_opt)
     /// to avoid unnecessary memory copy.
@@ -882,7 +966,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let key = key.as_ref();
         unsafe {
             let val = ffi_try!(ffi::rocksdb_get_pinned(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 key.as_ptr() as *const c_char,
                 key.len() as size_t,
@@ -922,7 +1006,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let key = key.as_ref();
         unsafe {
             let val = ffi_try!(ffi::rocksdb_get_pinned_cf(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 cf.inner(),
                 key.as_ptr() as *const c_char,
@@ -977,7 +1061,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let mut errors = vec![ptr::null_mut(); keys.len()];
         unsafe {
             ffi::rocksdb_multi_get(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 ptr_keys.len(),
                 ptr_keys.as_ptr(),
@@ -1033,7 +1117,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let mut errors = vec![ptr::null_mut(); ptr_keys.len()];
         unsafe {
             ffi::rocksdb_multi_get_cf(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 ptr_cfs.as_ptr(),
                 ptr_keys.len(),
@@ -1089,7 +1173,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi::rocksdb_batched_multi_get_cf(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 cf.inner(),
                 ptr_keys.len(),
@@ -1129,7 +1213,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let key = key.as_ref();
         unsafe {
             0 != ffi::rocksdb_key_may_exist(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 key.as_ptr() as *const c_char,
                 key.len() as size_t,
@@ -1159,7 +1243,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let key = key.as_ref();
         0 != unsafe {
             ffi::rocksdb_key_may_exist_cf(
-                self.inner,
+                self.inner.inner(),
                 readopts.inner,
                 cf.inner(),
                 key.as_ptr() as *const c_char,
@@ -1185,7 +1269,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         })?;
         Ok(unsafe {
             ffi_try!(ffi::rocksdb_create_column_family(
-                self.inner,
+                self.inner.inner(),
                 opts.inner,
                 cf_name.as_ptr(),
             ))
@@ -1324,7 +1408,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi_try!(ffi::rocksdb_put(
-                self.inner,
+                self.inner.inner(),
                 writeopts.inner,
                 key.as_ptr() as *const c_char,
                 key.len() as size_t,
@@ -1351,7 +1435,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi_try!(ffi::rocksdb_put_cf(
-                self.inner,
+                self.inner.inner(),
                 writeopts.inner,
                 cf.inner(),
                 key.as_ptr() as *const c_char,
@@ -1373,7 +1457,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi_try!(ffi::rocksdb_merge(
-                self.inner,
+                self.inner.inner(),
                 writeopts.inner,
                 key.as_ptr() as *const c_char,
                 key.len() as size_t,
@@ -1400,7 +1484,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi_try!(ffi::rocksdb_merge_cf(
-                self.inner,
+                self.inner.inner(),
                 writeopts.inner,
                 cf.inner(),
                 key.as_ptr() as *const c_char,
@@ -1421,7 +1505,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi_try!(ffi::rocksdb_delete(
-                self.inner,
+                self.inner.inner(),
                 writeopts.inner,
                 key.as_ptr() as *const c_char,
                 key.len() as size_t,
@@ -1440,7 +1524,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
         unsafe {
             ffi_try!(ffi::rocksdb_delete_cf(
-                self.inner,
+                self.inner.inner(),
                 writeopts.inner,
                 cf.inner(),
                 key.as_ptr() as *const c_char,
@@ -1450,31 +1534,6 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         }
     }
 
-    /// Removes the database entries in the range `["from", "to")` using given write options.
-    pub fn delete_range_cf_opt<K: AsRef<[u8]>>(
-        &self,
-        cf: &impl AsColumnFamilyRef,
-        from: K,
-        to: K,
-        writeopts: &WriteOptions,
-    ) -> Result<(), Error> {
-        let from = from.as_ref();
-        let to = to.as_ref();
-
-        unsafe {
-            ffi_try!(ffi::rocksdb_delete_range_cf(
-                self.inner,
-                writeopts.inner,
-                cf.inner(),
-                from.as_ptr() as *const c_char,
-                from.len() as size_t,
-                to.as_ptr() as *const c_char,
-                to.len() as size_t,
-            ));
-            Ok(())
-        }
-    }
-
     pub fn put<K, V>(&self, key: K, value: V) -> Result<(), Error>
     where
         K: AsRef<[u8]>,
@@ -1519,16 +1578,6 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         self.delete_cf_opt(cf, key.as_ref(), &WriteOptions::default())
     }
 
-    /// Removes the database entries in the range `["from", "to")` using default write options.
-    pub fn delete_range_cf<K: AsRef<[u8]>>(
-        &self,
-        cf: &impl AsColumnFamilyRef,
-        from: K,
-        to: K,
-    ) -> Result<(), Error> {
-        self.delete_range_cf_opt(cf, from, to, &WriteOptions::default())
-    }
-
     /// Runs a manual compaction on the Range of keys given. This is not likely to be needed for typical usage.
     pub fn compact_range<S: AsRef<[u8]>, E: AsRef<[u8]>>(&self, start: Option<S>, end: Option<E>) {
         unsafe {
@@ -1536,7 +1585,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             let end = end.as_ref().map(AsRef::as_ref);
 
             ffi::rocksdb_compact_range(
-                self.inner,
+                self.inner.inner(),
                 opt_bytes_to_ptr(start),
                 start.map_or(0, <[u8]>::len) as size_t,
                 opt_bytes_to_ptr(end),
@@ -1557,7 +1606,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             let end = end.as_ref().map(AsRef::as_ref);
 
             ffi::rocksdb_compact_range_opt(
-                self.inner,
+                self.inner.inner(),
                 opts.inner,
                 opt_bytes_to_ptr(start),
                 start.map_or(0, <[u8]>::len) as size_t,
@@ -1580,7 +1629,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             let end = end.as_ref().map(AsRef::as_ref);
 
             ffi::rocksdb_compact_range_cf(
-                self.inner,
+                self.inner.inner(),
                 cf.inner(),
                 opt_bytes_to_ptr(start),
                 start.map_or(0, <[u8]>::len) as size_t,
@@ -1603,7 +1652,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             let end = end.as_ref().map(AsRef::as_ref);
 
             ffi::rocksdb_compact_range_cf_opt(
-                self.inner,
+                self.inner.inner(),
                 cf.inner(),
                 opts.inner,
                 opt_bytes_to_ptr(start),
@@ -1621,7 +1670,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let count = opts.len() as i32;
         unsafe {
             ffi_try!(ffi::rocksdb_set_options(
-                self.inner,
+                self.inner.inner(),
                 count,
                 cnames.as_ptr(),
                 cvalues.as_ptr(),
@@ -1641,7 +1690,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let count = opts.len() as i32;
         unsafe {
             ffi_try!(ffi::rocksdb_set_options_cf(
-                self.inner,
+                self.inner.inner(),
                 cf.inner(),
                 count,
                 cnames.as_ptr(),
@@ -1696,7 +1745,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     pub fn property_value(&self, name: impl CStrLike) -> Result<Option<String>, Error> {
         Self::property_value_impl(
             name,
-            |prop_name| unsafe { ffi::rocksdb_property_value(self.inner, prop_name) },
+            |prop_name| unsafe { ffi::rocksdb_property_value(self.inner.inner(), prop_name) },
             |str_value| Ok(str_value.to_owned()),
         )
     }
@@ -1713,7 +1762,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         Self::property_value_impl(
             name,
             |prop_name| unsafe {
-                ffi::rocksdb_property_value_cf(self.inner, cf.inner(), prop_name)
+                ffi::rocksdb_property_value_cf(self.inner.inner(), cf.inner(), prop_name)
             },
             |str_value| Ok(str_value.to_owned()),
         )
@@ -1735,7 +1784,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     pub fn property_int_value(&self, name: impl CStrLike) -> Result<Option<u64>, Error> {
         Self::property_value_impl(
             name,
-            |prop_name| unsafe { ffi::rocksdb_property_value(self.inner, prop_name) },
+            |prop_name| unsafe { ffi::rocksdb_property_value(self.inner.inner(), prop_name) },
             Self::parse_property_int_value,
         )
     }
@@ -1752,7 +1801,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         Self::property_value_impl(
             name,
             |prop_name| unsafe {
-                ffi::rocksdb_property_value_cf(self.inner, cf.inner(), prop_name)
+                ffi::rocksdb_property_value_cf(self.inner.inner(), cf.inner(), prop_name)
             },
             Self::parse_property_int_value,
         )
@@ -1760,7 +1809,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
 
     /// The sequence number of the most recent transaction.
     pub fn latest_sequence_number(&self) -> u64 {
-        unsafe { ffi::rocksdb_get_latest_sequence_number(self.inner) }
+        unsafe { ffi::rocksdb_get_latest_sequence_number(self.inner.inner()) }
     }
 
     /// Iterate over batches of write operations since a given sequence.
@@ -1779,7 +1828,11 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
             // for creating and destroying it; fortunately we can pass a nullptr
             // here to get the default behavior
             let opts: *const ffi::rocksdb_wal_readoptions_t = ptr::null();
-            let iter = ffi_try!(ffi::rocksdb_get_updates_since(self.inner, seq_number, opts));
+            let iter = ffi_try!(ffi::rocksdb_get_updates_since(
+                self.inner.inner(),
+                seq_number,
+                opts
+            ));
             Ok(DBWALIterator { inner: iter })
         }
     }
@@ -1788,7 +1841,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     /// log files.
     pub fn try_catch_up_with_primary(&self) -> Result<(), Error> {
         unsafe {
-            ffi_try!(ffi::rocksdb_try_catch_up_with_primary(self.inner));
+            ffi_try!(ffi::rocksdb_try_catch_up_with_primary(self.inner.inner()));
         }
         Ok(())
     }
@@ -1851,7 +1904,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     ) -> Result<(), Error> {
         unsafe {
             ffi_try!(ffi::rocksdb_ingest_external_file(
-                self.inner,
+                self.inner.inner(),
                 cpaths.as_ptr(),
                 paths_v.len(),
                 opts.inner as *const _
@@ -1869,7 +1922,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     ) -> Result<(), Error> {
         unsafe {
             ffi_try!(ffi::rocksdb_ingest_external_file_cf(
-                self.inner,
+                self.inner.inner(),
                 cf.inner(),
                 cpaths.as_ptr(),
                 paths_v.len(),
@@ -1883,7 +1936,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     /// and end key
     pub fn live_files(&self) -> Result<Vec<LiveFile>, Error> {
         unsafe {
-            let files = ffi::rocksdb_livefiles(self.inner);
+            let files = ffi::rocksdb_livefiles(self.inner.inner());
             if files.is_null() {
                 Err(Error::new("Could not get live files".to_owned()))
             } else {
@@ -1941,7 +1994,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let to = to.as_ref();
         unsafe {
             ffi_try!(ffi::rocksdb_delete_file_in_range(
-                self.inner,
+                self.inner.inner(),
                 from.as_ptr() as *const c_char,
                 from.len() as size_t,
                 to.as_ptr() as *const c_char,
@@ -1962,7 +2015,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
         let to = to.as_ref();
         unsafe {
             ffi_try!(ffi::rocksdb_delete_file_in_range_cf(
-                self.inner,
+                self.inner.inner(),
                 cf.inner(),
                 from.as_ptr() as *const c_char,
                 from.len() as size_t,
@@ -1976,7 +2029,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     /// Request stopping background work, if wait is true wait until it's done.
     pub fn cancel_all_background_work(&self, wait: bool) {
         unsafe {
-            ffi::rocksdb_cancel_all_background_work(self.inner, c_uchar::from(wait));
+            ffi::rocksdb_cancel_all_background_work(self.inner.inner(), c_uchar::from(wait));
         }
     }
 
@@ -1987,7 +2040,10 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     ) -> Result<(), Error> {
         unsafe {
             // first mark the column family as dropped
-            ffi_try!(ffi::rocksdb_drop_column_family(self.inner, cf_inner));
+            ffi_try!(ffi::rocksdb_drop_column_family(
+                self.inner.inner(),
+                cf_inner
+            ));
         }
         // then finally reclaim any resources (mem, files) by destroying the only single column
         // family handle by drop()-ing it
@@ -1996,7 +2052,7 @@ impl<T: ThreadMode> DBWithThreadMode<T> {
     }
 }
 
-impl DBWithThreadMode<SingleThreaded> {
+impl<I: DBInner> DBCommon<SingleThreaded, I> {
     /// Creates column family with given name and options
     pub fn create_cf<N: AsRef<str>>(&mut self, name: N, opts: &Options) -> Result<(), Error> {
         let inner = self.create_inner_cf_handle(name.as_ref(), opts)?;
@@ -2021,7 +2077,7 @@ impl DBWithThreadMode<SingleThreaded> {
     }
 }
 
-impl DBWithThreadMode<MultiThreaded> {
+impl<I: DBInner> DBCommon<MultiThreaded, I> {
     /// Creates column family with given name and options
     pub fn create_cf<N: AsRef<str>>(&self, name: N, opts: &Options) -> Result<(), Error> {
         let inner = self.create_inner_cf_handle(name.as_ref(), opts)?;
@@ -2054,16 +2110,13 @@ impl DBWithThreadMode<MultiThreaded> {
     }
 }
 
-impl<T: ThreadMode> Drop for DBWithThreadMode<T> {
+impl<T: ThreadMode, I: DBInner> Drop for DBCommon<T, I> {
     fn drop(&mut self) {
-        unsafe {
+        self.cfs.drop_all_cfs_internal();
-            self.cfs.drop_all_cfs_internal();
-            ffi::rocksdb_close(self.inner);
-        }
     }
 }
 
-impl<T: ThreadMode> fmt::Debug for DBWithThreadMode<T> {
+impl<T: ThreadMode, I: DBInner> fmt::Debug for DBCommon<T, I> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "RocksDB {{ path: {:?} }}", self.path())
     }
@@ -2106,7 +2159,7 @@ fn convert_options(opts: &[(&str, &str)]) -> Result<Vec<(CString, CString)>, Err
         .collect()
 }
 
-fn convert_values(
+pub(crate) fn convert_values(
     values: Vec<*mut c_char>,
     values_sizes: Vec<usize>,
     errors: Vec<*mut c_char>,

src/db_iterator.rs

@@ -12,11 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::db::{DBAccess, DB};
+use crate::{
-use crate::{ffi, Error, ReadOptions, WriteBatch};
+    db::{DBAccess, DB},
+    ffi, Error, ReadOptions, WriteBatch,
+};
 use libc::{c_char, c_uchar, size_t};
-use std::marker::PhantomData;
+use std::{marker::PhantomData, slice};
-use std::slice;
 
 /// A type alias to keep compatibility. See [`DBRawIteratorWithThreadMode`] for details
 pub type DBRawIterator<'a> = DBRawIteratorWithThreadMode<'a, DB>;
@@ -87,7 +88,7 @@ pub struct DBRawIteratorWithThreadMode<'a, D: DBAccess> {
 
 impl<'a, D: DBAccess> DBRawIteratorWithThreadMode<'a, D> {
     pub(crate) fn new(db: &D, readopts: ReadOptions) -> Self {
-        let inner = unsafe { ffi::rocksdb_create_iterator(db.inner(), readopts.inner) };
+        let inner = unsafe { db.create_iterator(&readopts) };
         Self::from_inner(inner, readopts)
     }
 
@@ -96,16 +97,15 @@ impl<'a, D: DBAccess> DBRawIteratorWithThreadMode<'a, D> {
         cf_handle: *mut ffi::rocksdb_column_family_handle_t,
         readopts: ReadOptions,
     ) -> Self {
-        let inner =
+        let inner = unsafe { db.create_iterator_cf(cf_handle, &readopts) };
-            unsafe { ffi::rocksdb_create_iterator_cf(db.inner(), readopts.inner, cf_handle) };
         Self::from_inner(inner, readopts)
     }
 
     fn from_inner(inner: *mut ffi::rocksdb_iterator_t, readopts: ReadOptions) -> Self {
         // This unwrap will never fail since rocksdb_create_iterator and
-        // rocksdb_create_iterator_cf functions always return non-null.  They
+        // rocksdb_create_iterator_cf functions always return non-null. They
-        // use new and deference the result so any nulls would end up in SIGSEGV
+        // use new and deference the result so any nulls would end up with SIGSEGV
-        // there and we have bigger issue.
+        // there and we would have a bigger issue.
         let inner = std::ptr::NonNull::new(inner).unwrap();
         Self {
             inner,

src/db_options.rs

@@ -576,9 +576,9 @@ impl BlockBasedOptions {
     pub fn set_bloom_filter(&mut self, bits_per_key: c_double, block_based: bool) {
         unsafe {
             let bloom = if block_based {
-                ffi::rocksdb_filterpolicy_create_bloom(bits_per_key)
+                ffi::rocksdb_filterpolicy_create_bloom(bits_per_key as _)
             } else {
-                ffi::rocksdb_filterpolicy_create_bloom_full(bits_per_key)
+                ffi::rocksdb_filterpolicy_create_bloom_full(bits_per_key as _)
             };
 
             ffi::rocksdb_block_based_options_set_filter_policy(self.inner, bloom);

src/lib.rs

@@ -92,6 +92,7 @@ pub mod properties;
 mod slice_transform;
 mod snapshot;
 mod sst_file_writer;
+mod transactions;
 mod write_batch;
 
 pub use crate::{
@@ -100,7 +101,10 @@ pub use crate::{
         ColumnFamilyRef, DEFAULT_COLUMN_FAMILY_NAME,
     },
     compaction_filter::Decision as CompactionDecision,
-    db::{DBAccess, DBWithThreadMode, LiveFile, MultiThreaded, SingleThreaded, ThreadMode, DB},
+    db::{
+        DBAccess, DBCommon, DBWithThreadMode, LiveFile, MultiThreaded, SingleThreaded, ThreadMode,
+        DB,
+    },
     db_iterator::{
         DBIterator, DBIteratorWithThreadMode, DBRawIterator, DBRawIteratorWithThreadMode,
         DBWALIterator, Direction, IteratorMode,
@@ -120,7 +124,11 @@ pub use crate::{
     slice_transform::SliceTransform,
     snapshot::{Snapshot, SnapshotWithThreadMode},
     sst_file_writer::SstFileWriter,
-    write_batch::{WriteBatch, WriteBatchIterator},
+    transactions::{
+        OptimisticTransactionDB, OptimisticTransactionOptions, Transaction, TransactionDB,
+        TransactionDBOptions, TransactionOptions,
+    },
+    write_batch::{WriteBatch, WriteBatchIterator, WriteBatchWithTransaction},
 };
 
 use librocksdb_sys as ffi;
@@ -128,6 +136,27 @@ use librocksdb_sys as ffi;
 use std::error;
 use std::fmt;
 
+/// RocksDB error kind.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ErrorKind {
+    NotFound,
+    Corruption,
+    NotSupported,
+    InvalidArgument,
+    IOError,
+    MergeInProgress,
+    Incomplete,
+    ShutdownInProgress,
+    TimedOut,
+    Aborted,
+    Busy,
+    Expired,
+    TryAgain,
+    CompactionTooLarge,
+    ColumnFamilyDropped,
+    Unknown,
+}
+
 /// A simple wrapper round a string, used for errors reported from
 /// ffi calls.
 #[derive(Debug, Clone, PartialEq)]
@@ -143,6 +172,28 @@ impl Error {
     pub fn into_string(self) -> String {
         self.into()
     }
+
+    /// Parse corresponding [`ErrorKind`] from error message.
+    pub fn kind(&self) -> ErrorKind {
+        match self.message.split(':').next().unwrap_or("") {
+            "NotFound" => ErrorKind::NotFound,
+            "Corruption" => ErrorKind::Corruption,
+            "Not implemented" => ErrorKind::NotSupported,
+            "Invalid argument" => ErrorKind::InvalidArgument,
+            "IO error" => ErrorKind::IOError,
+            "Merge in progress" => ErrorKind::MergeInProgress,
+            "Result incomplete" => ErrorKind::Incomplete,
+            "Shutdown in progress" => ErrorKind::ShutdownInProgress,
+            "Operation timed out" => ErrorKind::TimedOut,
+            "Operation aborted" => ErrorKind::Aborted,
+            "Resource busy" => ErrorKind::Busy,
+            "Operation expired" => ErrorKind::Expired,
+            "Operation failed. Try again." => ErrorKind::TryAgain,
+            "Compaction too large" => ErrorKind::CompactionTooLarge,
+            "Column family dropped" => ErrorKind::ColumnFamilyDropped,
+            _ => ErrorKind::Unknown,
+        }
+    }
 }
 
 impl AsRef<str> for Error {
@@ -171,6 +222,11 @@ impl fmt::Display for Error {
 
 #[cfg(test)]
 mod test {
+    use crate::{
+        OptimisticTransactionDB, OptimisticTransactionOptions, Transaction, TransactionDB,
+        TransactionDBOptions, TransactionOptions,
+    };
+
     use super::{
         column_family::UnboundColumnFamily,
         db_options::{CacheWrapper, EnvWrapper},
@@ -209,6 +265,12 @@ mod test {
         is_send::<CacheWrapper>();
         is_send::<Env>();
         is_send::<EnvWrapper>();
+        is_send::<TransactionDB>();
+        is_send::<OptimisticTransactionDB>();
+        is_send::<Transaction<'_, TransactionDB>>();
+        is_send::<TransactionDBOptions>();
+        is_send::<OptimisticTransactionOptions>();
+        is_send::<TransactionOptions>();
     }
 
     #[test]
@@ -234,5 +296,10 @@ mod test {
         is_sync::<CacheWrapper>();
         is_sync::<Env>();
         is_sync::<EnvWrapper>();
+        is_sync::<TransactionDB>();
+        is_sync::<OptimisticTransactionDB>();
+        is_sync::<TransactionDBOptions>();
+        is_sync::<OptimisticTransactionOptions>();
+        is_sync::<TransactionOptions>();
     }
 }

src/perf.rs

@@ -14,7 +14,7 @@
 
 use libc::{c_int, c_uchar, c_void};
 
-use crate::{ffi, ffi_util::from_cstr, Cache, Error, DB};
+use crate::{db::DBInner, ffi, ffi_util::from_cstr, Cache, Error, DB};
 
 #[derive(Debug, Copy, Clone, PartialEq)]
 #[repr(i32)]
@@ -242,7 +242,7 @@ impl MemoryUsageBuilder {
     /// Add a DB instance to collect memory usage from it and add up in total stats
     fn add_db(&mut self, db: &DB) {
         unsafe {
-            ffi::rocksdb_memory_consumers_add_db(self.inner, db.inner);
+            ffi::rocksdb_memory_consumers_add_db(self.inner, db.inner.inner());
         }
     }
 

src/snapshot.rs

@@ -44,7 +44,7 @@ pub struct SnapshotWithThreadMode<'a, D: DBAccess> {
 impl<'a, D: DBAccess> SnapshotWithThreadMode<'a, D> {
     /// Creates a new `SnapshotWithThreadMode` of the database `db`.
     pub fn new(db: &'a D) -> Self {
-        let snapshot = unsafe { ffi::rocksdb_create_snapshot(db.inner()) };
+        let snapshot = unsafe { db.create_snapshot() };
         Self {
             db,
             inner: snapshot,
@@ -258,7 +258,7 @@ impl<'a, D: DBAccess> SnapshotWithThreadMode<'a, D> {
 impl<'a, D: DBAccess> Drop for SnapshotWithThreadMode<'a, D> {
     fn drop(&mut self) {
         unsafe {
-            ffi::rocksdb_release_snapshot(self.db.inner(), self.inner);
+            self.db.release_snapshot(self.inner);
         }
     }
 }

src/transactions/mod.rs

@@ -0,0 +1,24 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+mod optimistic_transaction_db;
+mod options;
+mod transaction;
+mod transaction_db;
+
+pub use optimistic_transaction_db::OptimisticTransactionDB;
+pub use options::{OptimisticTransactionOptions, TransactionDBOptions, TransactionOptions};
+pub use transaction::Transaction;
+pub use transaction_db::TransactionDB;

src/transactions/optimistic_transaction_db.rs

@@ -0,0 +1,294 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+use std::{collections::BTreeMap, ffi::CString, fs, iter, marker::PhantomData, path::Path, ptr};
+
+use libc::{c_char, c_int};
+
+use crate::{
+    db::DBCommon, db::DBInner, ffi, ffi_util::to_cpath, write_batch::WriteBatchWithTransaction,
+    ColumnFamilyDescriptor, Error, OptimisticTransactionOptions, Options, ThreadMode, Transaction,
+    WriteOptions, DEFAULT_COLUMN_FAMILY_NAME,
+};
+
+/// A type alias to RocksDB Optimistic Transaction DB.
+///
+/// Please read the official
+/// [guide](https://github.com/facebook/rocksdb/wiki/Transactions#optimistictransactiondb)
+/// to learn more about RocksDB OptimisticTransactionDB.
+///
+/// The default thread mode for [`OptimisticTransactionDB`] is [`SingleThreaded`]
+/// if feature `multi-threaded-cf` is not enabled.
+///
+/// See [`DBCommon`] for full list of methods.
+///
+/// # Examples
+///
+/// ```
+/// use rocksdb::{DB, Options, OptimisticTransactionDB, SingleThreaded};
+/// let path = "_path_for_optimistic_transaction_db";
+/// {
+///     let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(path).unwrap();
+///     db.put(b"my key", b"my value").unwrap();
+///     
+///     // create transaction
+///     let txn = db.transaction();
+///     txn.put(b"key2", b"value2");
+///     txn.put(b"key3", b"value3");
+///     txn.commit().unwrap();
+/// }
+/// let _ = DB::destroy(&Options::default(), path);
+/// ```
+///
+/// [`SingleThreaded`]: crate::SingleThreaded
+#[cfg(not(feature = "multi-threaded-cf"))]
+pub type OptimisticTransactionDB<T = crate::SingleThreaded> =
+    DBCommon<T, OptimisticTransactionDBInner>;
+#[cfg(feature = "multi-threaded-cf")]
+pub type OptimisticTransactionDB<T = crate::MultiThreaded> =
+    DBCommon<T, OptimisticTransactionDBInner>;
+
+pub struct OptimisticTransactionDBInner {
+    base: *mut ffi::rocksdb_t,
+    db: *mut ffi::rocksdb_optimistictransactiondb_t,
+}
+
+impl DBInner for OptimisticTransactionDBInner {
+    fn inner(&self) -> *mut ffi::rocksdb_t {
+        self.base
+    }
+}
+
+impl Drop for OptimisticTransactionDBInner {
+    fn drop(&mut self) {
+        unsafe {
+            ffi::rocksdb_optimistictransactiondb_close_base_db(self.base);
+            ffi::rocksdb_optimistictransactiondb_close(self.db);
+        }
+    }
+}
+
+/// Methods of `OptimisticTransactionDB`.
+impl<T: ThreadMode> OptimisticTransactionDB<T> {
+    /// Opens a database with default options.
+    pub fn open_default<P: AsRef<Path>>(path: P) -> Result<Self, Error> {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        Self::open(&opts, path)
+    }
+
+    /// Opens the database with the specified options.
+    pub fn open<P: AsRef<Path>>(opts: &Options, path: P) -> Result<Self, Error> {
+        Self::open_cf(opts, path, None::<&str>)
+    }
+
+    /// Opens a database with the given database options and column family names.
+    ///
+    /// Column families opened using this function will be created with default `Options`.
+    pub fn open_cf<P, I, N>(opts: &Options, path: P, cfs: I) -> Result<Self, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = N>,
+        N: AsRef<str>,
+    {
+        let cfs = cfs
+            .into_iter()
+            .map(|name| ColumnFamilyDescriptor::new(name.as_ref(), Options::default()));
+
+        Self::open_cf_descriptors_internal(opts, path, cfs)
+    }
+
+    /// Opens a database with the given database options and column family descriptors.
+    pub fn open_cf_descriptors<P, I>(opts: &Options, path: P, cfs: I) -> Result<Self, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = ColumnFamilyDescriptor>,
+    {
+        Self::open_cf_descriptors_internal(opts, path, cfs)
+    }
+
+    /// Internal implementation for opening RocksDB.
+    fn open_cf_descriptors_internal<P, I>(opts: &Options, path: P, cfs: I) -> Result<Self, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = ColumnFamilyDescriptor>,
+    {
+        let cfs: Vec<_> = cfs.into_iter().collect();
+        let outlive = iter::once(opts.outlive.clone())
+            .chain(cfs.iter().map(|cf| cf.options.outlive.clone()))
+            .collect();
+
+        let cpath = to_cpath(&path)?;
+
+        if let Err(e) = fs::create_dir_all(&path) {
+            return Err(Error::new(format!(
+                "Failed to create RocksDB directory: `{:?}`.",
+                e
+            )));
+        }
+
+        let db: *mut ffi::rocksdb_optimistictransactiondb_t;
+        let mut cf_map = BTreeMap::new();
+
+        if cfs.is_empty() {
+            db = Self::open_raw(opts, &cpath)?;
+        } else {
+            let mut cfs_v = cfs;
+            // Always open the default column family.
+            if !cfs_v.iter().any(|cf| cf.name == DEFAULT_COLUMN_FAMILY_NAME) {
+                cfs_v.push(ColumnFamilyDescriptor {
+                    name: String::from(DEFAULT_COLUMN_FAMILY_NAME),
+                    options: Options::default(),
+                });
+            }
+            // We need to store our CStrings in an intermediate vector
+            // so that their pointers remain valid.
+            let c_cfs: Vec<CString> = cfs_v
+                .iter()
+                .map(|cf| CString::new(cf.name.as_bytes()).unwrap())
+                .collect();
+
+            let cfnames: Vec<_> = c_cfs.iter().map(|cf| cf.as_ptr()).collect();
+
+            // These handles will be populated by DB.
+            let mut cfhandles: Vec<_> = cfs_v.iter().map(|_| ptr::null_mut()).collect();
+
+            let cfopts: Vec<_> = cfs_v
+                .iter()
+                .map(|cf| cf.options.inner as *const _)
+                .collect();
+
+            db = Self::open_cf_raw(opts, &cpath, &cfs_v, &cfnames, &cfopts, &mut cfhandles)?;
+
+            for handle in &cfhandles {
+                if handle.is_null() {
+                    return Err(Error::new(
+                        "Received null column family handle from DB.".to_owned(),
+                    ));
+                }
+            }
+
+            for (cf_desc, inner) in cfs_v.iter().zip(cfhandles) {
+                cf_map.insert(cf_desc.name.clone(), inner);
+            }
+        }
+
+        if db.is_null() {
+            return Err(Error::new("Could not initialize database.".to_owned()));
+        }
+
+        let base = unsafe { ffi::rocksdb_optimistictransactiondb_get_base_db(db) };
+        if base.is_null() {
+            unsafe {
+                ffi::rocksdb_optimistictransactiondb_close(db);
+            }
+            return Err(Error::new("Could not initialize database.".to_owned()));
+        }
+        let inner = OptimisticTransactionDBInner { base, db };
+
+        Ok(Self::new(
+            inner,
+            T::new_cf_map_internal(cf_map),
+            path.as_ref().to_path_buf(),
+            outlive,
+        ))
+    }
+
+    fn open_raw(
+        opts: &Options,
+        cpath: &CString,
+    ) -> Result<*mut ffi::rocksdb_optimistictransactiondb_t, Error> {
+        unsafe {
+            let db = ffi_try!(ffi::rocksdb_optimistictransactiondb_open(
+                opts.inner,
+                cpath.as_ptr()
+            ));
+            Ok(db)
+        }
+    }
+
+    fn open_cf_raw(
+        opts: &Options,
+        cpath: &CString,
+        cfs_v: &[ColumnFamilyDescriptor],
+        cfnames: &[*const c_char],
+        cfopts: &[*const ffi::rocksdb_options_t],
+        cfhandles: &mut [*mut ffi::rocksdb_column_family_handle_t],
+    ) -> Result<*mut ffi::rocksdb_optimistictransactiondb_t, Error> {
+        unsafe {
+            let db = ffi_try!(ffi::rocksdb_optimistictransactiondb_open_column_families(
+                opts.inner,
+                cpath.as_ptr(),
+                cfs_v.len() as c_int,
+                cfnames.as_ptr(),
+                cfopts.as_ptr(),
+                cfhandles.as_mut_ptr(),
+            ));
+            Ok(db)
+        }
+    }
+
+    /// Creates a transaction with default options.
+    pub fn transaction(&self) -> Transaction<Self> {
+        self.transaction_opt(
+            &WriteOptions::default(),
+            &OptimisticTransactionOptions::default(),
+        )
+    }
+
+    /// Creates a transaction with default options.
+    pub fn transaction_opt(
+        &self,
+        writeopts: &WriteOptions,
+        otxn_opts: &OptimisticTransactionOptions,
+    ) -> Transaction<Self> {
+        Transaction {
+            inner: unsafe {
+                ffi::rocksdb_optimistictransaction_begin(
+                    self.inner.db,
+                    writeopts.inner,
+                    otxn_opts.inner,
+                    std::ptr::null_mut(),
+                )
+            },
+            _marker: PhantomData::default(),
+        }
+    }
+
+    pub fn write_opt(
+        &self,
+        batch: WriteBatchWithTransaction<true>,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_optimistictransactiondb_write(
+                self.inner.db,
+                writeopts.inner,
+                batch.inner
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn write(&self, batch: WriteBatchWithTransaction<true>) -> Result<(), Error> {
+        self.write_opt(batch, &WriteOptions::default())
+    }
+
+    pub fn write_without_wal(&self, batch: WriteBatchWithTransaction<true>) -> Result<(), Error> {
+        let mut wo = WriteOptions::new();
+        wo.disable_wal(true);
+        self.write_opt(batch, &wo)
+    }
+}

src/transactions/options.rs

@@ -0,0 +1,297 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+use crate::ffi;
+use core::panic;
+
+pub struct TransactionOptions {
+    pub(crate) inner: *mut ffi::rocksdb_transaction_options_t,
+}
+
+unsafe impl Send for TransactionOptions {}
+unsafe impl Sync for TransactionOptions {}
+
+impl Default for TransactionOptions {
+    fn default() -> Self {
+        let txn_opts = unsafe { ffi::rocksdb_transaction_options_create() };
+        assert!(
+            !txn_opts.is_null(),
+            "Could not create RocksDB transaction options"
+        );
+        Self { inner: txn_opts }
+    }
+}
+
+impl TransactionOptions {
+    pub fn new() -> TransactionOptions {
+        TransactionOptions::default()
+    }
+
+    pub fn set_skip_prepare(&mut self, skip_prepare: bool) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_set_snapshot(self.inner, u8::from(skip_prepare));
+        }
+    }
+
+    /// Specifies use snapshot or not.
+    ///
+    /// Default: false.
+    ///
+    /// If a transaction has a snapshot set, the transaction will ensure that
+    /// any keys successfully written(or fetched via `get_for_update`) have not
+    /// been modified outside of this transaction since the time the snapshot was
+    /// set.
+    /// If a snapshot has not been set, the transaction guarantees that keys have
+    /// not been modified since the time each key was first written (or fetched via
+    /// `get_for_update`).
+    ///
+    /// Using snapshot will provide stricter isolation guarantees at the
+    /// expense of potentially more transaction failures due to conflicts with
+    /// other writes.
+    ///
+    /// Calling `set_snapshot` will not affect the version of Data returned by `get`
+    /// methods.
+    pub fn set_snapshot(&mut self, snapshot: bool) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_set_snapshot(self.inner, u8::from(snapshot));
+        }
+    }
+
+    /// Specifies whether detect deadlock or not.
+    ///
+    /// Setting to true means that before acquiring locks, this transaction will
+    /// check if doing so will cause a deadlock. If so, it will return with
+    /// Status::Busy.  The user should retry their transaction.
+    ///
+    /// Default: false.
+    pub fn set_deadlock_detect(&mut self, deadlock_detect: bool) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_deadlock_detect(
+                self.inner,
+                u8::from(deadlock_detect),
+            );
+        }
+    }
+
+    /// Specifies the wait timeout in milliseconds when a transaction attempts to lock a key.
+    ///
+    /// If 0, no waiting is done if a lock cannot instantly be acquired.
+    /// If negative, transaction lock timeout in `TransactionDBOptions` will be used.
+    ///
+    /// Default: -1.
+    pub fn set_lock_timeout(&mut self, lock_timeout: i64) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_lock_timeout(self.inner, lock_timeout);
+        }
+    }
+
+    /// Specifies expiration duration in milliseconds.
+    ///
+    /// If non-negative, transactions that last longer than this many milliseconds will fail to commit.
+    /// If not set, a forgotten transaction that is never committed, rolled back, or deleted
+    /// will never relinquish any locks it holds.  This could prevent keys from being by other writers.
+    ///
+    /// Default: -1.
+    pub fn set_expiration(&mut self, expiration: i64) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_expiration(self.inner, expiration);
+        }
+    }
+
+    /// Specifies the number of traversals to make during deadlock detection.
+    ///
+    /// Default: 50.
+    pub fn set_deadlock_detect_depth(&mut self, depth: i64) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_deadlock_detect_depth(self.inner, depth);
+        }
+    }
+
+    /// Specifies the maximum number of bytes used for the write batch. 0 means no limit.
+    ///
+    /// Default: 0.
+    pub fn set_max_write_batch_size(&mut self, size: usize) {
+        unsafe {
+            ffi::rocksdb_transaction_options_set_max_write_batch_size(self.inner, size);
+        }
+    }
+}
+
+impl Drop for TransactionOptions {
+    fn drop(&mut self) {
+        unsafe {
+            ffi::rocksdb_transaction_options_destroy(self.inner);
+        }
+    }
+}
+
+pub struct TransactionDBOptions {
+    pub(crate) inner: *mut ffi::rocksdb_transactiondb_options_t,
+}
+
+unsafe impl Send for TransactionDBOptions {}
+unsafe impl Sync for TransactionDBOptions {}
+
+impl Default for TransactionDBOptions {
+    fn default() -> Self {
+        let txn_db_opts = unsafe { ffi::rocksdb_transactiondb_options_create() };
+        assert!(
+            !txn_db_opts.is_null(),
+            "Could not create RocksDB transactiondb options"
+        );
+        Self { inner: txn_db_opts }
+    }
+}
+
+impl TransactionDBOptions {
+    pub fn new() -> TransactionDBOptions {
+        TransactionDBOptions::default()
+    }
+
+    /// Specifies the wait timeout in milliseconds when writing a key
+    /// outside of a transaction (ie. by calling `TransactionDB::put` directly).
+    ///
+    /// If 0, no waiting is done if a lock cannot instantly be acquired.
+    /// If negative, there is no timeout and will block indefinitely when acquiring
+    /// a lock.
+    ///
+    /// Not using a timeout can lead to deadlocks.  Currently, there
+    /// is no deadlock-detection to recover from a deadlock.  While DB writes
+    /// cannot deadlock with other DB writes, they can deadlock with a transaction.
+    /// A negative timeout should only be used if all transactions have a small
+    /// expiration set.
+    ///
+    /// Default: 1000(1s).
+    pub fn set_default_lock_timeout(&mut self, default_lock_timeout: i64) {
+        unsafe {
+            ffi::rocksdb_transactiondb_options_set_default_lock_timeout(
+                self.inner,
+                default_lock_timeout,
+            );
+        }
+    }
+
+    /// Specifies the default wait timeout in milliseconds when a stransaction
+    /// attempts to lock a key if not secified in `TransactionOptions`.
+    ///
+    /// If 0, no waiting is done if a lock cannot instantly be acquired.
+    /// If negative, there is no timeout.  Not using a timeout is not recommended
+    /// as it can lead to deadlocks.  Currently, there is no deadlock-detection to
+    /// recover from a deadlock.
+    ///
+    /// Default: 1000(1s).
+    pub fn set_txn_lock_timeout(&mut self, txn_lock_timeout: i64) {
+        unsafe {
+            ffi::rocksdb_transactiondb_options_set_transaction_lock_timeout(
+                self.inner,
+                txn_lock_timeout,
+            );
+        }
+    }
+
+    /// Specifies the maximum number of keys that can be locked at the same time
+    /// per column family.
+    ///
+    /// If the number of locked keys is greater than `max_num_locks`, transaction
+    /// `writes` (or `get_for_update`) will return an error.
+    /// If this value is not positive, no limit will be enforced.
+    ///
+    /// Default: -1.
+    pub fn set_max_num_locks(&mut self, max_num_locks: i64) {
+        unsafe {
+            ffi::rocksdb_transactiondb_options_set_max_num_locks(self.inner, max_num_locks);
+        }
+    }
+
+    /// Specifies lock table stripes count.
+    ///
+    /// Increasing this value will increase the concurrency by dividing the lock
+    /// table (per column family) into more sub-tables, each with their own
+    /// separate mutex.
+    ///
+    /// Default: 16.
+    pub fn set_num_stripes(&mut self, num_stripes: usize) {
+        unsafe {
+            ffi::rocksdb_transactiondb_options_set_num_stripes(self.inner, num_stripes);
+        }
+    }
+}
+
+impl Drop for TransactionDBOptions {
+    fn drop(&mut self) {
+        unsafe {
+            ffi::rocksdb_transactiondb_options_destroy(self.inner);
+        }
+    }
+}
+
+pub struct OptimisticTransactionOptions {
+    pub(crate) inner: *mut ffi::rocksdb_optimistictransaction_options_t,
+}
+
+unsafe impl Send for OptimisticTransactionOptions {}
+unsafe impl Sync for OptimisticTransactionOptions {}
+
+impl Default for OptimisticTransactionOptions {
+    fn default() -> Self {
+        let txn_opts = unsafe { ffi::rocksdb_optimistictransaction_options_create() };
+        assert!(
+            !txn_opts.is_null(),
+            "Could not create RocksDB optimistic transaction options"
+        );
+        Self { inner: txn_opts }
+    }
+}
+
+impl OptimisticTransactionOptions {
+    pub fn new() -> OptimisticTransactionOptions {
+        OptimisticTransactionOptions::default()
+    }
+
+    /// Specifies use snapshot or not.
+    ///
+    /// Default: false.
+    ///
+    /// If a transaction has a snapshot set, the transaction will ensure that
+    /// any keys successfully written(or fetched via `get_for_update`) have not
+    /// been modified outside of this transaction since the time the snapshot was
+    /// set.
+    /// If a snapshot has not been set, the transaction guarantees that keys have
+    /// not been modified since the time each key was first written (or fetched via
+    /// `get_for_update`).
+    ///
+    /// Using snapshot will provide stricter isolation guarantees at the
+    /// expense of potentially more transaction failures due to conflicts with
+    /// other writes.
+    ///
+    /// Calling `set_snapshot` will not affect the version of Data returned by `get`
+    /// methods.
+    pub fn set_snapshot(&mut self, snapshot: bool) {
+        unsafe {
+            ffi::rocksdb_optimistictransaction_options_set_set_snapshot(
+                self.inner,
+                u8::from(snapshot),
+            );
+        }
+    }
+}
+
+impl Drop for OptimisticTransactionOptions {
+    fn drop(&mut self) {
+        unsafe {
+            ffi::rocksdb_optimistictransaction_options_destroy(self.inner);
+        }
+    }
+}

src/transactions/transaction.rs

@@ -0,0 +1,881 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+use std::{marker::PhantomData, ptr};
+
+use crate::{
+    db::{convert_values, DBAccess},
+    ffi, AsColumnFamilyRef, DBIteratorWithThreadMode, DBPinnableSlice, DBRawIteratorWithThreadMode,
+    Direction, Error, IteratorMode, ReadOptions, SnapshotWithThreadMode, WriteBatchWithTransaction,
+};
+use libc::{c_char, c_void, size_t};
+
+/// RocksDB Transaction.
+///
+/// To use transactions, you must first create a [`TransactionDB`] or [`OptimisticTransactionDB`].
+///
+/// [`TransactionDB`]: crate::TransactionDB
+/// [`OptimisticTransactionDB`]: crate::OptimisticTransactionDB
+pub struct Transaction<'db, DB> {
+    pub(crate) inner: *mut ffi::rocksdb_transaction_t,
+    pub(crate) _marker: PhantomData<&'db DB>,
+}
+
+unsafe impl<'db, DB> Send for Transaction<'db, DB> {}
+
+impl<'db, DB> DBAccess for Transaction<'db, DB> {
+    unsafe fn create_snapshot(&self) -> *const ffi::rocksdb_snapshot_t {
+        ffi::rocksdb_transaction_get_snapshot(self.inner)
+    }
+
+    unsafe fn release_snapshot(&self, snapshot: *const ffi::rocksdb_snapshot_t) {
+        ffi::rocksdb_free(snapshot as *mut c_void);
+    }
+
+    unsafe fn create_iterator(&self, readopts: &ReadOptions) -> *mut ffi::rocksdb_iterator_t {
+        ffi::rocksdb_transaction_create_iterator(self.inner, readopts.inner)
+    }
+
+    unsafe fn create_iterator_cf(
+        &self,
+        cf_handle: *mut ffi::rocksdb_column_family_handle_t,
+        readopts: &ReadOptions,
+    ) -> *mut ffi::rocksdb_iterator_t {
+        ffi::rocksdb_transaction_create_iterator_cf(self.inner, readopts.inner, cf_handle)
+    }
+
+    fn get_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_opt(key, readopts)
+    }
+
+    fn get_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_cf_opt(cf, key, readopts)
+    }
+
+    fn get_pinned_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_opt(key, readopts)
+    }
+
+    fn get_pinned_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_cf_opt(cf, key, readopts)
+    }
+
+    fn multi_get_opt<K, I>(
+        &self,
+        keys: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = K>,
+    {
+        self.multi_get_opt(keys, readopts)
+    }
+
+    fn multi_get_cf_opt<'b, K, I, W>(
+        &self,
+        keys_cf: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = (&'b W, K)>,
+        W: AsColumnFamilyRef + 'b,
+    {
+        self.multi_get_cf_opt(keys_cf, readopts)
+    }
+}
+
+impl<'db, DB> Transaction<'db, DB> {
+    /// Write all batched keys to the DB atomically.
+    ///
+    /// May return any error that could be returned by `DB::write`.
+    ///
+    /// If this transaction was created by a [`TransactionDB`], an error of
+    /// the [`Expired`] kind may be returned if this transaction has
+    /// lived longer than expiration time in [`TransactionOptions`].
+    ///
+    /// If this transaction was created by an [`OptimisticTransactionDB`], an error of
+    /// the [`Busy`] kind may be returned if the transaction
+    /// could not guarantee that there are no write conflicts.
+    /// An error of the [`TryAgain`] kind may be returned if the memtable
+    /// history size is not large enough (see [`Options::set_max_write_buffer_size_to_maintain`]).
+    ///
+    /// [`Expired`]: crate::ErrorKind::Expired
+    /// [`TransactionOptions`]: crate::TransactionOptions
+    /// [`TransactionDB`]: crate::TransactionDB
+    /// [`OptimisticTransactionDB`]: crate::OptimisticTransactionDB
+    /// [`Busy`]: crate::ErrorKind::Busy
+    /// [`TryAgain`]: crate::ErrorKind::TryAgain
+    /// [`Options::set_max_write_buffer_size_to_maintain`]: crate::Options::set_max_write_buffer_size_to_maintain
+    pub fn commit(self) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_commit(self.inner));
+        }
+        Ok(())
+    }
+
+    pub fn set_name(&self, name: &[u8]) -> Result<(), Error> {
+        let ptr = name.as_ptr();
+        let len = name.len();
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_set_name(
+                self.inner, ptr as _, len as _
+            ));
+        }
+
+        Ok(())
+    }
+
+    pub fn get_name(&self) -> Option<Vec<u8>> {
+        unsafe {
+            let mut name_len = 0;
+            let name = ffi::rocksdb_transaction_get_name(self.inner, &mut name_len);
+            if name.is_null() {
+                None
+            } else {
+                let mut vec = vec![0; name_len];
+                std::ptr::copy_nonoverlapping(name as *mut u8, vec.as_mut_ptr(), name_len as usize);
+                ffi::rocksdb_free(name as *mut c_void);
+                Some(vec)
+            }
+        }
+    }
+
+    pub fn prepare(&self) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_prepare(self.inner));
+        }
+        Ok(())
+    }
+
+    /// Returns snapshot associated with transaction if snapshot was enabled in [`TransactionOptions`].
+    /// Otherwise, returns a snapshot with `nullptr` inside which doesn't effect read operations.
+    ///
+    /// [`TransactionOptions`]: crate::TransactionOptions
+    pub fn snapshot(&self) -> SnapshotWithThreadMode<Self> {
+        SnapshotWithThreadMode::new(self)
+    }
+
+    /// Discard all batched writes in this transaction.
+    pub fn rollback(&self) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_rollback(self.inner));
+            Ok(())
+        }
+    }
+
+    /// Record the state of the transaction for future calls to [`rollback_to_savepoint`].
+    /// May be called multiple times to set multiple save points.
+    ///
+    /// [`rollback_to_savepoint`]: Self::rollback_to_savepoint
+    pub fn set_savepoint(&self) {
+        unsafe {
+            ffi::rocksdb_transaction_set_savepoint(self.inner);
+        }
+    }
+
+    /// Undo all operations in this transaction since the most recent call to [`set_savepoint`]
+    /// and removes the most recent [`set_savepoint`].
+    ///
+    /// Returns error if there is no previous call to [`set_savepoint`].
+    ///
+    /// [`set_savepoint`]: Self::set_savepoint
+    pub fn rollback_to_savepoint(&self) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_rollback_to_savepoint(self.inner));
+            Ok(())
+        }
+    }
+
+    /// Get the bytes associated with a key value.
+    ///
+    /// See [`get_cf_opt`] for details.
+    ///
+    /// [`get_cf_opt`]: Self::get_cf_opt
+    pub fn get<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<Vec<u8>>, Error> {
+        self.get_opt(key, &ReadOptions::default())
+    }
+
+    pub fn get_pinned<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_opt(key, &ReadOptions::default())
+    }
+
+    /// Get the bytes associated with a key value and the given column family.
+    ///
+    /// See [`get_cf_opt`] for details.
+    ///
+    /// [`get_cf_opt`]: Self::get_cf_opt
+    pub fn get_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_cf_opt(cf, key, &ReadOptions::default())
+    }
+
+    pub fn get_pinned_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_cf_opt(cf, key, &ReadOptions::default())
+    }
+
+    /// Get the key and ensure that this transaction will only
+    /// be able to be committed if this key is not written outside this
+    /// transaction after it has first been read (or after the snapshot if a
+    /// snapshot is set in this transaction).
+    ///
+    /// See [`get_for_update_cf_opt`] for details.
+    ///
+    /// [`get_for_update_cf_opt`]: Self::get_for_update_cf_opt
+    pub fn get_for_update<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        exclusive: bool,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_for_update_opt(key, exclusive, &ReadOptions::default())
+    }
+
+    pub fn get_pinned_for_update<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        exclusive: bool,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_for_update_opt(key, exclusive, &ReadOptions::default())
+    }
+
+    /// Get the key in the given column family and ensure that this transaction will only
+    /// be able to be committed if this key is not written outside this
+    /// transaction after it has first been read (or after the snapshot if a
+    /// snapshot is set in this transaction).
+    ///
+    /// See [`get_for_update_cf_opt`] for details.
+    ///
+    /// [`get_for_update_cf_opt`]: Self::get_for_update_cf_opt
+    pub fn get_for_update_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        exclusive: bool,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_for_update_cf_opt(cf, key, exclusive, &ReadOptions::default())
+    }
+
+    pub fn get_pinned_for_update_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        exclusive: bool,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_for_update_cf_opt(cf, key, exclusive, &ReadOptions::default())
+    }
+
+    /// Returns the bytes associated with a key value with read options.
+    ///
+    /// See [`get_cf_opt`] for details.
+    ///
+    /// [`get_cf_opt`]: Self::get_cf_opt
+    pub fn get_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_opt(key, readopts)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    pub fn get_pinned_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        unsafe {
+            let val = ffi_try!(ffi::rocksdb_transaction_get_pinned(
+                self.inner,
+                readopts.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len(),
+            ));
+            if val.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(DBPinnableSlice::from_c(val)))
+            }
+        }
+    }
+
+    /// Get the bytes associated with a key value and the given column family with read options.
+    ///
+    /// This function will also read pending changes in this transaction.
+    /// Currently, this function will return an error of the [`MergeInProgress`] kind
+    /// if the most recent write to the queried key in this batch is a Merge.
+    ///
+    /// [`MergeInProgress`]: crate::ErrorKind::MergeInProgress
+    pub fn get_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_cf_opt(cf, key, readopts)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    pub fn get_pinned_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        unsafe {
+            let val = ffi_try!(ffi::rocksdb_transaction_get_pinned_cf(
+                self.inner,
+                readopts.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len(),
+            ));
+            if val.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(DBPinnableSlice::from_c(val)))
+            }
+        }
+    }
+
+    /// Get the key with read options and ensure that this transaction will only
+    /// be able to be committed if this key is not written outside this
+    /// transaction after it has first been read (or after the snapshot if a
+    /// snapshot is set in this transaction).
+    ///
+    /// See [`get_for_update_cf_opt`] for details.
+    ///
+    /// [`get_for_update_cf_opt`]: Self::get_for_update_cf_opt
+    pub fn get_for_update_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        exclusive: bool,
+        opts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_for_update_opt(key, exclusive, opts)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    pub fn get_pinned_for_update_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        exclusive: bool,
+        opts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        unsafe {
+            let val = ffi_try!(ffi::rocksdb_transaction_get_pinned_for_update(
+                self.inner,
+                opts.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                u8::from(exclusive),
+            ));
+            if val.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(DBPinnableSlice::from_c(val)))
+            }
+        }
+    }
+
+    /// Get the key in the given column family with read options
+    /// and ensure that this transaction will only
+    /// be able to be committed if this key is not written outside this
+    /// transaction after it has first been read (or after the snapshot if a
+    /// snapshot is set in this transaction).
+    ///
+    /// Currently, this function will return an error of the [`MergeInProgress`]
+    /// if the most recent write to the queried key in this batch is a Merge.
+    ///
+    /// If this transaction was created by a [`TransactionDB`], it can return error of kind:
+    /// * [`Busy`] if there is a write conflict.
+    /// * [`TimedOut`] if a lock could not be acquired.
+    /// * [`TryAgain`] if the memtable history size is not large enough.
+    /// * [`MergeInProgress`] if merge operations cannot be resolved.
+    /// * or other errors if this key could not be read.
+    ///
+    /// If this transaction was created by an `[OptimisticTransactionDB]`, `get_for_update_opt`
+    /// can cause [`commit`] to fail. Otherwise, it could return any error that could
+    /// be returned by `[DB::get]`.
+    ///
+    /// [`Busy`]: crate::ErrorKind::Busy
+    /// [`TimedOut`]: crate::ErrorKind::TimedOut
+    /// [`TryAgain`]: crate::ErrorKind::TryAgain
+    /// [`MergeInProgress`]: crate::ErrorKind::MergeInProgress
+    /// [`TransactionDB`]: crate::TransactionDB
+    /// [`OptimisticTransactionDB`]: crate::OptimisticTransactionDB
+    /// [`commit`]: Self::commit
+    /// [`DB::get`]: crate::DB::get
+    pub fn get_for_update_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        exclusive: bool,
+        opts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_for_update_cf_opt(cf, key, exclusive, opts)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    pub fn get_pinned_for_update_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        exclusive: bool,
+        opts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        unsafe {
+            let val = ffi_try!(ffi::rocksdb_transaction_get_pinned_for_update_cf(
+                self.inner,
+                opts.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                u8::from(exclusive),
+            ));
+            if val.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(DBPinnableSlice::from_c(val)))
+            }
+        }
+    }
+
+    /// Return the values associated with the given keys.
+    pub fn multi_get<K, I>(&self, keys: I) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = K>,
+    {
+        self.multi_get_opt(keys, &ReadOptions::default())
+    }
+
+    /// Return the values associated with the given keys using read options.
+    pub fn multi_get_opt<K, I>(
+        &self,
+        keys: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = K>,
+    {
+        let (keys, keys_sizes): (Vec<Box<[u8]>>, Vec<_>) = keys
+            .into_iter()
+            .map(|k| (Box::from(k.as_ref()), k.as_ref().len()))
+            .unzip();
+        let ptr_keys: Vec<_> = keys.iter().map(|k| k.as_ptr() as *const c_char).collect();
+
+        let mut values = vec![ptr::null_mut(); keys.len()];
+        let mut values_sizes = vec![0_usize; keys.len()];
+        let mut errors = vec![ptr::null_mut(); keys.len()];
+        unsafe {
+            ffi::rocksdb_transaction_multi_get(
+                self.inner,
+                readopts.inner,
+                ptr_keys.len(),
+                ptr_keys.as_ptr(),
+                keys_sizes.as_ptr(),
+                values.as_mut_ptr(),
+                values_sizes.as_mut_ptr(),
+                errors.as_mut_ptr(),
+            );
+        }
+
+        convert_values(values, values_sizes, errors)
+    }
+
+    /// Return the values associated with the given keys and column families.
+    pub fn multi_get_cf<'a, 'b: 'a, K, I, W>(
+        &'a self,
+        keys: I,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = (&'b W, K)>,
+        W: 'b + AsColumnFamilyRef,
+    {
+        self.multi_get_cf_opt(keys, &ReadOptions::default())
+    }
+
+    /// Return the values associated with the given keys and column families using read options.
+    pub fn multi_get_cf_opt<'a, 'b: 'a, K, I, W>(
+        &'a self,
+        keys: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = (&'b W, K)>,
+        W: 'b + AsColumnFamilyRef,
+    {
+        let (cfs_and_keys, keys_sizes): (Vec<(_, Box<[u8]>)>, Vec<_>) = keys
+            .into_iter()
+            .map(|(cf, key)| ((cf, Box::from(key.as_ref())), key.as_ref().len()))
+            .unzip();
+        let ptr_keys: Vec<_> = cfs_and_keys
+            .iter()
+            .map(|(_, k)| k.as_ptr() as *const c_char)
+            .collect();
+        let ptr_cfs: Vec<_> = cfs_and_keys
+            .iter()
+            .map(|(c, _)| c.inner() as *const _)
+            .collect();
+
+        let mut values = vec![ptr::null_mut(); ptr_keys.len()];
+        let mut values_sizes = vec![0_usize; ptr_keys.len()];
+        let mut errors = vec![ptr::null_mut(); ptr_keys.len()];
+        unsafe {
+            ffi::rocksdb_transaction_multi_get_cf(
+                self.inner,
+                readopts.inner,
+                ptr_cfs.as_ptr(),
+                ptr_keys.len(),
+                ptr_keys.as_ptr(),
+                keys_sizes.as_ptr(),
+                values.as_mut_ptr(),
+                values_sizes.as_mut_ptr(),
+                errors.as_mut_ptr(),
+            );
+        }
+
+        convert_values(values, values_sizes, errors)
+    }
+
+    /// Put the key value in default column family and do conflict checking on the key.
+    ///
+    /// See [`put_cf`] for details.
+    ///
+    /// [`put_cf`]: Self::put_cf
+    pub fn put<K: AsRef<[u8]>, V: AsRef<[u8]>>(&self, key: K, value: V) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_put(
+                self.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t,
+            ));
+            Ok(())
+        }
+    }
+
+    /// Put the key value in the given column famuly and do conflict checking on the key.
+    ///
+    /// If this transaction was created by a [`TransactionDB`], it can return error of kind:
+    /// * [`Busy`] if there is a write conflict.
+    /// * [`TimedOut`] if a lock could not be acquired.
+    /// * [`TryAgain`] if the memtable history size is not large enough.
+    /// * [`MergeInProgress`] if merge operations cannot be resolved.
+    /// * or other errors on unexpected failures.
+    ///
+    /// [`Busy`]: crate::ErrorKind::Busy
+    /// [`TimedOut`]: crate::ErrorKind::TimedOut
+    /// [`TryAgain`]: crate::ErrorKind::TryAgain
+    /// [`MergeInProgress`]: crate::ErrorKind::MergeInProgress
+    /// [`TransactionDB`]: crate::TransactionDB
+    /// [`OptimisticTransactionDB`]: crate::OptimisticTransactionDB
+    pub fn put_cf<K: AsRef<[u8]>, V: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        value: V,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_put_cf(
+                self.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t,
+            ));
+            Ok(())
+        }
+    }
+
+    /// Merge value with existing value of key, and also do conflict checking on the key.
+    ///
+    /// See [`merge_cf`] for details.
+    ///
+    /// [`merge_cf`]: Self::merge_cf
+    pub fn merge<K: AsRef<[u8]>, V: AsRef<[u8]>>(&self, key: K, value: V) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_merge(
+                self.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t
+            ));
+            Ok(())
+        }
+    }
+
+    /// Merge `value` with existing value of `key` in the given column family,
+    /// and also do conflict checking on the key.
+    ///
+    /// If this transaction was created by a [`TransactionDB`], it can return error of kind:
+    /// * [`Busy`] if there is a write conflict.
+    /// * [`TimedOut`] if a lock could not be acquired.
+    /// * [`TryAgain`] if the memtable history size is not large enough.
+    /// * [`MergeInProgress`] if merge operations cannot be resolved.
+    /// * or other errors on unexpected failures.
+    ///
+    /// [`Busy`]: crate::ErrorKind::Busy
+    /// [`TimedOut`]: crate::ErrorKind::TimedOut
+    /// [`TryAgain`]: crate::ErrorKind::TryAgain
+    /// [`MergeInProgress`]: crate::ErrorKind::MergeInProgress
+    /// [`TransactionDB`]: crate::TransactionDB
+    pub fn merge_cf<K: AsRef<[u8]>, V: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        value: V,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_merge_cf(
+                self.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t
+            ));
+            Ok(())
+        }
+    }
+
+    /// Delete the key value if it exists and do conflict checking on the key.
+    ///
+    /// See [`delete_cf`] for details.
+    ///
+    /// [`delete_cf`]: Self::delete_cf
+    pub fn delete<K: AsRef<[u8]>>(&self, key: K) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_delete(
+                self.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t
+            ));
+        }
+        Ok(())
+    }
+
+    /// Delete the key value in the given column family and do conflict checking.
+    ///
+    /// If this transaction was created by a [`TransactionDB`], it can return error of kind:
+    /// * [`Busy`] if there is a write conflict.
+    /// * [`TimedOut`] if a lock could not be acquired.
+    /// * [`TryAgain`] if the memtable history size is not large enough.
+    /// * [`MergeInProgress`] if merge operations cannot be resolved.
+    /// * or other errors on unexpected failures.
+    ///
+    /// [`Busy`]: crate::ErrorKind::Busy
+    /// [`TimedOut`]: crate::ErrorKind::TimedOut
+    /// [`TryAgain`]: crate::ErrorKind::TryAgain
+    /// [`MergeInProgress`]: crate::ErrorKind::MergeInProgress
+    /// [`TransactionDB`]: crate::TransactionDB
+    pub fn delete_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_delete_cf(
+                self.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn iterator<'a: 'b, 'b>(
+        &'a self,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let readopts = ReadOptions::default();
+        self.iterator_opt(mode, readopts)
+    }
+
+    pub fn iterator_opt<'a: 'b, 'b>(
+        &'a self,
+        mode: IteratorMode,
+        readopts: ReadOptions,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        DBIteratorWithThreadMode::new(self, readopts, mode)
+    }
+
+    /// Opens an iterator using the provided ReadOptions.
+    /// This is used when you want to iterate over a specific ColumnFamily with a modified ReadOptions.
+    pub fn iterator_cf_opt<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        readopts: ReadOptions,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        DBIteratorWithThreadMode::new_cf(self, cf_handle.inner(), readopts, mode)
+    }
+
+    /// Opens an iterator with `set_total_order_seek` enabled.
+    /// This must be used to iterate across prefixes when `set_memtable_factory` has been called
+    /// with a Hash-based implementation.
+    pub fn full_iterator<'a: 'b, 'b>(
+        &'a self,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_total_order_seek(true);
+        DBIteratorWithThreadMode::new(self, opts, mode)
+    }
+
+    pub fn prefix_iterator<'a: 'b, 'b, P: AsRef<[u8]>>(
+        &'a self,
+        prefix: P,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_prefix_same_as_start(true);
+        DBIteratorWithThreadMode::new(
+            self,
+            opts,
+            IteratorMode::From(prefix.as_ref(), Direction::Forward),
+        )
+    }
+
+    pub fn iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let opts = ReadOptions::default();
+        DBIteratorWithThreadMode::new_cf(self, cf_handle.inner(), opts, mode)
+    }
+
+    pub fn full_iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_total_order_seek(true);
+        DBIteratorWithThreadMode::new_cf(self, cf_handle.inner(), opts, mode)
+    }
+
+    pub fn prefix_iterator_cf<'a, P: AsRef<[u8]>>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        prefix: P,
+    ) -> DBIteratorWithThreadMode<'a, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_prefix_same_as_start(true);
+        DBIteratorWithThreadMode::<'a, Self>::new_cf(
+            self,
+            cf_handle.inner(),
+            opts,
+            IteratorMode::From(prefix.as_ref(), Direction::Forward),
+        )
+    }
+
+    /// Opens a raw iterator over the database, using the default read options
+    pub fn raw_iterator<'a: 'b, 'b>(&'a self) -> DBRawIteratorWithThreadMode<'b, Self> {
+        let opts = ReadOptions::default();
+        DBRawIteratorWithThreadMode::new(self, opts)
+    }
+
+    /// Opens a raw iterator over the given column family, using the default read options
+    pub fn raw_iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+    ) -> DBRawIteratorWithThreadMode<'b, Self> {
+        let opts = ReadOptions::default();
+        DBRawIteratorWithThreadMode::new_cf(self, cf_handle.inner(), opts)
+    }
+
+    /// Opens a raw iterator over the database, using the given read options
+    pub fn raw_iterator_opt<'a: 'b, 'b>(
+        &'a self,
+        readopts: ReadOptions,
+    ) -> DBRawIteratorWithThreadMode<'b, Self> {
+        DBRawIteratorWithThreadMode::new(self, readopts)
+    }
+
+    /// Opens a raw iterator over the given column family, using the given read options
+    pub fn raw_iterator_cf_opt<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        readopts: ReadOptions,
+    ) -> DBRawIteratorWithThreadMode<'b, Self> {
+        DBRawIteratorWithThreadMode::new_cf(self, cf_handle.inner(), readopts)
+    }
+
+    pub fn get_writebatch(&self) -> WriteBatchWithTransaction<true> {
+        unsafe {
+            let wi = ffi::rocksdb_transaction_get_writebatch_wi(self.inner);
+            let mut len: usize = 0;
+            let ptr = ffi::rocksdb_writebatch_wi_data(wi, &mut len as _);
+            let data = std::slice::from_raw_parts(ptr, len).to_owned();
+            let writebatch = ffi::rocksdb_writebatch_create_from(data.as_ptr(), data.len());
+            WriteBatchWithTransaction { inner: writebatch }
+        }
+    }
+
+    pub fn rebuild_from_writebatch(
+        &self,
+        writebatch: &WriteBatchWithTransaction<true>,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transaction_rebuild_from_writebatch(
+                self.inner,
+                writebatch.inner
+            ));
+        }
+        Ok(())
+    }
+}
+
+impl<'db, DB> Drop for Transaction<'db, DB> {
+    fn drop(&mut self) {
+        unsafe {
+            ffi::rocksdb_transaction_destroy(self.inner);
+        }
+    }
+}

src/transactions/transaction_db.rs

@@ -0,0 +1,983 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+use std::{
+    collections::BTreeMap,
+    ffi::CString,
+    fs, iter,
+    marker::PhantomData,
+    path::{Path, PathBuf},
+    ptr,
+    sync::{Arc, Mutex},
+};
+
+use crate::{
+    column_family::UnboundColumnFamily,
+    db::{convert_values, DBAccess},
+    db_options::OptionsMustOutliveDB,
+    ffi,
+    ffi_util::to_cpath,
+    AsColumnFamilyRef, BoundColumnFamily, ColumnFamily, ColumnFamilyDescriptor,
+    DBIteratorWithThreadMode, DBPinnableSlice, DBRawIteratorWithThreadMode, Direction, Error,
+    IteratorMode, MultiThreaded, Options, ReadOptions, SingleThreaded, SnapshotWithThreadMode,
+    ThreadMode, Transaction, TransactionDBOptions, TransactionOptions, WriteBatchWithTransaction,
+    WriteOptions, DB, DEFAULT_COLUMN_FAMILY_NAME,
+};
+use ffi::rocksdb_transaction_t;
+use libc::{c_char, c_int, c_void, size_t};
+
+#[cfg(not(feature = "multi-threaded-cf"))]
+type DefaultThreadMode = crate::SingleThreaded;
+#[cfg(feature = "multi-threaded-cf")]
+type DefaultThreadMode = crate::MultiThreaded;
+
+/// RocksDB TransactionDB.
+///
+/// Please read the official [guide](https://github.com/facebook/rocksdb/wiki/Transactions)
+/// to learn more about RocksDB TransactionDB.
+///
+/// The default thread mode for [`TransactionDB`] is [`SingleThreaded`]
+/// if feature `multi-threaded-cf` is not enabled.
+///
+/// ```
+/// use rocksdb::{DB, Options, TransactionDB, SingleThreaded};
+/// let path = "_path_for_transaction_db";
+/// {
+///     let db: TransactionDB = TransactionDB::open_default(path).unwrap();
+///     db.put(b"my key", b"my value").unwrap();
+///     
+///     // create transaction
+///     let txn = db.transaction();
+///     txn.put(b"key2", b"value2");
+///     txn.put(b"key3", b"value3");
+///     txn.commit().unwrap();
+/// }
+/// let _ = DB::destroy(&Options::default(), path);
+/// ```
+///
+/// [`SingleThreaded`]: crate::SingleThreaded
+pub struct TransactionDB<T: ThreadMode = DefaultThreadMode> {
+    pub(crate) inner: *mut ffi::rocksdb_transactiondb_t,
+    cfs: T,
+    path: PathBuf,
+    // prepared 2pc transactions.
+    prepared: Mutex<Vec<*mut rocksdb_transaction_t>>,
+    _outlive: Vec<OptionsMustOutliveDB>,
+}
+
+unsafe impl<T: ThreadMode> Send for TransactionDB<T> {}
+unsafe impl<T: ThreadMode> Sync for TransactionDB<T> {}
+
+impl<T: ThreadMode> DBAccess for TransactionDB<T> {
+    unsafe fn create_snapshot(&self) -> *const ffi::rocksdb_snapshot_t {
+        ffi::rocksdb_transactiondb_create_snapshot(self.inner)
+    }
+
+    unsafe fn release_snapshot(&self, snapshot: *const ffi::rocksdb_snapshot_t) {
+        ffi::rocksdb_transactiondb_release_snapshot(self.inner, snapshot);
+    }
+
+    unsafe fn create_iterator(&self, readopts: &ReadOptions) -> *mut ffi::rocksdb_iterator_t {
+        ffi::rocksdb_transactiondb_create_iterator(self.inner, readopts.inner)
+    }
+
+    unsafe fn create_iterator_cf(
+        &self,
+        cf_handle: *mut ffi::rocksdb_column_family_handle_t,
+        readopts: &ReadOptions,
+    ) -> *mut ffi::rocksdb_iterator_t {
+        ffi::rocksdb_transactiondb_create_iterator_cf(self.inner, readopts.inner, cf_handle)
+    }
+
+    fn get_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_opt(key, readopts)
+    }
+
+    fn get_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_cf_opt(cf, key, readopts)
+    }
+
+    fn get_pinned_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_opt(key, readopts)
+    }
+
+    fn get_pinned_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_cf_opt(cf, key, readopts)
+    }
+
+    fn multi_get_opt<K, I>(
+        &self,
+        keys: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = K>,
+    {
+        self.multi_get_opt(keys, readopts)
+    }
+
+    fn multi_get_cf_opt<'b, K, I, W>(
+        &self,
+        keys_cf: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = (&'b W, K)>,
+        W: AsColumnFamilyRef + 'b,
+    {
+        self.multi_get_cf_opt(keys_cf, readopts)
+    }
+}
+
+impl<T: ThreadMode> TransactionDB<T> {
+    /// Opens a database with default options.
+    pub fn open_default<P: AsRef<Path>>(path: P) -> Result<Self, Error> {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        let txn_db_opts = TransactionDBOptions::default();
+        Self::open(&opts, &txn_db_opts, path)
+    }
+
+    /// Opens the database with the specified options.
+    pub fn open<P: AsRef<Path>>(
+        opts: &Options,
+        txn_db_opts: &TransactionDBOptions,
+        path: P,
+    ) -> Result<Self, Error> {
+        Self::open_cf(opts, txn_db_opts, path, None::<&str>)
+    }
+
+    /// Opens a database with the given database options and column family names.
+    ///
+    /// Column families opened using this function will be created with default `Options`.
+    pub fn open_cf<P, I, N>(
+        opts: &Options,
+        txn_db_opts: &TransactionDBOptions,
+        path: P,
+        cfs: I,
+    ) -> Result<Self, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = N>,
+        N: AsRef<str>,
+    {
+        let cfs = cfs
+            .into_iter()
+            .map(|name| ColumnFamilyDescriptor::new(name.as_ref(), Options::default()));
+
+        Self::open_cf_descriptors_internal(opts, txn_db_opts, path, cfs)
+    }
+
+    /// Opens a database with the given database options and column family descriptors.
+    pub fn open_cf_descriptors<P, I>(
+        opts: &Options,
+        txn_db_opts: &TransactionDBOptions,
+        path: P,
+        cfs: I,
+    ) -> Result<Self, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = ColumnFamilyDescriptor>,
+    {
+        Self::open_cf_descriptors_internal(opts, txn_db_opts, path, cfs)
+    }
+
+    /// Internal implementation for opening RocksDB.
+    fn open_cf_descriptors_internal<P, I>(
+        opts: &Options,
+        txn_db_opts: &TransactionDBOptions,
+        path: P,
+        cfs: I,
+    ) -> Result<Self, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = ColumnFamilyDescriptor>,
+    {
+        let cfs: Vec<_> = cfs.into_iter().collect();
+        let outlive = iter::once(opts.outlive.clone())
+            .chain(cfs.iter().map(|cf| cf.options.outlive.clone()))
+            .collect();
+
+        let cpath = to_cpath(&path)?;
+
+        if let Err(e) = fs::create_dir_all(&path) {
+            return Err(Error::new(format!(
+                "Failed to create RocksDB directory: `{:?}`.",
+                e
+            )));
+        }
+
+        let db: *mut ffi::rocksdb_transactiondb_t;
+        let mut cf_map = BTreeMap::new();
+
+        if cfs.is_empty() {
+            db = Self::open_raw(opts, txn_db_opts, &cpath)?;
+        } else {
+            let mut cfs_v = cfs;
+            // Always open the default column family.
+            if !cfs_v.iter().any(|cf| cf.name == DEFAULT_COLUMN_FAMILY_NAME) {
+                cfs_v.push(ColumnFamilyDescriptor {
+                    name: String::from(DEFAULT_COLUMN_FAMILY_NAME),
+                    options: Options::default(),
+                });
+            }
+            // We need to store our CStrings in an intermediate vector
+            // so that their pointers remain valid.
+            let c_cfs: Vec<CString> = cfs_v
+                .iter()
+                .map(|cf| CString::new(cf.name.as_bytes()).unwrap())
+                .collect();
+
+            let cfnames: Vec<_> = c_cfs.iter().map(|cf| cf.as_ptr()).collect();
+
+            // These handles will be populated by DB.
+            let mut cfhandles: Vec<_> = cfs_v.iter().map(|_| ptr::null_mut()).collect();
+
+            let cfopts: Vec<_> = cfs_v
+                .iter()
+                .map(|cf| cf.options.inner as *const _)
+                .collect();
+
+            db = Self::open_cf_raw(
+                opts,
+                txn_db_opts,
+                &cpath,
+                &cfs_v,
+                &cfnames,
+                &cfopts,
+                &mut cfhandles,
+            )?;
+
+            for handle in &cfhandles {
+                if handle.is_null() {
+                    return Err(Error::new(
+                        "Received null column family handle from DB.".to_owned(),
+                    ));
+                }
+            }
+
+            for (cf_desc, inner) in cfs_v.iter().zip(cfhandles) {
+                cf_map.insert(cf_desc.name.clone(), inner);
+            }
+        }
+
+        if db.is_null() {
+            return Err(Error::new("Could not initialize database.".to_owned()));
+        }
+
+        let prepared = unsafe {
+            let mut cnt = 0;
+            let ptr = ffi::rocksdb_transactiondb_get_prepared_transactions(db, &mut cnt);
+            let mut vec = vec![std::ptr::null_mut(); cnt];
+            std::ptr::copy_nonoverlapping(ptr, vec.as_mut_ptr(), cnt);
+            if !ptr.is_null() {
+                ffi::rocksdb_free(ptr as *mut c_void);
+            }
+            vec
+        };
+
+        Ok(TransactionDB {
+            inner: db,
+            cfs: T::new_cf_map_internal(cf_map),
+            path: path.as_ref().to_path_buf(),
+            prepared: Mutex::new(prepared),
+            _outlive: outlive,
+        })
+    }
+
+    fn open_raw(
+        opts: &Options,
+        txn_db_opts: &TransactionDBOptions,
+        cpath: &CString,
+    ) -> Result<*mut ffi::rocksdb_transactiondb_t, Error> {
+        unsafe {
+            let db = ffi_try!(ffi::rocksdb_transactiondb_open(
+                opts.inner,
+                txn_db_opts.inner,
+                cpath.as_ptr()
+            ));
+            Ok(db)
+        }
+    }
+
+    fn open_cf_raw(
+        opts: &Options,
+        txn_db_opts: &TransactionDBOptions,
+        cpath: &CString,
+        cfs_v: &[ColumnFamilyDescriptor],
+        cfnames: &[*const c_char],
+        cfopts: &[*const ffi::rocksdb_options_t],
+        cfhandles: &mut [*mut ffi::rocksdb_column_family_handle_t],
+    ) -> Result<*mut ffi::rocksdb_transactiondb_t, Error> {
+        unsafe {
+            let db = ffi_try!(ffi::rocksdb_transactiondb_open_column_families(
+                opts.inner,
+                txn_db_opts.inner,
+                cpath.as_ptr(),
+                cfs_v.len() as c_int,
+                cfnames.as_ptr(),
+                cfopts.as_ptr(),
+                cfhandles.as_mut_ptr(),
+            ));
+            Ok(db)
+        }
+    }
+
+    fn create_inner_cf_handle(
+        &self,
+        name: &str,
+        opts: &Options,
+    ) -> Result<*mut ffi::rocksdb_column_family_handle_t, Error> {
+        let cf_name = if let Ok(c) = CString::new(name.as_bytes()) {
+            c
+        } else {
+            return Err(Error::new(
+                "Failed to convert path to CString when creating cf".to_owned(),
+            ));
+        };
+        Ok(unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_create_column_family(
+                self.inner,
+                opts.inner,
+                cf_name.as_ptr(),
+            ))
+        })
+    }
+
+    pub fn list_cf<P: AsRef<Path>>(opts: &Options, path: P) -> Result<Vec<String>, Error> {
+        DB::list_cf(opts, path)
+    }
+
+    pub fn destroy<P: AsRef<Path>>(opts: &Options, path: P) -> Result<(), Error> {
+        DB::destroy(opts, path)
+    }
+
+    pub fn repair<P: AsRef<Path>>(opts: &Options, path: P) -> Result<(), Error> {
+        DB::repair(opts, path)
+    }
+
+    pub fn path(&self) -> &Path {
+        self.path.as_path()
+    }
+
+    /// Creates a transaction with default options.
+    pub fn transaction(&self) -> Transaction<Self> {
+        self.transaction_opt(&WriteOptions::default(), &TransactionOptions::default())
+    }
+
+    /// Creates a transaction with options.
+    pub fn transaction_opt<'a>(
+        &'a self,
+        write_opts: &WriteOptions,
+        txn_opts: &TransactionOptions,
+    ) -> Transaction<'a, Self> {
+        Transaction {
+            inner: unsafe {
+                ffi::rocksdb_transaction_begin(
+                    self.inner,
+                    write_opts.inner,
+                    txn_opts.inner,
+                    std::ptr::null_mut(),
+                )
+            },
+            _marker: PhantomData::default(),
+        }
+    }
+
+    /// Get all prepared transactions for recovery.
+    ///
+    /// This function is expected to call once after open database.
+    /// User should commit or rollback all transactions before start other transactions.
+    pub fn prepared_transactions(&self) -> Vec<Transaction<Self>> {
+        self.prepared
+            .lock()
+            .unwrap()
+            .drain(0..)
+            .map(|inner| Transaction {
+                inner,
+                _marker: PhantomData::default(),
+            })
+            .collect()
+    }
+
+    /// Returns the bytes associated with a key value.
+    pub fn get<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned(key).map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    /// Returns the bytes associated with a key value and the given column family.
+    pub fn get_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_cf(cf, key)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    /// Returns the bytes associated with a key value with read options.
+    pub fn get_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_opt(key, readopts)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    /// Returns the bytes associated with a key value and the given column family with read options.
+    pub fn get_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<Vec<u8>>, Error> {
+        self.get_pinned_cf_opt(cf, key, readopts)
+            .map(|x| x.map(|v| v.as_ref().to_vec()))
+    }
+
+    pub fn get_pinned<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_opt(key, &ReadOptions::default())
+    }
+
+    /// Returns the bytes associated with a key value and the given column family.
+    pub fn get_pinned_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        self.get_pinned_cf_opt(cf, key, &ReadOptions::default())
+    }
+
+    /// Returns the bytes associated with a key value with read options.
+    pub fn get_pinned_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        let key = key.as_ref();
+        unsafe {
+            let val = ffi_try!(ffi::rocksdb_transactiondb_get_pinned(
+                self.inner,
+                readopts.inner,
+                key.as_ptr() as *const c_char,
+                key.len() as size_t,
+            ));
+            if val.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(DBPinnableSlice::from_c(val)))
+            }
+        }
+    }
+
+    /// Returns the bytes associated with a key value and the given column family with read options.
+    pub fn get_pinned_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        readopts: &ReadOptions,
+    ) -> Result<Option<DBPinnableSlice>, Error> {
+        unsafe {
+            let val = ffi_try!(ffi::rocksdb_transactiondb_get_pinned_cf(
+                self.inner,
+                readopts.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+            ));
+            if val.is_null() {
+                Ok(None)
+            } else {
+                Ok(Some(DBPinnableSlice::from_c(val)))
+            }
+        }
+    }
+
+    /// Return the values associated with the given keys.
+    pub fn multi_get<K, I>(&self, keys: I) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = K>,
+    {
+        self.multi_get_opt(keys, &ReadOptions::default())
+    }
+
+    /// Return the values associated with the given keys using read options.
+    pub fn multi_get_opt<K, I>(
+        &self,
+        keys: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = K>,
+    {
+        let (keys, keys_sizes): (Vec<Box<[u8]>>, Vec<_>) = keys
+            .into_iter()
+            .map(|k| (Box::from(k.as_ref()), k.as_ref().len()))
+            .unzip();
+        let ptr_keys: Vec<_> = keys.iter().map(|k| k.as_ptr() as *const c_char).collect();
+
+        let mut values = vec![ptr::null_mut(); keys.len()];
+        let mut values_sizes = vec![0_usize; keys.len()];
+        let mut errors = vec![ptr::null_mut(); keys.len()];
+        unsafe {
+            ffi::rocksdb_transactiondb_multi_get(
+                self.inner,
+                readopts.inner,
+                ptr_keys.len(),
+                ptr_keys.as_ptr(),
+                keys_sizes.as_ptr(),
+                values.as_mut_ptr(),
+                values_sizes.as_mut_ptr(),
+                errors.as_mut_ptr(),
+            );
+        }
+
+        convert_values(values, values_sizes, errors)
+    }
+
+    /// Return the values associated with the given keys and column families.
+    pub fn multi_get_cf<'a, 'b: 'a, K, I, W>(
+        &'a self,
+        keys: I,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = (&'b W, K)>,
+        W: 'b + AsColumnFamilyRef,
+    {
+        self.multi_get_cf_opt(keys, &ReadOptions::default())
+    }
+
+    /// Return the values associated with the given keys and column families using read options.
+    pub fn multi_get_cf_opt<'a, 'b: 'a, K, I, W>(
+        &'a self,
+        keys: I,
+        readopts: &ReadOptions,
+    ) -> Vec<Result<Option<Vec<u8>>, Error>>
+    where
+        K: AsRef<[u8]>,
+        I: IntoIterator<Item = (&'b W, K)>,
+        W: 'b + AsColumnFamilyRef,
+    {
+        let (cfs_and_keys, keys_sizes): (Vec<(_, Box<[u8]>)>, Vec<_>) = keys
+            .into_iter()
+            .map(|(cf, key)| ((cf, Box::from(key.as_ref())), key.as_ref().len()))
+            .unzip();
+        let ptr_keys: Vec<_> = cfs_and_keys
+            .iter()
+            .map(|(_, k)| k.as_ptr() as *const c_char)
+            .collect();
+        let ptr_cfs: Vec<_> = cfs_and_keys
+            .iter()
+            .map(|(c, _)| c.inner() as *const _)
+            .collect();
+
+        let mut values = vec![ptr::null_mut(); ptr_keys.len()];
+        let mut values_sizes = vec![0_usize; ptr_keys.len()];
+        let mut errors = vec![ptr::null_mut(); ptr_keys.len()];
+        unsafe {
+            ffi::rocksdb_transactiondb_multi_get_cf(
+                self.inner,
+                readopts.inner,
+                ptr_cfs.as_ptr(),
+                ptr_keys.len(),
+                ptr_keys.as_ptr(),
+                keys_sizes.as_ptr(),
+                values.as_mut_ptr(),
+                values_sizes.as_mut_ptr(),
+                errors.as_mut_ptr(),
+            );
+        }
+
+        convert_values(values, values_sizes, errors)
+    }
+
+    pub fn put<K, V>(&self, key: K, value: V) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        self.put_opt(key, value, &WriteOptions::default())
+    }
+
+    pub fn put_cf<K, V>(&self, cf: &impl AsColumnFamilyRef, key: K, value: V) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        self.put_cf_opt(cf, key, value, &WriteOptions::default())
+    }
+
+    pub fn put_opt<K, V>(&self, key: K, value: V, writeopts: &WriteOptions) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_put(
+                self.inner,
+                writeopts.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn put_cf_opt<K, V>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        value: V,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_put_cf(
+                self.inner,
+                writeopts.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn write(&self, batch: WriteBatchWithTransaction<true>) -> Result<(), Error> {
+        self.write_opt(batch, &WriteOptions::default())
+    }
+
+    pub fn write_opt(
+        &self,
+        batch: WriteBatchWithTransaction<true>,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_write(
+                self.inner,
+                writeopts.inner,
+                batch.inner
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn merge<K, V>(&self, key: K, value: V) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        self.merge_opt(key, value, &WriteOptions::default())
+    }
+
+    pub fn merge_cf<K, V>(&self, cf: &impl AsColumnFamilyRef, key: K, value: V) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        self.merge_cf_opt(cf, key, value, &WriteOptions::default())
+    }
+
+    pub fn merge_opt<K, V>(&self, key: K, value: V, writeopts: &WriteOptions) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_merge(
+                self.inner,
+                writeopts.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t,
+            ));
+            Ok(())
+        }
+    }
+
+    pub fn merge_cf_opt<K, V>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        value: V,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error>
+    where
+        K: AsRef<[u8]>,
+        V: AsRef<[u8]>,
+    {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_merge_cf(
+                self.inner,
+                writeopts.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+                value.as_ref().as_ptr() as *const c_char,
+                value.as_ref().len() as size_t,
+            ));
+            Ok(())
+        }
+    }
+
+    pub fn delete<K: AsRef<[u8]>>(&self, key: K) -> Result<(), Error> {
+        self.delete_opt(key, &WriteOptions::default())
+    }
+
+    pub fn delete_cf<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+    ) -> Result<(), Error> {
+        self.delete_cf_opt(cf, key, &WriteOptions::default())
+    }
+
+    pub fn delete_opt<K: AsRef<[u8]>>(
+        &self,
+        key: K,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_delete(
+                self.inner,
+                writeopts.inner,
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn delete_cf_opt<K: AsRef<[u8]>>(
+        &self,
+        cf: &impl AsColumnFamilyRef,
+        key: K,
+        writeopts: &WriteOptions,
+    ) -> Result<(), Error> {
+        unsafe {
+            ffi_try!(ffi::rocksdb_transactiondb_delete_cf(
+                self.inner,
+                writeopts.inner,
+                cf.inner(),
+                key.as_ref().as_ptr() as *const c_char,
+                key.as_ref().len() as size_t,
+            ));
+        }
+        Ok(())
+    }
+
+    pub fn iterator<'a: 'b, 'b>(
+        &'a self,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let readopts = ReadOptions::default();
+        self.iterator_opt(mode, readopts)
+    }
+
+    pub fn iterator_opt<'a: 'b, 'b>(
+        &'a self,
+        mode: IteratorMode,
+        readopts: ReadOptions,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        DBIteratorWithThreadMode::new(self, readopts, mode)
+    }
+
+    /// Opens an iterator using the provided ReadOptions.
+    /// This is used when you want to iterate over a specific ColumnFamily with a modified ReadOptions
+    pub fn iterator_cf_opt<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        readopts: ReadOptions,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        DBIteratorWithThreadMode::new_cf(self, cf_handle.inner(), readopts, mode)
+    }
+
+    /// Opens an iterator with `set_total_order_seek` enabled.
+    /// This must be used to iterate across prefixes when `set_memtable_factory` has been called
+    /// with a Hash-based implementation.
+    pub fn full_iterator<'a: 'b, 'b>(
+        &'a self,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_total_order_seek(true);
+        DBIteratorWithThreadMode::new(self, opts, mode)
+    }
+
+    pub fn prefix_iterator<'a: 'b, 'b, P: AsRef<[u8]>>(
+        &'a self,
+        prefix: P,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_prefix_same_as_start(true);
+        DBIteratorWithThreadMode::new(
+            self,
+            opts,
+            IteratorMode::From(prefix.as_ref(), Direction::Forward),
+        )
+    }
+
+    pub fn iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let opts = ReadOptions::default();
+        DBIteratorWithThreadMode::new_cf(self, cf_handle.inner(), opts, mode)
+    }
+
+    pub fn full_iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        mode: IteratorMode,
+    ) -> DBIteratorWithThreadMode<'b, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_total_order_seek(true);
+        DBIteratorWithThreadMode::new_cf(self, cf_handle.inner(), opts, mode)
+    }
+
+    pub fn prefix_iterator_cf<'a, P: AsRef<[u8]>>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        prefix: P,
+    ) -> DBIteratorWithThreadMode<'a, Self> {
+        let mut opts = ReadOptions::default();
+        opts.set_prefix_same_as_start(true);
+        DBIteratorWithThreadMode::<'a, Self>::new_cf(
+            self,
+            cf_handle.inner(),
+            opts,
+            IteratorMode::From(prefix.as_ref(), Direction::Forward),
+        )
+    }
+
+    /// Opens a raw iterator over the database, using the default read options
+    pub fn raw_iterator<'a: 'b, 'b>(&'a self) -> DBRawIteratorWithThreadMode<'b, Self> {
+        let opts = ReadOptions::default();
+        DBRawIteratorWithThreadMode::new(self, opts)
+    }
+
+    /// Opens a raw iterator over the given column family, using the default read options
+    pub fn raw_iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+    ) -> DBRawIteratorWithThreadMode<'b, Self> {
+        let opts = ReadOptions::default();
+        DBRawIteratorWithThreadMode::new_cf(self, cf_handle.inner(), opts)
+    }
+
+    /// Opens a raw iterator over the database, using the given read options
+    pub fn raw_iterator_opt<'a: 'b, 'b>(
+        &'a self,
+        readopts: ReadOptions,
+    ) -> DBRawIteratorWithThreadMode<'b, Self> {
+        DBRawIteratorWithThreadMode::new(self, readopts)
+    }
+
+    /// Opens a raw iterator over the given column family, using the given read options
+    pub fn raw_iterator_cf_opt<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &impl AsColumnFamilyRef,
+        readopts: ReadOptions,
+    ) -> DBRawIteratorWithThreadMode<'b, Self> {
+        DBRawIteratorWithThreadMode::new_cf(self, cf_handle.inner(), readopts)
+    }
+
+    pub fn snapshot(&self) -> SnapshotWithThreadMode<Self> {
+        SnapshotWithThreadMode::<Self>::new(self)
+    }
+}
+
+impl TransactionDB<SingleThreaded> {
+    /// Creates column family with given name and options.
+    pub fn create_cf<N: AsRef<str>>(&mut self, name: N, opts: &Options) -> Result<(), Error> {
+        let inner = self.create_inner_cf_handle(name.as_ref(), opts)?;
+        self.cfs
+            .cfs
+            .insert(name.as_ref().to_string(), ColumnFamily { inner });
+        Ok(())
+    }
+
+    /// Returns the underlying column family handle.
+    pub fn cf_handle(&self, name: &str) -> Option<&ColumnFamily> {
+        self.cfs.cfs.get(name)
+    }
+}
+
+impl TransactionDB<MultiThreaded> {
+    /// Creates column family with given name and options.
+    pub fn create_cf<N: AsRef<str>>(&self, name: N, opts: &Options) -> Result<(), Error> {
+        let inner = self.create_inner_cf_handle(name.as_ref(), opts)?;
+        self.cfs.cfs.write().unwrap().insert(
+            name.as_ref().to_string(),
+            Arc::new(UnboundColumnFamily { inner }),
+        );
+        Ok(())
+    }
+
+    /// Returns the underlying column family handle.
+    pub fn cf_handle(&self, name: &str) -> Option<Arc<BoundColumnFamily>> {
+        self.cfs
+            .cfs
+            .read()
+            .unwrap()
+            .get(name)
+            .cloned()
+            .map(UnboundColumnFamily::bound_column_family)
+    }
+}
+
+impl<T: ThreadMode> Drop for TransactionDB<T> {
+    fn drop(&mut self) {
+        unsafe {
+            self.prepared_transactions().clear();
+            self.cfs.drop_all_cfs_internal();
+            ffi::rocksdb_transactiondb_close(self.inner);
+        }
+    }
+}

src/write_batch.rs

@@ -16,25 +16,37 @@ use crate::{ffi, AsColumnFamilyRef};
 use libc::{c_char, c_void, size_t};
 use std::slice;
 
+/// A type alias to keep compatibility. See [`WriteBatchWithTransaction`] for details
+pub type WriteBatch = WriteBatchWithTransaction<false>;
+
 /// An atomic batch of write operations.
 ///
+/// [`delete_range`] is not supported in [`Transaction`].
+///
 /// Making an atomic commit of several writes:
 ///
 /// ```
-/// use rocksdb::{DB, Options, WriteBatch};
+/// use rocksdb::{DB, Options, WriteBatchWithTransaction};
 ///
 /// let path = "_path_for_rocksdb_storage1";
 /// {
 ///     let db = DB::open_default(path).unwrap();
-///     let mut batch = WriteBatch::default();
+///     let mut batch = WriteBatchWithTransaction::<false>::default();
 ///     batch.put(b"my key", b"my value");
 ///     batch.put(b"key2", b"value2");
 ///     batch.put(b"key3", b"value3");
+///
+///     // DeleteRange is supported when use without transaction
+///     batch.delete_range(b"key2", b"key3");
+///
 ///     db.write(batch); // Atomically commits the batch
 /// }
 /// let _ = DB::destroy(&Options::default(), path);
 /// ```
-pub struct WriteBatch {
+///
+/// [`DeleteRange`]: Self::delete_range
+/// [`Transaction`]: crate::Transaction
+pub struct WriteBatchWithTransaction<const TRANSACTION: bool> {
     pub(crate) inner: *mut ffi::rocksdb_writebatch_t,
 }
 
@@ -77,7 +89,7 @@ unsafe extern "C" fn writebatch_delete_callback(state: *mut c_void, k: *const c_
     leaked_cb.delete(key.to_vec().into_boxed_slice());
 }
 
-impl WriteBatch {
+impl<const TRANSACTION: bool> WriteBatchWithTransaction<TRANSACTION> {
     pub fn len(&self) -> usize {
         unsafe { ffi::rocksdb_writebatch_count(self.inner) as usize }
     }
@@ -219,6 +231,15 @@ impl WriteBatch {
         }
     }
 
+    /// Clear all updates buffered in this batch.
+    pub fn clear(&mut self) {
+        unsafe {
+            ffi::rocksdb_writebatch_clear(self.inner);
+        }
+    }
+}
+
+impl WriteBatchWithTransaction<false> {
     /// Remove database entries from start key to end key.
     ///
     /// Removes the database entries in the range ["begin_key", "end_key"), i.e.,
@@ -257,16 +278,9 @@ impl WriteBatch {
             );
         }
     }
-
-    /// Clear all updates buffered in this batch.
-    pub fn clear(&mut self) {
-        unsafe {
-            ffi::rocksdb_writebatch_clear(self.inner);
-        }
-    }
 }
 
-impl Default for WriteBatch {
+impl<const TRANSACTION: bool> Default for WriteBatchWithTransaction<TRANSACTION> {
     fn default() -> Self {
         Self {
             inner: unsafe { ffi::rocksdb_writebatch_create() },
@@ -274,7 +288,7 @@ impl Default for WriteBatch {
     }
 }
 
-impl Drop for WriteBatch {
+impl<const TRANSACTION: bool> Drop for WriteBatchWithTransaction<TRANSACTION> {
     fn drop(&mut self) {
         unsafe {
             ffi::rocksdb_writebatch_destroy(self.inner);
@@ -282,4 +296,4 @@ impl Drop for WriteBatch {
     }
 }
 
-unsafe impl Send for WriteBatch {}
+unsafe impl<const TRANSACTION: bool> Send for WriteBatchWithTransaction<TRANSACTION> {}

tests/fail/snapshot_outlive_transaction.rs

@@ -0,0 +1,9 @@
+use rocksdb::{TransactionDB, SingleThreaded};
+
+fn main() {
+    let db = TransactionDB::<SingleThreaded>::open_default("foo").unwrap();
+    let _snapshot = {
+        let txn = db.transaction();
+        txn.snapshot()
+    };
+}

tests/fail/snapshot_outlive_transaction.stderr

@@ -0,0 +1,10 @@
+error[E0597]: `txn` does not live long enough
+ --> tests/fail/snapshot_outlive_transaction.rs:7:9
+  |
+5 |     let _snapshot = {
+  |         --------- borrow later stored here
+6 |         let txn = db.transaction();
+7 |         txn.snapshot()
+  |         ^^^^^^^^^^^^^^ borrowed value does not live long enough
+8 |     };
+  |     - `txn` dropped here while still borrowed

tests/fail/snapshot_outlive_transaction_db.rs

@@ -0,0 +1,8 @@
+use rocksdb::{TransactionDB, SingleThreaded};
+
+fn main() {
+    let _snapshot = {
+        let db = TransactionDB::<SingleThreaded>::open_default("foo").unwrap();
+        db.snapshot()
+    };
+}

tests/fail/snapshot_outlive_transaction_db.stderr

@@ -0,0 +1,10 @@
+error[E0597]: `db` does not live long enough
+ --> tests/fail/snapshot_outlive_transaction_db.rs:6:9
+  |
+4 |     let _snapshot = {
+  |         --------- borrow later stored here
+5 |         let db = TransactionDB::<SingleThreaded>::open_default("foo").unwrap();
+6 |         db.snapshot()
+  |         ^^^^^^^^^^^^^ borrowed value does not live long enough
+7 |     };
+  |     - `db` dropped here while still borrowed

tests/fail/transaction_outlive_transaction_db.rs

@@ -0,0 +1,8 @@
+use rocksdb::{TransactionDB, SingleThreaded};
+
+fn main() {
+    let _txn = {
+        let db = TransactionDB::<SingleThreaded>::open_default("foo").unwrap();
+        db.transaction()
+    };
+}

tests/fail/transaction_outlive_transaction_db.stderr

@@ -0,0 +1,10 @@
+error[E0597]: `db` does not live long enough
+ --> tests/fail/transaction_outlive_transaction_db.rs:6:9
+  |
+4 |     let _txn = {
+  |         ---- borrow later stored here
+5 |         let db = TransactionDB::<SingleThreaded>::open_default("foo").unwrap();
+6 |         db.transaction()
+  |         ^^^^^^^^^^^^^^^^ borrowed value does not live long enough
+7 |     };
+  |     - `db` dropped here while still borrowed

tests/test_db.rs

@@ -21,8 +21,8 @@ use pretty_assertions::assert_eq;
 use rocksdb::{
     perf::get_memory_usage_stats, BlockBasedOptions, BottommostLevelCompaction, Cache,
     ColumnFamilyDescriptor, CompactOptions, CuckooTableOptions, DBAccess, DBCompactionStyle,
-    DBWithThreadMode, Env, Error, FifoCompactOptions, IteratorMode, MultiThreaded, Options,
+    DBWithThreadMode, Env, Error, ErrorKind, FifoCompactOptions, IteratorMode, MultiThreaded,
-    PerfContext, PerfMetric, ReadOptions, SingleThreaded, SliceTransform, Snapshot,
+    Options, PerfContext, PerfMetric, ReadOptions, SingleThreaded, SliceTransform, Snapshot,
     UniversalCompactOptions, UniversalCompactionStopStyle, WriteBatch, DB,
 };
 use util::{assert_iter, pair, DBPath};
@@ -72,7 +72,7 @@ fn errors_do_stuff() {
     match DB::destroy(&opts, &path) {
         Err(s) => {
             let message = s.to_string();
-            assert!(message.contains("IO error:"));
+            assert_eq!(s.kind(), ErrorKind::IOError);
             assert!(message.contains("_rust_rocksdb_error"));
             assert!(message.contains("/LOCK:"));
         }

tests/test_optimistic_transaction_db.rs

@@ -0,0 +1,577 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+mod util;
+
+use rocksdb::{
+    CuckooTableOptions, DBAccess, Direction, Error, ErrorKind, IteratorMode,
+    OptimisticTransactionDB, OptimisticTransactionOptions, Options, ReadOptions, SingleThreaded,
+    SliceTransform, SnapshotWithThreadMode, WriteBatchWithTransaction, WriteOptions, DB,
+};
+use util::DBPath;
+
+#[test]
+fn open_default() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_open_default");
+    {
+        let db: OptimisticTransactionDB<SingleThreaded> =
+            OptimisticTransactionDB::open_default(&path).unwrap();
+
+        assert!(db.put(b"k1", b"v1111").is_ok());
+
+        let r: Result<Option<Vec<u8>>, Error> = db.get(b"k1");
+
+        assert_eq!(r.unwrap().unwrap(), b"v1111");
+        assert!(db.delete(b"k1").is_ok());
+        assert!(db.get(b"k1").unwrap().is_none());
+    }
+}
+
+#[test]
+fn open_cf() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_open_cf");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db: OptimisticTransactionDB<SingleThreaded> =
+            OptimisticTransactionDB::open_cf(&opts, &path, ["cf1", "cf2"]).unwrap();
+
+        let cf1 = db.cf_handle("cf1").unwrap();
+        let cf2 = db.cf_handle("cf2").unwrap();
+
+        db.put(b"k0", b"v0").unwrap();
+        db.put_cf(&cf1, b"k1", b"v1").unwrap();
+        db.put_cf(&cf2, b"k2", b"v2").unwrap();
+
+        assert_eq!(db.get(b"k0").unwrap().unwrap(), b"v0");
+        assert!(db.get(b"k1").unwrap().is_none());
+        assert!(db.get(b"k2").unwrap().is_none());
+
+        assert!(db.get_cf(&cf1, b"k0").unwrap().is_none());
+        assert_eq!(db.get_cf(&cf1, b"k1").unwrap().unwrap(), b"v1");
+        assert!(db.get_cf(&cf1, b"k2").unwrap().is_none());
+
+        assert!(db.get_cf(&cf2, b"k0").unwrap().is_none());
+        assert!(db.get_cf(&cf2, b"k1").unwrap().is_none());
+        assert_eq!(db.get_cf(&cf2, b"k2").unwrap().unwrap(), b"v2");
+    }
+}
+
+#[test]
+fn multi_get() {
+    let path = DBPath::new("_rust_rocksdb_multi_get");
+
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+        let initial_snap = db.snapshot();
+        db.put(b"k1", b"v1").unwrap();
+        let k1_snap = db.snapshot();
+        db.put(b"k2", b"v2").unwrap();
+
+        let _ = db.multi_get(&[b"k0"; 40]);
+
+        let assert_values = |values: Vec<_>| {
+            assert_eq!(3, values.len());
+            assert_eq!(values[0], None);
+            assert_eq!(values[1], Some(b"v1".to_vec()));
+            assert_eq!(values[2], Some(b"v2".to_vec()));
+        };
+
+        let values = db
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+
+        let values = DBAccess::multi_get_opt(&db, &[b"k0", b"k1", b"k2"], &Default::default())
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+
+        let values = db
+            .snapshot()
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+
+        let none_values = initial_snap
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_eq!(none_values, vec![None; 3]);
+
+        let k1_only = k1_snap
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_eq!(k1_only, vec![None, Some(b"v1".to_vec()), None]);
+
+        let txn = db.transaction();
+        let values = txn
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+    }
+}
+
+#[test]
+fn multi_get_cf() {
+    let path = DBPath::new("_rust_rocksdb_multi_get_cf");
+
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db: OptimisticTransactionDB =
+            OptimisticTransactionDB::open_cf(&opts, &path, &["cf0", "cf1", "cf2"]).unwrap();
+
+        let cf0 = db.cf_handle("cf0").unwrap();
+
+        let cf1 = db.cf_handle("cf1").unwrap();
+        db.put_cf(&cf1, b"k1", b"v1").unwrap();
+
+        let cf2 = db.cf_handle("cf2").unwrap();
+        db.put_cf(&cf2, b"k2", b"v2").unwrap();
+
+        let values = db
+            .multi_get_cf(vec![(&cf0, b"k0"), (&cf1, b"k1"), (&cf2, b"k2")])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+        assert_eq!(3, values.len());
+        assert_eq!(values[0], None);
+        assert_eq!(values[1], Some(b"v1".to_vec()));
+        assert_eq!(values[2], Some(b"v2".to_vec()));
+
+        let txn = db.transaction();
+        let values = txn
+            .multi_get_cf(vec![(&cf0, b"k0"), (&cf1, b"k1"), (&cf2, b"k2")])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_eq!(3, values.len());
+        assert_eq!(values[0], None);
+        assert_eq!(values[1], Some(b"v1".to_vec()));
+        assert_eq!(values[2], Some(b"v2".to_vec()));
+    }
+}
+
+#[test]
+fn destroy_on_open() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_destroy_on_open");
+    let _db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+    let opts = Options::default();
+    // The TransactionDB will still be open when we try to destroy it and the lock should fail.
+    match DB::destroy(&opts, &path) {
+        Err(s) => {
+            let message = s.to_string();
+            assert_eq!(s.kind(), ErrorKind::IOError);
+            assert!(message.contains("_rust_rocksdb_optimistic_transaction_db_destroy_on_open"));
+            assert!(message.contains("/LOCK:"));
+        }
+        Ok(_) => panic!("should fail"),
+    }
+}
+
+#[test]
+fn writebatch() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_writebatch");
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+        {
+            // test put
+            let mut batch = WriteBatchWithTransaction::<true>::default();
+            assert!(db.get(b"k1").unwrap().is_none());
+            assert_eq!(batch.len(), 0);
+            assert!(batch.is_empty());
+            batch.put(b"k1", b"v1111");
+            batch.put(b"k2", b"v2222");
+            batch.put(b"k3", b"v3333");
+            assert_eq!(batch.len(), 3);
+            assert!(!batch.is_empty());
+            assert!(db.get(b"k1").unwrap().is_none());
+            let p = db.write(batch);
+            assert!(p.is_ok());
+            let r: Result<Option<Vec<u8>>, Error> = db.get(b"k1");
+            assert_eq!(r.unwrap().unwrap(), b"v1111");
+        }
+        {
+            // test delete
+            let mut batch = WriteBatchWithTransaction::<true>::default();
+            batch.delete(b"k1");
+            assert_eq!(batch.len(), 1);
+            assert!(!batch.is_empty());
+            let p = db.write(batch);
+            assert!(p.is_ok());
+            assert!(db.get(b"k1").unwrap().is_none());
+        }
+        {
+            // test size_in_bytes
+            let mut batch = WriteBatchWithTransaction::<true>::default();
+            let before = batch.size_in_bytes();
+            batch.put(b"k1", b"v1234567890");
+            let after = batch.size_in_bytes();
+            assert!(before + 10 <= after);
+        }
+    }
+}
+
+#[test]
+fn iterator_test() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_iteratortest");
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+
+        let k1: Box<[u8]> = b"k1".to_vec().into_boxed_slice();
+        let k2: Box<[u8]> = b"k2".to_vec().into_boxed_slice();
+        let k3: Box<[u8]> = b"k3".to_vec().into_boxed_slice();
+        let k4: Box<[u8]> = b"k4".to_vec().into_boxed_slice();
+        let v1: Box<[u8]> = b"v1111".to_vec().into_boxed_slice();
+        let v2: Box<[u8]> = b"v2222".to_vec().into_boxed_slice();
+        let v3: Box<[u8]> = b"v3333".to_vec().into_boxed_slice();
+        let v4: Box<[u8]> = b"v4444".to_vec().into_boxed_slice();
+
+        db.put(&*k1, &*v1).unwrap();
+        db.put(&*k2, &*v2).unwrap();
+        db.put(&*k3, &*v3).unwrap();
+        let expected = vec![
+            (k1.clone(), v1.clone()),
+            (k2.clone(), v2.clone()),
+            (k3.clone(), v3.clone()),
+        ];
+
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test that it's idempotent
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test in reverse
+        let iter = db.iterator(IteratorMode::End);
+        let mut tmp_vec = iter.collect::<Vec<_>>();
+        tmp_vec.reverse();
+
+        let old_iter = db.iterator(IteratorMode::Start);
+        db.put(&*k4, &*v4).unwrap();
+        let expected2 = vec![
+            (k1, v1),
+            (k2, v2),
+            (k3.clone(), v3.clone()),
+            (k4.clone(), v4.clone()),
+        ];
+        assert_eq!(old_iter.collect::<Vec<_>>(), expected);
+
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected2);
+
+        let iter = db.iterator(IteratorMode::From(b"k3", Direction::Forward));
+        assert_eq!(iter.collect::<Vec<_>>(), vec![(k3, v3), (k4, v4)]);
+    }
+}
+
+#[test]
+fn snapshot_test() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_snapshottest");
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+
+        assert!(db.put(b"k1", b"v1111").is_ok());
+
+        let snap = db.snapshot();
+        assert_eq!(snap.get(b"k1").unwrap().unwrap(), b"v1111");
+
+        assert!(db.put(b"k2", b"v2222").is_ok());
+
+        assert!(db.get(b"k2").unwrap().is_some());
+        assert!(snap.get(b"k2").unwrap().is_none());
+    }
+}
+
+#[test]
+fn prefix_extract_and_iterate_test() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_prefix_extract_and_iterate");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        opts.set_prefix_extractor(SliceTransform::create_fixed_prefix(2));
+
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open(&opts, &path).unwrap();
+        db.put(b"p1_k1", b"v1").unwrap();
+        db.put(b"p2_k2", b"v2").unwrap();
+        db.put(b"p1_k3", b"v3").unwrap();
+        db.put(b"p1_k4", b"v4").unwrap();
+        db.put(b"p2_k5", b"v5").unwrap();
+
+        let mut readopts = ReadOptions::default();
+        readopts.set_prefix_same_as_start(true);
+        readopts.set_iterate_lower_bound(b"p1".to_vec());
+        readopts.set_pin_data(true);
+
+        let iter = db.iterator_opt(IteratorMode::Start, readopts);
+        let expected: Vec<_> = vec![(b"p1_k1", b"v1"), (b"p1_k3", b"v3"), (b"p1_k4", b"v4")]
+            .into_iter()
+            .map(|(k, v)| (k.to_vec().into_boxed_slice(), v.to_vec().into_boxed_slice()))
+            .collect();
+        assert_eq!(expected, iter.collect::<Vec<_>>());
+    }
+}
+
+#[test]
+fn cuckoo() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_cuckoo");
+
+    {
+        let mut opts = Options::default();
+        let mut factory_opts = CuckooTableOptions::default();
+        factory_opts.set_hash_ratio(0.8);
+        factory_opts.set_max_search_depth(20);
+        factory_opts.set_cuckoo_block_size(10);
+        factory_opts.set_identity_as_first_hash(true);
+        factory_opts.set_use_module_hash(false);
+
+        opts.set_cuckoo_table_factory(&factory_opts);
+        opts.create_if_missing(true);
+
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open(&opts, &path).unwrap();
+        db.put(b"k1", b"v1").unwrap();
+        db.put(b"k2", b"v2").unwrap();
+        let r: Result<Option<Vec<u8>>, Error> = db.get(b"k1");
+
+        assert_eq!(r.unwrap().unwrap(), b"v1");
+        let r: Result<Option<Vec<u8>>, Error> = db.get(b"k2");
+
+        assert_eq!(r.unwrap().unwrap(), b"v2");
+        assert!(db.delete(b"k1").is_ok());
+        assert!(db.get(b"k1").unwrap().is_none());
+    }
+}
+
+#[test]
+fn transaction() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_transaction");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open(&opts, &path).unwrap();
+
+        // put outside of transaction
+        db.put(b"k1", b"v1").unwrap();
+        assert_eq!(db.get(b"k1").unwrap().unwrap(), b"v1");
+
+        {
+            let txn1 = db.transaction();
+            txn1.put(b"k1", b"v2").unwrap();
+
+            // get outside of transaction
+            assert_eq!(db.get(b"k1").unwrap().unwrap().as_slice(), b"v1");
+
+            // modify same key in another transaction
+            let txn2 = db.transaction();
+            txn2.put(b"k1", b"v3").unwrap();
+            txn2.commit().unwrap();
+
+            // txn1 should fail with ErrorKind::Busy
+            let err = txn1.commit().unwrap_err();
+            assert_eq!(err.kind(), ErrorKind::Busy);
+        }
+
+        {
+            let txn1 = db.transaction();
+            txn1.put(b"k2", b"v2").unwrap();
+
+            let txn2 = db.transaction();
+            assert!(txn2.get_for_update(b"k2", true).unwrap().is_none());
+
+            // txn1 commit, txn2 should fail with Busy.
+            txn1.commit().unwrap();
+            assert_eq!(txn2.commit().unwrap_err().kind(), ErrorKind::Busy);
+        }
+    }
+}
+
+#[test]
+fn transaction_iterator() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_transaction_iterator");
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+
+        let k1: Box<[u8]> = b"k1".to_vec().into_boxed_slice();
+        let k2: Box<[u8]> = b"k2".to_vec().into_boxed_slice();
+        let k3: Box<[u8]> = b"k3".to_vec().into_boxed_slice();
+        let k4: Box<[u8]> = b"k4".to_vec().into_boxed_slice();
+        let v1: Box<[u8]> = b"v1111".to_vec().into_boxed_slice();
+        let v2: Box<[u8]> = b"v2222".to_vec().into_boxed_slice();
+        let v3: Box<[u8]> = b"v3333".to_vec().into_boxed_slice();
+        let v4: Box<[u8]> = b"v4444".to_vec().into_boxed_slice();
+
+        db.put(&*k1, &*v1).unwrap();
+        db.put(&*k2, &*v2).unwrap();
+        db.put(&*k3, &*v3).unwrap();
+        let expected = vec![
+            (k1.clone(), v1.clone()),
+            (k2.clone(), v2.clone()),
+            (k3.clone(), v3.clone()),
+        ];
+
+        let txn = db.transaction();
+
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test that it's idempotent
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test in reverse
+        let iter = txn.iterator(IteratorMode::End);
+        let mut tmp_vec = iter.collect::<Vec<_>>();
+        tmp_vec.reverse();
+
+        let old_iter = txn.iterator(IteratorMode::Start);
+        txn.put(&*k4, &*v4).unwrap();
+        let expected2 = vec![
+            (k1, v1),
+            (k2, v2),
+            (k3.clone(), v3.clone()),
+            (k4.clone(), v4.clone()),
+        ];
+        assert_eq!(old_iter.collect::<Vec<_>>(), expected);
+
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected2);
+
+        let iter = txn.iterator(IteratorMode::From(b"k3", Direction::Forward));
+        assert_eq!(iter.collect::<Vec<_>>(), vec![(k3, v3), (k4, v4)]);
+    }
+}
+
+#[test]
+fn transaction_rollback() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_transaction_rollback");
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+        let txn = db.transaction();
+
+        txn.rollback().unwrap();
+
+        txn.put(b"k1", b"v1").unwrap();
+        txn.set_savepoint();
+        txn.put(b"k2", b"v2").unwrap();
+
+        assert_eq!(txn.get(b"k1").unwrap().unwrap(), b"v1");
+        assert_eq!(txn.get(b"k2").unwrap().unwrap(), b"v2");
+
+        txn.rollback_to_savepoint().unwrap();
+        assert_eq!(txn.get(b"k1").unwrap().unwrap(), b"v1");
+        assert!(txn.get(b"k2").unwrap().is_none());
+
+        txn.rollback().unwrap();
+        assert!(txn.get(b"k1").unwrap().is_none());
+
+        txn.commit().unwrap();
+
+        assert!(db.get(b"k2").unwrap().is_none());
+    }
+}
+
+#[test]
+fn transaction_cf() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_transaction_cf");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db: OptimisticTransactionDB =
+            OptimisticTransactionDB::open_cf(&opts, &path, ["cf1", "cf2"]).unwrap();
+
+        let cf1 = db.cf_handle("cf1").unwrap();
+        let cf2 = db.cf_handle("cf2").unwrap();
+
+        let txn = db.transaction();
+        txn.put(b"k0", b"v0").unwrap();
+        txn.put_cf(&cf1, b"k1", b"v1").unwrap();
+        txn.put_cf(&cf2, b"k2", b"v2").unwrap();
+
+        assert_eq!(txn.get(b"k0").unwrap().unwrap(), b"v0");
+        assert!(txn.get(b"k1").unwrap().is_none());
+        assert!(txn.get(b"k2").unwrap().is_none());
+
+        assert!(txn.get_cf(&cf1, b"k0").unwrap().is_none());
+        assert_eq!(txn.get_cf(&cf1, b"k1").unwrap().unwrap(), b"v1");
+        assert!(txn.get_cf(&cf1, b"k2").unwrap().is_none());
+
+        assert!(txn.get_cf(&cf2, b"k0").unwrap().is_none());
+        assert!(txn.get_cf(&cf2, b"k1").unwrap().is_none());
+        assert_eq!(txn.get_cf(&cf2, b"k2").unwrap().unwrap(), b"v2");
+
+        txn.commit().unwrap();
+    }
+}
+
+#[test]
+fn transaction_snapshot() {
+    let path = DBPath::new("_rust_rocksdb_optimistic_transaction_db_transaction_snapshot");
+    {
+        let db: OptimisticTransactionDB = OptimisticTransactionDB::open_default(&path).unwrap();
+
+        let txn = db.transaction();
+        let snapshot = txn.snapshot();
+        assert!(snapshot.get(b"k1").unwrap().is_none());
+        db.put(b"k1", b"v1").unwrap();
+        assert_eq!(snapshot.get(b"k1").unwrap().unwrap(), b"v1");
+
+        let mut opts = OptimisticTransactionOptions::default();
+        opts.set_snapshot(true);
+        let txn = db.transaction_opt(&WriteOptions::default(), &opts);
+        db.put(b"k2", b"v2").unwrap();
+        {
+            let snapshot = SnapshotWithThreadMode::new(&txn);
+            assert!(snapshot.get(b"k2").unwrap().is_none());
+            assert_eq!(txn.get(b"k2").unwrap().unwrap(), b"v2");
+        }
+        txn.get_for_update(b"k2", true).unwrap();
+        assert_eq!(txn.commit().unwrap_err().kind(), ErrorKind::Busy);
+
+        let txn = db.transaction_opt(&WriteOptions::default(), &opts);
+        let snapshot = txn.snapshot();
+        txn.put(b"k3", b"v3").unwrap();
+        assert!(db.get(b"k3").unwrap().is_none());
+        // put operation should also visible to snapshot,
+        // because this snapshot is associated with a transaction
+        assert_eq!(snapshot.get(b"k3").unwrap().unwrap(), b"v3");
+    }
+}

tests/test_transaction_db.rs

@@ -0,0 +1,689 @@
+// Copyright 2021 Yiyuan Liu
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+mod util;
+
+use pretty_assertions::assert_eq;
+
+use rocksdb::{
+    CuckooTableOptions, DBAccess, Direction, Error, ErrorKind, IteratorMode, Options, ReadOptions,
+    SliceTransform, TransactionDB, TransactionDBOptions, TransactionOptions,
+    WriteBatchWithTransaction, WriteOptions, DB,
+};
+use util::DBPath;
+
+#[test]
+fn open_default() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_open_default");
+
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        assert!(db.put(b"k1", b"v1111").is_ok());
+
+        let r: Result<Option<Vec<u8>>, Error> = db.get(b"k1");
+
+        assert_eq!(r.unwrap().unwrap(), b"v1111");
+        assert!(db.delete(b"k1").is_ok());
+        assert!(db.get(b"k1").unwrap().is_none());
+    }
+}
+
+#[test]
+fn open_cf() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_open_cf");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db: TransactionDB = TransactionDB::open_cf(
+            &opts,
+            &TransactionDBOptions::default(),
+            &path,
+            ["cf1", "cf2"],
+        )
+        .unwrap();
+
+        let cf1 = db.cf_handle("cf1").unwrap();
+        let cf2 = db.cf_handle("cf2").unwrap();
+
+        db.put(b"k0", b"v0").unwrap();
+        db.put_cf(&cf1, b"k1", b"v1").unwrap();
+        db.put_cf(&cf2, b"k2", b"v2").unwrap();
+
+        assert_eq!(db.get(b"k0").unwrap().unwrap(), b"v0");
+        assert!(db.get(b"k1").unwrap().is_none());
+        assert!(db.get(b"k2").unwrap().is_none());
+
+        assert!(db.get_cf(&cf1, b"k0").unwrap().is_none());
+        assert_eq!(db.get_cf(&cf1, b"k1").unwrap().unwrap(), b"v1");
+        assert!(db.get_cf(&cf1, b"k2").unwrap().is_none());
+
+        assert!(db.get_cf(&cf2, b"k0").unwrap().is_none());
+        assert!(db.get_cf(&cf2, b"k1").unwrap().is_none());
+        assert_eq!(db.get_cf(&cf2, b"k2").unwrap().unwrap(), b"v2");
+    }
+}
+
+#[test]
+fn put_get() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_put_get");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+        assert!(db.put(b"k1", b"v1111").is_ok());
+        assert!(db.put(b"k2", b"v22222222").is_ok());
+
+        let v1 = db.get(b"k1").unwrap().unwrap();
+        let v2 = db.get(b"k2").unwrap().unwrap();
+        assert_eq!(v1.as_slice(), b"v1111");
+        assert_eq!(v2.as_slice(), b"v22222222");
+    }
+}
+
+#[test]
+fn multi_get() {
+    let path = DBPath::new("_rust_rocksdb_multi_get");
+
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+        let initial_snap = db.snapshot();
+        db.put(b"k1", b"v1").unwrap();
+        let k1_snap = db.snapshot();
+        db.put(b"k2", b"v2").unwrap();
+
+        let _ = db.multi_get(&[b"k0"; 40]);
+
+        let assert_values = |values: Vec<_>| {
+            assert_eq!(3, values.len());
+            assert_eq!(values[0], None);
+            assert_eq!(values[1], Some(b"v1".to_vec()));
+            assert_eq!(values[2], Some(b"v2".to_vec()));
+        };
+
+        let values = db
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+
+        let values = DBAccess::multi_get_opt(&db, &[b"k0", b"k1", b"k2"], &Default::default())
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+
+        let values = db
+            .snapshot()
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+
+        let none_values = initial_snap
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_eq!(none_values, vec![None; 3]);
+
+        let k1_only = k1_snap
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_eq!(k1_only, vec![None, Some(b"v1".to_vec()), None]);
+
+        let txn = db.transaction();
+        let values = txn
+            .multi_get(&[b"k0", b"k1", b"k2"])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_values(values);
+    }
+}
+
+#[test]
+fn multi_get_cf() {
+    let path = DBPath::new("_rust_rocksdb_multi_get_cf");
+
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db: TransactionDB = TransactionDB::open_cf(
+            &opts,
+            &TransactionDBOptions::default(),
+            &path,
+            &["cf0", "cf1", "cf2"],
+        )
+        .unwrap();
+
+        let cf0 = db.cf_handle("cf0").unwrap();
+
+        let cf1 = db.cf_handle("cf1").unwrap();
+        db.put_cf(&cf1, b"k1", b"v1").unwrap();
+
+        let cf2 = db.cf_handle("cf2").unwrap();
+        db.put_cf(&cf2, b"k2", b"v2").unwrap();
+
+        let values = db
+            .multi_get_cf(vec![(&cf0, b"k0"), (&cf1, b"k1"), (&cf2, b"k2")])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+        assert_eq!(3, values.len());
+        assert_eq!(values[0], None);
+        assert_eq!(values[1], Some(b"v1".to_vec()));
+        assert_eq!(values[2], Some(b"v2".to_vec()));
+
+        let txn = db.transaction();
+        let values = txn
+            .multi_get_cf(vec![(&cf0, b"k0"), (&cf1, b"k1"), (&cf2, b"k2")])
+            .into_iter()
+            .map(Result::unwrap)
+            .collect::<Vec<_>>();
+
+        assert_eq!(3, values.len());
+        assert_eq!(values[0], None);
+        assert_eq!(values[1], Some(b"v1".to_vec()));
+        assert_eq!(values[2], Some(b"v2".to_vec()));
+    }
+}
+
+#[test]
+fn destroy_on_open() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_destroy_on_open");
+    let _db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+    let opts = Options::default();
+    // The TransactionDB will still be open when we try to destroy it and the lock should fail.
+    match DB::destroy(&opts, &path) {
+        Err(s) => {
+            let message = s.to_string();
+            assert_eq!(s.kind(), ErrorKind::IOError);
+            assert!(message.contains("_rust_rocksdb_transaction_db_destroy_on_open"));
+            assert!(message.contains("/LOCK:"));
+        }
+        Ok(_) => panic!("should fail"),
+    }
+}
+
+#[test]
+fn writebatch() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_writebatch");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+        {
+            // test put
+            let mut batch = WriteBatchWithTransaction::<true>::default();
+            assert!(db.get(b"k1").unwrap().is_none());
+            assert_eq!(batch.len(), 0);
+            assert!(batch.is_empty());
+            batch.put(b"k1", b"v1111");
+            batch.put(b"k2", b"v2222");
+            batch.put(b"k3", b"v3333");
+            assert_eq!(batch.len(), 3);
+            assert!(!batch.is_empty());
+            assert!(db.get(b"k1").unwrap().is_none());
+            let p = db.write(batch);
+            assert!(p.is_ok());
+            let r: Result<Option<Vec<u8>>, Error> = db.get(b"k1");
+            assert_eq!(r.unwrap().unwrap(), b"v1111");
+        }
+        {
+            // test delete
+            let mut batch = WriteBatchWithTransaction::<true>::default();
+            batch.delete(b"k1");
+            assert_eq!(batch.len(), 1);
+            assert!(!batch.is_empty());
+            let p = db.write(batch);
+            assert!(p.is_ok());
+            assert!(db.get(b"k1").unwrap().is_none());
+        }
+        {
+            // test size_in_bytes
+            let mut batch = WriteBatchWithTransaction::<true>::default();
+            let before = batch.size_in_bytes();
+            batch.put(b"k1", b"v1234567890");
+            let after = batch.size_in_bytes();
+            assert!(before + 10 <= after);
+        }
+    }
+}
+
+#[test]
+fn iterator_test() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_iteratortest");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        let k1: Box<[u8]> = b"k1".to_vec().into_boxed_slice();
+        let k2: Box<[u8]> = b"k2".to_vec().into_boxed_slice();
+        let k3: Box<[u8]> = b"k3".to_vec().into_boxed_slice();
+        let k4: Box<[u8]> = b"k4".to_vec().into_boxed_slice();
+        let v1: Box<[u8]> = b"v1111".to_vec().into_boxed_slice();
+        let v2: Box<[u8]> = b"v2222".to_vec().into_boxed_slice();
+        let v3: Box<[u8]> = b"v3333".to_vec().into_boxed_slice();
+        let v4: Box<[u8]> = b"v4444".to_vec().into_boxed_slice();
+
+        db.put(&*k1, &*v1).unwrap();
+        db.put(&*k2, &*v2).unwrap();
+        db.put(&*k3, &*v3).unwrap();
+        let expected = vec![
+            (k1.clone(), v1.clone()),
+            (k2.clone(), v2.clone()),
+            (k3.clone(), v3.clone()),
+        ];
+
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test that it's idempotent
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test in reverse
+        let iter = db.iterator(IteratorMode::End);
+        let mut tmp_vec = iter.collect::<Vec<_>>();
+        tmp_vec.reverse();
+
+        let old_iter = db.iterator(IteratorMode::Start);
+        db.put(&*k4, &*v4).unwrap();
+        let expected2 = vec![
+            (k1, v1),
+            (k2, v2),
+            (k3.clone(), v3.clone()),
+            (k4.clone(), v4.clone()),
+        ];
+        assert_eq!(old_iter.collect::<Vec<_>>(), expected);
+
+        let iter = db.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected2);
+
+        let iter = db.iterator(IteratorMode::From(b"k3", Direction::Forward));
+        assert_eq!(iter.collect::<Vec<_>>(), vec![(k3, v3), (k4, v4)]);
+    }
+}
+
+#[test]
+fn snapshot_test() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_snapshottest");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        assert!(db.put(b"k1", b"v1111").is_ok());
+
+        let snap = db.snapshot();
+        assert_eq!(snap.get(b"k1").unwrap().unwrap(), b"v1111");
+
+        assert!(db.put(b"k2", b"v2222").is_ok());
+
+        assert!(db.get(b"k2").unwrap().is_some());
+        assert!(snap.get(b"k2").unwrap().is_none());
+    }
+}
+
+#[test]
+fn prefix_extract_and_iterate_test() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_prefix_extract_and_iterate");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        opts.set_prefix_extractor(SliceTransform::create_fixed_prefix(2));
+        let txn_db_opts = TransactionDBOptions::default();
+
+        let db: TransactionDB = TransactionDB::open(&opts, &txn_db_opts, &path).unwrap();
+        db.put(b"p1_k1", b"v1").unwrap();
+        db.put(b"p2_k2", b"v2").unwrap();
+        db.put(b"p1_k3", b"v3").unwrap();
+        db.put(b"p1_k4", b"v4").unwrap();
+        db.put(b"p2_k5", b"v5").unwrap();
+
+        let mut readopts = ReadOptions::default();
+        readopts.set_prefix_same_as_start(true);
+        readopts.set_iterate_lower_bound(b"p1".to_vec());
+        readopts.set_pin_data(true);
+
+        let iter = db.iterator_opt(IteratorMode::Start, readopts);
+        let expected: Vec<_> = vec![(b"p1_k1", b"v1"), (b"p1_k3", b"v3"), (b"p1_k4", b"v4")]
+            .into_iter()
+            .map(|(k, v)| (k.to_vec().into_boxed_slice(), v.to_vec().into_boxed_slice()))
+            .collect();
+        assert_eq!(expected, iter.collect::<Vec<_>>());
+    }
+}
+
+#[test]
+fn cuckoo() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_cuckoo");
+
+    {
+        let mut opts = Options::default();
+        let txn_db_opts = TransactionDBOptions::default();
+        let mut factory_opts = CuckooTableOptions::default();
+        factory_opts.set_hash_ratio(0.8);
+        factory_opts.set_max_search_depth(20);
+        factory_opts.set_cuckoo_block_size(10);
+        factory_opts.set_identity_as_first_hash(true);
+        factory_opts.set_use_module_hash(false);
+
+        opts.set_cuckoo_table_factory(&factory_opts);
+        opts.create_if_missing(true);
+
+        let db: TransactionDB = TransactionDB::open(&opts, &txn_db_opts, &path).unwrap();
+        db.put(b"k1", b"v1").unwrap();
+        db.put(b"k2", b"v2").unwrap();
+        let r: Result<Option<Vec<u8>>, Error> = db.get(b"k1");
+
+        assert_eq!(r.unwrap().unwrap(), b"v1");
+        let r: Result<Option<Vec<u8>>, Error> = db.get(b"k2");
+
+        assert_eq!(r.unwrap().unwrap(), b"v2");
+        assert!(db.delete(b"k1").is_ok());
+        assert!(db.get(b"k1").unwrap().is_none());
+    }
+}
+
+#[test]
+fn transaction() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_transaction");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        let mut txn_db_opts = TransactionDBOptions::default();
+        txn_db_opts.set_txn_lock_timeout(10);
+
+        let db: TransactionDB = TransactionDB::open(&opts, &txn_db_opts, &path).unwrap();
+
+        // put outside of transaction
+        db.put(b"k1", b"v1").unwrap();
+        assert_eq!(db.get(b"k1").unwrap().unwrap(), b"v1");
+
+        let txn1 = db.transaction();
+        txn1.put(b"k1", b"v2").unwrap();
+
+        // get outside of transaction
+        assert_eq!(db.get(b"k1").unwrap().unwrap().as_slice(), b"v1");
+
+        // modify same key in another transaction, should get TimedOut
+        let txn2 = db.transaction();
+        let err = txn2.put(b"k1", b"v3").unwrap_err();
+        assert_eq!(err.kind(), ErrorKind::TimedOut);
+
+        // modify same key directly, should also get TimedOut
+        let err = db.put(b"k1", b"v4").unwrap_err();
+        assert_eq!(err.kind(), ErrorKind::TimedOut);
+
+        txn1.commit().unwrap();
+        assert_eq!(db.get(b"k1").unwrap().unwrap().as_slice(), b"v2");
+    }
+}
+
+#[test]
+fn transaction_iterator() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_transaction_iterator");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        let k1: Box<[u8]> = b"k1".to_vec().into_boxed_slice();
+        let k2: Box<[u8]> = b"k2".to_vec().into_boxed_slice();
+        let k3: Box<[u8]> = b"k3".to_vec().into_boxed_slice();
+        let k4: Box<[u8]> = b"k4".to_vec().into_boxed_slice();
+        let v1: Box<[u8]> = b"v1111".to_vec().into_boxed_slice();
+        let v2: Box<[u8]> = b"v2222".to_vec().into_boxed_slice();
+        let v3: Box<[u8]> = b"v3333".to_vec().into_boxed_slice();
+        let v4: Box<[u8]> = b"v4444".to_vec().into_boxed_slice();
+
+        db.put(&*k1, &*v1).unwrap();
+        db.put(&*k2, &*v2).unwrap();
+        db.put(&*k3, &*v3).unwrap();
+        let expected = vec![
+            (k1.clone(), v1.clone()),
+            (k2.clone(), v2.clone()),
+            (k3.clone(), v3.clone()),
+        ];
+
+        let txn = db.transaction();
+
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test that it's idempotent
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected);
+
+        // Test in reverse
+        let iter = txn.iterator(IteratorMode::End);
+        let mut tmp_vec = iter.collect::<Vec<_>>();
+        tmp_vec.reverse();
+
+        let old_iter = txn.iterator(IteratorMode::Start);
+        txn.put(&*k4, &*v4).unwrap();
+        let expected2 = vec![
+            (k1, v1),
+            (k2, v2),
+            (k3.clone(), v3.clone()),
+            (k4.clone(), v4.clone()),
+        ];
+        assert_eq!(old_iter.collect::<Vec<_>>(), expected);
+
+        let iter = txn.iterator(IteratorMode::Start);
+        assert_eq!(iter.collect::<Vec<_>>(), expected2);
+
+        let iter = txn.iterator(IteratorMode::From(b"k3", Direction::Forward));
+        assert_eq!(iter.collect::<Vec<_>>(), vec![(k3, v3), (k4, v4)]);
+    }
+}
+
+#[test]
+fn transaction_rollback() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_transaction_rollback");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+        let txn = db.transaction();
+
+        txn.rollback().unwrap();
+
+        txn.put(b"k1", b"v1").unwrap();
+        txn.set_savepoint();
+        txn.put(b"k2", b"v2").unwrap();
+
+        assert_eq!(txn.get(b"k1").unwrap().unwrap(), b"v1");
+        assert_eq!(txn.get(b"k2").unwrap().unwrap(), b"v2");
+
+        txn.rollback_to_savepoint().unwrap();
+        assert_eq!(txn.get(b"k1").unwrap().unwrap(), b"v1");
+        assert!(txn.get(b"k2").unwrap().is_none());
+
+        txn.rollback().unwrap();
+        assert!(txn.get(b"k1").unwrap().is_none());
+
+        txn.commit().unwrap();
+
+        assert!(db.get(b"k2").unwrap().is_none());
+    }
+}
+
+#[test]
+fn transaction_cf() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_transaction_cf");
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db: TransactionDB = TransactionDB::open_cf(
+            &opts,
+            &TransactionDBOptions::default(),
+            &path,
+            ["cf1", "cf2"],
+        )
+        .unwrap();
+
+        let cf1 = db.cf_handle("cf1").unwrap();
+        let cf2 = db.cf_handle("cf2").unwrap();
+
+        let txn = db.transaction();
+        txn.put(b"k0", b"v0").unwrap();
+        txn.put_cf(&cf1, b"k1", b"v1").unwrap();
+        txn.put_cf(&cf2, b"k2", b"v2").unwrap();
+
+        assert_eq!(txn.get(b"k0").unwrap().unwrap(), b"v0");
+        assert!(txn.get(b"k1").unwrap().is_none());
+        assert!(txn.get(b"k2").unwrap().is_none());
+
+        assert!(txn.get_cf(&cf1, b"k0").unwrap().is_none());
+        assert_eq!(txn.get_cf(&cf1, b"k1").unwrap().unwrap(), b"v1");
+        assert!(txn.get_cf(&cf1, b"k2").unwrap().is_none());
+
+        assert!(txn.get_cf(&cf2, b"k0").unwrap().is_none());
+        assert!(txn.get_cf(&cf2, b"k1").unwrap().is_none());
+        assert_eq!(txn.get_cf(&cf2, b"k2").unwrap().unwrap(), b"v2");
+
+        txn.commit().unwrap();
+    }
+}
+
+#[test]
+fn transaction_snapshot() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_transaction_snapshot");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        let txn = db.transaction();
+        let snapshot = txn.snapshot();
+        assert!(snapshot.get(b"k1").unwrap().is_none());
+        db.put(b"k1", b"v1").unwrap();
+        assert_eq!(snapshot.get(b"k1").unwrap().unwrap(), b"v1");
+
+        let mut opts = TransactionOptions::default();
+        opts.set_snapshot(true);
+        let txn = db.transaction_opt(&WriteOptions::default(), &opts);
+        db.put(b"k2", b"v2").unwrap();
+        let snapshot = txn.snapshot();
+        assert!(snapshot.get(b"k2").unwrap().is_none());
+        assert_eq!(txn.get(b"k2").unwrap().unwrap(), b"v2");
+        assert_eq!(
+            txn.get_for_update(b"k2", true).unwrap_err().kind(),
+            ErrorKind::Busy
+        );
+    }
+}
+
+#[test]
+fn two_phase_commit() {
+    let path = DBPath::new("_rust_rocksdb_transaction_db_2pc");
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        let txn = db.transaction();
+        txn.put(b"k1", b"v1").unwrap();
+        txn.set_name(b"txn1").unwrap();
+        txn.prepare().unwrap();
+        txn.commit().unwrap();
+
+        let txn = db.transaction();
+        txn.put(b"k2", b"v2").unwrap();
+        let err = txn.prepare().unwrap_err();
+        assert_eq!(err.kind(), ErrorKind::InvalidArgument);
+
+        let mut opt = TransactionOptions::new();
+        opt.set_skip_prepare(false);
+        let txn = db.transaction_opt(&WriteOptions::default(), &opt);
+        txn.put(b"k3", b"v3").unwrap();
+        let err = txn.prepare().unwrap_err();
+        assert_eq!(err.kind(), ErrorKind::InvalidArgument);
+    }
+
+    DB::destroy(&Options::default(), &path).unwrap();
+
+    {
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        let txn = db.transaction();
+        txn.put(b"k1", b"v1").unwrap();
+        txn.set_name(b"t1").unwrap();
+        txn.prepare().unwrap();
+
+        let txn2 = db.transaction();
+        txn2.put(b"k2", b"v1").unwrap();
+        txn2.set_name(b"t2").unwrap();
+        txn2.prepare().unwrap();
+
+        let txn3 = db.transaction();
+        let err = txn3.set_name(b"t1").unwrap_err();
+        assert_eq!(err.kind(), ErrorKind::InvalidArgument);
+
+        // k1 and k2 should locked after we restore prepared transactions.
+        let err = db.put(b"k1", b"v2").unwrap_err();
+        assert_eq!(err.kind(), ErrorKind::TimedOut);
+    }
+
+    {
+        // recovery
+        let mut opt = TransactionDBOptions::new();
+        opt.set_default_lock_timeout(1);
+        let db: TransactionDB = TransactionDB::open_default(&path).unwrap();
+
+        // get prepared transactions
+        let txns = db.prepared_transactions();
+        assert_eq!(txns.len(), 2);
+
+        for (_, txn) in txns.into_iter().enumerate() {
+            let name = txn.get_name().unwrap();
+
+            if name == b"t1" {
+                txn.commit().unwrap();
+            } else if name == b"t2" {
+                txn.rollback().unwrap();
+            } else {
+                unreachable!();
+            }
+        }
+
+        assert_eq!(db.get(b"k1").unwrap().unwrap(), b"v1");
+        assert!(db.get(b"k2").unwrap().is_none());
+    }
+}
+
+#[test]
+fn test_snapshot_outlive_transaction_db() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/fail/snapshot_outlive_transaction_db.rs");
+}
+
+#[test]
+fn test_txn_outlive_transaction_db() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/fail/transaction_outlive_transaction_db.rs");
+}
+
+#[test]
+fn test_snapshot_outlive_txn() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/fail/snapshot_outlive_transaction.rs");
+}