Fix lifetime parameter for iterators (#391)

Cargo.toml

@@ -23,7 +23,9 @@ zstd = ["librocksdb-sys/zstd"]
 zlib = ["librocksdb-sys/zlib"]
 bzip2 = ["librocksdb-sys/bzip2"]
 
-
 [dependencies]
 libc = "0.2"
 librocksdb-sys = { path = "librocksdb-sys", version = "6.4.6" }
+
+[dev-dependencies]
+trybuild = "1.0.21"

src/db.rs

@@ -1106,12 +1106,12 @@ impl DB {
         self.cfs.get(name)
     }
 
-    pub fn iterator<'a, 'b: 'a>(&'a self, mode: IteratorMode) -> DBIterator<'b> {
+    pub fn iterator<'a: 'b, 'b>(&'a self, mode: IteratorMode) -> DBIterator<'b> {
         let readopts = ReadOptions::default();
         self.iterator_opt(mode, &readopts)
     }
 
-    pub fn iterator_opt<'a, 'b: 'a>(
+    pub fn iterator_opt<'a: 'b, 'b>(
         &'a self,
         mode: IteratorMode,
         readopts: &ReadOptions,
@@ -1121,25 +1121,25 @@ impl DB {
 
     /// 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(
+    pub fn iterator_cf_opt<'a: 'b, 'b>(
-        &self,
+        &'a self,
         cf_handle: &ColumnFamily,
         readopts: &ReadOptions,
         mode: IteratorMode,
-    ) -> DBIterator {
+    ) -> DBIterator<'b> {
         DBIterator::new_cf(self, cf_handle, &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: 'a>(&'a self, mode: IteratorMode) -> DBIterator<'b> {
+    pub fn full_iterator<'a: 'b, 'b>(&'a self, mode: IteratorMode) -> DBIterator<'b> {
         let mut opts = ReadOptions::default();
         opts.set_total_order_seek(true);
         DBIterator::new(self, &opts, mode)
     }
 
-    pub fn prefix_iterator<'a, 'b: 'a, P: AsRef<[u8]>>(&'a self, prefix: P) -> DBIterator<'b> {
+    pub fn prefix_iterator<'a: 'b, 'b, P: AsRef<[u8]>>(&'a self, prefix: P) -> DBIterator<'b> {
         let mut opts = ReadOptions::default();
         opts.set_prefix_same_as_start(true);
         DBIterator::new(
@@ -1149,22 +1149,30 @@ impl DB {
         )
     }
 
-    pub fn iterator_cf(&self, cf_handle: &ColumnFamily, mode: IteratorMode) -> DBIterator {
+    pub fn iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &ColumnFamily,
+        mode: IteratorMode,
+    ) -> DBIterator<'b> {
         let opts = ReadOptions::default();
         DBIterator::new_cf(self, cf_handle, &opts, mode)
     }
 
-    pub fn full_iterator_cf(&self, cf_handle: &ColumnFamily, mode: IteratorMode) -> DBIterator {
+    pub fn full_iterator_cf<'a: 'b, 'b>(
+        &'a self,
+        cf_handle: &ColumnFamily,
+        mode: IteratorMode,
+    ) -> DBIterator<'b> {
         let mut opts = ReadOptions::default();
         opts.set_total_order_seek(true);
         DBIterator::new_cf(self, cf_handle, &opts, mode)
     }
 
-    pub fn prefix_iterator_cf<P: AsRef<[u8]>>(
+    pub fn prefix_iterator_cf<'a: 'b, 'b, P: AsRef<[u8]>>(
-        &self,
+        &'a self,
         cf_handle: &ColumnFamily,
         prefix: P,
-    ) -> DBIterator {
+    ) -> DBIterator<'b> {
         let mut opts = ReadOptions::default();
         opts.set_prefix_same_as_start(true);
         DBIterator::new_cf(
@@ -1176,28 +1184,28 @@ impl DB {
     }
 
     /// Opens a raw iterator over the database, using the default read options
-    pub fn raw_iterator(&self) -> DBRawIterator {
+    pub fn raw_iterator<'a: 'b, 'b>(&'a self) -> DBRawIterator<'b> {
         let opts = ReadOptions::default();
         DBRawIterator::new(self, &opts)
     }
 
     /// Opens a raw iterator over the given column family, using the default read options
-    pub fn raw_iterator_cf(&self, cf_handle: &ColumnFamily) -> DBRawIterator {
+    pub fn raw_iterator_cf<'a: 'b, 'b>(&'a self, cf_handle: &ColumnFamily) -> DBRawIterator<'b> {
         let opts = ReadOptions::default();
         DBRawIterator::new_cf(self, cf_handle, &opts)
     }
 
     /// Opens a raw iterator over the database, using the given read options
-    pub fn raw_iterator_opt(&self, readopts: &ReadOptions) -> DBRawIterator {
+    pub fn raw_iterator_opt<'a: 'b, 'b>(&'a self, readopts: &ReadOptions) -> DBRawIterator<'b> {
         DBRawIterator::new(self, readopts)
     }
 
     /// Opens a raw iterator over the given column family, using the given read options
-    pub fn raw_iterator_cf_opt(
+    pub fn raw_iterator_cf_opt<'a: 'b, 'b>(
-        &self,
+        &'a self,
         cf_handle: &ColumnFamily,
         readopts: &ReadOptions,
-    ) -> DBRawIterator {
+    ) -> DBRawIterator<'b> {
         DBRawIterator::new_cf(self, cf_handle, readopts)
     }
 

tests/fail/iterator_outlive_db.rs

@@ -0,0 +1,8 @@
+use rocksdb::{IteratorMode, DB};
+
+fn main() {
+    let _iter = {
+        let db = DB::open_default("foo").unwrap();
+        db.iterator(IteratorMode::Start)
+    };
+}

tests/fail/iterator_outlive_db.stderr

@@ -0,0 +1,10 @@
+error[E0597]: `db` does not live long enough
+ --> $DIR/iterator_outlive_db.rs:6:9
+  |
+4 |     let _iter = {
+  |         ----- borrow later stored here
+5 |         let db = DB::open_default("foo").unwrap();
+6 |         db.iterator(IteratorMode::Start)
+  |         ^^ borrowed value does not live long enough
+7 |     };
+  |     - `db` dropped here while still borrowed

tests/test_iterator.rs

@@ -299,7 +299,7 @@ fn test_full_iterator() {
     assert!(DB::destroy(&opts, path).is_ok());
 }
 
-fn custom_iter(db: &DB) -> impl Iterator<Item = usize> {
+fn custom_iter<'a>(db: &'a DB) -> impl Iterator<Item = usize> + 'a {
     db.iterator(IteratorMode::Start)
         .map(|(_, db_value)| db_value.len())
 }
@@ -316,3 +316,9 @@ fn test_custom_iterator() {
     let opts = Options::default();
     assert!(DB::destroy(&opts, path).is_ok());
 }
+
+#[test]
+fn test_iterator_outlive_db() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/fail/iterator_outlive_db.rs");
+}