Storage: Manages strings GC using merge operation

Removes old strings during compaction

lib/src/storage/fallback_backend.rs

@@ -1,21 +1,40 @@
 //! TODO: This storage is dramatically naive.
 
+use std::collections::btree_map::Entry;
 use std::collections::BTreeMap;
+use std::ffi::CString;
 use std::io::Result;
+use std::iter::{once, Once};
 use std::sync::{Arc, RwLock};
 
 pub struct ColumnFamilyDefinition {
     pub name: &'static str,
+    pub merge_operator: Option<MergeOperator>,
+    pub compaction_filter: Option<CompactionFilter>,
 }
 
 #[derive(Clone)]
-pub struct Db(Arc<RwLock<BTreeMap<ColumnFamily, BTreeMap<Vec<u8>, Vec<u8>>>>>);
+pub struct Db(Arc<RwLock<BTreeMap<ColumnFamily, Tree>>>);
+
+#[derive(Default)]
+struct Tree {
+    tree: BTreeMap<Vec<u8>, Vec<u8>>,
+    merge_operator: Option<MergeOperator>,
+    compaction_filter: Option<CompactionFilter>,
+}
 
 impl Db {
     pub fn new(column_families: Vec<ColumnFamilyDefinition>) -> Result<Self> {
         let mut trees = BTreeMap::new();
         for cf in column_families {
-            trees.insert(ColumnFamily(cf.name), BTreeMap::default());
+            trees.insert(
+                ColumnFamily(cf.name),
+                Tree {
+                    tree: BTreeMap::default(),
+                    merge_operator: cf.merge_operator,
+                    compaction_filter: cf.compaction_filter,
+                },
+            );
         }
         trees.entry(ColumnFamily("default")).or_default(); // We make sure that "default" key exists.
         Ok(Self(Arc::new(RwLock::new(trees))))
@@ -30,7 +49,7 @@ impl Db {
         }
     }
 
-    pub fn flush(&self) -> Result<()> {
+    pub fn flush(&self, _column_family: &ColumnFamily) -> Result<()> {
         Ok(())
     }
 
@@ -41,6 +60,7 @@ impl Db {
             .unwrap()
             .get(column_family)
             .unwrap()
+            .tree
             .get(key)
             .map(|v| v.to_vec()))
     }
@@ -52,6 +72,7 @@ impl Db {
             .unwrap()
             .get(column_family)
             .unwrap()
+            .tree
             .contains_key(key.as_ref()))
     }
 
@@ -62,12 +83,18 @@ impl Db {
         value: &[u8],
         _low_priority: bool,
     ) -> Result<()> {
-        self.0
-            .write()
-            .unwrap()
-            .get_mut(column_family)
-            .unwrap()
-            .insert(key.into(), value.into());
+        let mut db = self.0.write().unwrap();
+        let tree = db.get_mut(column_family).unwrap();
+        let action = if let Some(filter) = &tree.compaction_filter {
+            (filter.filter)(key, value)
+        } else {
+            CompactionAction::Keep
+        };
+        match action {
+            CompactionAction::Keep => tree.tree.insert(key.into(), value.into()),
+            CompactionAction::Remove => tree.tree.remove(key),
+            CompactionAction::Replace(value) => tree.tree.insert(key.into(), value),
+        };
         Ok(())
     }
 
@@ -92,17 +119,70 @@ impl Db {
             .unwrap()
             .get_mut(column_family)
             .unwrap()
+            .tree
             .remove(key.as_ref())
             .is_some())
     }
 
+    pub fn merge(
+        &self,
+        column_family: &ColumnFamily,
+        key: &[u8],
+        value: &[u8],
+        _low_priority: bool,
+    ) -> Result<()> {
+        let mut db = self.0.write().unwrap();
+        let tree = db.get_mut(column_family).unwrap();
+        match tree.tree.entry(key.into()) {
+            Entry::Vacant(e) => {
+                let value = if let Some(merge) = &tree.merge_operator {
+                    (merge.full)(key, None, once(value))
+                } else {
+                    value.into()
+                };
+                let action = if let Some(filter) = &tree.compaction_filter {
+                    (filter.filter)(key, &value)
+                } else {
+                    CompactionAction::Keep
+                };
+                match action {
+                    CompactionAction::Keep => {
+                        e.insert(value);
+                    }
+                    CompactionAction::Remove => (),
+                    CompactionAction::Replace(value) => {
+                        e.insert(value);
+                    }
+                }
+            }
+            Entry::Occupied(mut e) => {
+                let value = if let Some(merge) = &tree.merge_operator {
+                    (merge.full)(key, Some(&e.get()), once(value))
+                } else {
+                    value.into()
+                };
+                let action = if let Some(filter) = &tree.compaction_filter {
+                    (filter.filter)(key, &value)
+                } else {
+                    CompactionAction::Keep
+                };
+                match action {
+                    CompactionAction::Keep => e.insert(value),
+                    CompactionAction::Remove => e.remove(),
+                    CompactionAction::Replace(value) => e.insert(value),
+                };
+            }
+        }
+        Ok(())
+    }
+
     pub fn iter(&self, column_family: &ColumnFamily) -> Iter {
         self.scan_prefix(column_family, &[])
     }
 
     pub fn scan_prefix(&self, column_family: &ColumnFamily, prefix: &[u8]) -> Iter {
         let trees = self.0.read().unwrap();
-        let tree = trees.get(column_family).unwrap();
+        let tree = &trees.get(column_family).unwrap().tree;
         let data: Vec<_> = if prefix.is_empty() {
             tree.iter().map(|(k, v)| (k.clone(), v.clone())).collect()
         } else {
@@ -117,7 +197,14 @@ impl Db {
     }
 
     pub fn len(&self, column_family: &ColumnFamily) -> Result<usize> {
-        Ok(self.0.read().unwrap().get(column_family).unwrap().len())
+        Ok(self
+            .0
+            .read()
+            .unwrap()
+            .get(column_family)
+            .unwrap()
+            .tree
+            .len())
     }
 
     pub fn is_empty(&self, column_family: &ColumnFamily) -> Result<bool> {
@@ -127,6 +214,7 @@ impl Db {
             .unwrap()
             .get(column_family)
             .unwrap()
+            .tree
             .is_empty())
     }
 }
@@ -156,3 +244,23 @@ impl Iter {
         Ok(())
     }
 }
+
+pub struct MergeOperator {
+    pub full: fn(&[u8], Option<&[u8]>, SlicesIterator<'_>) -> Vec<u8>,
+    pub partial: fn(&[u8], SlicesIterator<'_>) -> Vec<u8>,
+    pub name: CString,
+}
+
+pub type SlicesIterator<'a> = Once<&'a [u8]>;
+
+pub struct CompactionFilter {
+    pub filter: fn(&[u8], &[u8]) -> CompactionAction,
+    pub name: CString,
+}
+
+#[allow(dead_code)]
+pub enum CompactionAction {
+    Keep,
+    Remove,
+    Replace(Vec<u8>),
+}

lib/src/storage/mod.rs

@@ -8,9 +8,16 @@ use crate::storage::binary_encoder::{
 };
 use crate::storage::numeric_encoder::{EncodedQuad, EncodedTerm, StrHash, StrLookup, TermEncoder};
 #[cfg(target_arch = "wasm32")]
-use fallback_backend::{ColumnFamily, ColumnFamilyDefinition, Db, Iter};
+use fallback_backend::{
+    ColumnFamily, ColumnFamilyDefinition, CompactionAction, CompactionFilter, Db, Iter,
+    MergeOperator,
+};
 #[cfg(not(target_arch = "wasm32"))]
-use rocksdb_backend::{ColumnFamily, ColumnFamilyDefinition, Db, Iter};
+use rocksdb_backend::{
+    ColumnFamily, ColumnFamilyDefinition, CompactionAction, CompactionFilter, Db, Iter,
+    MergeOperator,
+};
+use std::ffi::CString;
 #[cfg(not(target_arch = "wasm32"))]
 use std::path::Path;
 
@@ -66,20 +73,104 @@ impl Storage {
 
     fn column_families() -> Vec<ColumnFamilyDefinition> {
         vec![
-            ColumnFamilyDefinition { name: ID2STR_CF },
-            ColumnFamilyDefinition { name: SPOG_CF },
-            ColumnFamilyDefinition { name: POSG_CF },
-            ColumnFamilyDefinition { name: OSPG_CF },
-            ColumnFamilyDefinition { name: GSPO_CF },
-            ColumnFamilyDefinition { name: GPOS_CF },
-            ColumnFamilyDefinition { name: GOSP_CF },
-            ColumnFamilyDefinition { name: DSPO_CF },
-            ColumnFamilyDefinition { name: DPOS_CF },
-            ColumnFamilyDefinition { name: DOSP_CF },
-            ColumnFamilyDefinition { name: GRAPHS_CF },
+            ColumnFamilyDefinition {
+                name: ID2STR_CF,
+                merge_operator: Some(Self::str2id_merge()),
+                compaction_filter: Some(Self::str2id_filter()),
+            },
+            ColumnFamilyDefinition {
+                name: SPOG_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: POSG_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: OSPG_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: GSPO_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: GPOS_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: GOSP_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: DSPO_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: DPOS_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: DOSP_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
+            ColumnFamilyDefinition {
+                name: GRAPHS_CF,
+                merge_operator: None,
+                compaction_filter: None,
+            },
         ]
     }
 
+    fn str2id_merge() -> MergeOperator {
+        fn merge_counted_values<'a>(values: impl Iterator<Item = &'a [u8]>) -> Vec<u8> {
+            let (counter, str) =
+                values.fold((0, [].as_ref()), |(prev_counter, prev_str), current| {
+                    (
+                        prev_counter + i32::from_be_bytes(current[..4].try_into().unwrap()),
+                        if prev_str.is_empty() {
+                            &current[4..]
+                        } else {
+                            prev_str
+                        },
+                    )
+                });
+            let mut buffer = Vec::with_capacity(str.len() + 4);
+            buffer.extend_from_slice(&counter.to_be_bytes());
+            buffer.extend_from_slice(str);
+            buffer
+        }
+
+        MergeOperator {
+            full: |_, previous, values| merge_counted_values(previous.into_iter().chain(values)),
+            partial: |_, values| merge_counted_values(values),
+            name: CString::new("id2str_merge").unwrap(),
+        }
+    }
+
+    fn str2id_filter() -> CompactionFilter {
+        CompactionFilter {
+            filter: |_, value| {
+                let counter = i32::from_be_bytes(value[..4].try_into().unwrap());
+                if counter > 0 {
+                    CompactionAction::Keep
+                } else {
+                    CompactionAction::Remove
+                }
+            },
+            name: CString::new("id2str_compaction_filter").unwrap(),
+        }
+    }
+
     fn setup(db: Db) -> std::io::Result<Self> {
         let this = Self {
             default_cf: db.column_family(DEFAULT_CF).unwrap(),
@@ -107,24 +198,26 @@ impl Storage {
                         .insert_empty(&this.graphs_cf, &encode_term(&quad.graph_name), false)?;
                 }
             }
+            this.db.flush(&this.graphs_cf)?;
             version = 1;
             this.set_version(version)?;
-            this.db.flush()?;
+            this.db.flush(&this.default_cf)?;
         }
         if version == 1 {
             // We migrate to v2
             let mut iter = this.db.iter(&this.id2str_cf);
             while let (Some(key), Some(value)) = (iter.key(), iter.value()) {
                 let mut new_value = Vec::with_capacity(value.len() + 4);
-                new_value.extend_from_slice(&u32::MAX.to_be_bytes());
+                new_value.extend_from_slice(&i32::MAX.to_be_bytes());
                 new_value.extend_from_slice(value);
                 this.db.insert(&this.id2str_cf, key, &new_value, false)?;
                 iter.next();
             }
             iter.status()?;
+            this.db.flush(&this.id2str_cf)?;
             version = 2;
             this.set_version(version)?;
-            this.db.flush()?;
+            this.db.flush(&this.default_cf)?;
         }
 
         match version {
@@ -684,13 +777,30 @@ impl Storage {
 
     #[cfg(not(target_arch = "wasm32"))]
     pub fn flush(&self) -> std::io::Result<()> {
-        self.db.flush()
+        self.db.flush(&self.default_cf)?;
+        self.db.flush(&self.gpos_cf)?;
+        self.db.flush(&self.gpos_cf)?;
+        self.db.flush(&self.gosp_cf)?;
+        self.db.flush(&self.spog_cf)?;
+        self.db.flush(&self.posg_cf)?;
+        self.db.flush(&self.ospg_cf)?;
+        self.db.flush(&self.dspo_cf)?;
+        self.db.flush(&self.dpos_cf)?;
+        self.db.flush(&self.dosp_cf)?;
+        self.db.flush(&self.id2str_cf)
     }
 
     pub fn get_str(&self, key: &StrHash) -> std::io::Result<Option<String>> {
         self.db
             .get(&self.id2str_cf, &key.to_be_bytes())?
-            .map(|v| String::from_utf8(v[4..].to_vec()))
+            .and_then(|v| {
+                let count = i32::from_be_bytes(v[..4].try_into().unwrap());
+                if count > 0 {
+                    Some(String::from_utf8(v[4..].to_vec()))
+                } else {
+                    None
+                }
+            })
             .transpose()
             .map_err(invalid_data_error)
     }
@@ -774,37 +884,20 @@ impl TermEncoder for Storage {
     type Error = std::io::Error;
 
     fn insert_str(&self, key: &StrHash, value: &str) -> std::io::Result<()> {
-        if let Some(value) = self.db.get(&self.id2str_cf, &key.to_be_bytes())? {
-            let mut value = value.to_vec();
-            let number = u32::from_be_bytes(value[..4].try_into().map_err(invalid_data_error)?);
-            let new_number = number.saturating_add(1);
-            value[..4].copy_from_slice(&new_number.to_be_bytes());
-            self.db
-                .insert(&self.id2str_cf, &key.to_be_bytes(), &value, true)?
-        } else {
-            let mut buffer = Vec::with_capacity(value.len() + 4);
-            buffer.extend_from_slice(&1_u32.to_be_bytes());
-            buffer.extend_from_slice(value.as_bytes());
-            self.db
-                .insert(&self.id2str_cf, &key.to_be_bytes(), &buffer, false)?;
-        }
-        Ok(())
+        let mut buffer = Vec::with_capacity(value.len() + 4);
+        buffer.extend_from_slice(&1_i32.to_be_bytes());
+        buffer.extend_from_slice(value.as_bytes());
+        self.db
+            .merge(&self.id2str_cf, &key.to_be_bytes(), &buffer, false)
     }
 
     fn remove_str(&self, key: &StrHash) -> std::io::Result<()> {
-        if let Some(value) = self.db.get(&self.id2str_cf, &key.to_be_bytes())? {
-            let number = u32::from_be_bytes(value[..4].try_into().map_err(invalid_data_error)?);
-            let new_number = number.saturating_sub(1);
-            if new_number == 0 {
-                self.db.remove(&self.id2str_cf, &key.to_be_bytes(), true)?;
-            } else {
-                let mut value = value.to_vec();
-                value[..4].copy_from_slice(&new_number.to_be_bytes());
-                self.db
-                    .insert(&self.id2str_cf, &key.to_be_bytes(), &value, true)?;
-            }
-        }
-        Ok(())
+        self.db.merge(
+            &self.id2str_cf,
+            &key.to_be_bytes(),
+            &(-1_i32).to_be_bytes(),
+            true,
+        )
     }
 }
 
@@ -860,6 +953,8 @@ mod tests {
         storage.insert(quad)?;
         storage.insert(quad2)?;
         storage.remove(quad2)?;
+        storage.flush()?;
+        storage.db.compact(&storage.id2str_cf)?;
         assert!(storage
             .get_str(&StrHash::new("http://example.com/s"))?
             .is_some());

lib/src/storage/rocksdb_backend.rs

@@ -1,9 +1,11 @@
 //! Code inspired by [https://github.com/rust-rocksdb/rust-rocksdb][Rust RocksDB] under Apache License 2.0.
+//!
+//! TODO: still has some memory leaks if the database opening fails
 
 #![allow(unsafe_code)]
 
 use crate::error::invalid_input_error;
-use libc::{self, c_char, c_void};
+use libc::{self, c_char, c_int, c_uchar, c_void, size_t};
 use oxrocksdb_sys::*;
 use std::borrow::Borrow;
 use std::env::temp_dir;
@@ -39,6 +41,8 @@ macro_rules! ffi_result_impl {
 
 pub struct ColumnFamilyDefinition {
     pub name: &'static str,
+    pub merge_operator: Option<MergeOperator>,
+    pub compaction_filter: Option<CompactionFilter>,
 }
 
 #[derive(Clone)]
@@ -55,9 +59,12 @@ struct DbHandler {
     write_options: *mut rocksdb_writeoptions_t,
     low_priority_write_options: *mut rocksdb_writeoptions_t,
     flush_options: *mut rocksdb_flushoptions_t,
+    compaction_options: *mut rocksdb_compactoptions_t,
     env: Option<*mut rocksdb_env_t>,
-    column_families: Vec<ColumnFamilyDefinition>,
+    column_family_names: Vec<&'static str>,
     cf_handles: Vec<*mut rocksdb_column_family_handle_t>,
+    cf_options: Vec<*mut rocksdb_options_t>,
+    cf_compaction_filters: Vec<*mut rocksdb_compactionfilter_t>,
 }
 
 impl Drop for DbHandler {
@@ -67,15 +74,22 @@ impl Drop for DbHandler {
                 rocksdb_column_family_handle_destroy(*cf_handle);
             }
             rocksdb_transactiondb_close(self.db);
+            for cf_option in &self.cf_options {
+                rocksdb_options_destroy(*cf_option);
+            }
             rocksdb_readoptions_destroy(self.read_options);
             rocksdb_writeoptions_destroy(self.write_options);
             rocksdb_writeoptions_destroy(self.low_priority_write_options);
             rocksdb_flushoptions_destroy(self.flush_options);
+            rocksdb_compactoptions_destroy(self.compaction_options);
             rocksdb_transactiondb_options_destroy(self.txn_options);
             rocksdb_options_destroy(self.options);
             if let Some(env) = self.env {
                 rocksdb_env_destroy(env);
             }
+            for cf_compact in &self.cf_compaction_filters {
+                rocksdb_compactionfilter_destroy(*cf_compact);
+            }
         }
     }
 }
@@ -145,47 +159,76 @@ impl Db {
             };
 
             if !column_families.iter().any(|c| c.name == "default") {
-                column_families.push(ColumnFamilyDefinition { name: "default" })
+                column_families.push(ColumnFamilyDefinition {
+                    name: "default",
+                    merge_operator: None,
+                    compaction_filter: None,
+                })
             }
-            let c_column_families = column_families
+            let column_family_names = column_families.iter().map(|c| c.name).collect::<Vec<_>>();
+            let c_column_families = column_family_names
                 .iter()
-                .map(|cf| CString::new(cf.name))
+                .map(|name| CString::new(*name))
                 .collect::<std::result::Result<Vec<_>, _>>()
                 .map_err(invalid_input_error)?;
-            let cf_options: Vec<*const rocksdb_options_t> = vec![options; column_families.len()];
+            let mut cf_compaction_filters = Vec::new();
+            let cf_options = column_families
+                .into_iter()
+                .map(|cf| {
+                    let options = rocksdb_options_create_copy(options);
+                    if let Some(merge) = cf.merge_operator {
+                        // mergeoperator delete is done automatically
+                        let merge = rocksdb_mergeoperator_create(
+                            Box::into_raw(Box::new(merge)) as *mut c_void,
+                            Some(merge_destructor),
+                            Some(merge_full),
+                            Some(merge_partial),
+                            Some(merge_delete_value),
+                            Some(merge_name),
+                        );
+                        assert!(
+                            !merge.is_null(),
+                            "rocksdb_mergeoperator_create returned null"
+                        );
+                        rocksdb_options_set_merge_operator(options, merge);
+                    }
+                    if let Some(compact) = cf.compaction_filter {
+                        let compact = rocksdb_compactionfilter_create(
+                            Box::into_raw(Box::new(compact)) as *mut c_void,
+                            Some(compactionfilter_destructor),
+                            Some(compactionfilter_filter),
+                            Some(compactionfilter_name),
+                        );
+                        assert!(
+                            !compact.is_null(),
+                            "rocksdb_compactionfilter_create returned null"
+                        );
+                        rocksdb_options_set_compaction_filter(options, compact);
+                        cf_compaction_filters.push(compact);
+                    }
+                    options
+                })
+                .collect::<Vec<_>>();
 
             let mut cf_handles: Vec<*mut rocksdb_column_family_handle_t> =
-                vec![ptr::null_mut(); column_families.len()];
+                vec![ptr::null_mut(); column_family_names.len()];
             let db = ffi_result!(rocksdb_transactiondb_open_column_families(
                 options,
                 txn_options,
                 c_path.as_ptr(),
-                column_families.len().try_into().unwrap(),
+                c_column_families.len().try_into().unwrap(),
                 c_column_families
                     .iter()
                     .map(|cf| cf.as_ptr())
                     .collect::<Vec<_>>()
                     .as_ptr(),
-                cf_options.as_ptr(),
+                cf_options.as_ptr() as *const *const rocksdb_options_t,
                 cf_handles.as_mut_ptr(),
-            ))
-            .map_err(|e| {
-                rocksdb_options_destroy(options);
-                rocksdb_transactiondb_options_destroy(txn_options);
-                if let Some(env) = env {
-                    rocksdb_env_destroy(env);
-                }
-                e
-            })?;
+            ))?;
             assert!(!db.is_null(), "rocksdb_create returned null");
             for handle in &cf_handles {
                 if handle.is_null() {
                     rocksdb_transactiondb_close(db);
-                    rocksdb_options_destroy(options);
-                    rocksdb_transactiondb_options_destroy(txn_options);
-                    if let Some(env) = env {
-                        rocksdb_env_destroy(env);
-                    }
                     return Err(other_error(
                         "Received null column family handle from RocksDB.",
                     ));
@@ -220,6 +263,12 @@ impl Db {
                 "rocksdb_flushoptions_create returned null"
             );
 
+            let compaction_options = rocksdb_compactoptions_create();
+            assert!(
+                !compaction_options.is_null(),
+                "rocksdb_compactoptions_create returned null"
+            );
+
             Ok(DbHandler {
                 db,
                 options,
@@ -228,24 +277,48 @@ impl Db {
                 write_options,
                 low_priority_write_options,
                 flush_options,
+                compaction_options,
                 env,
-                column_families,
+                column_family_names,
                 cf_handles,
+                cf_options,
+                cf_compaction_filters,
             })
         }
     }
 
     pub fn column_family(&self, name: &'static str) -> Option<ColumnFamily> {
-        for (cf, cf_handle) in self.0.column_families.iter().zip(&self.0.cf_handles) {
-            if cf.name == name {
+        for (cf, cf_handle) in self.0.column_family_names.iter().zip(&self.0.cf_handles) {
+            if *cf == name {
                 return Some(ColumnFamily(*cf_handle));
             }
         }
         None
     }
 
-    pub fn flush(&self) -> Result<()> {
-        unsafe { ffi_result!(rocksdb_transactiondb_flush(self.0.db, self.0.flush_options)) }
+    pub fn flush(&self, column_family: &ColumnFamily) -> Result<()> {
+        unsafe {
+            ffi_result!(rocksdb_transactiondb_flush_cf(
+                self.0.db,
+                self.0.flush_options,
+                column_family.0,
+            ))
+        }
+    }
+
+    #[cfg(test)]
+    pub fn compact(&self, column_family: &ColumnFamily) -> Result<()> {
+        unsafe {
+            ffi_result!(rocksdb_transactiondb_compact_range_cf_opt(
+                self.0.db,
+                column_family.0,
+                self.0.compaction_options,
+                ptr::null(),
+                0,
+                ptr::null(),
+                0
+            ))
+        }
     }
 
     pub fn get(
@@ -300,6 +373,30 @@ impl Db {
         }
     }
 
+    pub fn merge(
+        &self,
+        column_family: &ColumnFamily,
+        key: &[u8],
+        value: &[u8],
+        low_priority: bool,
+    ) -> Result<()> {
+        unsafe {
+            ffi_result!(rocksdb_transactiondb_merge_cf(
+                self.0.db,
+                if low_priority {
+                    self.0.low_priority_write_options
+                } else {
+                    self.0.write_options
+                },
+                column_family.0,
+                key.as_ptr() as *const c_char,
+                key.len(),
+                value.as_ptr() as *const c_char,
+                value.len(),
+            ))
+        }
+    }
+
     pub fn insert_empty(
         &self,
         column_family: &ColumnFamily,
@@ -521,3 +618,161 @@ fn convert_error(ptr: *const c_char) -> Error {
 fn other_error(error: impl Into<Box<dyn std::error::Error + Send + Sync>>) -> Error {
     Error::new(ErrorKind::InvalidInput, error)
 }
+
+pub struct MergeOperator {
+    pub full: fn(&[u8], Option<&[u8]>, SlicesIterator<'_>) -> Vec<u8>,
+    pub partial: fn(&[u8], SlicesIterator<'_>) -> Vec<u8>,
+    pub name: CString,
+}
+
+unsafe extern "C" fn merge_destructor(operator: *mut c_void) {
+    Box::from_raw(operator as *mut MergeOperator);
+}
+
+unsafe extern "C" fn merge_full(
+    operator: *mut c_void,
+    key: *const c_char,
+    key_length: size_t,
+    existing_value: *const c_char,
+    existing_value_len: size_t,
+    operands_list: *const *const c_char,
+    operands_list_length: *const size_t,
+    num_operands: c_int,
+    success: *mut u8,
+    new_value_length: *mut size_t,
+) -> *mut c_char {
+    let operator = &*(operator as *const MergeOperator);
+    let num_operands = usize::try_from(num_operands).unwrap();
+    let result = (operator.full)(
+        slice::from_raw_parts(key as *const u8, key_length),
+        if existing_value.is_null() {
+            None
+        } else {
+            Some(slice::from_raw_parts(
+                existing_value as *const u8,
+                existing_value_len,
+            ))
+        },
+        SlicesIterator {
+            slices: slice::from_raw_parts(operands_list, num_operands),
+            lengths: slice::from_raw_parts(operands_list_length, num_operands),
+            cursor: 0,
+        },
+    );
+    *new_value_length = result.len();
+    *success = 1_u8;
+    Box::into_raw(result.into_boxed_slice()) as *mut c_char
+}
+
+pub unsafe extern "C" fn merge_partial(
+    operator: *mut c_void,
+    key: *const c_char,
+    key_length: size_t,
+    operands_list: *const *const c_char,
+    operands_list_length: *const size_t,
+    num_operands: c_int,
+    success: *mut u8,
+    new_value_length: *mut size_t,
+) -> *mut c_char {
+    let operator = &*(operator as *const MergeOperator);
+    let num_operands = usize::try_from(num_operands).unwrap();
+    let result = (operator.partial)(
+        slice::from_raw_parts(key as *const u8, key_length),
+        SlicesIterator {
+            slices: slice::from_raw_parts(operands_list, num_operands),
+            lengths: slice::from_raw_parts(operands_list_length, num_operands),
+            cursor: 0,
+        },
+    );
+    *new_value_length = result.len();
+    *success = 1_u8;
+    Box::into_raw(result.into_boxed_slice()) as *mut c_char
+}
+
+unsafe extern "C" fn merge_delete_value(
+    _operator: *mut c_void,
+    value: *const c_char,
+    value_length: size_t,
+) {
+    if !value.is_null() {
+        Box::from_raw(slice::from_raw_parts_mut(value as *mut u8, value_length));
+    }
+}
+
+unsafe extern "C" fn merge_name(operator: *mut c_void) -> *const c_char {
+    let operator = &*(operator as *const MergeOperator);
+    operator.name.as_ptr()
+}
+
+pub struct SlicesIterator<'a> {
+    slices: &'a [*const c_char],
+    lengths: &'a [size_t],
+    cursor: usize,
+}
+
+impl<'a> Iterator for SlicesIterator<'a> {
+    type Item = &'a [u8];
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.cursor >= self.slices.len() {
+            None
+        } else {
+            let slice = unsafe {
+                slice::from_raw_parts(
+                    self.slices[self.cursor] as *const u8,
+                    self.lengths[self.cursor],
+                )
+            };
+            self.cursor += 1;
+            Some(slice)
+        }
+    }
+}
+
+pub struct CompactionFilter {
+    pub filter: fn(&[u8], &[u8]) -> CompactionAction,
+    pub name: CString,
+}
+
+#[allow(dead_code)]
+pub enum CompactionAction {
+    Keep,
+    Remove,
+    Replace(Vec<u8>),
+}
+
+unsafe extern "C" fn compactionfilter_destructor(filter: *mut c_void) {
+    Box::from_raw(filter as *mut CompactionFilter);
+}
+
+unsafe extern "C" fn compactionfilter_filter(
+    filter: *mut c_void,
+    _level: c_int,
+    key: *const c_char,
+    key_length: size_t,
+    existing_value: *const c_char,
+    value_length: size_t,
+    new_value: *mut *mut c_char,
+    new_value_length: *mut size_t,
+    value_changed: *mut c_uchar,
+) -> c_uchar {
+    let filter = &*(filter as *const CompactionFilter);
+    match (filter.filter)(
+        slice::from_raw_parts(key as *const u8, key_length),
+        slice::from_raw_parts(existing_value as *const u8, value_length),
+    ) {
+        CompactionAction::Keep => 0,
+        CompactionAction::Remove => 1,
+        CompactionAction::Replace(new_val) => {
+            *new_value_length = new_val.len();
+            *value_changed = 1_u8;
+            *new_value = Box::into_raw(new_val.into_boxed_slice()) as *mut c_char;
+            0
+        }
+    }
+}
+
+unsafe extern "C" fn compactionfilter_name(filter: *mut c_void) -> *const c_char {
+    let filter = &*(filter as *const CompactionFilter);
+    filter.name.as_ptr()
+}

rocksdb-sys/api/c.cc

@@ -20,11 +20,26 @@ rocksdb_pinnableslice_t* rocksdb_transactiondb_get_pinned_cf(
     return v;
 }
 
-void rocksdb_transactiondb_flush(
+void rocksdb_transactiondb_flush_cf(
         rocksdb_transactiondb_t* db,
         const rocksdb_flushoptions_t* options,
+        rocksdb_column_family_handle_t* column_family,
         char** errptr) {
-    SaveError(errptr, db->rep->Flush(options->rep));
+    SaveError(errptr, db->rep->Flush(options->rep, column_family->rep));
+}
+
+void rocksdb_transactiondb_compact_range_cf_opt(rocksdb_transactiondb_t* db,
+                                  rocksdb_column_family_handle_t* column_family,
+                                  rocksdb_compactoptions_t* opt,
+                                  const char* start_key, size_t start_key_len,
+                                  const char* limit_key, size_t limit_key_len,
+                                  char** errptr) {
+    Slice a, b;
+    SaveError(errptr, db->rep->CompactRange(
+            opt->rep, column_family->rep,
+            // Pass nullptr Slice if corresponding "const char*" is nullptr
+            (start_key ? (a = Slice(start_key, start_key_len), &a) : nullptr),
+            (limit_key ? (b = Slice(limit_key, limit_key_len), &b) : nullptr)));
 }
 
 rocksdb_writeoptions_t* rocksdb_writeoptions_create_copy(rocksdb_writeoptions_t* options) {

rocksdb-sys/api/c.h

@@ -11,9 +11,14 @@ extern ROCKSDB_LIBRARY_API rocksdb_pinnableslice_t* rocksdb_transactiondb_get_pi
         rocksdb_column_family_handle_t* column_family, const char* key,
         size_t keylen, char** errptr);
 
+extern ROCKSDB_LIBRARY_API void rocksdb_transactiondb_flush_cf(
+        rocksdb_transactiondb_t* db, const rocksdb_flushoptions_t* options,
+        rocksdb_column_family_handle_t* column_family, char** errptr);
 
-extern ROCKSDB_LIBRARY_API void rocksdb_transactiondb_flush(
-        rocksdb_transactiondb_t* db, const rocksdb_flushoptions_t* options, char** errptr);
+extern ROCKSDB_LIBRARY_API void rocksdb_transactiondb_compact_range_cf_opt(
+        rocksdb_transactiondb_t* db, rocksdb_column_family_handle_t* column_family,
+        rocksdb_compactoptions_t* opt, const char* start_key, size_t start_key_len,
+        const char* limit_key, size_t limit_key_len, char** errptr);
 
 extern ROCKSDB_LIBRARY_API rocksdb_writeoptions_t* rocksdb_writeoptions_create_copy(
         rocksdb_writeoptions_t*);