Add Db::commit_changes_shared (#247)

* Add `commit_changes_shared` that passes values as `Arc`s.

* Cleanup + changelog.

* Update doc.

Author: igankevich

CHANGELOG.md

@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog].
 
 ## [Unreleased]
 
+- Add `Db::commit_changes_shared` that passes values as `Arc<Vec<u8>>`, potentially without an extra copy.
+
 ## [v0.5.2] - 2024-05-28
 
 - Compilation support for riscv64

src/btree/mod.rs

@@ -383,7 +383,10 @@ pub mod commit_overlay {
 			BTreeChangeSet { col, changes: Default::default() }
 		}
 
-		pub fn push(&mut self, change: Operation<Value, Value>) -> Result<()> {
+		pub fn push<K: Into<RcKey>, V: Into<RcValue>>(
+			&mut self,
+			change: Operation<K, V>,
+		) -> Result<()> {
 			// No key hashing
 			self.changes.push(match change {
 				Operation::Set(k, v) => Operation::Set(k.into(), v.into()),

src/column.rs

@@ -1129,9 +1129,9 @@ impl HashColumn {
 	}
 
 	/// returns value for the root node and vector of NodeChange for nodes.
-	pub fn claim_tree_values(
+	pub fn claim_tree_values<K, V>(
 		&self,
-		change: &Operation<Value, Value>,
+		change: &Operation<K, V>,
 	) -> Result<(Vec<u8>, Vec<NodeChange>)> {
 		match change {
 			Operation::InsertTree(_key, node) => {

src/db.rs

@@ -103,6 +103,12 @@ impl From<Value> for RcValue {
 	}
 }
 
+impl From<Arc<Value>> for RcValue {
+	fn from(value: Arc<Value>) -> Self {
+		Self(value)
+	}
+}
+
 #[cfg(test)]
 impl<const N: usize> TryFrom<RcValue> for [u8; N] {
 	type Error = <[u8; N] as TryFrom<Vec<u8>>>::Error;
@@ -495,9 +501,10 @@ impl DbInner {
 		}))
 	}
 
-	fn commit_changes<I>(&self, tx: I) -> Result<()>
+	fn commit_changes<I, V>(&self, tx: I) -> Result<()>
 	where
-		I: IntoIterator<Item = (ColId, Operation<Vec<u8>, Vec<u8>>)>,
+		I: IntoIterator<Item = (ColId, Operation<Vec<u8>, V>)>,
+		V: Into<RcValue>,
 	{
 		let mut commit: CommitChangeSet = Default::default();
 		for (col, change) in tx.into_iter() {
@@ -564,7 +571,8 @@ impl DbInner {
 							},
 							Operation::ReferenceTree(..) => {
 								if !self.options.columns[col as usize].append_only {
-									let root_operation = Operation::Reference(change.key());
+									let root_operation =
+										Operation::<&_, V>::Reference(change.key());
 									commit
 										.indexed
 										.entry(col)
@@ -1562,6 +1570,16 @@ impl Db {
 		self.inner.commit_changes(tx)
 	}
 
+	/// Commit a set of changes to the database.
+	///
+	/// This method passes values as `Arc<Vec<u8>>` potentially eliminating an extra copy.
+	pub fn commit_changes_shared<I>(&self, tx: I) -> Result<()>
+	where
+		I: IntoIterator<Item = (ColId, Operation<Vec<u8>, Arc<Vec<u8>>>)>,
+	{
+		self.inner.commit_changes(tx)
+	}
+
 	pub(crate) fn commit_raw(&self, commit: CommitChangeSet) -> Result<()> {
 		self.inner.commit_raw(commit)
 	}
@@ -2091,9 +2109,9 @@ impl IndexedChangeSet {
 		}
 	}
 
-	fn push<K: AsRef<[u8]>>(
+	fn push<K: AsRef<[u8]>, V: Into<RcValue>>(
 		&mut self,
-		change: Operation<K, Vec<u8>>,
+		change: Operation<K, V>,
 		options: &Options,
 		db_version: u32,
 	) -> Result<()> {