optimize get w/ zero-copy ref handle

Signed-off-by: Jason Volk <jason@zemos.net>

src/database/handle.rs

@@ -0,0 +1,25 @@
+use std::ops::Deref;
+
+use rocksdb::DBPinnableSlice;
+
+pub struct Handle<'a> {
+	val: DBPinnableSlice<'a>,
+}
+
+impl<'a> From<DBPinnableSlice<'a>> for Handle<'a> {
+	fn from(val: DBPinnableSlice<'a>) -> Self {
+		Self {
+			val,
+		}
+	}
+}
+
+impl Deref for Handle<'_> {
+	type Target = [u8];
+
+	fn deref(&self) -> &Self::Target { &self.val }
+}
+
+impl AsRef<[u8]> for Handle<'_> {
+	fn as_ref(&self) -> &[u8] { &self.val }
+}

src/database/map.rs

@@ -5,7 +5,7 @@ use rocksdb::{
 	AsColumnFamilyRef, ColumnFamily, Direction, IteratorMode, ReadOptions, WriteBatchWithTransaction, WriteOptions,
 };
 
-use crate::{or_else, result, watchers::Watchers, Engine, Iter};
+use crate::{or_else, result, watchers::Watchers, Engine, Handle, Iter};
 
 pub struct Map {
 	name: String,
@@ -32,11 +32,11 @@ impl Map {
 		}))
 	}
 
-	pub fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>> {
+	pub fn get(&self, key: &[u8]) -> Result<Option<Handle<'_>>> {
 		let read_options = &self.read_options;
-		let res = self.db.db.get_cf_opt(&self.cf(), key, read_options);
+		let res = self.db.db.get_pinned_cf_opt(&self.cf(), key, read_options);
 
-		result(res)
+		Ok(result(res)?.map(Handle::from))
 	}
 
 	pub fn multi_get(&self, keys: &[&[u8]]) -> Result<Vec<Option<Vec<u8>>>> {

src/database/mod.rs

@@ -1,6 +1,7 @@
 mod cork;
 mod database;
 mod engine;
+mod handle;
 mod iter;
 mod map;
 pub mod maps;
@@ -13,6 +14,7 @@ extern crate rust_rocksdb as rocksdb;
 
 pub use database::Database;
 pub(crate) use engine::Engine;
+pub use handle::Handle;
 pub use iter::Iter;
 pub use map::Map;
 pub(crate) use util::{or_else, result};