kv/KeyValueDB: add a new interface for single delete.

This is useful for log-insert-merge tree based key value store, such as
RocksDB, to avoid more LSM compactions for already deleted key value pairs.

Signed-off-by: Jianjian Huo <jianjian.huo@ssi.samsung.com>

diff --git a/src/kv/KeyValueDB.h b/src/kv/KeyValueDB.h
index aef93a3eb3c422f155d8bc88004b9da83e70a22d..92296f534dcba7ddef5a2268d86e76d44403f2e4 100644 (file)
--- a/src/kv/KeyValueDB.h
+++ b/src/kv/KeyValueDB.h
@@ -88,6 +88,16 @@ public:
       const std::string &k           ///< [in] Key to remove
       ) = 0;
 
+    /// Remove Single Key which exists and was not overwritten.
+    /// This API is only related to performance optimization, and should only be 
+    /// re-implemented by log-insert-merge tree based keyvalue stores(such as RocksDB). 
+    /// If a key is overwritten (by calling set multiple times), then the result
+    /// of calling rm_single_key on this key is undefined.
+    virtual void rm_single_key(
+      const std::string &prefix,   ///< [in] Prefix to search for
+      const std::string &k           ///< [in] Key to remove
+      ) { return rmkey(prefix, k);}
+
     /// Removes keys beginning with prefix
     virtual void rmkeys_by_prefix(
       const std::string &prefix ///< [in] Prefix by which to remove keys