diff --git a/bench_test.go b/bench_test.go
new file mode 100644
index 0000000000..1c29d54bc7
--- /dev/null
+++ b/bench_test.go
@@ -0,0 +1,30 @@
+package tidb
+
+import (
+	"testing"
+
+	"github.com/ngaut/log"
+)
+
+func BenchmarkBasic(b *testing.B) {
+	store, err := NewStore("memory://bench")
+	if err != nil {
+		b.Fatal(err)
+	}
+	log.SetLevel(log.LOG_LEVEL_ERROR)
+	se, err := CreateSession(store)
+	if err != nil {
+		b.Fatal(err)
+	}
+	for i := 0; i < b.N; i++ {
+		rs, err := se.Execute("select 1")
+		if err != nil {
+			b.Fatal(err)
+		}
+		row, err := rs[0].Next()
+		if err != nil || row == nil {
+			b.Fatal(err)
+		}
+		rs[0].Close()
+	}
+}
diff --git a/kv/compactor.go b/kv/compactor.go
index 47ebd7a619..1687225e82 100644
--- a/kv/compactor.go
+++ b/kv/compactor.go
@@ -36,5 +36,5 @@ type Compactor interface {
 	// OnDelete is the hook point on Txn.Delete.
 	OnDelete(k Key)
 	// Compact is the function removes the given key.
-	Compact(ctx interface{}, k Key) error
+	Compact(k Key) error
 }
diff --git a/session.go b/session.go
index 64c7e57ca9..5906ef7abd 100644
--- a/session.go
+++ b/session.go
@@ -355,6 +355,7 @@ func (s *session) isAutocommit(ctx context.Context) bool {
 			log.Errorf("Get global sys var error: %v", err)
 			return false
 		}
+		variable.GetSessionVars(ctx).Systems["autocommit"] = autocommit
 		ok = true
 	}
 	if ok && (autocommit == "ON" || autocommit == "on" || autocommit == "1") {
diff --git a/store/localstore/compactor.go b/store/localstore/compactor.go
index 0d02b0bf0a..3fdea00dfb 100644
--- a/store/localstore/compactor.go
+++ b/store/localstore/compactor.go
@@ -125,7 +125,7 @@ func (gc *localstoreCompactor) checkExpiredKeysWorker() {
 			gc.mu.Unlock()
 			log.Info("GC trigger")
 			for k := range m {
-				err := gc.Compact(nil, []byte(k))
+				err := gc.Compact([]byte(k))
 				if err != nil {
 					log.Error(err)
 				}
@@ -159,7 +159,7 @@ func (gc *localstoreCompactor) filterExpiredKeys(keys []kv.EncodedKey) []kv.Enco
 	return ret
 }
 
-func (gc *localstoreCompactor) Compact(ctx interface{}, k kv.Key) error {
+func (gc *localstoreCompactor) Compact(k kv.Key) error {
 	keys, err := gc.getAllVersions(k)
 	if err != nil {
 		return errors.Trace(err)