added valNP (no pointer value) argument to Txn obj tp increase perfor…

…mance (see GetFast for more details)

mdbx/txn.go

@@ -57,10 +57,11 @@ const (
 //
 // See MDBX_txn.
 type Txn struct {
-	env  *Env
-	_txn *C.MDBX_txn
-	key  *C.MDBX_val
-	val  *C.MDBX_val
+	env   *Env
+	_txn  *C.MDBX_txn
+	key   *C.MDBX_val
+	valNP C.MDBX_val
+	val   *C.MDBX_val
 
 	errLogf func(format string, v ...interface{})
 
@@ -605,6 +606,26 @@ func (txn *Txn) Get(dbi DBI, key []byte) ([]byte, error) {
 	return b, nil
 }
 
+func (txn *Txn) GetFast(dbi DBI, key []byte) ([]byte, error) {
+	var k *C.char
+	if len(key) > 0 {
+		k = (*C.char)(unsafe.Pointer(&key[0]))
+	}
+	ret := C.mdbxgo_get(
+		txn._txn, C.MDBX_dbi(dbi),
+		k, C.size_t(len(key)),
+		&txn.valNP,
+	)
+	err := operrno("mdbx_get", ret)
+	if err != nil {
+		txn.valNP = C.MDBX_val{}
+		return nil, err
+	}
+	b := castToBytes(&txn.valNP)
+	txn.valNP = C.MDBX_val{}
+	return b, nil
+}
+
 // Put stores an item in database dbi.
 //
 // See mdbx_put.

mdbx/txn_test.go

@@ -1299,6 +1299,42 @@ func BenchmarkTxn_Get(b *testing.B) {
 	}
 }
 
+func BenchmarkTxn_GetFast(b *testing.B) {
+	env, _ := setup(b)
+
+	var db DBI
+	k := make([]byte, 8)
+	binary.BigEndian.PutUint64(k, uint64(1))
+
+	if err := env.Update(func(txn *Txn) (err error) {
+		db, err = txn.OpenRoot(0)
+		if err != nil {
+			return err
+		}
+		err = txn.Put(db, k, k, 0)
+		if err != nil {
+			return err
+		}
+		return nil
+	}); err != nil {
+		b.Errorf("dbi: %v", err)
+		return
+	}
+
+	if err := env.View(func(txn *Txn) (err error) {
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			_, err := txn.GetFast(db, k)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	}); err != nil {
+		b.Errorf("put: %v", err)
+	}
+}
+
 func TestTxnEnvWarmup(t *testing.T) {
 	env, _ := setup(t)