Merge pull request denisenkom#635 from nussjustin/optimize-in

Optimize In performance by reducing allocations for common queries

bind.go

@@ -151,7 +151,14 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {
 	var flatArgsCount int
 	var anySlices bool
 
-	meta := make([]argMeta, len(args))
+	var stackMeta [32]argMeta
+
+	var meta []argMeta
+	if len(args) <= len(stackMeta) {
+		meta = stackMeta[:len(args)]
+	} else {
+		meta = make([]argMeta, len(args))
+	}
 
 	for i, arg := range args {
 		if a, ok := arg.(driver.Valuer); ok {
@@ -185,7 +192,9 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {
 	}
 
 	newArgs := make([]interface{}, 0, flatArgsCount)
-	buf := make([]byte, 0, len(query)+len(", ?")*flatArgsCount)
+
+	var buf strings.Builder
+	buf.Grow(len(query) + len(", ?")*flatArgsCount)
 
 	var arg, offset int
 
@@ -211,10 +220,10 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {
 		}
 
 		// write everything up to and including our ? character
-		buf = append(buf, query[:offset+i+1]...)
+		buf.WriteString(query[:offset+i+1])
 
 		for si := 1; si < argMeta.length; si++ {
-			buf = append(buf, ", ?"...)
+			buf.WriteString(", ?")
 		}
 
 		newArgs = appendReflectSlice(newArgs, argMeta.v, argMeta.length)
@@ -225,13 +234,13 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {
 		offset = 0
 	}
 
-	buf = append(buf, query...)
+	buf.WriteString(query)
 
 	if arg < len(meta) {
 		return "", nil, errors.New("number of bindVars less than number arguments")
 	}
 
-	return string(buf), newArgs, nil
+	return buf.String(), newArgs, nil
 }
 
 func appendReflectSlice(args []interface{}, v reflect.Value, vlen int) []interface{} {
@@ -240,11 +249,11 @@ func appendReflectSlice(args []interface{}, v reflect.Value, vlen int) []interfa
 		args = append(args, val...)
 	case []int:
 		for i := range val {
-			args = append(args, val[i])
+			args = append(args, &val[i])
 		}
 	case []string:
 		for i := range val {
-			args = append(args, val[i])
+			args = append(args, &val[i])
 		}
 	default:
 		for si := 0; si < vlen; si++ {