Use strings.Builder to avoid an allocation for In

nussjustin · nussjustin · commit 84af78b8c7b6 · 2020-07-18T11:38:07.000+02:00
diff --git a/bind.go b/bind.go
@@ -169,7 +169,9 @@ 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
 
@@ -195,10 +197,10 @@ 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)
@@ -209,13 +211,13 @@ 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{} {

Original file line number	Diff line number	Diff line change
`@@ -169,7 +169,9 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {`
`169`	`169`	`}`
`170`	`170`
`171`	`171`	`newArgs := make([]interface{}, 0, flatArgsCount)`
`172`		`- buf := make([]byte, 0, len(query)+len(", ?")*flatArgsCount)`
	`172`	`+`
	`173`	`+ var buf strings.Builder`
	`174`	`+ buf.Grow(len(query) + len(", ?")*flatArgsCount)`
`173`	`175`
`174`	`176`	`var arg, offset int`
`175`	`177`
`@@ -195,10 +197,10 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {`
`195`	`197`	`}`
`196`	`198`
`197`	`199`	`// write everything up to and including our ? character`
`198`		`- buf = append(buf, query[:offset+i+1]...)`
	`200`	`+ buf.WriteString(query[:offset+i+1])`
`199`	`201`
`200`	`202`	`for si := 1; si < argMeta.length; si++ {`
`201`		`- buf = append(buf, ", ?"...)`
	`203`	`+ buf.WriteString(", ?")`
`202`	`204`	`}`
`203`	`205`
`204`	`206`	`newArgs = appendReflectSlice(newArgs, argMeta.v, argMeta.length)`
`@@ -209,13 +211,13 @@ func In(query string, args ...interface{}) (string, []interface{}, error) {`
`209`	`211`	`offset = 0`
`210`	`212`	`}`
`211`	`213`
`212`		`- buf = append(buf, query...)`
	`214`	`+ buf.WriteString(query)`
`213`	`215`
`214`	`216`	`if arg < len(meta) {`
`215`	`217`	`return "", nil, errors.New("number of bindVars less than number arguments")`
`216`	`218`	`}`
`217`	`219`
`218`		`- return string(buf), newArgs, nil`
	`220`	`+ return buf.String(), newArgs, nil`
`219`	`221`	`}`
`220`	`222`
`221`	`223`	`func appendReflectSlice(args []interface{}, v reflect.Value, vlen int) []interface{} {`