fix insert sort (#42)

builder.go

@@ -245,6 +245,23 @@ func (b *Builder) Or(cond Cond) *Builder {
 	return b
 }
 
+type insertColsSorter struct {
+	cols []string
+	vals []interface{}
+}
+
+func (s insertColsSorter) Len() int {
+	return len(s.cols)
+}
+func (s insertColsSorter) Swap(i, j int) {
+	s.cols[i], s.cols[j] = s.cols[j], s.cols[i]
+	s.vals[i], s.vals[j] = s.vals[j], s.vals[i]
+}
+
+func (s insertColsSorter) Less(i, j int) bool {
+	return s.cols[i] < s.cols[j]
+}
+
 // Insert sets insert SQL
 func (b *Builder) Insert(eq ...interface{}) *Builder {
 	if len(eq) > 0 {
@@ -275,10 +292,10 @@ func (b *Builder) Insert(eq ...interface{}) *Builder {
 	}
 
 	if len(b.insertCols) == len(b.insertVals) {
-		sort.Slice(b.insertVals, func(i, j int) bool {
-			return b.insertCols[i] < b.insertCols[j]
+		sort.Sort(insertColsSorter{
+			cols: b.insertCols,
+			vals: b.insertVals,
 		})
-		sort.Strings(b.insertCols)
 	}
 	b.optype = insertType
 	return b

builder_insert_test.go

@@ -15,6 +15,10 @@ func TestBuilderInsert(t *testing.T) {
 	assert.NoError(t, err)
 	assert.EqualValues(t, "INSERT INTO table1 (c,d) Values (1,2)", sql)
 
+	sql, err = Insert(Eq{"e": 3}, Eq{"c": 1}, Eq{"d": 2}).Into("table1").ToBoundSQL()
+	assert.NoError(t, err)
+	assert.EqualValues(t, "INSERT INTO table1 (c,d,e) Values (1,2,3)", sql)
+
 	sql, err = Insert(Eq{"c": 1, "d": Expr("SELECT b FROM t WHERE d=? LIMIT 1", 2)}).Into("table1").ToBoundSQL()
 	assert.NoError(t, err)
 	assert.EqualValues(t, "INSERT INTO table1 (c,d) Values (1,(SELECT b FROM t WHERE d=2 LIMIT 1))", sql)