buildinFunc: add a strcmp function

Add a function needed in #310 .
pingcap · Feb 29, 2016 · 431879e · 431879e
1 parent 73d6ce5
commit 431879e
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Showing 8 changed files with 5,721 additions and 5,596 deletions.
diff --git a/expression/builtin/builtin.go b/expression/builtin/builtin.go
@@ -107,6 +107,7 @@ var Funcs = map[string]Func{
 	"repeat":    {builtinRepeat, 2, 2, true, false},
 	"replace":   {builtinReplace, 3, 3, true, false},
 	"upper":     {builtinUpper, 1, 1, true, false},
+	"strcmp":    {builtinStrcmp, 2, 2, true, false},
 
 	// information functions
 	"current_user":  {builtinCurrentUser, 0, 0, false, false},

diff --git a/expression/builtin/string.go b/expression/builtin/string.go
@@ -147,6 +147,23 @@ func builtinUpper(args []interface{}, ctx map[interface{}]interface{}) (interfac
 	}
 }
 
+// See: https://dev.mysql.com/doc/refman/5.7/en/string-comparison-functions.html
+func builtinStrcmp(args []interface{}, ctx map[interface{}]interface{}) (interface{}, error) {
+	if args[0] == nil || args[1] == nil {
+		return nil, nil
+	}
+	left, err := types.ToString(args[0])
+	if err != nil {
+		return nil, errors.Trace(err)
+	}
+	right, err := types.ToString(args[1])
+	if err != nil {
+		return nil, errors.Trace(err)
+	}
+	res := types.CompareString(left, right)
+	return res, nil
+}
+
 // See: https://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_replace
 func builtinReplace(args []interface{}, ctx map[interface{}]interface{}) (interface{}, error) {
 	for _, arg := range args {

diff --git a/expression/builtin/string_test.go b/expression/builtin/string_test.go
@@ -167,6 +167,33 @@ func (s *testBuiltinSuite) TestLowerAndUpper(c *C) {
 	}
 }
 
+func (s *testBuiltinSuite) TestStrcmp(c *C) {
+	tbl := []struct {
+		Input  []interface{}
+		Expect interface{}
+	}{
+		{[]interface{}{"1", "2"}, -1},
+		{[]interface{}{"2", "1"}, 1},
+		{[]interface{}{"123", "2"}, -1},
+		{[]interface{}{"1", "213"}, -1},
+		{[]interface{}{"123", "123"}, 0},
+		{[]interface{}{"", "123"}, -1},
+		{[]interface{}{"123", ""}, 1},
+		{[]interface{}{"", ""}, 0},
+		{[]interface{}{nil, "123"}, nil},
+		{[]interface{}{"123", nil}, nil},
+		{[]interface{}{nil, nil}, nil},
+		{[]interface{}{"", nil}, nil},
+		{[]interface{}{nil, ""}, nil},
+	}
+
+	for _, t := range tbl {
+		v, err := builtinStrcmp(t.Input, nil)
+		c.Assert(err, IsNil)
+		c.Assert(v, Equals, t.Expect)
+	}
+}
+
 func (s *testBuiltinSuite) TestReplace(c *C) {
 	tbl := []struct {
 		Input  []interface{}

diff --git a/optimizer/typeinferer.go b/optimizer/typeinferer.go
@@ -276,6 +276,8 @@ func (v *typeInferrer) handleFuncCallExpr(x *ast.FuncCallExpr) {
 		"concat", "concat_ws", "left", "lower", "repeat", "replace", "upper":
 		tp = types.NewFieldType(mysql.TypeVarString)
 		chs = v.defaultCharset
+	case "strcmp":
+		tp = types.NewFieldType(mysql.TypeLonglong)
 	case "connection_id":
 		tp = types.NewFieldType(mysql.TypeLonglong)
 		tp.Flag |= mysql.UnsignedFlag