expression:implement function password. (#3275)

expression/builtin_encryption.go

@@ -28,6 +28,7 @@ import (
 	"github.com/juju/errors"
 	"github.com/pingcap/tidb/context"
 	"github.com/pingcap/tidb/mysql"
+	"github.com/pingcap/tidb/util"
 	"github.com/pingcap/tidb/util/encrypt"
 	"github.com/pingcap/tidb/util/types"
 )
@@ -395,7 +396,29 @@ type builtinPasswordSig struct {
 // eval evals a builtinPasswordSig.
 // See https://dev.mysql.com/doc/refman/5.7/en/encryption-functions.html#function_password
 func (b *builtinPasswordSig) eval(row []types.Datum) (d types.Datum, err error) {
-	return d, errFunctionNotExists.GenByArgs("PASSWORD")
+	args, err := b.evalArgs(row)
+	if err != nil {
+		return d, errors.Trace(err)
+	}
+
+	arg := args[0]
+	if arg.IsNull() {
+		d.SetString("")
+		return d, nil
+	}
+
+	pass, err := args[0].ToString()
+	if err != nil {
+		return d, errors.Trace(err)
+	}
+
+	if len(pass) == 0 {
+		d.SetString("")
+		return d, nil
+	}
+
+	d.SetString(util.EncodePassword(pass))
+	return d, nil
 }
 
 type randomBytesFunctionClass struct {

expression/builtin_encryption_test.go

@@ -300,3 +300,24 @@ func (s *testEvaluatorSuite) TestUncompressLength(c *C) {
 		c.Assert(out.GetInt64(), Equals, test.expect)
 	}
 }
+func (s *testEvaluatorSuite) TestPassword(c *C) {
+	defer testleak.AfterTest(c)()
+	tests := []struct {
+		in     interface{}
+		expect interface{}
+	}{
+		{nil, string("")},
+		{string(""), string("")},
+		{string("abc"), string("*0D3CED9BEC10A777AEC23CCC353A8C08A633045E")},
+	}
+
+	fc := funcs[ast.PasswordFunc]
+	for _, test := range tests {
+		arg := types.NewDatum(test.in)
+		f, err := fc.getFunction(datumsToConstants([]types.Datum{arg}), s.ctx)
+		c.Assert(err, IsNil)
+		out, err := f.eval(nil)
+		c.Assert(err, IsNil)
+		c.Assert(out.GetString(), Equals, test.expect)
+	}
+}

expression/typeinferer.go

@@ -431,6 +431,9 @@ func (v *typeInferrer) handleFuncCallExpr(x *ast.FuncCallExpr) {
 		tp = x.Args[0].GetType()
 	case ast.RowFunc:
 		tp = x.Args[0].GetType()
+	case ast.PasswordFunc:
+		tp = types.NewFieldType(mysql.TypeVarString)
+		chs = v.defaultCharset
 	default:
 		tp = types.NewFieldType(mysql.TypeUnspecified)
 	}

expression/typeinferer_test.go

@@ -329,6 +329,7 @@ func (ts *testTypeInferrerSuite) TestInferType(c *C) {
 		{`inet6_ntoa(inet6_aton('FE80::AAAA:0000:00C2:0002'))`, mysql.TypeVarString,
 			charset.CharsetUTF8, 0},
 		{`is_ipv4_mapped(c_varbinary)`, mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag},
+		{`password("abc")`, mysql.TypeVarString, charset.CharsetUTF8, 0},
 		{`json_type('3')`, mysql.TypeVarString, charset.CharsetUTF8, 0},
 	}
 	for _, tt := range tests {