experssion: implement MD5 builtin function (pingcap#2780)

* experssion: implement MD5 builtin function

Author: coocood

expression/builtin_encryption.go

@@ -14,6 +14,9 @@
 package expression
 
 import (
+	"crypto/md5"
+	"fmt"
+
 	"github.com/juju/errors"
 	"github.com/pingcap/tidb/context"
 	"github.com/pingcap/tidb/util/encrypt"
@@ -447,7 +450,23 @@ type builtinMD5Sig struct {
 
 // See https://dev.mysql.com/doc/refman/5.7/en/encryption-functions.html#function_md5
 func (b *builtinMD5Sig) eval(row []types.Datum) (d types.Datum, err error) {
-	return d, errFunctionNotExists.GenByArgs("MD5")
+	args, err := b.evalArgs(row)
+	if err != nil {
+		return types.Datum{}, errors.Trace(err)
+	}
+	// This function takes one argument.
+	arg := args[0]
+	if arg.IsNull() {
+		return
+	}
+	bin, err := arg.ToBytes()
+	if err != nil {
+		return d, errors.Trace(err)
+	}
+	sum := md5.Sum(bin)
+	hexStr := fmt.Sprintf("%x", sum)
+	d.SetString(hexStr)
+	return d, nil
 }
 
 type oldPasswordFunctionClass struct {

expression/builtin_encryption_test.go

@@ -35,6 +35,22 @@ var aesCases = []struct {
 	{"pingcap", "123", "996E0CA8688D7AD20819B90B273E01C6"},
 }
 
+type md5Test struct {
+	out interface{}
+	in  interface{}
+}
+
+var md5Cases = []md5Test{
+	{"d41d8cd98f00b204e9800998ecf8427e", ""},
+	{"0cc175b9c0f1b6a831c399e269772661", "a"},
+	{"187ef4436122d1cc2f40dc2b92f0eba0", "ab"},
+	{"900150983cd24fb0d6963f7d28e17f72", "abc"},
+	{"202cb962ac59075b964b07152d234b70", 123},
+	{"202cb962ac59075b964b07152d234b70", "123"},
+	{"46ddc40585caa8abc07c460b3485781e", 123.123},
+	{nil, nil},
+}
+
 func (s *testEvaluatorSuite) TestAESEncrypt(c *C) {
 	defer testleak.AfterTest(c)()
 	fc := funcs[ast.AesEncrypt]
@@ -88,3 +104,17 @@ func fromHex(str string) (d types.Datum) {
 	d.SetBytes(h)
 	return d
 }
+
+func (s *testEvaluatorSuite) TestMD5(c *C) {
+	defer testleak.AfterTest(c)()
+	fc := funcs[ast.MD5]
+	for _, test := range md5Cases {
+		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, DeepEquals, types.NewDatum(test.out))
+	}
+	s.testNullInput(c, ast.AesDecrypt)
+}

plan/typeinferer.go

@@ -396,6 +396,10 @@ func (v *typeInferrer) handleFuncCallExpr(x *ast.FuncCallExpr) {
 	case ast.AesEncrypt, ast.AesDecrypt:
 		tp = types.NewFieldType(mysql.TypeVarString)
 		chs = v.defaultCharset
+	case ast.MD5:
+		tp = types.NewFieldType(mysql.TypeVarString)
+		chs = v.defaultCharset
+		tp.Flen = 32
 	default:
 		tp = types.NewFieldType(mysql.TypeUnspecified)
 	}

plan/typeinferer_test.go

@@ -234,6 +234,7 @@ func (ts *testTypeInferrerSuite) TestInferType(c *C) {
 		{"timestamp('2003-12-31 12:00:00','12:00:00')", mysql.TypeDatetime, charset.CharsetBin},
 		{`aes_encrypt("pingcap", "fit2cloud@2014")`, mysql.TypeVarString, "utf8"},
 		{`aes_decrypt("pingcap", "fit2cloud@2014")`, mysql.TypeVarString, "utf8"},
+		{`md5(123)`, mysql.TypeVarString, "utf8"},
 	}
 	for _, ca := range cases {
 		ctx := testKit.Se.(context.Context)

util/types/datum.go

@@ -1333,6 +1333,20 @@ func (d *Datum) ToString() (string, error) {
 	}
 }
 
+// ToBytes gets the bytes representation of the datum.
+func (d *Datum) ToBytes() ([]byte, error) {
+	switch d.k {
+	case KindString, KindBytes:
+		return d.GetBytes(), nil
+	default:
+		str, err := d.ToString()
+		if err != nil {
+			return nil, errors.Trace(err)
+		}
+		return []byte(str), nil
+	}
+}
+
 func invalidConv(d *Datum, tp byte) (Datum, error) {
 	return Datum{}, errors.Errorf("cannot convert %v to type %s", d, TypeStr(tp))
 }

util/types/datum_test.go

@@ -300,3 +300,22 @@ func (ts *testDatumSuite) TestBitOps(c *C) {
 		c.Assert(result.GetUint64(), Equals, ca.result.GetUint64())
 	}
 }
+
+func (ts *testDatumSuite) TestToBytes(c *C) {
+	testCases := []struct {
+		a   Datum
+		out []byte
+	}{
+		{NewIntDatum(1), []byte("1")},
+		{NewDecimalDatum(NewDecFromInt(1)), []byte("1")},
+		{NewFloat64Datum(1.23), []byte("1.23")},
+		{NewStringDatum("abc"), []byte("abc")},
+	}
+	sc := new(variable.StatementContext)
+	sc.IgnoreTruncate = true
+	for _, ca := range testCases {
+		bin, err := ca.a.ToBytes()
+		c.Assert(err, IsNil)
+		c.Assert(bin, BytesEquals, ca.out)
+	}
+}