expression: implement vectorized evaluation for builtinLowerStr (#1…

…2013)

expression/bench_test.go

@@ -242,7 +242,7 @@ func (g *defaultGener) gen() interface{} {
 		}
 		return *j
 	case types.ETString:
-		return fmt.Sprintf("%v", rand.Int())
+		return randString()
 	}
 	return nil
 }
@@ -327,6 +327,22 @@ func fillColumn(eType types.EvalType, chk *chunk.Chunk, colIdx int, testCase vec
 	}
 }
 
+func randString() string {
+	n := 10 + rand.Intn(10)
+	buf := make([]byte, n)
+	for i := range buf {
+		x := rand.Intn(62)
+		if x < 10 {
+			buf[i] = byte('0' + x)
+		} else if x-10 < 26 {
+			buf[i] = byte('a' + x - 10)
+		} else {
+			buf[i] = byte('A' + x - 10 - 26)
+		}
+	}
+	return string(buf)
+}
+
 func eType2FieldType(eType types.EvalType) *types.FieldType {
 	switch eType {
 	case types.ETInt:

expression/builtin_string_vec.go

@@ -1,13 +1,56 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package expression
 
 import (
 	"math"
 	"strings"
+	"unicode/utf8"
 
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
 )
 
+func (b *builtinLowerSig) vecEvalString(input *chunk.Chunk, result *chunk.Column) error {
+	if err := b.args[0].VecEvalString(b.ctx, input, result); err != nil {
+		return err
+	}
+	if types.IsBinaryStr(b.args[0].GetType()) {
+		return nil
+	}
+
+Loop:
+	for i := 0; i < input.NumRows(); i++ {
+		str := result.GetBytes(i)
+		for _, c := range str {
+			if c >= utf8.RuneSelf {
+				continue Loop
+			}
+		}
+		for i := range str {
+			if str[i] >= 'A' && str[i] <= 'Z' {
+				str[i] += 'a' - 'A'
+			}
+		}
+	}
+	return nil
+}
+
+func (b *builtinLowerSig) vectorized() bool {
+	return true
+}
+
 func (b *builtinRepeatSig) vecEvalString(input *chunk.Chunk, result *chunk.Column) error {
 	n := input.NumRows()
 	buf, err := b.bufAllocator.get(types.ETString, n)

expression/builtin_string_vec_test.go

@@ -25,6 +25,9 @@ var vecBuiltinStringCases = map[string][]vecExprBenchCase{
 	ast.Repeat: {
 		{types.ETString, []types.EvalType{types.ETString, types.ETInt}, []dataGenerator{&randLenStrGener{10, 20}, &rangeInt64Gener{-10, 10}}},
 	},
+	ast.Lower: {
+		{types.ETString, []types.EvalType{types.ETString}, nil},
+	},
 }
 
 func (s *testEvaluatorSuite) TestVectorizedBuiltinStringEvalOneVec(c *C) {