expression: implement vectorized evaluation for `builtinGreatestStrin…

…gSig` (pingcap#12778)
k-ye · Oct 21, 2019 · 6182871 · 6182871
1 parent 691199b
commit 6182871
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Showing 2 changed files with 47 additions and 2 deletions.
diff --git a/expression/builtin_compare_vec.go b/expression/builtin_compare_vec.go
@@ -902,11 +902,54 @@ func (b *builtinNullEQDurationSig) vecEvalInt(input *chunk.Chunk, result *chunk.
 }
 
 func (b *builtinGreatestStringSig) vectorized() bool {
-	return false
+	return true
 }
 
 func (b *builtinGreatestStringSig) vecEvalString(input *chunk.Chunk, result *chunk.Column) error {
-	return errors.Errorf("not implemented")
+	if err := b.args[0].VecEvalString(b.ctx, input, result); err != nil {
+		return err
+	}
+
+	n := input.NumRows()
+	buf1, err := b.bufAllocator.get(types.ETString, n)
+	if err != nil {
+		return err
+	}
+	defer b.bufAllocator.put(buf1)
+	buf2, err := b.bufAllocator.get(types.ETString, n)
+	if err != nil {
+		return err
+	}
+	defer b.bufAllocator.put(buf2)
+
+	src := result
+	arg := buf1
+	dst := buf2
+	for j := 1; j < len(b.args); j++ {
+		if err := b.args[j].VecEvalString(b.ctx, input, arg); err != nil {
+			return err
+		}
+		for i := 0; i < n; i++ {
+			if src.IsNull(i) || arg.IsNull(i) {
+				dst.AppendNull()
+				continue
+			}
+			srcStr := src.GetString(i)
+			argStr := arg.GetString(i)
+			if types.CompareString(srcStr, argStr) > 0 {
+				dst.AppendString(srcStr)
+			} else {
+				dst.AppendString(argStr)
+			}
+		}
+		src, dst = dst, src
+		arg.ReserveString(n)
+		dst.ReserveString(n)
+	}
+	if len(b.args)%2 == 0 {
+		src.CopyConstruct(result)
+	}
+	return nil
 }
 
 func (b *builtinLTDurationSig) vectorized() bool {

diff --git a/expression/builtin_compare_vec_test.go b/expression/builtin_compare_vec_test.go
@@ -43,6 +43,8 @@ var vecBuiltinCompareCases = map[string][]vecExprBenchCase{
 		{retEvalType: types.ETDecimal, childrenTypes: []types.EvalType{types.ETDecimal, types.ETDecimal, types.ETDecimal}},
 		{retEvalType: types.ETInt, childrenTypes: []types.EvalType{types.ETInt, types.ETInt, types.ETInt}},
 		{retEvalType: types.ETReal, childrenTypes: []types.EvalType{types.ETReal, types.ETReal, types.ETReal}},
+		{retEvalType: types.ETString, childrenTypes: []types.EvalType{types.ETString, types.ETString}},
+		{retEvalType: types.ETString, childrenTypes: []types.EvalType{types.ETString, types.ETString, types.ETString}},
 	},
 	ast.Least: {
 		{retEvalType: types.ETDecimal, childrenTypes: []types.EvalType{types.ETDecimal, types.ETDecimal, types.ETDecimal}},