expression: implement vectorized evaluation for `builtinLeastDecimalS…

…ig` (#12150)

expression/builtin_compare_vec.go

@@ -55,3 +55,38 @@ func (b *builtinGreatestDecimalSig) vecEvalDecimal(input *chunk.Chunk, result *c
 func (b *builtinGreatestDecimalSig) vectorized() bool {
 	return true
 }
+
+func (b *builtinLeastDecimalSig) vecEvalDecimal(input *chunk.Chunk, result *chunk.Column) error {
+	n := input.NumRows()
+	buf, err := b.bufAllocator.get(types.ETDecimal, n)
+	if err != nil {
+		return err
+	}
+	defer b.bufAllocator.put(buf)
+	if err := b.args[0].VecEvalDecimal(b.ctx, input, result); err != nil {
+		return err
+	}
+
+	d64s := result.Decimals()
+	for j := 1; j < len(b.args); j++ {
+		if err := b.args[j].VecEvalDecimal(b.ctx, input, buf); err != nil {
+			return err
+		}
+
+		result.MergeNulls(buf)
+		for i := 0; i < n; i++ {
+			if result.IsNull(i) {
+				continue
+			}
+			v := buf.GetDecimal(i)
+			if v.Compare(&d64s[i]) < 0 {
+				d64s[i] = *v
+			}
+		}
+	}
+	return nil
+}
+
+func (b *builtinLeastDecimalSig) vectorized() bool {
+	return true
+}

expression/builtin_compare_vec_test.go

@@ -25,6 +25,9 @@ var vecBuiltinCompareCases = map[string][]vecExprBenchCase{
 	ast.Greatest: {
 		{types.ETDecimal, []types.EvalType{types.ETDecimal, types.ETDecimal, types.ETDecimal}, nil},
 	},
+	ast.Least: {
+		{types.ETDecimal, []types.EvalType{types.ETDecimal, types.ETDecimal, types.ETDecimal}, nil},
+	},
 }
 
 func (s *testEvaluatorSuite) TestVectorizedBuiltinCompareEvalOneVec(c *C) {