executor: pre-allocate memory for slices (pingcap#5071)

enson16855 · Nov 13, 2017 · 6f8db31 · 6f8db31
1 parent cedc35c
commit 6f8db31
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/executor/builder.go b/executor/builder.go
@@ -545,7 +545,8 @@ func (b *executorBuilder) buildMergeJoin(v *plan.PhysicalMergeJoin) Executor {
 }
 
 func (b *executorBuilder) buildHashJoin(v *plan.PhysicalHashJoin) Executor {
-	var leftHashKey, rightHashKey []*expression.Column
+	leftHashKey := make([]*expression.Column, 0, len(v.EqualConditions))
+	rightHashKey := make([]*expression.Column, 0, len(v.EqualConditions))
 	for _, eqCond := range v.EqualConditions {
 		ln, _ := eqCond.GetArgs()[0].(*expression.Column)
 		rn, _ := eqCond.GetArgs()[1].(*expression.Column)
@@ -584,7 +585,8 @@ func (b *executorBuilder) buildHashJoin(v *plan.PhysicalHashJoin) Executor {
 }
 
 func (b *executorBuilder) buildSemiJoin(v *plan.PhysicalHashSemiJoin) *HashSemiJoinExec {
-	var leftHashKey, rightHashKey []*expression.Column
+	leftHashKey := make([]*expression.Column, 0, len(v.EqualConditions))
+	rightHashKey := make([]*expression.Column, 0, len(v.EqualConditions))
 	for _, eqCond := range v.EqualConditions {
 		ln, _ := eqCond.GetArgs()[0].(*expression.Column)
 		rn, _ := eqCond.GetArgs()[1].(*expression.Column)