Preserve lateralness when replanning join.

Author: nicktobey

sql/analyzer/unnest_exists_subqueries.go

@@ -193,7 +193,11 @@ func unnestExistSubqueries(ctx *sql.Context, scope *plan.Scope, a *Analyzer, fil
 				ret = plan.NewAntiJoinIncludingNulls(ret, s.inner, cond).WithComment(comment)
 				qFlags.Set(sql.QFlagInnerJoin)
 			case plan.JoinTypeSemi:
-				ret = plan.NewCrossJoin(ret, s.inner).WithComment(comment)
+				if sq.Correlated().Empty() {
+					ret = plan.NewCrossJoin(ret, s.inner).WithComment(comment)
+				} else {
+					ret = plan.NewLateralCrossJoin(ret, s.inner).WithComment(comment)
+				}
 				qFlags.Set(sql.QFlagCrossJoin)
 			default:
 				return filter, transform.SameTree, fmt.Errorf("hoistSelectExists failed on unexpected join type")

sql/memo/exec_builder.go

@@ -299,7 +299,7 @@ func (b *ExecBuilder) buildMergeJoin(j *MergeJoin, children ...sql.Node) (sql.No
 
 func (b *ExecBuilder) buildLateralJoin(j *LateralJoin, children ...sql.Node) (sql.Node, error) {
 	if len(j.Filter) == 0 {
-		return plan.NewCrossJoin(children[0], children[1]), nil
+		return plan.NewLateralCrossJoin(children[0], children[1]), nil
 	}
 	filters := b.buildFilterConjunction(j.Filter...)
 	return plan.NewJoin(children[0], children[1], j.Op.AsLateral(), filters), nil

sql/plan/join.go

@@ -532,6 +532,10 @@ func NewCrossJoin(left, right sql.Node) *JoinNode {
 	return NewJoin(left, right, JoinTypeCross, nil)
 }
 
+func NewLateralCrossJoin(left, right sql.Node) *JoinNode {
+	return NewJoin(left, right, JoinTypeLateralCross, nil)
+}
+
 // NaturalJoin is a join that automatically joins by all the columns with the
 // same name.
 // NaturalJoin is a placeholder node, it should be transformed into an INNER