sql/schemachanger: fix incorrect filter for pk index swaps

Previously, we adjusted the schema changer rules to ensure that
old secondary indexes are only dropped when the new secondary index is
usable. Unfortunately, one of the rules had an incorrect filter. To
address this, this patch fixes the filter to expect the new secondary
index, which will have the new flag.

Fixes: #154751

Release note: None

Author: fqazi

pkg/sql/schemachanger/scplan/internal/rules/current/dep_swap_index.go

@@ -152,8 +152,8 @@ func init() {
 		func(from, to NodeVars) rel.Clauses {
 			newIndex := MkNodeVars("new-index")
 			return append(rel.Clauses{
-				to.Type((*scpb.PrimaryIndex)(nil)),
 				from.Type((*scpb.SecondaryIndex)(nil)),
+				to.Type((*scpb.PrimaryIndex)(nil)),
 				JoinOnDescID(from, to, "table-id"),
 				from.TargetStatus(scpb.ToAbsent),
 				from.CurrentStatus(scpb.Status_VALIDATED),
@@ -163,9 +163,9 @@ func init() {
 				to.El.AttrEqVar(screl.IndexID, "new-primary-index-id"),
 				// Only active this rule on secondary indexes created after 25.4
 				FilterElements("only apply to secondary indexes created after 25.4",
-					from, to,
-					func(from *scpb.PrimaryIndex, to *scpb.SecondaryIndex) bool {
-						return to.HideForPrimaryKeyRecreated
+					newIndex, to,
+					func(newIndex *scpb.SecondaryIndex, to *scpb.PrimaryIndex) bool {
+						return newIndex.HideForPrimaryKeyRecreated
 					}),
 			},
 				IsPotentialSecondaryIndexSwapWithNodeVars(from, newIndex, "index-id", "table-id")...)