Add ALTER .. NO DEPENDS ON

Commit f2fcad27d59c (9.6 era) added the ability to mark objects as
dependent an extension, but forgot to add a way for such dependencies to
be removed.  This commit fixes that oversight.

Strictly speaking this should be backpatched to 9.6, but due to lack of
demand we're not doing so at this time.

Discussion: https://postgr.es/m/20200217225333.GA30974@alvherre.pgsql
Reviewed-by: ahsan hadi <ahsan.hadi@gmail.com>
Reviewed-by: Ibrar Ahmed <ibrar.ahmad@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>

1 files changed, 49 insertions, 0 deletions

diff --git a/src/backend/catalog/pg_depend.c b/src/backend/catalog/pg_depend.c
index 596dafe19c..fa38ee9477 100644
--- a/src/backend/catalog/pg_depend.c
+++ b/src/backend/catalog/pg_depend.c
@@ -279,6 +279,55 @@ deleteDependencyRecordsForClass(Oid classId, Oid objectId,
 }
 
 /*
+ * deleteDependencyRecordsForSpecific -- delete all records with given depender
+ * classId/objectId, dependee classId/objectId, of the given deptype.
+ * Returns the number of records deleted.
+ */
+long
+deleteDependencyRecordsForSpecific(Oid classId, Oid objectId, char deptype,
+								   Oid refclassId, Oid refobjectId)
+{
+	long		count = 0;
+	Relation	depRel;
+	ScanKeyData key[2];
+	SysScanDesc scan;
+	HeapTuple	tup;
+
+	depRel = table_open(DependRelationId, RowExclusiveLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_depend_classid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(classId));
+	ScanKeyInit(&key[1],
+				Anum_pg_depend_objid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(objectId));
+
+	scan = systable_beginscan(depRel, DependDependerIndexId, true,
+							  NULL, 2, key);
+
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_depend depform = (Form_pg_depend) GETSTRUCT(tup);
+
+		if (depform->refclassid == refclassId &&
+			depform->refobjid == refobjectId &&
+			depform->deptype == deptype)
+		{
+			CatalogTupleDelete(depRel, &tup->t_self);
+			count++;
+		}
+	}
+
+	systable_endscan(scan);
+
+	table_close(depRel, RowExclusiveLock);
+
+	return count;
+}
+
+/*
  * Adjust dependency record(s) to point to a different object of the same type
  *
  * classId/objectId specify the referencing object.