Function RelationFlushRelation

src/backend/utils/cache/relcache.c:2922–2950

* RelationFlushRelation * * Rebuild the relation if it is open (refcount > 0), else blow it away. * This is used when we receive a cache invalidation event for the rel. */

 *	 This is used when we receive a cache invalidation event for the rel.
 */
static void
RelationFlushRelation(Relation relation)
{
	if (relation->rd_createSubid != InvalidSubTransactionId ||
		relation->rd_firstRelfilenodeSubid != InvalidSubTransactionId)
	{
		/*
		 * New relcache entries are always rebuilt, not flushed; else we'd
		 * forget the "new" status of the relation.  Ditto for the
		 * new-relfilenode status.
		 *
		 * The rel could have zero refcnt here, so temporarily increment the
		 * refcnt to ensure it's safe to rebuild it.  We can assume that the
		 * current transaction has some lock on the rel already.
		 */
		RelationIncrementReferenceCount(relation);
		RelationClearRelation(relation, true);
		RelationDecrementReferenceCount(relation);
	}
	else
	{
		/*
		 * Pre-existing rels can be dropped from the relcache if not open.
		 */
		bool		rebuild = !RelationHasReferenceCountZero(relation);

		RelationClearRelation(relation, rebuild);
	}
}

/*
 * RelationForgetRelation - caller reports that it dropped the relation