Function ATGetQueueEntry

src/backend/commands/tablecmds.c:7750–7781

* ATGetQueueEntry: find or create an entry in the ALTER TABLE work queue */

 * ATGetQueueEntry: find or create an entry in the ALTER TABLE work queue
 */
static AlteredTableInfo *
ATGetQueueEntry(List **wqueue, Relation rel)
{
	Oid			relid = RelationGetRelid(rel);
	AlteredTableInfo *tab;
	ListCell   *ltab;

	foreach(ltab, *wqueue)
	{
		tab = (AlteredTableInfo *) lfirst(ltab);
		if (tab->relid == relid)
			return tab;
	}

	/*
	 * Not there, so add it.  Note that we make a copy of the relation's
	 * existing descriptor before anything interesting can happen to it.
	 */
	tab = makeNode(AlteredTableInfo);
	tab->relid = relid;
	tab->rel = NULL;			/* set later */
	tab->relkind = rel->rd_rel->relkind;
	tab->oldDesc = CreateTupleDescCopyConstr(RelationGetDescr(rel));
	tab->newAccessMethod = InvalidOid;
	tab->newTableSpace = InvalidOid;
	tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
	tab->chgPersistence = false;

	*wqueue = lappend(*wqueue, tab);

	return tab;
}

/*
 * ATSimplePermissions