Function RelationSetNewRelfilenode

src/backend/utils/cache/relcache.c:3895–4044

* RelationSetNewRelfilenode * * Assign a new relfilenode (physical file name), and possibly a new * persistence setting, to the relation. * * This allows a full rewrite of the relation to be done with transactional * safety (since the filenode assignment can be rolled back). Note however * that there is no simple way to access the relation's old data for the * remainder of the current tra

 * Caller must already hold exclusive lock on the relation.
 */
void
RelationSetNewRelfilenode(Relation relation, char persistence)
{
	Oid newrelfilenode;
	Relation	pg_class;
	HeapTuple	tuple;
	Form_pg_class classform;
	MultiXactId minmulti = InvalidMultiXactId;
	TransactionId freezeXid = InvalidTransactionId;
	RelFileNode newrnode;

	/* Allocate a new relfilenode */
	newrelfilenode = GetNewRelFileNode(relation->rd_rel->reltablespace, NULL,
									   persistence);

	/*
	 * Get a writable copy of the pg_class tuple for the given relation.
	 */
	pg_class = table_open(RelationRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopy1(RELOID,
								ObjectIdGetDatum(RelationGetRelid(relation)));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "could not find tuple for relation %u",
			 RelationGetRelid(relation));
	classform = (Form_pg_class) GETSTRUCT(tuple);

	/*
	 * Schedule unlinking of the old storage at transaction commit.
	 */
	RelationDropStorage(relation);


	/*
	 * Create storage for the main fork of the new relfilenode.  If it's a
	 * table-like object, call into the table AM to do so, which'll also
	 * create the table's init fork if needed.
	 *
	 * NOTE: If relevant for the AM, any conflict in relfilenode value will be
	 * caught here, if GetNewRelFileNode messes up for any reason.
	 */
	newrnode = relation->rd_node;
	newrnode.relNode = newrelfilenode;

	switch (relation->rd_rel->relkind)
	{
		case RELKIND_INDEX:
		case RELKIND_SEQUENCE:
			{
				/* handle these directly, at least for now */
				SMgrRelation srel;

				srel = RelationCreateStorage(newrnode, persistence,
											 0 /* default storage implementation */,
											 relation);
				smgrclose(srel);
			}
			break;