Function postgresPlanDirectModify

contrib/postgres_fdw/postgres_fdw.c:2436–2628

* postgresPlanDirectModify * Consider a direct foreign table modification * * Decide whether it is safe to modify a foreign table directly, and if so, * rewrite subplan accordingly. */

 * rewrite subplan accordingly.
 */
static bool
postgresPlanDirectModify(PlannerInfo *root,
						 ModifyTable *plan,
						 Index resultRelation,
						 int subplan_index)
{
	CmdType		operation = plan->operation;
	RelOptInfo *foreignrel;
	RangeTblEntry *rte;
	PgFdwRelationInfo *fpinfo;
	Relation	rel;
	StringInfoData sql;
	ForeignScan *fscan;
	List	   *processed_tlist = NIL;
	List	   *targetAttrs = NIL;
	List	   *remote_exprs;
	List	   *params_list = NIL;
	List	   *returningList = NIL;
	List	   *retrieved_attrs = NIL;

	/*
	 * Decide whether it is safe to modify a foreign table directly.
	 */

	/*
	 * The table modification must be an UPDATE or DELETE.
	 */
	if (operation != CMD_UPDATE && operation != CMD_DELETE)
		return false;

	/*
	 * Try to locate the ForeignScan subplan that's scanning resultRelation.
	 */
	fscan = find_modifytable_subplan(root, plan, resultRelation, subplan_index);
	if (!fscan)
		return false;

	/*
	 * It's unsafe to modify a foreign table directly if there are any quals
	 * that should be evaluated locally.
	 */
	if (fscan->scan.plan.qual != NIL)
		return false;

	/* Safe to fetch data about the target foreign rel */
	if (fscan->scan.scanrelid == 0)
	{
		foreignrel = find_join_rel(root, fscan->fs_relids);
		/* We should have a rel for this foreign join. */
		Assert(foreignrel);
	}
	else
		foreignrel = root->simple_rel_array[resultRelation];
	rte = root->simple_rte_array[resultRelation];
	fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;

	/*
	 * It's unsafe to update a foreign table directly, if any expressions to