Function postgresBeginDirectModify

contrib/postgres_fdw/postgres_fdw.c:2634–2747

* postgresBeginDirectModify * Prepare a direct foreign table modification */

 *		Prepare a direct foreign table modification
 */
static void
postgresBeginDirectModify(ForeignScanState *node, int eflags)
{
	ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
	EState	   *estate = node->ss.ps.state;
	PgFdwDirectModifyState *dmstate;
	Index		rtindex;
	RangeTblEntry *rte;
	Oid			userid;
	ForeignTable *table;
	UserMapping *user;
	int			numParams;

	/*
	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
	 */
	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
		return;

	/*
	 * We'll save private state in node->fdw_state.
	 */
	dmstate = (PgFdwDirectModifyState *) palloc0(sizeof(PgFdwDirectModifyState));
	node->fdw_state = (void *) dmstate;

	/*
	 * Identify which user to do the remote access as.  This should match what
	 * ExecCheckRTEPerms() does.
	 */
	rtindex = node->resultRelInfo->ri_RangeTableIndex;
	rte = exec_rt_fetch(rtindex, estate);
	userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();

	/* Get info about foreign table. */
	if (fsplan->scan.scanrelid == 0)
		dmstate->rel = ExecOpenScanRelation(estate, rtindex, eflags);
	else
		dmstate->rel = node->ss.ss_currentRelation;
	table = GetForeignTable(RelationGetRelid(dmstate->rel));
	user = GetUserMapping(userid, table->serverid);

	/*
	 * Get connection to the foreign server.  Connection manager will
	 * establish new connection if necessary.
	 */
	dmstate->conn = GetConnection(user, false, &dmstate->conn_state);

	/* Update the foreign-join-related fields. */
	if (fsplan->scan.scanrelid == 0)
	{
		/* Save info about foreign table. */
		dmstate->resultRel = dmstate->rel;

		/*
		 * Set dmstate->rel to NULL to teach get_returning_data() and
		 * make_tuple_from_result_row() that columns fetched from the remote
		 * server are described by fdw_scan_tlist of the foreign-scan plan
		 * node, not the tuple descriptor for the target relation.