Function postgresForeignAsyncNotify

contrib/postgres_fdw/postgres_fdw.c:7044–7077

* postgresForeignAsyncNotify * Fetch some more tuples from a file descriptor that becomes ready, * requesting next tuple. */

 *		requesting next tuple.
 */
static void
postgresForeignAsyncNotify(AsyncRequest *areq)
{
	ForeignScanState *node = (ForeignScanState *) areq->requestee;
	PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;

	/* The core code would have initialized the callback_pending flag */
	Assert(!areq->callback_pending);

	/*
	 * If process_pending_request() has been invoked on the given request
	 * before we get here, we might have some tuples already; in which case
	 * produce the next tuple
	 */
	if (fsstate->next_tuple < fsstate->num_tuples)
	{
		produce_tuple_asynchronously(areq, true);
		return;
	}

	/* We must have run out of tuples */
	Assert(fsstate->next_tuple >= fsstate->num_tuples);

	/* The request should be currently in-process */
	Assert(fsstate->conn_state->pendingAreq == areq);

	/* On error, report the original query, not the FETCH. */
	if (!PQconsumeInput(fsstate->conn))
		pgfdw_report_error(ERROR, NULL, fsstate->conn, false, fsstate->query);

	fetch_more_data(node);

	produce_tuple_asynchronously(areq, true);
}

/*
 * Asynchronously produce next tuple from a foreign PostgreSQL table.