Function postgresExplainForeignScan

contrib/postgres_fdw/postgres_fdw.c:2821–2922

* postgresExplainForeignScan * Produce extra output for EXPLAIN of a ForeignScan on a foreign table */

 *		Produce extra output for EXPLAIN of a ForeignScan on a foreign table
 */
static void
postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
	ForeignScan *plan = castNode(ForeignScan, node->ss.ps.plan);
	List	   *fdw_private = plan->fdw_private;

	/*
	 * Identify foreign scans that are really joins or upper relations.  The
	 * input looks something like "(1) LEFT JOIN (2)", and we must replace the
	 * digit string(s), which are RT indexes, with the correct relation names.
	 * We do that here, not when the plan is created, because we can't know
	 * what aliases ruleutils.c will assign at plan creation time.
	 */
	if (list_length(fdw_private) > FdwScanPrivateRelations)
	{
		StringInfo	relations;
		char	   *rawrelations;
		char	   *ptr;
		int			minrti,
					rtoffset;

		rawrelations = strVal(list_nth(fdw_private, FdwScanPrivateRelations));

		/*
		 * A difficulty with using a string representation of RT indexes is
		 * that setrefs.c won't update the string when flattening the
		 * rangetable.  To find out what rtoffset was applied, identify the
		 * minimum RT index appearing in the string and compare it to the
		 * minimum member of plan->fs_relids.  (We expect all the relids in
		 * the join will have been offset by the same amount; the Asserts
		 * below should catch it if that ever changes.)
		 */
		minrti = INT_MAX;
		ptr = rawrelations;
		while (*ptr)
		{
			if (isdigit((unsigned char) *ptr))
			{
				int			rti = strtol(ptr, &ptr, 10);

				if (rti < minrti)
					minrti = rti;
			}
			else
				ptr++;
		}
		rtoffset = bms_next_member(plan->fs_relids, -1) - minrti;

		/* Now we can translate the string */
		relations = makeStringInfo();
		ptr = rawrelations;
		while (*ptr)
		{
			if (isdigit((unsigned char) *ptr))
			{
				int			rti = strtol(ptr, &ptr, 10);
				RangeTblEntry *rte;
				char	   *relname;