Function conversion_error_callback

contrib/postgres_fdw/postgres_fdw.c:7404–7493

* Callback function which is called when error occurs during column value * conversion. Print names of column and relation. * * Note that this function mustn't do any catalog lookups, since we are in * an already-failed transaction. Fortunately, we can get the needed info * from the relation or the query's rangetable instead. */

 * from the relation or the query's rangetable instead.
 */
static void
conversion_error_callback(void *arg)
{
	ConversionLocation *errpos = (ConversionLocation *) arg;
	Relation	rel = errpos->rel;
	ForeignScanState *fsstate = errpos->fsstate;
	const char *attname = NULL;
	const char *relname = NULL;
	bool		is_wholerow = false;

	/*
	 * If we're in a scan node, always use aliases from the rangetable, for
	 * consistency between the simple-relation and remote-join cases.  Look at
	 * the relation's tupdesc only if we're not in a scan node.
	 */
	if (fsstate)
	{
		/* ForeignScan case */
		ForeignScan *fsplan = castNode(ForeignScan, fsstate->ss.ps.plan);
		int			varno = 0;
		AttrNumber	colno = 0;

		if (fsplan->scan.scanrelid > 0)
		{
			/* error occurred in a scan against a foreign table */
			varno = fsplan->scan.scanrelid;
			colno = errpos->cur_attno;
		}
		else
		{
			/* error occurred in a scan against a foreign join */
			TargetEntry *tle;

			tle = list_nth_node(TargetEntry, fsplan->fdw_scan_tlist,
								errpos->cur_attno - 1);

			/*
			 * Target list can have Vars and expressions.  For Vars, we can
			 * get some information, however for expressions we can't.  Thus
			 * for expressions, just show generic context message.
			 */
			if (IsA(tle->expr, Var))
			{
				Var		   *var = (Var *) tle->expr;

				varno = var->varno;
				colno = var->varattno;
			}
		}

		if (varno > 0)
		{
			EState	   *estate = fsstate->ss.ps.state;
			RangeTblEntry *rte = exec_rt_fetch(varno, estate);

			relname = rte->eref->aliasname;

			if (colno == 0)