Function deparseVar

contrib/postgres_fdw/deparse.c:2538–2594

* Deparse given Var node into context->buf. * * If the Var belongs to the foreign relation, just print its remote name. * Otherwise, it's effectively a Param (and will in fact be a Param at * run time). Handle it the same way we handle plain Params --- see * deparseParam for comments. */

 * deparseParam for comments.
 */
static void
deparseVar(Var *node, deparse_expr_cxt *context)
{
	Relids		relids = context->scanrel->relids;
	int			relno;
	int			colno;

	/* Qualify columns when multiple relations are involved. */
	bool		qualify_col = (bms_membership(relids) == BMS_MULTIPLE);

	/*
	 * If the Var belongs to the foreign relation that is deparsed as a
	 * subquery, use the relation and column alias to the Var provided by the
	 * subquery, instead of the remote name.
	 */
	if (is_subquery_var(node, context->scanrel, &relno, &colno))
	{
		appendStringInfo(context->buf, "%s%d.%s%d",
						 SUBQUERY_REL_ALIAS_PREFIX, relno,
						 SUBQUERY_COL_ALIAS_PREFIX, colno);
		return;
	}

	if (bms_is_member(node->varno, relids) && node->varlevelsup == 0)
		deparseColumnRef(context->buf, node->varno, node->varattno,
						 planner_rt_fetch(node->varno, context->root),
						 qualify_col);
	else
	{
		/* Treat like a Param */
		if (context->params_list)
		{
			int			pindex = 0;
			ListCell   *lc;

			/* find its index in params_list */
			foreach(lc, *context->params_list)
			{
				pindex++;
				if (equal(node, (Node *) lfirst(lc)))
					break;
			}
			if (lc == NULL)
			{
				/* not in list, so add it */
				pindex++;
				*context->params_list = lappend(*context->params_list, node);
			}

			printRemoteParam(pindex, node->vartype, node->vartypmod, context);
		}
		else
		{
			printRemotePlaceholder(node->vartype, node->vartypmod, context);
		}
	}
}