Function get_variable

src/backend/utils/adt/ruleutils.c:7108–7326

* Display a Var appropriately. * * In some cases (currently only when recursing into an unnamed join) * the Var's varlevelsup has to be interpreted with respect to a context * above the current one; levelsup indicates the offset. * * If istoplevel is true, the Var is at the top level of a SELECT's * targetlist, which means we need special treatment of whole-row Vars. * Instead of the norma

 * it is a whole-row Var or a subplan output reference).
 */
static char *
get_variable(Var *var, int levelsup, bool istoplevel, deparse_context *context)
{
	StringInfo	buf = context->buf;
	RangeTblEntry *rte;
	AttrNumber	attnum;
	int			netlevelsup;
	deparse_namespace *dpns;
	Index		varno;
	AttrNumber	varattno;
	deparse_columns *colinfo;
	char	   *refname;
	char	   *attname;

	/* Find appropriate nesting depth */
	netlevelsup = var->varlevelsup + levelsup;
	if (netlevelsup >= list_length(context->namespaces))
		elog(ERROR, "bogus varlevelsup: %d offset %d",
			 var->varlevelsup, levelsup);
	dpns = (deparse_namespace *) list_nth(context->namespaces,
										  netlevelsup);

	/*
	 * If we have a syntactic referent for the Var, and we're working from a
	 * parse tree, prefer to use the syntactic referent.  Otherwise, fall back
	 * on the semantic referent.  (Forcing use of the semantic referent when
	 * printing plan trees is a design choice that's perhaps more motivated by
	 * backwards compatibility than anything else.  But it does have the
	 * advantage of making plans more explicit.)
	 */
	if (var->varnosyn > 0 && dpns->plan == NULL)
	{
		varno = var->varnosyn;
		varattno = var->varattnosyn;
	}
	else
	{
		varno = var->varno;
		varattno = var->varattno;
	}

	/*
	 * Try to find the relevant RTE in this rtable.  In a plan tree, it's
	 * likely that varno is OUTER_VAR or INNER_VAR, in which case we must dig
	 * down into the subplans, or INDEX_VAR, which is resolved similarly. Also
	 * find the aliases previously assigned for this RTE.
	 */
	if (varno >= 1 && varno <= list_length(dpns->rtable))
	{
		/*
		 * We might have been asked to map child Vars to some parent relation.
		 */
		if (context->appendparents && dpns->appendrels)
		{
			Index		pvarno = varno;
			AttrNumber	pvarattno = varattno;
			AppendRelInfo *appinfo = dpns->appendrels[pvarno];
			bool		found = false;