Function assign_aggregate_collations

src/backend/parser/parse_collate.c:885–904

* Aggref is a special case because expressions used only for ordering * shouldn't be taken to conflict with each other or with regular args, * indeed shouldn't affect the aggregate's result collation at all. * We handle this by applying assign_expr_collations() to them rather than * passing down our loccontext. * * Note that we recurse to each TargetEntry, not directly to its contained * ex

 * contain only SortGroupClause nodes which we need not process.
 */
static void
assign_aggregate_collations(Aggref *aggref,
							assign_collations_context *loccontext)
{
	ListCell   *lc;

	/* Plain aggregates have no direct args */
	Assert(aggref->aggdirectargs == NIL);

	/* Process aggregated args, holding resjunk ones at arm's length */
	foreach(lc, aggref->args)
	{
		TargetEntry *tle = lfirst_node(TargetEntry, lc);

		if (tle->resjunk)
			assign_expr_collations(loccontext->pstate, (Node *) tle);
		else
			(void) assign_collations_walker((Node *) tle, loccontext);
	}
}

/*
 * For ordered-set aggregates, it's somewhat unclear how best to proceed.