Function transformAggregateCall

src/backend/parser/parse_agg.c:106–253

* transformAggregateCall - * Finish initial transformation of an aggregate call * * parse_func.c has recognized the function as an aggregate, and has set up * all the fields of the Aggref except aggargtypes, aggdirectargs, args, * aggorder, aggdistinct and agglevelsup. The passed-in args list has been * through standard expression transformation and type coercion to match the * agg's decl

 * pstate level.
 */
void
transformAggregateCall(ParseState *pstate, Aggref *agg,
					   List *args, List *aggorder, bool agg_distinct)
{
	List	   *argtypes = NIL;
	List	   *tlist = NIL;
	List	   *torder = NIL;
	List	   *tdistinct = NIL;
	AttrNumber	attno = 1;
	int			save_next_resno;
	ListCell   *lc;

	if (AGGKIND_IS_ORDERED_SET(agg->aggkind))
	{
		/*
		 * For an ordered-set agg, the args list includes direct args and
		 * aggregated args; we must split them apart.
		 */
		int			numDirectArgs = list_length(args) - list_length(aggorder);
		List	   *aargs;
		ListCell   *lc2;

		Assert(numDirectArgs >= 0);

		aargs = list_copy_tail(args, numDirectArgs);
		agg->aggdirectargs = list_truncate(args, numDirectArgs);

		/*
		 * Build a tlist from the aggregated args, and make a sortlist entry
		 * for each one.  Note that the expressions in the SortBy nodes are
		 * ignored (they are the raw versions of the transformed args); we are
		 * just looking at the sort information in the SortBy nodes.
		 */
		forboth(lc, aargs, lc2, aggorder)
		{
			Expr	   *arg = (Expr *) lfirst(lc);
			SortBy	   *sortby = (SortBy *) lfirst(lc2);
			TargetEntry *tle;

			/* We don't bother to assign column names to the entries */
			tle = makeTargetEntry(arg, attno++, NULL, false);
			tlist = lappend(tlist, tle);

			torder = addTargetToSortList(pstate, tle,
										 torder, tlist, sortby);
		}

		/* Never any DISTINCT in an ordered-set agg */
		Assert(!agg_distinct);
	}
	else
	{
		/* Regular aggregate, so it has no direct args */
		agg->aggdirectargs = NIL;

		/*
		 * Transform the plain list of Exprs into a targetlist.
		 */