Function parseCheckAggregates

src/backend/parser/parse_agg.c:1131–1305

* parseCheckAggregates * Check for aggregates where they shouldn't be and improper grouping. * This function should be called after the target list and qualifications * are finalized. * * Misplaced aggregates are now mostly detected in transformAggregateCall, * but it seems more robust to check for aggregates in recursive queries * only after everything is finalized. In any case it's hard

 *	query for that.
 */
void
parseCheckAggregates(ParseState *pstate, Query *qry)
{
	List	   *gset_common = NIL;
	List	   *groupClauses = NIL;
	List	   *groupClauseCommonVars = NIL;
	bool		have_non_var_grouping;
	List	   *func_grouped_rels = NIL;
	ListCell   *l;
	bool		hasJoinRTEs;
	bool		hasSelfRefRTEs;
	Node	   *clause;

	/* This should only be called if we found aggregates or grouping */
	Assert(pstate->p_hasAggs || qry->groupClause || qry->havingQual || qry->groupingSets);

	/*
	 * If we have grouping sets, expand them and find the intersection of all
	 * sets.
	 */
	if (qry->groupingSets)
	{
		/*
		 * The limit of 4096 is arbitrary and exists simply to avoid resource
		 * issues from pathological constructs.
		 */
		List	   *gsets = expand_grouping_sets(qry->groupingSets, qry->groupDistinct, 4096);

		if (!gsets)
			ereport(ERROR,
					(errcode(ERRCODE_STATEMENT_TOO_COMPLEX),
					 errmsg("too many grouping sets present (maximum 4096)"),
					 parser_errposition(pstate,
										qry->groupClause
										? exprLocation((Node *) qry->groupClause)
										: exprLocation((Node *) qry->groupingSets))));

		/*
		 * The intersection will often be empty, so help things along by
		 * seeding the intersect with the smallest set.
		 */
		gset_common = linitial(gsets);

		if (gset_common)
		{
			for_each_from(l, gsets, 1)
			{
				gset_common = list_intersection_int(gset_common, lfirst(l));
				if (!gset_common)
					break;
			}
		}

		/*
		 * If there was only one grouping set in the expansion, AND if the
		 * groupClause is non-empty (meaning that the grouping set is not
		 * empty either), then we can ditch the grouping set and pretend we
		 * just had a normal GROUP BY.