Function initialize_aggregates

src/backend/executor/nodeAgg.c:701–730

* Initialize all aggregate transition states for a new group of input values. * * If there are multiple grouping sets, we initialize only the first numReset * of them (the grouping sets are ordered so that the most specific one, which * is reset most often, is first). As a convenience, if numReset is 0, we * reinitialize all sets. * * NB: This cannot be used for hash aggregates, as for thos

 * When called, CurrentMemoryContext should be the per-query context.
 */
static void
initialize_aggregates(AggState *aggstate,
					  AggStatePerGroup *pergroups,
					  int numReset)
{
	int			transno;
	int			numGroupingSets = Max(aggstate->phase->numsets, 1);
	int			setno = 0;
	int			numTrans = aggstate->numtrans;
	AggStatePerTrans transstates = aggstate->pertrans;

	if (numReset == 0)
		numReset = numGroupingSets;

	for (setno = 0; setno < numReset; setno++)
	{
		AggStatePerGroup pergroup = pergroups[setno];

		select_current_set(aggstate, setno, false);

		for (transno = 0; transno < numTrans; transno++)
		{
			AggStatePerTrans pertrans = &transstates[transno];
			AggStatePerGroup pergroupstate = &pergroup[transno];
			if (!bms_is_member(transno, aggstate->aggs_used))
				continue;
			initialize_aggregate(aggstate, pertrans, pergroupstate);
		}
	}
}

/*
 * Given new input value(s), advance the transition function of one aggregate