Function ExecReScanAgg

src/backend/executor/nodeAgg.c:4741–4869

* It's quite different from upstream, because Cloudberry share some same works * with ExecEagerFreeAgg() here. */

 * with ExecEagerFreeAgg() here.
 */
void
ExecReScanAgg(AggState *node)
{
	ExprContext *econtext = node->ss.ps.ps_ExprContext;
	PlanState  *outerPlan = outerPlanState(node);
	int			transno;
	int			numGroupingSets = Max(node->maxsets, 1);
	int			setno;

	node->agg_done = false;

	/*
	 * Greenplum: on streaming mode, the hash table's status is complex, just
	 * don't reuse it at all.
	 */
	if (node->aggstrategy == AGG_HASHED && !node->streaming)
	{
		/*
		 * In the hashed case, if we haven't yet built the hash table then we
		 * can just return; nothing done yet, so nothing to undo. If subnode's
		 * chgParam is not NULL then it will be re-scanned by ExecProcNode,
		 * else no reason to re-scan it at all.
		 */
		if (!node->table_filled)
			return;

		/*
		 * If we do have the hash table, and it never spilled, and the subplan
		 * does not have any parameter changes, and none of our own parameter
		 * changes affect input expressions of the aggregated functions, then
		 * we can just rescan the existing hash table; no need to build it
		 * again.
		 */
		if (ReuseHashTable(node))
		{
			ResetTupleHashIterator(node->perhash[0].hashtable,
								   &node->perhash[0].hashiter);
			select_current_set(node, 0, true);
			return;
		}
	}

	/* Make sure we have closed any open tuplesorts */
	for (transno = 0; transno < node->numtrans; transno++)
	{
		if (!bms_is_member(transno, node->aggs_used))
			continue;
		for (setno = 0; setno < numGroupingSets; setno++)
		{
			AggStatePerTrans pertrans = &node->pertrans[transno];

			if (pertrans->sortstates[setno])
			{
				tuplesort_end(pertrans->sortstates[setno]);
				pertrans->sortstates[setno] = NULL;
			}
		}
	}