Function hash_agg_check_limits

src/backend/executor/nodeAgg.c:1926–1945

* hash_agg_check_limits * * After adding a new group to the hash table, check whether we need to enter * spill mode. Allocations may happen without adding new groups (for instance, * if the transition state size grows), so this check is imperfect. */

 * if the transition state size grows), so this check is imperfect.
 */
static void
hash_agg_check_limits(AggState *aggstate)
{
	uint64		ngroups = aggstate->hash_ngroups_current;
	Size		meta_mem = MemoryContextMemAllocated(aggstate->hash_metacxt,
													 true);
	Size		hashkey_mem = MemoryContextMemAllocated(aggstate->hashcontext->ecxt_per_tuple_memory,
														true);

	/*
	 * Don't spill unless there's at least one group in the hash table so we
	 * can be sure to make progress even in edge cases.
	 */
	if (aggstate->hash_ngroups_current > 0 &&
		(meta_mem + hashkey_mem > aggstate->hash_mem_limit ||
		 ngroups > aggstate->hash_ngroups_limit))
	{
		hash_agg_enter_spill_mode(aggstate);
	}
}

/*
 * Enter "spill mode", meaning that no new groups are added to any of the hash