Function lookup_hash_entries

src/backend/executor/nodeAgg.c:2270–2319

* Look up hash entries for the current tuple in all hashed grouping sets. * * Be aware that lookup_hash_entry can reset the tmpcontext. * * Some entries may be left NULL if we are in "spill mode". The same tuple * will belong to different groups for each grouping set, so may match a group * already in memory for one set and match a group not in memory for another * set. When in "spill mode"

 * efficient.
 */
static void
lookup_hash_entries(AggState *aggstate)
{
	AggStatePerGroup *pergroup = aggstate->hash_pergroup;
	TupleTableSlot *outerslot = aggstate->tmpcontext->ecxt_outertuple;
	int			setno;

	for (setno = 0; setno < aggstate->num_hashes; setno++)
	{
		AggStatePerHash perhash = &aggstate->perhash[setno];
		TupleHashTable hashtable = perhash->hashtable;
		TupleTableSlot *hashslot = perhash->hashslot;
		TupleHashEntry entry;
		uint32		hash;
		bool		isnew = false;
		bool	   *p_isnew;

		/* if hash table already spilled, don't create new entries */
		p_isnew = (aggstate->hash_spill_mode || (aggstate->streaming && aggstate->table_filled)) ? NULL : &isnew;

		select_current_set(aggstate, setno, true);
		prepare_hash_slot(perhash,
						  outerslot,
						  hashslot);

		entry = LookupTupleHashEntry(hashtable, hashslot,
									 p_isnew, &hash);

		if (entry != NULL)
		{
			if (isnew)
				initialize_hash_entry(aggstate, hashtable, entry);
			pergroup[setno] = entry->additional;
		}
		else if (!aggstate->streaming)
		{
			HashAggSpill *spill = &aggstate->hash_spills[setno];
			TupleTableSlot *slot = aggstate->tmpcontext->ecxt_outertuple;

			if (spill->partitions == NULL)
				hashagg_spill_init(aggstate, spill, aggstate->hash_tapeinfo, 0,
								   perhash->aggnode->numGroups,
								   aggstate->hashentrysize);
			perhash->num_spill_parts += spill->npartitions;

			hashagg_spill_tuple(aggstate, spill, slot, hash);
			pergroup[setno] = NULL;
		}
	}
}

/*
 * ExecAgg -