Function agg_retrieve_hash_table_in_memory

src/backend/executor/nodeAgg.c:3013–3130

* Retrieve the groups from the in-memory hash tables without considering any * spilled tuples. */

 * spilled tuples.
 */
static TupleTableSlot *
agg_retrieve_hash_table_in_memory(AggState *aggstate)
{
	ExprContext *econtext;
	AggStatePerAgg peragg;
	AggStatePerGroup pergroup;
	TupleHashEntryData *entry;
	TupleTableSlot *firstSlot;
	TupleTableSlot *result;
	AggStatePerHash perhash;

	/*
	 * get state info from node.
	 *
	 * econtext is the per-output-tuple expression context.
	 */
	econtext = aggstate->ss.ps.ps_ExprContext;
	peragg = aggstate->peragg;
	firstSlot = aggstate->ss.ss_ScanTupleSlot;

	/*
	 * Note that perhash (and therefore anything accessed through it) can
	 * change inside the loop, as we change between grouping sets.
	 */
	perhash = &aggstate->perhash[aggstate->current_set];

	/*
	 * We loop retrieving groups until we find one satisfying
	 * aggstate->ss.ps.qual
	 */
	for (;;)
	{
		TupleTableSlot *hashslot = perhash->hashslot;
		int			i;

		CHECK_FOR_INTERRUPTS();

		/*
		 * Find the next entry in the hash table
		 */
		entry = ScanTupleHashTable(perhash->hashtable, &perhash->hashiter);
		if (entry == NULL)
		{
			int			nextset = aggstate->current_set + 1;

			if (nextset < aggstate->num_hashes)
			{
				/*
				 * Switch to next grouping set, reinitialize, and restart the
				 * loop.
				 */
				select_current_set(aggstate, nextset, true);

				perhash = &aggstate->perhash[aggstate->current_set];

				ResetTupleHashIterator(perhash->hashtable, &perhash->hashiter);

				continue;