Function agg_retrieve_hash_table

src/backend/executor/nodeAgg.c:2951–3007

* ExecAgg for hashed case: retrieving groups from hash table * * After exhausting in-memory tuples, also try refilling the hash table using * previously-spilled tuples. Only returns NULL after all in-memory and * spilled tuples are exhausted. */

 * spilled tuples are exhausted.
 */
static TupleTableSlot *
agg_retrieve_hash_table(AggState *aggstate)
{
	TupleTableSlot *result = NULL;

	while (result == NULL)
	{
		result = agg_retrieve_hash_table_in_memory(aggstate);
		if (result == NULL)
		{
			if (aggstate->streaming)
			{
				/* outer plan is already done, halt the agg */
				if (aggstate->input_done)
				{
					aggstate->agg_done = true;
					break;
				}

				/*
				 * reset hash tables and related structures, codes are copied
				 * from agg_refill_hash_table()
				 */
				{
					/* there could be residual pergroup pointers; clear them */
					for (int setoff = 0;
						 setoff < aggstate->maxsets + aggstate->num_hashes;
						 setoff++)
						aggstate->all_pergroups[setoff] = NULL;

					/* free memory and reset hash tables */
					ReScanExprContext(aggstate->hashcontext);
					for (int setno = 0; setno < aggstate->num_hashes; setno++)
						ResetTupleHashTable(aggstate->perhash[setno].hashtable);

					aggstate->hash_ngroups_current = 0;

					aggstate->table_filled = false;
				}

				/* refill the hash table from outer, since streaming doesn't spill */
				agg_fill_hash_table(aggstate);

				/* halt if outer got nothing but NULL in the above agg_fill_hash_table() */
				if (aggstate->agg_done)
					break;
			}
			else if (!agg_refill_hash_table(aggstate))
			{
				aggstate->agg_done = true;
				break;
			}
		}
	}

	return result;
}