Function hashagg_spill_init

src/backend/executor/nodeAgg.c:3214–3237

* hashagg_spill_init * * Called after we determined that spilling is necessary. Chooses the number * of partitions to create, and initializes them. */

 * of partitions to create, and initializes them.
 */
static void
hashagg_spill_init(AggState *aggstate, HashAggSpill *spill, HashTapeInfo *tapeinfo, int used_bits,
				   double input_groups, double hashentrysize)
{
	int			npartitions;
	int			partition_bits;

	npartitions = hash_choose_num_partitions(aggstate, input_groups, hashentrysize,
											 used_bits, &partition_bits);

	spill->partitions = palloc0(sizeof(int) * npartitions);
	spill->ntuples = palloc0(sizeof(int64) * npartitions);
	spill->hll_card = palloc0(sizeof(hyperLogLogState) * npartitions);

	hashagg_tapeinfo_assign(tapeinfo, spill->partitions, npartitions);

	spill->tapeset = tapeinfo->tapeset;
	spill->shift = 32 - used_bits - partition_bits;
	spill->mask = (npartitions - 1) << spill->shift;
	spill->npartitions = npartitions;

	for (int i = 0; i < npartitions; i++)
		initHyperLogLog(&spill->hll_card[i], HASHAGG_HLL_BIT_WIDTH);
}

/*
 * hashagg_spill_tuple