Function PersistentDestReceiverReceive

pg_documentdb/src/commands/cursors.c:1261–1308

static bool
PersistentDestReceiverReceive(TupleTableSlot *slot,
							  DestReceiver *destReceiver)
{
	PersistentTupleDestReceiver *receiver =
		(PersistentTupleDestReceiver *) destReceiver;
	BsonStoreTupleDestReceiverBase *base = &receiver->base;

	bool isNull = false;
	Datum result = slot_getattr(slot, 1, &isNull);
	if (isNull)
	{
		if (receiver->isSingleResult)
		{
			/*
			 * For single-result receivers (count/distinct): NULL means "no data".
			 * Return false (stop) — nothing to fetch; the caller reads
			 * receiver->singleResult which stays NULL.
			 */
			return false;
		}
		else
		{
			/*
			 * For multi-row persistent receivers: NULL data rows are
			 * skipped.  Return true (continue) so the executor keeps sending
			 * rows, matching the old SPI path behaviour.  The col2 continuation
			 * token is intentionally not processed here — for non-tailable
			 * cursors the old SPI path (FetchCursorAndWriteUntilPageOrSize)
			 * also skips continuation when isDataNull is true.  Tailable
			 * cursors use a separate code path (DrainTailableQuery /
			 * FetchTailableCursorAndWriteUntilPageOrSize).
			 */
			return true;
		}
	}

	if (receiver->isSingleResult)
	{
		MemoryContext oldContext = MemoryContextSwitchTo(base->writerContext);
		receiver->singleResult = (pgbson *) PG_DETOAST_DATUM_COPY(result);
		MemoryContextSwitchTo(oldContext);
		return false; /* stop after first row */
	}

	pgbson *resultBson = DatumGetPgBsonPacked(result);
	return PersistentDestReceiveCore(resultBson, receiver);
}


static void