Function load_tuple_array

src/backend/executor/nodeGatherMerge.c:597–627

* Read tuple(s) for given reader in nowait mode, and load into its tuple * array, until we have MAX_TUPLE_STORE of them or would have to block. */

 * array, until we have MAX_TUPLE_STORE of them or would have to block.
 */
static void
load_tuple_array(GatherMergeState *gm_state, int reader)
{
	GMReaderTupleBuffer *tuple_buffer;
	int			i;

	/* Don't do anything if this is the leader. */
	if (reader == 0)
		return;

	tuple_buffer = &gm_state->gm_tuple_buffers[reader - 1];

	/* If there's nothing in the array, reset the counters to zero. */
	if (tuple_buffer->nTuples == tuple_buffer->readCounter)
		tuple_buffer->nTuples = tuple_buffer->readCounter = 0;

	/* Try to fill additional slots in the array. */
	for (i = tuple_buffer->nTuples; i < MAX_TUPLE_STORE; i++)
	{
		MinimalTuple tuple;

		tuple = gm_readnext_tuple(gm_state,
								  reader,
								  true,
								  &tuple_buffer->done);
		if (!tuple)
			break;
		tuple_buffer->tuple[i] = tuple;
		tuple_buffer->nTuples++;
	}
}

/*
 * Store the next tuple for a given reader into the appropriate slot.