Function ExecAppendAsyncGetNext

src/backend/executor/nodeAppend.c:956–997

---------------------------------------------------------------- * ExecAppendAsyncGetNext * * Get the next tuple from any of the asynchronous subplans. * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
static bool
ExecAppendAsyncGetNext(AppendState *node, TupleTableSlot **result)
{
	*result = NULL;

	/* We should never be called when there are no valid async subplans. */
	Assert(node->as_nasyncremain > 0);

	/* Request a tuple asynchronously. */
	if (ExecAppendAsyncRequest(node, result))
		return true;

	while (node->as_nasyncremain > 0)
	{
		CHECK_FOR_INTERRUPTS();

		/* Wait or poll for async events. */
		ExecAppendAsyncEventWait(node);

		/* Request a tuple asynchronously. */
		if (ExecAppendAsyncRequest(node, result))
			return true;

		/* Break from loop if there's any sync subplan that isn't complete. */
		if (!node->as_syncdone)
			break;
	}

	/*
	 * If all sync subplans are complete, we're totally done scanning the
	 * given node.  Otherwise, we're done with the asynchronous stuff but must
	 * continue scanning the sync subplans.
	 */
	if (node->as_syncdone)
	{
		Assert(node->as_nasyncremain == 0);
		*result = ExecClearTuple(node->ps.ps_ResultTupleSlot);
		return true;
	}

	return false;
}

/* ----------------------------------------------------------------
 *		ExecAppendAsyncRequest