Function mppExecutorWait

src/backend/executor/execUtils.c:2085–2166

* QD wait for QEs to finish and check their results. */

 * QD wait for QEs to finish and check their results.
 */
uint64 mppExecutorWait(QueryDesc *queryDesc)
{
	EState	   *estate;
	ExecSlice  *currentSlice;
	int 		primaryWriterSliceIndex;
	uint64		es_processed = 0;

	/* caller must have switched into per-query memory context already */
	estate = queryDesc->estate;

	currentSlice = getCurrentSlice(estate, LocallyExecutingSliceIndex(estate));
	primaryWriterSliceIndex = PrimaryWriterSliceIndex(estate);

	/*
	 * If QD, wait for QEs to finish and check their results.
	 */
	if (estate->dispatcherState && estate->dispatcherState->primaryResults)
	{
		CdbDispatchResults *pr = NULL;
		CdbDispatcherState *ds = estate->dispatcherState;
		DispatchWaitMode waitMode = DISPATCH_WAIT_NONE;
		ErrorData *qeError = NULL;

		/*
		 * If we are finishing a query before all the tuples of the query
		 * plan were fetched we must call ExecSquelchNode before checking
		 * the dispatch results in order to tell the nodes below we no longer
		 * need any more tuples.
		 */
		if (!estate->es_got_eos)
		{
			ExecSquelchNode(queryDesc->planstate, true);
		}

		/*
		 * Wait for completion of all QEs.  We send a "graceful" query
		 * finish, not cancel signal.  Since the query has succeeded,
		 * don't confuse QEs by sending erroneous message.
		 */
		if (estate->cancelUnfinished)
			waitMode = DISPATCH_WAIT_FINISH;

		cdbdisp_checkDispatchResult(ds, waitMode);

		pr = cdbdisp_getDispatchResults(ds, &qeError);

		if (qeError)
		{
			FlushErrorState();
			ReThrowError(qeError);
		}

		if (ProcessDispatchResult_hook)
			ProcessDispatchResult_hook(ds);

		/* collect pgstat from QEs for current transaction level */
		pgstat_combine_from_qe(pr, primaryWriterSliceIndex);