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Fix oversight in commit 1ec7fca859. 

I failed to account for the possibility that when
ExecAppendAsyncEventWait() notifies multiple async-capable nodes using
postgres_fdw, a preceding node might invoke process_pending_request() to
process a pending asynchronous request made by a succeeding node.  In
that case the succeeding node should produce a tuple to return to the
parent Append node from tuples fetched by process_pending_request() when
notified.  Repair.

Per buildfarm via Michael Paquier.  Back-patch to v14, like the previous
commit.

Thanks to Tom Lane for testing.

Discussion: https://postgr.es/m/YQP0UPT8KmPiHTMs%40paquier.xyz
This commit is contained in:
Etsuro Fujita 2021-08-02 12:45:00 +09:00
parent eaf5321c35
commit a8ed9bd59d
2 changed files with 29 additions and 13 deletions
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22
contrib/postgres_fdw/postgres_fdw.c
View File

@ -6896,12 +6896,26 @@ postgresForeignAsyncNotify(AsyncRequest *areq)
ForeignScanState *node = (ForeignScanState *) areq->requestee;
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
/* The request should be currently in-process */
Assert(fsstate->conn_state->pendingAreq == areq);
/* The core code would have initialized the callback_pending flag */
Assert(!areq->callback_pending);
/*
* If process_pending_request() has been invoked on the given request
* before we get here, we might have some tuples already; in which case
* produce the next tuple
*/
if (fsstate->next_tuple < fsstate->num_tuples)
{
produce_tuple_asynchronously(areq, true);
return;
}
/* We must have run out of tuples */
Assert(fsstate->next_tuple >= fsstate->num_tuples);
/* The request should be currently in-process */
Assert(fsstate->conn_state->pendingAreq == areq);
/* On error, report the original query, not the FETCH. */
if (!PQconsumeInput(fsstate->conn))
pgfdw_report_error(ERROR, NULL, fsstate->conn, false, fsstate->query);
@ -7027,7 +7041,7 @@ process_pending_request(AsyncRequest *areq)
/*
* If we didn't get any tuples, must be end of data; complete the request
* now. Otherwise, we postpone completing the request until we are called
* from postgresForeignAsyncConfigureWait().
* from postgresForeignAsyncConfigureWait()/postgresForeignAsyncNotify().
*/
if (fsstate->next_tuple >= fsstate->num_tuples)
{

20
src/backend/executor/nodeAppend.c
View File

@ -1082,16 +1082,18 @@ ExecAppendAsyncEventWait(AppendState *node)
{
AsyncRequest *areq = (AsyncRequest *) w->user_data;
/*
* Mark it as no longer needing a callback. We must do this
* before dispatching the callback in case the callback resets the
* flag.
*/
Assert(areq->callback_pending);
areq->callback_pending = false;
if (areq->callback_pending)
{
/*
* Mark it as no longer needing a callback. We must do this
* before dispatching the callback in case the callback resets
* the flag.
*/
areq->callback_pending = false;
/* Do the actual work. */
ExecAsyncNotify(areq);
/* Do the actual work. */
ExecAsyncNotify(areq);
}
}
}
}