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Handle interrupts while waiting on Append's async subplans

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We did not wake up on interrupts while waiting on async events on an
async-capable append node. For example, if you tried to cancel the
query, nothing would happen until one of the async subplans becomes
readable. To fix, add WL_LATCH_SET to the WaitEventSet.

Backpatch down to v14 where async Append execution was introduced.

Discussion: https://www.postgresql.org/message-id/37a40570-f558-40d3-b5ea-5c2079b3b30b@iki.fi
This commit is contained in:
Heikki Linnakangas 2025-03-12 20:53:09 +02:00
parent ca0830e5a2
commit e731e9d5ee
1 changed files with 25 additions and 3 deletions
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28
src/backend/executor/nodeAppend.c
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@ -1016,7 +1016,7 @@ ExecAppendAsyncRequest(AppendState *node, TupleTableSlot **result)
static void
ExecAppendAsyncEventWait(AppendState *node)
{
int nevents = node->as_nasyncplans + 1;
int nevents = node->as_nasyncplans + 2;
long timeout = node->as_syncdone ? -1 : 0;
WaitEvent occurred_event[EVENT_BUFFER_SIZE];
int noccurred;
@ -1041,8 +1041,8 @@ ExecAppendAsyncEventWait(AppendState *node)
}
/*
* No need for further processing if there are no configured events other
* than the postmaster death event.
* No need for further processing if none of the subplans configured any
* events.
*/
if (GetNumRegisteredWaitEvents(node->as_eventset) == 1)
{
@ -1051,6 +1051,21 @@ ExecAppendAsyncEventWait(AppendState *node)
return;
}
/*
* Add the process latch to the set, so that we wake up to process the
* standard interrupts with CHECK_FOR_INTERRUPTS().
*
* NOTE: For historical reasons, it's important that this is added to the
* WaitEventSet after the ExecAsyncConfigureWait() calls. Namely,
* postgres_fdw calls "GetNumRegisteredWaitEvents(set) == 1" to check if
* any other events are in the set. That's a poor design, it's
* questionable for postgres_fdw to be doing that in the first place, but
* we cannot change it now. The pattern has possibly been copied to other
* extensions too.
*/
AddWaitEventToSet(node->as_eventset, WL_LATCH_SET, PGINVALID_SOCKET,
MyLatch, NULL);
/* Return at most EVENT_BUFFER_SIZE events in one call. */
if (nevents > EVENT_BUFFER_SIZE)
nevents = EVENT_BUFFER_SIZE;
@ -1092,6 +1107,13 @@ ExecAppendAsyncEventWait(AppendState *node)
ExecAsyncNotify(areq);
}
}
/* Handle standard interrupts */
if ((w->events & WL_LATCH_SET) != 0)
{
ResetLatch(MyLatch);
CHECK_FOR_INTERRUPTS();
}
}
}