On 2020/04/08 3:01, Ashwin Agrawal wrote:
On Mon, Apr 6, 2020 at 2:14 PM Andres Freund <and...@anarazel.de
<mailto:and...@anarazel.de>> wrote:
> How about we change it to this ?
Hm. Better. But I think it might need at least a compiler barrier /
volatile memory load? Unlikely here, but otherwise the compiler could
theoretically just stash the variable somewhere locally (it's not likely
to be a problem because it'd not be long ago that we acquired an lwlock,
which is a full barrier).
That's the part, I am not fully sure about. But reading the comment above
SyncRepUpdateSyncStandbysDefined(), it seems fine.
> Bring back the check which existed based on GUC but instead of just
blindly
> returning based on just GUC not being set, check
> WalSndCtl->sync_standbys_defined. Thoughts?
Hm. Is there any reason not to just check
WalSndCtl->sync_standbys_defined? rather than both !SyncStandbysDefined()
and WalSndCtl->sync_standbys_defined?
Agree, just checking for WalSndCtl->sync_standbys_defined seems fine.
So the consensus is something like the following? Patch attached.
/*
- * Fast exit if user has not requested sync replication.
+ * Fast exit if user has not requested sync replication, or there are no
+ * sync replication standby names defined.
*/
- if (!SyncRepRequested())
+ if (!SyncRepRequested() ||
+ !((volatile WalSndCtlData *) WalSndCtl)->sync_standbys_defined)
return;
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
diff --git a/src/backend/replication/syncrep.c
b/src/backend/replication/syncrep.c
index ffd5b31eb2..c6df3f4da6 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -163,9 +163,11 @@ SyncRepWaitForLSN(XLogRecPtr lsn, bool commit)
mode = Min(SyncRepWaitMode, SYNC_REP_WAIT_FLUSH);
/*
- * Fast exit if user has not requested sync replication.
+ * Fast exit if user has not requested sync replication, or there are no
+ * sync replication standby names defined.
*/
- if (!SyncRepRequested())
+ if (!SyncRepRequested() ||
+ !((volatile WalSndCtlData *) WalSndCtl)->sync_standbys_defined)
return;
Assert(SHMQueueIsDetached(&(MyProc->syncRepLinks)));
