On 2020/03/10 13:54, Masahiko Sawada wrote:
On Tue, 10 Mar 2020 at 00:57, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
On 2020/03/09 14:10, Masahiko Sawada wrote:
On Mon, 9 Mar 2020 at 13:24, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
On 2020/03/08 13:52, Masahiko Sawada wrote:
On Thu, 5 Mar 2020 at 20:16, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
On 2020/03/05 16:58, Masahiko Sawada wrote:
On Wed, 4 Mar 2020 at 15:21, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
On 2020/03/04 14:31, Masahiko Sawada wrote:
On Wed, 4 Mar 2020 at 13:48, Fujii Masao <masao.fu...@oss.nttdata.com> wrote:
On 2020/03/04 13:27, Michael Paquier wrote:
On Wed, Mar 04, 2020 at 01:13:19PM +0900, Masahiko Sawada wrote:
Yeah, so 0001 patch sets existing wait events to recovery conflict
resolution. For instance, it sets (PG_WAIT_LOCK | LOCKTAG_TRANSACTION)
to the recovery conflict on a snapshot. 0003 patch improves these wait
events by adding the new type of wait event such as
WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT. Therefore 0001 (and 0002) patch
is the fix for existing versions and 0003 patch is an improvement for
only PG13. Did you mean even 0001 patch doesn't fit for back-patching?
Yes, it looks like a improvement rather than bug fix.
Okay, understand.
I got my eyes on this patch set. The full patch set is in my opinion
just a set of improvements, and not bug fixes, so I would refrain from
back-backpatching.
I think that the issue (i.e., "waiting" is reported twice needlessly
in PS display) that 0002 patch tries to fix is a bug. So it should be
fixed even in the back branches.
So we need only two patches: one fixes process title issue and another
improve wait event. I've attached updated patches.
Thanks for updating the patches! I started reading 0001 patch.
Thank you for reviewing this patch.
- /*
- * Report via ps if we have been waiting for more than
500 msec
- * (should that be configurable?)
- */
- if (update_process_title && new_status == NULL &&
- TimestampDifferenceExceeds(waitStart,
GetCurrentTimestamp(),
-
500))
The patch changes ResolveRecoveryConflictWithSnapshot() and
ResolveRecoveryConflictWithTablespace() so that they always add
"waiting" into the PS display, whether wait is really necessary or not.
But isn't it better to display "waiting" in PS basically when wait is
necessary, like originally ResolveRecoveryConflictWithVirtualXIDs()
does as the above?
You're right. Will fix it.
ResolveRecoveryConflictWithDatabase(Oid dbid)
{
+ char *new_status = NULL;
+
+ /* Report via ps we are waiting */
+ new_status = set_process_title_waiting();
In ResolveRecoveryConflictWithDatabase(), there seems no need to
display "waiting" in PS because no wait occurs when recovery conflict
with database happens.
Isn't the startup process waiting for other backend to terminate?
Yeah, you're right. I agree that "waiting" should be reported in this case.
Currently ResolveRecoveryConflictWithLock() and
ResolveRecoveryConflictWithBufferPin() don't call
ResolveRecoveryConflictWithVirtualXIDs and don't report "waiting"
in PS display. You changed them so that they report "waiting". I agree
to have this change. But this change is an improvement rather than
a bug fix, i.e., we should apply this change only in v13?
Did you mean ResolveRecoveryConflictWithDatabase and
ResolveRecoveryConflictWithBufferPin?
Yes! Sorry for my typo.
In the current code as far as I
researched there are two cases where we don't add "waiting" and one
case where we doubly add "waiting".
ResolveRecoveryConflictWithDatabase and
ResolveRecoveryConflictWithBufferPin don't update the ps title.
Although the path where GetCurrentTimestamp() >= ltime is false in
ResolveRecoveryConflictWithLock also doesn't update the ps title, it's
already updated in WaitOnLock. On the other hand, the path where
GetCurrentTimestamp() >= ltime is true in
ResolveRecoveryConflictWithLock updates the ps title but it's wrong as
I reported.
I've split the patch into two patches: 0001 patch fixes the issue
about doubly updating ps title, 0002 patch makes the recovery conflict
resolution on database and buffer pin update the ps title.
Thanks for splitting the patches. I think that 0001 patch can be back-patched.
- /*
- * Report via ps if we have been waiting for more than
500 msec
- * (should that be configurable?)
- */
- if (update_process_title && new_status == NULL &&
- TimestampDifferenceExceeds(waitStart,
GetCurrentTimestamp(),
-
500))
Originally, "waiting" is reported in PS if we've been waiting for more than
500 msec, as the above does. But you got rid of those codes in the patch.
Did you confirm that it's safe to do that? If not, isn't it better to apply
the attached patch?
In WaitOnLock() we update the ps title regardless of waiting time. So
I thought we can change it to make these behavior consistent. But
considering back-patch, your patch looks better than mine.
Yeah, so I pushed the 0001 patch at first!
I will review the other patches later.
Thank you!
For 0002 patch which makes ResolveRecoveryConflictWithDatabase and
ResolveRecoveryConflictWithBufferPin update the ps title, I think
these are better to wait for 5ms before updating the ps title like
ResolveRecoveryConflictWithVirtualXIDs, for consistency among recovery
conflict resolution functions, but what do you think?
Maybe yes.
As another idea, for consistency, we can change all
ResolveRecoveryConflictWithXXX() so that they don't wait
at all before reporting "waiting". But if we don't do that,
"waiting" can be reported even when we can immediately
cancel or terminate the conflicting transactions (e.g., in
case of max_standby_streaming_delay=0). To avoid this
issue, I think it's better to wait for 500ms.
The 0002 patch changes ResolveRecoveryConflictWithBufferPin()
so that it updates PS every time. But this seems not good
because the update can happen very frequently. Thought?
Regards,
--
Fujii Masao
NTT DATA CORPORATION
Advanced Platform Technology Group
Research and Development Headquarters
