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List: postgresql-general
Subject: Re: 9.6.11- could not truncate directory "pg_serial": apparent wraparound
From: Pavel Suderevsky <psuderevsky () gmail ! com>
Date: 2019-06-27 16:47:29
Message-ID: CAEBTBzuCS6MuE_Agk7jMPwMofHu2QY_6enf1_WaAaemSS+nVLA () mail ! gmail ! com
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Hi,
Got this issue again.
Settings on the platform (PG 9.6.11):
max_pred_locks_per_transaction = 3000
max_connections = 800
Despite the fact that documentation says:
> with the exception of fast-path locks, each lock manager will deliver a
consistent set of results
I've noticed the following:
1. pg_locks showed 2 million SIReadLocks for the pid that has been in the
"idle" state for a dozen of seconds already.
2. pg_locks showed count of 5 million SIReadLock granted although I
expected a limit of 2.4 million SIReadLocks with settings provided above.
And still no any signs of serializable transactions that could live for a 1
billion xids.
--
Pavel Suderevsky
E: psuderevsky(at)gmail(dot)com
вт, 9 апр. 2019 г. в 16:00, Pavel Suderevsky <psuderevsky@gmail.com>:
> On Sun, Apr 7, 2019 at 2:31 AM Pavel Suderevsky <psuderevsky@gmail.com>
>> wrote:
>> > Probably if you advise me what could cause "pg_serial": apparent
>> wraparound messages I would have more chances to handle all the performance
>> issues.
>>
>> Did you see that warning at some point before the later error?
>>
> Thomas,
>
> Thank you for your reply!
>
> No, there have never been such warnings.
>
> I wonder if this condition required you to have a serializable
>> transaction running (or prepared) while you consume 2^30 AKA ~1
>> billion xids. I think it is unreachable in v11+ because commit
>> e5eb4fa8 allowed for more SLRU pages to avoid this artificially early
>> wrap.
>
>
> Do I understand right that this is about Virtual txids? Have no idea how
> even a something close to a billion of transaction ids could be consumed on
> this system.
>
> --
> Pavel Suderevsky
> E: psuderevsky@gmail.com
>
[Attachment #3 (text/html)]
<div dir="ltr">Hi,<div><br></div><div>Got this issue again.</div><div>Settings on the \
platform (PG 9.6.11):</div><div>max_pred_locks_per_transaction = \
3000<br></div><div>max_connections = 800<br></div><div><br></div><div>Despite the \
fact that documentation says: </div><div>> with the exception of fast-path \
locks, each lock manager will deliver a consistent set of results</div><div>I've \
noticed the following:</div><div>1. pg_locks showed 2 million SIReadLocks for the pid \
that has been in the "idle" state for a dozen of seconds \
already.</div><div>2. pg_locks showed count of 5 million SIReadLock granted although \
I expected a limit of 2.4 million SIReadLocks with settings provided \
above.</div><div><br></div><div>And still no any signs of serializable transactions \
that could live for a 1 billion xids. </div><div><span \
style="color:rgb(13,10,11);font-family:monospace,monospace;font-size:10.7333px;white-space:pre-wrap">--</span><br \
style="box-sizing:border-box;color:rgb(13,10,11);font-family:monospace,monospace;font-size:10.7333px;white-space:pre-wrap"><span \
style="color:rgb(13,10,11);font-family:monospace,monospace;font-size:10.7333px;white-space:pre-wrap">Pavel \
Suderevsky</span><br \
style="box-sizing:border-box;color:rgb(13,10,11);font-family:monospace,monospace;font-size:10.7333px;white-space:pre-wrap"><span \
style="color:rgb(13,10,11);font-family:monospace,monospace;font-size:10.7333px;white-space:pre-wrap">E: \
psuderevsky(at)gmail(dot)com</span> <br></div></div><br><div \
class="gmail_quote"><div dir="ltr" class="gmail_attr">вт, 9 апр. 2019 г. в \
16:00, Pavel Suderevsky <<a \
href="mailto:psuderevsky@gmail.com">psuderevsky@gmail.com</a>>:<br></div><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div \
class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Sun, Apr 7, 2019 at \
2:31 AM Pavel Suderevsky <<a href="mailto:psuderevsky@gmail.com" \
target="_blank">psuderevsky@gmail.com</a>> wrote:<br> > Probably if you advise \
me what could cause "pg_serial": apparent wraparound messages I would have \
more chances to handle all the performance issues.<br><br> Did you see that warning \
at some point before the later \
error?<br></blockquote>Thomas,<div><br></div><div>Thank you for your \
reply!</div><div><br></div><div>No, there have never been such \
warnings.</div><div><br></div><div><blockquote class="gmail_quote" style="margin:0px \
0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">I wonder if \
this condition required you to have a serializable<br>transaction running (or \
prepared) while you consume 2^30 AKA ~1<br>billion xids. I think it is unreachable \
in v11+ because commit<br>e5eb4fa8 allowed for more SLRU pages to avoid this \
artificially early<br>wrap. </blockquote><div> </div><div>Do I understand right \
that this is about Virtual txids? Have no idea how even a something close to a \
billion of transaction ids could be consumed on this system.</div><div> \
</div></div><div>--</div><div>Pavel Suderevsky</div><div>E: <a \
href="mailto:psuderevsky@gmail.com" target="_blank">psuderevsky@gmail.com</a> \
</div></div></div> </blockquote></div>
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