Performance with the new security release?

On 04/22/2013 10:38 AM, Anne Rosset wrote:

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Does your application do a lot of rapidfire reconnection to PostgreSQL?
i.e. hundreds of new connections per minute?

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

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On 04/22/2013 10:38 AM, Anne Rosset wrote:

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Does your application do a lot of rapidfire reconnection to the
database? As in hundreds of new connections per minute?

Mind you, if it does, I strongly recommend pgbouncer ...

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

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Hi Josh,
Thanks for your reply.
I don't think this is the case since we are using jboss/jdbc driver with a connection pool.

Thanks,
Anne

-----Original Message-----
From: Josh Berkus [mailto:josh@agliodbs.com]
Sent: Monday, April 22, 2013 10:58 AM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 04/22/2013 10:38 AM, Anne Rosset wrote:

While we are digging into this, I would like to know if it is
possible that the release has some impact on performance. After
reading this "It was created as a side effect of a refactoring effort
to make establishing new connections to a PostgreSQL server faster,
and the associated code more maintainable.", I am thinking it is quite possible.

Does your application do a lot of rapidfire reconnection to the database? As in hundreds of new connections per minute?

Mind you, if it does, I strongly recommend pgbouncer ...

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also done
at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released
security update releases for multiple PG versions). Also which version
were you running before?

There were some changes to analyze/vacuum in the previous set of minor
releases that could cause performance issues in some cases (ie if
statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of
pattern that might help narrow the issue?

Steve

Anne

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Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation"?

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also
done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_tnRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for
truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also
done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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Hi Steve,
Yes I see these messages in our log. Is there a solution to this?
Thanks,
Anne
-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 1:26 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if
statistics are no longer being updated because analyze can't get the exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_tnRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also
done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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To make changes to your subscription:
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On 13-04-22 04:41 PM, Anne Rosset wrote:

Hi Steve,
Yes I see these messages in our log. Is there a solution to this?
Thanks,
Anne

A manual analyze of the effected tables should work and give you updated
statistics. If your problem is just statistics then that should help.
A manual vacuum will , unfortunately, behave like the auto-vacuum. The
only way to get vacuum past this (until this issue is fixed) is for
vacuum to be able to get that exclusive lock. If there are times of
the day your database is less busy you might have some luck turning off
auto-vacuum on these tables and doing manual vacuums during those times.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 1:26 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if
statistics are no longer being updated because analyze can't get the exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_tnRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also
done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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Thanks Steve.
I have read that a fix has been put in release 9.2.3 for this issue. Is that right?
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 4:35 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:41 PM, Anne Rosset wrote:

Hi Steve,
Yes I see these messages in our log. Is there a solution to this?
Thanks,
Anne

A manual analyze of the effected tables should work and give you updated statistics. If your problem is just statistics then that should help.
A manual vacuum will , unfortunately, behave like the auto-vacuum. The only way to get vacuum past this (until this issue is fixed) is for
vacuum to be able to get that exclusive lock. If there are times of
the day your database is less busy you might have some luck turning off auto-vacuum on these tables and doing manual vacuums during those times.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 1:26 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if
statistics are no longer being updated because analyze can't get the exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_t
nRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also
done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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On 13-04-22 11:46 PM, Anne Rosset wrote:

Thanks Steve.
I have read that a fix has been put in release 9.2.3 for this issue. Is that right?
Thanks,
Anne

No this issue is present in 9.0.13, 9.1.9 and 9.2.4 (as well as 9.2.3).

There is talk about fixing this for the next set of minor releases but I
haven't yet seen a patch.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 4:35 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:41 PM, Anne Rosset wrote:

Hi Steve,
Yes I see these messages in our log. Is there a solution to this?
Thanks,
Anne

A manual analyze of the effected tables should work and give you updated statistics. If your problem is just statistics then that should help.
A manual vacuum will , unfortunately, behave like the auto-vacuum. The only way to get vacuum past this (until this issue is fixed) is for
vacuum to be able to get that exclusive lock. If there are times of
the day your database is less busy you might have some luck turning off auto-vacuum on these tables and doing manual vacuums during those times.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 1:26 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if
statistics are no longer being updated because analyze can't get the exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_t
nRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were also
done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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Thanks Steve.
I found this: http://www.postgresql.org/docs/current/static/release-9-2-3.html
"
Fix performance problems with autovacuum truncation in busy workloads (Jan Wieck)
Truncation of empty pages at the end of a table requires exclusive lock, but autovacuum was coded to fail (and release the table lock) when there are conflicting lock requests. Under load, it is easily possible that truncation would never occur, resulting in table bloat. Fix by performing a partial truncation, releasing the lock, then attempting to re-acquire the lock and continue. This fix also greatly reduces the average time before autovacuum releases the lock after a conflicting request arrives."

So that is not the fix?

(Sorry to ask a second time but I really need to make sure).
Thanks,
Anne

-----Original Message-----

From: Steve Singer [mailto:steve@ssinger.info]
Sent: Tuesday, April 23, 2013 6:33 AM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 11:46 PM, Anne Rosset wrote:

Thanks Steve.
I have read that a fix has been put in release 9.2.3 for this issue. Is that right?
Thanks,
Anne

No this issue is present in 9.0.13, 9.1.9 and 9.2.4 (as well as 9.2.3).

There is talk about fixing this for the next set of minor releases but I haven't yet seen a patch.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 4:35 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:41 PM, Anne Rosset wrote:

Hi Steve,
Yes I see these messages in our log. Is there a solution to this?
Thanks,
Anne

A manual analyze of the effected tables should work and give you updated statistics. If your problem is just statistics then that should help.
A manual vacuum will , unfortunately, behave like the auto-vacuum. The only way to get vacuum past this (until this issue is fixed) is for
vacuum to be able to get that exclusive lock. If there are times of
the day your database is less busy you might have some luck turning off auto-vacuum on these tables and doing manual vacuums during those times.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 1:26 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if
statistics are no longer being updated because analyze can't get the exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_
t
nRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were
also done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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Anne Rosset wrote:

Thanks Steve.
I found this: http://www.postgresql.org/docs/current/static/release-9-2-3.html
"
Fix performance problems with autovacuum truncation in busy workloads (Jan Wieck)
Truncation of empty pages at the end of a table requires exclusive lock, but autovacuum was coded to fail (and release the table lock) when there are conflicting lock requests. Under load, it is easily possible that truncation would never occur, resulting in table bloat. Fix by performing a partial truncation, releasing the lock, then attempting to re-acquire the lock and continue. This fix also greatly reduces the average time before autovacuum releases the lock after a conflicting request arrives."

So that is not the fix?

(Sorry to ask a second time but I really need to make sure).

That's the commit that created the bug, AFAIU. It's a fix for a serious
problem, but we overlooked that it introduced some other problems which
is what you're now seeing.

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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On 13-04-23 10:04 AM, Anne Rosset wrote:

Thanks Steve.
I found this: http://www.postgresql.org/docs/current/static/release-9-2-3.html
"
Fix performance problems with autovacuum truncation in busy workloads (Jan Wieck)
Truncation of empty pages at the end of a table requires exclusive lock, but autovacuum was coded to fail (and release the table lock) when there are conflicting lock requests. Under load, it is easily possible that truncation would never occur, resulting in table bloat. Fix by performing a partial truncation, releasing the lock, then attempting to re-acquire the lock and continue. This fix also greatly reduces the average time before autovacuum releases the lock after a conflicting request arrives."

So that is not the fix?

No, that is the change that caused this problem. That fix addresses a
slightly different set of symptoms where the truncate as part of an
auto-vacuum doesn't happen because the lock gets pre-empted. An
unintended/undesirable consequence of that fix was that it means if
vacuum can't do the truncate stage because it can't obtain the lock in
the first place then statistics don't get updated.

(Sorry to ask a second time but I really need to make sure).
Thanks,
Anne

-----Original Message-----

From: Steve Singer [mailto:steve@ssinger.info]
Sent: Tuesday, April 23, 2013 6:33 AM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 11:46 PM, Anne Rosset wrote:

Thanks Steve.
I have read that a fix has been put in release 9.2.3 for this issue. Is that right?
Thanks,
Anne

No this issue is present in 9.0.13, 9.1.9 and 9.2.4 (as well as 9.2.3).

There is talk about fixing this for the next set of minor releases but I haven't yet seen a patch.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 4:35 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:41 PM, Anne Rosset wrote:

Hi Steve,
Yes I see these messages in our log. Is there a solution to this?
Thanks,
Anne

A manual analyze of the effected tables should work and give you updated statistics. If your problem is just statistics then that should help.
A manual vacuum will , unfortunately, behave like the auto-vacuum. The only way to get vacuum past this (until this issue is fixed) is for
vacuum to be able to get that exclusive lock. If there are times of
the day your database is less busy you might have some luck turning off auto-vacuum on these tables and doing manual vacuums during those times.

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 1:26 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 04:15 PM, Anne Rosset wrote:

Hi Steve,
Thanks for your reply.
We are now running 9.0.13. Before it was 9.0.7.
How can I find out if we are running into this issue: "ie if
statistics are no longer being updated because analyze can't get the exclusive lock for truncation"?

This issue is discussed in the thread
/messages/by-id/CAMkU=1xYXOJp=jLAASPdSAqab-HwhA_
t
nRhy+JUe=4=b=v3KoQ@mail.gmail.com

If your seeing messages in your logs of the form:

automatic vacuum of table XXX.YYY cannot (re)acquire exclusive lock for truncate scan"

then you might be hitting this issue.

I will dig into our logs to see for the query times.
Thanks,
Anne

-----Original Message-----
From: Steve Singer [mailto:steve@ssinger.info]
Sent: Monday, April 22, 2013 12:59 PM
To: Anne Rosset
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Performance with the new security release?

On 13-04-22 01:38 PM, Anne Rosset wrote:

Hi,
We are seeing some overall performance degradation in our application
since we installed the security release. Other commits were
also done at the same time in the application so we don't know yet if the
degradation has any relationship with the security release.

While we are digging into this, I would like to know if it is possible
that the release has some impact on performance. After reading this
"It was created as a side effect of a refactoring effort to make
establishing new connections to a PostgreSQL server faster, and the
associated code more maintainable.", I am thinking it is quite possible.

Please let me know. Thanks,

Exactly which version of PostgreSQL are you running? (we released security update releases for multiple PG versions). Also which version were you running before?

There were some changes to analyze/vacuum in the previous set of minor releases that could cause performance issues in some cases (ie if statistics are no longer being updated because analyze can't get the
exclusive lock for truncation). There might be other unintended
performance related changes.

Are all queries taking longer or only some? Can you find any sort of pattern that might help narrow the issue?

Steve

Anne

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