Thread: Different execution plans in PG17 and pgBouncer...
Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Regards,Mladen Marinović
On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.
What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
Regards,Mladen Marinović
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
Regards,Mladen Marinović
On 5/5/25 11:30, Ruben Morais wrote:
HI,Could be a hint but test with jit to off.If not wrong as you change from 11 to 17, that could be a cause, just try it because in some cases plans changed when jit is on.
Not only JIT but also other extensions (such as timescale) could greatly affect the plan.
He could find if any GUC are set for the particular user :
select * from pg_db_role_setting where setrole = to_regrole('<unlucky_user>');
Regards,Rúben MoraisOn Mon, May 5, 2025 at 11:07 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
Regards,Mladen Marinović
On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.
ok, this is something, at least one more extreme thought ruled out. How about search_path ? is this the SAME user that is issuing the statements in pgadmin VS pgbouncer ?
Is there a connect_query inside pgbouncer's conf ?
you have to show all configuration involved and also full logging on the backend for said user.
Regards,Mladen Marinović
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
Regards,Mladen Marinović
On 5/5/25 13:27, Mladen Marinović wrote:On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.
ok, this is something, at least one more extreme thought ruled out. How about search_path ? is this the SAME user that is issuing the statements in pgadmin VS pgbouncer ?
search_path
-----------------
"$user", public
(1 row)
Is there a connect_query inside pgbouncer's conf ?
you have to show all configuration involved and also full logging on the backend for said user.
Regards,Mladen Marinović
Hi , you had better try vacuum analyze for the whole db , pgbouncer connection layer can not causeslow queries.
From: Mladen Marinović <marin@kset.org>
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.Regards,Mladen Marinović
Sent: Monday, May 5, 2025 12:52 PM
To: SERHAD ERDEM <serhade@hotmail.com>
Cc: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>; pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...
Hi , you had better try vacuum analyze for the whole db , pgbouncer connection layer can not causeslow queries.
From: Mladen Marinović <marin@kset.org>
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.Regards,Mladen Marinović
On Mon, May 5, 2025 at 8:52 AM, Mladen Marinović<marin@kset.org> wrote:On Mon, May 5, 2025 at 2:38 PM SERHAD ERDEM <serhade@hotmail.com> wrote:Hi , you had better try vacuum analyze for the whole db , pgbouncer connection layer can not causeslow queries.I did that already. But the slow query is the consequence of the different plan, not the statistics.From: Mladen Marinović <marin@kset.org>
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.Regards,Mladen Marinović
Is the query using parameter markers? Is the source executing the query forcing a "bad" data type casting?On Mon, May 5, 2025 at 8:52 AM, Mladen Marinović<marin@kset.org> wrote:On Mon, May 5, 2025 at 2:38 PM SERHAD ERDEM <serhade@hotmail.com> wrote:Hi , you had better try vacuum analyze for the whole db , pgbouncer connection layer can not causeslow queries.I did that already. But the slow query is the consequence of the different plan, not the statistics.From: Mladen Marinović <marin@kset.org>
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.Regards,Mladen Marinović
Sent: Monday, May 5, 2025 1:26 PM
To: Efrain J. Berdecia <ejberdecia@yahoo.com>
Cc: SERHAD ERDEM <serhade@hotmail.com>; Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>; pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...
Is the query using parameter markers? Is the source executing the query forcing a "bad" data type casting?On Mon, May 5, 2025 at 8:52 AM, Mladen Marinović<marin@kset.org> wrote:On Mon, May 5, 2025 at 2:38 PM SERHAD ERDEM <serhade@hotmail.com> wrote:Hi , you had better try vacuum analyze for the whole db , pgbouncer connection layer can not causeslow queries.I did that already. But the slow query is the consequence of the different plan, not the statistics.From: Mladen Marinović <marin@kset.org>
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.Regards,Mladen Marinović
On 2025-May-05, Mladen Marinović wrote: > Hi, > > Mystery not solved...but identified. The pool is in transaction mode and > some connections use set enable_mergejoin=off, but they do not set it back > to on. Maybe instead of "SET enable_mergejoin=off" these connections could be changed to use SET LOCAL enable_mergejoin=off. That way, the setting reverts to its original value automatically at the end of the transaction. It seems more appropriate when using transaction mode anyway. -- Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
Hi,Mystery not solved...but identified. The pool is in transaction mode and some connections use set enable_mergejoin=off, but they do not set it back to on. Upon getting the connection from the pool the parameter is still set to off causing the planner to not use this kind of join which results in different plans when using this tainted pgbouncer connection instead of the clean one from pg17.The problem is that server_reset_query is not used when the pool is in transaction mode. Now, we have to see how to fix this problem.
But you've got this : https://www.pgbouncer.org/config.html
"
server_reset_query_always
Whether server_reset_query should be run in all pooling modes. When this setting is off (default), the server_reset_query will be run only in pools that are in sessions-pooling mode. Connections in transaction-pooling mode should not have any need for a reset query.
This setting is for working around broken setups that run applications that use session features over a transaction-pooled PgBouncer. It changes non-deterministic breakage to deterministic breakage: Clients always lose their state after each transaction.
"
Regards,Mladen MarinovićOn Mon, May 5, 2025 at 3:10 PM Efrain J. Berdecia <ejberdecia@yahoo.com> wrote:Is the query using parameter markers? Is the source executing the query forcing a "bad" data type casting?On Mon, May 5, 2025 at 8:52 AM, Mladen Marinović<marin@kset.org> wrote:On Mon, May 5, 2025 at 2:38 PM SERHAD ERDEM <serhade@hotmail.com> wrote:Hi , you had better try vacuum analyze for the whole db , pgbouncer connection layer can not causeslow queries.I did that already. But the slow query is the consequence of the different plan, not the statistics.From: Mladen Marinović <marin@kset.org>
Sent: Monday, May 5, 2025 12:27 PM
To: Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com>
Cc: pgsql-general@lists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Different execution plans in PG17 and pgBouncer...On Mon, May 5, 2025 at 12:07 PM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 11:00, Mladen Marinović wrote:On Mon, May 5, 2025 at 11:24 AM Achilleas Mantzios <a.mantzios@cloud.gatewaynet.com> wrote:
On 5/5/25 09:52, Mladen Marinović wrote:Hi,We recently migrated our production instances from PG11 to PG17. While doing so we upgraded our pgBouncer instances from 1.12 to 1.24. As everything worked on the test servers we pushed this to production a few weeks ago. We did not notice any problems until a few days ago (but the problems were here from the start). The main manifestation of the problems is a service that runs a fixed query to get a backlog of unprocessed data (limited to a 1000 rows). When testing the query using pgAdmin connected directly to the database we get a result in cca. 20 seconds. The same query runs for 2 hours when using pgBouncer to connect to the same database.
That's a huge jump, I hope you guys did extensive testing of your app. In which language is your app written? If java, then define prepareThreshold=0 in your jdbc and set max_prepared_statements = 0 in pgbouncer.
Mainly python, but the problem was noticed in a java service.Prepare treshold was already set to 0. We changed the max_prepared_statements to 0 from the default (200) but no change was noticed.How about search paths ? any difference on those between the two runs ? Do you set search_path in pgbouncer ? what is "cca." btw ?
The more interesting part is that when we issue an explain of the same query we get different plans. We did this a few seconds apart so there should be no difference in collected statistics. We ruled out prepared statements, as we suspected the generic plan might be the problem, but it is not. Is there any pgBouncer or PG17 parameter that might be the cause of this?
Does this spawn any connections (such as dblink) ? are there limits per user/db pool_size in pgbouncer ?
No additional connection nor dbling. Just plain SQL (CTE, SELECT, INSERT, UPDATE, DELETE,...) There are limits, but they are not hit. The query just uses a different plan and runs slower because of that.Pgbouncer, in contrast to its old friend PgPool-II is completely passive, just passes through SQL to the server as fast as possible as it can. But I am sure you know that. Good luck, keep us posted!
Yes, that is what puzzles me.What is the pgbouncer's timeout in the server connections ?
How about "idle in transaction" ? do you get any of those? What's the isolation level ?
How about the user ? is this the same user doing pgadmin queries VS via the app ?
Can you identify the user under which the problem is manifested and :
ALTER user "unlucky_user" SET log_statement = 'all';
ALTER user "unlucky_user" SET log_min_duration_statement = 0; -- to help you debug the prepared statements .. just in case , and other stuff not printed by log_statement = all.
None of those parameters should affect the fact that when issuing the explain select query (the statement is not prepared) from psql directly gives a different result than issuing it over the pgbouncer connection. The result is repeatable.We have rolled back pgbouncer to 1.12. and it seems the problem persists. This is one of the weirdest things I have ever seen with PostgreSQL.Regards,Mladen Marinović