RE: Pg10 : Client Configuration for Parallelism ?

From: <laurent(dot)dechambe(at)orange(dot)com>
To: Andreas Joseph Krogh <andreas(at)visena(dot)com>, "pgsql-performance(at)lists(dot)postgresql(dot)org" <pgsql-performance(at)lists(dot)postgresql(dot)org>
Subject: RE: Pg10 : Client Configuration for Parallelism ?
Date: 2019-04-17 09:51:02
Message-ID: 16873_1555494663_5CB6F707_16873_40_4_A971FB43DFBC3D4C859ACB3316C9FF4632D98C75@OPEXCAUBM42.corporate.adroot.infra.ftgroup
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As answered to Andreas Kretschmer all settings are identical.

I have made some other tests, even testing a basic jdbc program (open connection, execute statement, display result, close connection)

Here are the logs (with log_error_verbosity = verbose) :

<DBEAVER>
2019-04-17 11:30:42 CEST;35895;thedbuser;thedb;00000;LOG: 00000: execute <unnamed>: SELECT COUNT(1) FROM big_table
2019-04-17 11:30:42 CEST;35895;thedbuser;thedb;00000;LOCATION: exec_execute_message, postgres.c:1959
2019-04-17 11:31:08 CEST;35895;thedbuser;thedb;00000;LOG: 00000: duration: 25950.908 ms
2019-04-17 11:31:08 CEST;35895;thedbuser;thedb;00000;LOCATION: exec_execute_message, postgres.c:2031

<BASIC JDBC>
2019-04-17 11:31:20 CEST;37257;thedbuser;thedb;00000;LOG: 00000: execute <unnamed>: SELECT COUNT(1) FROM big_table
2019-04-17 11:31:20 CEST;37257;thedbuser;thedb;00000;LOCATION: exec_execute_message, postgres.c:1959
2019-04-17 11:31:32 CEST;37257;thedbuser;thedb;00000;LOG: 00000: duration: 11459.943 ms
2019-04-17 11:31:32 CEST;37257;thedbuser;thedb;00000;LOCATION: exec_execute_message, postgres.c:2031

<PGADMIN4>
2019-04-17 11:32:56 CEST;37324;thedbuser;thedb;00000;LOG: 00000: statement: SELECT COUNT(1) FROM big_table;
2019-04-17 11:32:56 CEST;37324;thedbuser;thedb;00000;LOCATION: exec_simple_query, postgres.c:940
2019-04-17 11:33:08 CEST;37324;thedbuser;thedb;00000;LOG: 00000: duration: 11334.677 ms
2019-04-17 11:33:08 CEST;37313;thedbuser;thedb;00000;LOG: 00000: statement: SELECT oid, format_type(oid, NULL) AS typname FROM pg_type WHERE oid IN (20) ORDER BY oid;
2019-04-17 11:33:08 CEST;37313;thedbuser;thedb;00000;LOCATION: exec_simple_query, postgres.c:940
2019-04-17 11:33:08 CEST;37313;thedbuser;thedb;00000;LOG: 00000: duration: 0.900 ms
2019-04-17 11:33:08 CEST;37313;thedbuser;thedb;00000;LOCATION: exec_simple_query, postgres.c:1170

I don’t see any difference a part from the query duration. Note that while monitoring the server I saw that there was parallelism with JDBC program and PGAdmin4, but not with Dbeaver. And the JDBC driver is the same in both “Basic JDBC” and DBeaver.

Regards.

Laurent.

De : Andreas Joseph Krogh [mailto:andreas(at)visena(dot)com]
Envoyé : mercredi 17 avril 2019 11:08
À : pgsql-performance(at)lists(dot)postgresql(dot)org
Objet : Sv: Pg10 : Client Configuration for Parallelism ?

På onsdag 17. april 2019 kl. 08:30:28, skrev <laurent(dot)dechambe(at)orange(dot)com<mailto:laurent(dot)dechambe(at)orange(dot)com>>:
Hi,

I am working on PostgreSQL 10.5 and I have a discrepancy between clients regarding parallelism feature.

For a simple query (say a simple SELECT COUNT(*) FROM BIG_TABLE), I can see PostgreSQL use parallelism when the query is launched from psql or PgAdmin4. However the same query launched with DBeaver (ie connected through JDBC) does not use parallelism.

SELECT current_setting('max_parallel_workers_per_gather') gives 10 from my session.

Is there a client configuration that prevents from using parallelism ?

Thanks.

Laurent

Set in postgresql.conf:

log_statement = 'all'

reload settings and check the logs for what statemets are acutally issued.

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