We make 2 comparisions between partitioned(256 HASH) and no-partitioned(same data volume,same table attributes) , do same "UPDATE,DELETE " .
1. with partitioned tables , the "RES" from top command memory increased quickly to 160MB and keep stable there.
From auto_explain trace, we did saw partition pruning to specific partition when execution the prepared sql statement by Postgresql JDBC .
2. with no-partitioned tables, the "RES" from top command memory only keep 24MB stable there.
Same auto_explain , and only table and index scan there by prepared sql statement by Postgresql JDBC.
3. with psql client , run the UPDATE/DELETE sql locally, partition pruning works and the "RES" memory" is much less, it's about 9MB .
Yesterday, when workload test, a lot of Postgresql JDBC connections use 150-160MB memory , so we got ERROR: out of memory
Detail: Failed on request of size 240 in memory context "MessageContext". And other non-postgresql process like top command even failed into no-memory error.
So, looks like something with Postgresql JDBC driver lead to the high memory consumption when table is partitioned , even when table is no partitioned , compared with psql client, it consumes more memory. Any suggestions to tune that ? PG V13 , OS RHEL8 , Virtua machine on VMWARE. We make shared_buffers=36% physical memory , effective_cache_size=70%physical memory , total physical memory is about 128GB.
Thanks,
James
-----Original Message-----
From: James Pang (chaolpan) <chaolpan@xxxxxxxxx>
Sent: Monday, September 5, 2022 8:52 PM
To: Justin Pryzby <pryzby@xxxxxxxxxxxxx>
Cc: pgsql-performance@xxxxxxxxxxxxxxxxxxxx
Subject: RE: Postgresql JDBC process consumes more memory than psql client
PG V13, yes JDBC use prepared statements , from psql use pruned ,but even all partitions it NOT consumes too much memory. Any idea how to print SQL plan from JDBC driver ?
-----Original Message-----
From: Justin Pryzby <pryzby@xxxxxxxxxxxxx>
Sent: Monday, September 5, 2022 8:47 PM
To: James Pang (chaolpan) <chaolpan@xxxxxxxxx>
Cc: pgsql-performance@xxxxxxxxxxxxxxxxxxxx
Subject: Re: Postgresql JDBC process consumes more memory than psql client
On Mon, Sep 05, 2022 at 12:40:46PM +0000, James Pang (chaolpan) wrote:
> We run same update or delete SQL statement " DELETE FROM ... WHERE ... " the table is a hash partition table (256 hash partitions). When run the sql from Postgresql JDBC driver, it soon increased to 150MB memory (RES filed from top command), but when run the same SQL from psql , it only consumes about 10MB memory. UPDATE statements is similar , need 100MB memory, even it delete or update 0 rows. Any specific control about Postgresql JDBC driver ?
It sounds like JDBC is using prepared statements, and partitions maybe weren't pruned by the server. What is the query plan from psql vs from jdbc ?
https://wiki.postgresql.org/wiki/Slow_Query_Questions
What version is the postgres server ?
That affects pruning as well as memory use.
https://www.postgresql.org/docs/14/release-14.html
Improve the performance of updates and deletes on partitioned tables with many partitions (Amit Langote, Tom Lane)
This change greatly reduces the planner's overhead for such cases, and also allows updates/deletes on partitioned tables to use execution-time partition pruning.
Actually, this is about the same response as when you asked in June, except that was about UPDATE.
https://www.postgresql.org/message-id/PH0PR11MB519134D4171A126776E3E063D6B89@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
--
Justin
