Re: many backends hang on MultiXactOffsetSLRU

[Amine Tengilimoglu <aminetengilimoglu@xxxxxxxxx>]

     Hi,

           I encountered this in a project we migrated to PostgreSQL before, and unfortunately, it’s a situation that completely degrades performance. We identified the cause as savepoints being used excessively and without control. Once they reduced the number of savepoints, the issue was resolved. However, the documentation also mentions that it could be caused by foreign keys.

  Kind regards..  

James Pang <jamespang886@xxxxxxxxx>, 10 Eyl 2024 Sal, 10:33 tarihinde şunu yazdı:

Hi experts,

    we have a Postgresql v14.8 database, almost thousands of backends hang on MultiXactOffsetSLRU at the same time, all of these sessions running same query "SELECT ....", from OS and postgresql slow log, we found all of these query on "BIND" stage.

 LOG:  duration: 36631.688 ms  bind S_813: SELECT
LOG:  duration: 36859.786 ms  bind S_1111: SELECT
LOG:  duration: 35868.148 ms  bind <unnamed>: SELECT
LOG:  duration: 36906.471 ms  bind <unnamed>: SELECT
LOG:  duration: 35955.489 ms  bind <unnamed>: SELECT
LOG:  duration: 36833.510 ms  bind <unnamed>: SELECT
LOG:  duration: 36839.535 ms  bind S_1219: SELECT

...

this database hang on MultiXactOffsetSLRU and MultiXactOffsetBuffer long time.  

could you direct me why they are hanging on 'BIND‘ stage with MultiXactOffsetSLRU ? 

Thanks,

James