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  1. MariaDB Server
  2. MDEV-23527

mariadb-10.5 hangs on "query cache lock" on DROP DATABASE

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    Details

    • Type: Bug
    • Status: Open (View Workflow)
    • Priority: Critical
    • Resolution: Unresolved
    • Affects Version/s: 10.5.5
    • Fix Version/s: None
    • Component/s: Locking, Query Cache
    • Labels:
      None
    • Environment:
      mariadb 10.5.5-1
      archlinux 5.7.12-arch1-1

      query_cache_type = 1
      query_cache_size = 64M

      Description

      ever since upgrading to 10.5 (from 10.4.14) we experience strange hangs of the mariadb server. This is a nice example:

      818 xx localhost xxx-2_1-unittest Query 14945 closing tables DROP DATABASE IF EXISTS `xxx-2_1-20200821055757` 0.000
      2002 xxx localhost xxx-1_3-20200821055909 Killed 14879 Waiting for query cache lock INSERT INTO xxx 0.000
      2030 root localhost   Query 0 starting show processlist 0.000

      there seems to be no real relation between the DROP and the INSERT as they operate on completely different databases (they have no relation). I also have examples where there are multiple (killed) Waiting for query cache lock threads and a single DROP closing tables

      The mariadbd consumes 100% CPU but I'm not sure what it's doing. strace shows some futex calls

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            Assignee:
            Unassigned Unassigned
            Reporter:
            sjon sjon
            Votes:
            2 Vote for this issue
            Watchers:
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              Dates

              Created:
              Updated:

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