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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

    • Bug
    • Status: Closed (View Workflow)
    • Critical
    • Resolution: Duplicate
    • 10.5.5, 10.6
    • N/A
    • Locking, Query Cache
    • 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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        Issue Links

          duplicates

          Bug - A problem which impairs or prevents the functions of the product. MDEV-29760 DROP DATABASE hangs when particular query cache is present

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

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            People

              danblack Daniel Black
              sjon sjon
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              Dates

                Created:
                Updated:
                Resolved:

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