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  1. MariaDB Server
  2. MDEV-9462

Out of memory using explain on 2 empty tables


    • Sprint:


      Tested on MySQL 5.5.29 as well as MariaDB 10.0.21, bug not present. The explain returns the desired result (56 rows).

      The bug is easily reproducible on MariaDB 10.1 by running the attached explain_bug.sql script on any test database. All it does is create 2 empty tables and running an explain.

      The result is

      ERROR 5 (HY000) at line 79 in file: '/home/tnguyen/explailn_bug.sql': Out of memory (Needed 5784 bytes)

      MySQL error log:

      2016-01-25 16:47:45 139975536690944 [ERROR] mysqld: Out of memory (Needed 5784 bytes)
      2016-01-25 16:47:45 139975536690944 [ERROR] Out of memory; check if mysqld or some other process uses all available memory; if not, you may have to use 'ulimit' to allow mysqld to use more memory or you can add more swap space

      ulimit -a:

      core file size          (blocks, -c) 0
      data seg size           (kbytes, -d) unlimited
      scheduling priority             (-e) 0
      file size               (blocks, -f) unlimited
      pending signals                 (-i) 47584
      max locked memory       (kbytes, -l) 64
      max memory size         (kbytes, -m) unlimited
      open files                      (-n) 1024
      pipe size            (512 bytes, -p) 8
      POSIX message queues     (bytes, -q) 819200
      real-time priority              (-r) 0
      stack size              (kbytes, -s) 8192
      cpu time               (seconds, -t) unlimited
      max user processes              (-u) 47584
      virtual memory          (kbytes, -v) unlimited
      file locks                      (-x) unlimited


      This bug is causing previously working ETL code to fail after a database upgrade, even though we don't have any real memory issue as it was working fine on older db versions.

      Also attached the same my.cnf that I used to test on 10.0.21 and 10.1.9 & 10.1.10.




            • Assignee:
              sanja Oleksandr Byelkin
              tnguyen Hung Tam Nguyen
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