What is truth?

Today I found myself questioning reality itself.

This database query returned 7 rows:

MariaDB [db]> select * from wp_icl_strings where context = 'theme' order by id desc;

This database query returned 1511 rows:

MariaDB [db]> select * from wp_icl_strings where context = 'theme';

As anyone who knows SQL should know, these 2 queries should definitely be returning the same number of rows.

I tried repeating the queries, just to make sure. I got the same results.

As this bizarre result came at a time that I was already fighting a maddening bug in WPML string translations, it felt like I had now entered a reality where 1 + 1 had suddenly started to equal 3.

Fortunately for my sanity, the database server also agreed that this broke reality:

MariaDB [db]> check table wp_icl_strings;
ERROR 2013 (HY000): Lost connection to MySQL server during query
...
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111)
ERROR: Can't connect to the server

Yes, trying to check that table for consistency successfully crashed MariaDB.

Just for fun, I tried it again, and found that yep, I can crash this database on demand now.

The logs were a bit more revealing:

Jul 29 14:47:56 dbserver-3 mysqld[1496634]: 2021-07-29 14:47:56 62 [ERROR] InnoDB: Corruption of an index tree: table `db`.`wp_icl_strings` index `language_context`, father ptr page no 679, child page no 303
Jul 29 14:47:56 dbserver-3 mysqld[1496634]: PHYSICAL RECORD: n_fields 3; compact format; info bits 0
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  0: len 2; hex 656e; asc en;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  1: len 3; hex 616366; asc acf;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  2: len 8; hex 000000000000443b; asc       D;;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]: 2021-07-29 14:47:56 62 [Note] InnoDB: n_owned: 0; heap_no: 2; next rec: 147
Jul 29 14:47:56 dbserver-3 mysqld[1496634]: PHYSICAL RECORD: n_fields 4; compact format; info bits 0
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  0: len 2; hex 656e; asc en;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  1: len 7; hex 57696467657473; asc Widgets;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  2: len 8; hex 00000000060f0657; asc        W;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]:  3: len 4; hex 000002a7; asc     ;;
Jul 29 14:47:56 dbserver-3 mysqld[1496634]: 2021-07-29 14:47:56 62 [Note] InnoDB: n_owned: 0; heap_no: 32; next rec: 151
Jul 29 14:47:56 dbserver-3 mysqld[1496634]: 2021-07-29 14:47:56 62 [ERROR] [FATAL] InnoDB: You should dump + drop + reimport the table to fix the corruption. If the crash happens at database startup. Please refer to https://mariadb.com/kb/en/library/innodb-recovery-modes/ for information about forcing recovery. Then dump + drop + reimport.

Sure enough, the advice there to dump + drop + reimport the table to fix the corruption was exactly what needed to be done. A simple fix that took no time at all.

If only the rest of reality were so easy to fix.

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  1. In FORTRAN, you could modify “constants”, and you could get weird results like this.

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