Hey,

I have a job that migrates an old database to in a different format (my custom, php based forum migrating to a django-based one).

Recently, I've seen the mariadb server crashing randomly, leaving other databases and their tables corrupted. I can't just pinpoint out the exact issue, but I can provide the traceback and coredump, in hopes of you finding and fixing the bug ASAP.

This posted crashlog is from executing mariadb-check -c --all-databases -S /tmp/mysql.sock, that according to its output, crashes on a certain CHECK TABLE command.

The crash log from mysqld.err:
===
2021-09-04 11:15:41 0x80f1b5d00 InnoDB: Assertion failure in file /wrkdirs/usr/ports/databases/mariadb105-server/work/mariadb-10.5.
12/storage/innobase/btr/btr0btr.cc line 4763
InnoDB: Failing assertion: !page_is_empty(page) || (level == 0 && page_get_page_no(page) == dict_index_get_page(index))
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to https://jira.mariadb.org/
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: https://mariadb.com/kb/en/library/innodb-recovery-modes/
InnoDB: about forcing recovery.
210904 11:15:41 [ERROR] mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.

To report this bug, see https://mariadb.com/kb/en/reporting-bugs

We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail.

Server version: 10.5.12-MariaDB
key_buffer_size=16777216
read_buffer_size=8388608
max_used_connections=35
max_threads=153
thread_count=34
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 11300560 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x81e206b98
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0x7fffdafdef38 thread_stack 0x49000
0x130cd7c <my_print_stacktrace+0x3c> at /usr/local/libexec/mariadbd
0xc6e6af <handle_fatal_signal+0x28f> at /usr/local/libexec/mariadbd
0x801904e00 <_pthread_sigmask+0x530> at /lib/libthr.so.3

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0x81e24def0): CHECK TABLE `forum_event_eventresponse`

Connection ID (thread ID): 138
Status: NOT_KILLED

Optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=on,table_elimination=on,extended_keys=on,exists_to_in=on,orderby_uses_equalities=on,condition_pushdown_for_derived=on,split_materialized=on,condition_pushdown_for_subquery=on,rowid_filter=on,condition_pushdown_from_having=on,not_null_range_scan=off

The manual page at https://mariadb.com/kb/en/how-to-produce-a-full-stack-trace-for-mysqld/ contains information that should help you find out what is causing the crash.
Core pattern: %N.core
===

Since I couldn't upload the core file here (max filesize exceeded), please download the gzipped coredump from here: https://wetransfer.com/downloads/58bcaac03b364010532ebddd214c7dbd20210904093632/a91858186386ac9749129b6f2632db3520210904093659/8c9aa0