170909 16:12:14 [ERROR] mysqld got signal 11 ; 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: 10.2.8-MariaDB-10.2.8+maria~stretch-log key_buffer_size=134217728 read_buffer_size=2097152 max_used_connections=3 max_threads=201 thread_count=10 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1368152 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. Thread pointer: 0x7fa8440008c8 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 = 0x7fa8efcbac48 thread_stack 0x30000 /usr/sbin/mysqld(my_print_stacktrace+0x2e)[0x55d309d5a07e] /usr/sbin/mysqld(handle_fatal_signal+0x3cd)[0x55d3097c217d] /lib/x86_64-linux-gnu/libpthread.so.0(+0x110c0)[0x7faa14a180c0] /usr/sbin/mysqld(_ZN20Field_iterator_table11create_itemEP3THD+0x8e)[0x55d3096cabee] /usr/sbin/mysqld(_Z13insert_fieldsP3THDP23Name_resolution_contextPKcS4_P13List_iteratorI4ItemEb+0x3a9)[0x55d3095e8019] /usr/sbin/mysqld(_Z10setup_wildP3THDP10TABLE_LISTR4ListI4ItemEPS5_j+0x176)[0x55d3095e8526] /usr/sbin/mysqld(_Z20mysql_prepare_deleteP3THDP10TABLE_LISTjR4ListI4ItemEPPS4_+0xa6)[0x55d3098f09a6] /usr/sbin/mysqld(_Z12mysql_deleteP3THDP10TABLE_LISTP4ItemP10SQL_I_ListI8st_orderEyyP13select_result+0x2a1)[0x55d3098f0d91] /usr/sbin/mysqld(_Z21mysql_execute_commandP3THD+0x26b6)[0x55d30962abe6] /usr/sbin/mysqld(_Z11mysql_parseP3THDPcjP12Parser_statebb+0x28a)[0x55d30963122a] /usr/sbin/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcjbb+0x1fb6)[0x55d309634086] /usr/sbin/mysqld(_Z10do_commandP3THD+0x167)[0x55d3096349c7] /usr/sbin/mysqld(_Z11tp_callbackP13TP_connection+0x11f)[0x55d3097383bf] /usr/sbin/mysqld(+0x6293c8)[0x55d30979a3c8] /lib/x86_64-linux-gnu/libpthread.so.0(+0x7494)[0x7faa14a0e494] /lib/x86_64-linux-gnu/libc.so.6(clone+0x3f)[0x7faa12cf5aff] Trying to get some variables. Some pointers may be invalid and cause the dump to abort. Query (0x7fa8440112d0): delete from t1 where id not in (select id from t2) returning * Connection ID (thread ID): 13 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=on,mrr_cost_based=on,mrr_sort_keys=on,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 The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash.