(gdb) bt
#0  0x000056152a474f49 in ?? ()
#1  0x000056152a64f7b0 in JOIN::optimize() ()
#2  0x000056152a64f887 in mysql_select(THD*, TABLE_LIST*, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) ()
#3  0x000056152a6502c7 in handle_select(THD*, LEX*, select_result*, unsigned long) ()
#4  0x000056152a5dbfe1 in ?? ()
#5  0x000056152a5eaf35 in mysql_execute_command(THD*) ()
#6  0x000056152a5d64cf in mysql_parse(THD*, char*, unsigned int, Parser_state*, bool, bool) ()
#7  0x000056152a5e34c5 in dispatch_command(enum_server_command, THD*, char*, unsigned int, bool, bool) ()
#8  0x000056152a5e5d73 in do_command(THD*) ()
#9  0x000056152a6efb01 in do_handle_one_connection(CONNECT*, bool) ()
#10 0x000056152a6eff7d in handle_one_connection ()
#11 0x000056152aa5c11f in ?? ()
#12 0x00007f82546d3609 in start_thread (arg=<optimized out>) at pthread_create.c:477
#13 0x00007f82542bf133 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95