故障分析 | 一条 SELECT 语句跑崩了 MySQL ，怎么回事？

作者：刘开洋

爱可生交付服务团队北京 DBA，对数据库及周边技术有浓厚的学习兴趣，喜欢看书，追求技术。

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在很多疑难问题的排查中，小编最近又遇到了一个 select 语句执行就会导致 MySQL 崩溃的问题，特来分享给大家。

先看下报错

一般来讲，只要数据库崩了，那么错误日志一定会留下线索的，先来看下具体的报错：

06:08:23 UTC - mysqld got signal 11 ;
Most likely, you have hit a bug, but this error can also be caused by malfunctioning hardware.
Thread pointer: 0x7f55ac0008c0
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 = 7f56f4074d80 thread_stack 0x46000
/usr/local/mysql/bin/mysqld(my_print_stacktrace(unsigned char const*, unsigned long)+0x2e) [0x1f1b71e]
/usr/local/mysql/bin/mysqld(handle_fatal_signal+0x323) [0xfcfac3]
/lib64/libpthread.so.0(+0xf630) [0x7f5c28c85630]
/usr/local/mysql/bin/mysqld(actual_key_parts(KEY const*)+0xa) [0xef55ca]
/usr/local/mysql/bin/mysqld(calculate_key_len(TABLE*, unsigned int, unsigned long)+0x28) [0x10da428]
/usr/local/mysql/bin/mysqld(handler::ha_index_read_map(unsigned char*, unsigned char const*, unsigned long, ha_rkey_function)+0x261) [0x10dac51]
/usr/local/mysql/bin/mysqld(check_unique_constraint(TABLE*)+0xa3) [0xe620e3]
/usr/local/mysql/bin/mysqld(do_sj_dups_weedout(THD*, SJ_TMP_TABLE*)+0x111) [0xe62361]
/usr/local/mysql/bin/mysqld(WeedoutIterator::Read()+0