MySQL失去了连接到本地MySQL服务器

我试图对存储在大型MySQL数据库中的数据进行一些分析。 我有两个表分别有130mio和600'000条目,我想要运行以下查询:

select hashes.hash, hashes.hash LIKE 'block%' as block, min(timestamp) as min, max(timestamp) as max, max(timestamp)-min(timestamp) as diff from timings left join hashes on (id=timings.hash) group by timings.hash 

但经过一段随机的时间(在1到18分钟之间变化),我得到以下几点:

 $ time mysql timings -e "<query>" > diff2.tsv ERROR 2013 (HY000) at line 1: Lost connection to MySQL server during query real 7m34.158s user 0m0.004s sys 0m0.000s 

我在日志中绝对没有消息。 任何想法,为什么这可能发生?