The replica actually accepts packets up to the limit set by its slave_max_allowed_packet setting， which default to the maximum setting of 1GB， to prevent a replication failure due to a large packet. However， the value of slave_pending_jobs_size_max controls the memory that is made available on the replica to hold incoming packets. The specified memory is shared among all the replica worker queues.
晚上一个在企业做IT的朋友打电话来说，他们使用的一个软件这几天突然查询很慢，让我帮忙分析一下并看一下有没有什么解决方案，具体情况是这样:数据库用的是sqlserver2008，查询的数据表也不是很多，只有几十万条，以前都很快的，这几天查询一下出结果要一分多钟。
