mysql-show profile 中 query end 状态含义

mysqlupdatequery endshow profile

表2000行, id主键,98%update正常,突然有一条很慢, 使用show profile查询的结果是下面这个状态占用时间比较长,
{
"Status": "query end",
"Duration": "1.751142",
"CPU_user": "0.008999",
"CPU_system": "0.003999",
"Context_voluntary": "98",
"Context_involuntary": "0",
"Block_ops_in": "8",
"Block_ops_out": "32",
"Messages_sent": "0",
"Messages_received": "0",
"Page_faults_major": "0",
"Page_faults_minor": "0",
"Swaps": "0",
"Source_function": "mysql_execute_command",
"Source_file": "sql_parse.cc",
"Source_line": "4465"
},
请问这个 "Status": "query end", 状态是什么状态, 这个状态下在执行什么事情?
"Context_voluntary": "98", "Block_ops_in": "8", "Block_ops_out": "32" 这些字段的含义是什么?

大多数时候这些字段都是0, 为什么突然一条这几个字段很高?