Question

使用以下参数激活慢查询日志：

log_slow_queries = /var/log/mysql/mysql-slow.log
long_query_time = 10
log-queries-not-using-indexes

现在看来MySQL只记录没有索引的查询

这是日志的样本

# Time: 130709 15:33:54
# User@Host: xxxxxx[yyyyyy] @ localhost []
# Query_time: 0.000467  Lock_time: 0.000105 Rows_sent: 1  Rows_examined: 0
SET timestamp=1373376834;
SELECT count(`id`) as `totale` FROM ( SELECT `id` FROM `gg_evento` WHERE `team_home` = 51620 AND `status_home` = 3 AND `status_guest` = 3 UNION ALL SELECT `id` FROM `gg_evento` WHERE `team_guest` = 51620 AND `status_home` = 3 AND `status_guest` = 3) AS sq2 WHERE 1 LIMIT 1;

但是，此查询已经过优化。

mysql> explain SELECT count(`id`) as `totale` FROM ( SELECT `id` FROM `gg_evento` WHERE `team_home` = 51620 AND `status_home` = 3 AND `status_guest` = 3 UNION ALL SELECT `id` FROM `gg_evento` WHERE `team_guest` = 51620 AND `status_home` = 3 AND `status_guest` = 3) AS sq2 WHERE 1 LIMIT 1\G
*************************** 1. row ***************************
           id: 1
  select_type: PRIMARY
        table: NULL
         type: NULL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: NULL
        Extra: Select tables optimized away
*************************** 2. row ***************************
           id: 2
  select_type: DERIVED
        table: gg_evento
         type: ref
possible_keys: fk_evento_team_home,IDX_PARTITE_NON_TERMINATE,IDX_CARICA_SFIDANTI
          key: fk_evento_team_home
      key_len: 4
          ref: 
         rows: 1
        Extra: Using where
*************************** 3. row ***************************
           id: 3
  select_type: UNION
        table: gg_evento
         type: ref
possible_keys: IDX_TOTALE_GIOCATE_GUEST
          key: IDX_TOTALE_GIOCATE_GUEST
      key_len: 13
          ref: 
         rows: 1
        Extra: Using where; Using index
*************************** 4. row ***************************
           id: NULL
  select_type: UNION RESULT
        table: <union2,3>
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: NULL
        Extra: 
4 rows in set (0.00 sec)

我在MySQL文档中看到了这个警告：

This option does not necessarily mean that no index is used

但是...

我不明白记录的查询是否正确，或者我是否有可以修复的优化问题
如果这个查询是误报，有办法避免mysql登录吗？

有关它的任何想法？谢谢你米歇尔

Answer 1

您可以尝试min_examined_row_limit（https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_min_examined_row_limit）

如您的示例所示＆＃34; Rows_examined：0＆＃34;，设置a / m变量可以禁止记录。

set global  min_examined_row_limit = 2;

MySQL log-queries-not-using-indexes和UNION误报或错误？

1 个答案: