MySQL暖程序

Question

你通常如何预热你的数据库？

我对数据库中的每个表运行类似的查询：

SELECT * FROM ip_log ORDER BY ID;
SELECT ip, member_id FROM ip_log ORDER BY ip, member_id;

这是最好的方法，还是有更酷的方法？

Answer 1

如果您想预热 MyISAM 密钥缓冲区，您可以运行以下命令：

SELECT DISTINCT CONCAT('SELECT ',ndxcollist,' FROM ',db,'.',tb,' ORDER 
BY ',ndxcollist,';') SelectQueryToLoadCache
FROM (SELECT engine,table_schema db,table_name tb,index_name,
GROUP_CONCAT(column_name ORDER BY seq_in_index) ndxcollist
FROM (SELECT 
B.engine,A.table_schema,A.table_name,A.index_name,A.column_name,A.seq_in_index
FROM information_schema.statistics A INNER JOIN
(SELECT engine,table_schema,table_name
FROM information_schema.tables
WHERE engine='MyISAM' AND table_schema
NOT IN ('information_schema','mysql')) B
USING (table_schema,table_name)
WHERE A.index_type <> 'FULLTEXT'
ORDER BY table_schema,table_name,index_name,seq_in_index) A
GROUP BY table_schema,table_name,index_name) AA
ORDER BY db,tb
;

这是输出：

+----------------------------------------------------------------------+
| SelectQueryToLoadCache                                               |
+----------------------------------------------------------------------+
| SELECT start_time FROM annarbor.sq_20110722 ORDER     BY start_time; |
| SELECT id FROM junk.category ORDER     BY id;                        |
| SELECT id FROM junk.mytabletolimit ORDER     BY id;                  |
| SELECT parent_id FROM junk.observations ORDER     BY parent_id;      |
| SELECT id FROM junk.observations ORDER     BY id;                    |
| SELECT parent_id FROM junk.pctable ORDER     BY parent_id;           |
| SELECT id FROM junk.pctable ORDER     BY id;                         |
| SELECT id FROM junk.products ORDER     BY id;                        |
| SELECT id FROM junk.subcategory ORDER     BY id;                     |
| SELECT id FROM test.acties ORDER     BY id;                          |
| SELECT id FROM test.deletekeys ORDER     BY id;                      |
| SELECT email FROM test.emailtable ORDER     BY email;                |
| SELECT id FROM test.emailtable ORDER     BY id;                      |
| SELECT id FROM test.ft_test ORDER     BY id;                         |
| SELECT id_key FROM test.id_key_table ORDER     BY id_key;            |
| SELECT id_key FROM test.id_key_table_keys ORDER     BY id_key;       |
| SELECT id FROM test.mytabletodeletefrom ORDER     BY id;             |
| SELECT NGRAM_ID FROM test.ngram_key ORDER     BY NGRAM_ID;           |
| SELECT NGRAM FROM test.ngram_key ORDER     BY NGRAM;                 |
| SELECT NGRAM_ID FROM test.ngram_rec ORDER     BY NGRAM_ID;           |
| SELECT num FROM test.notforeverdata_matches ORDER     BY num;        |
| SELECT id FROM test.pamela ORDER     BY id;                          |
| SELECT id FROM test.rolando ORDER     BY id;                         |
| SELECT num FROM test.rolando2 ORDER     BY num;                      |
| SELECT CourseName FROM test.tab ORDER     BY CourseName;             |
| SELECT CourseName FROM test.tab_to_zap ORDER     BY CourseName;      |
| SELECT academy FROM test.under99color ORDER     BY academy;          |
| SELECT id FROM test.under99color ORDER     BY id;                    |
| SELECT id_key FROM test.weekly_batch ORDER     BY id_key;            |
| SELECT id FROM test.worktable ORDER     BY id;                       |
+----------------------------------------------------------------------+
30 rows in set (0.81 sec)

mysql>

这将显示您可以针对 MyISAM 表运行的每个可能的查询，仅选择索引列字段。运行这些查询将填充 MyISAM 密钥缓冲区。

这是一个类似的查询，用于进行预加载 InnoDB 缓冲池的查询

SELECT DISTINCT
    CONCAT('SELECT ',ndxcollist,' FROM ',db,'.',tb,
    ' ORDER BY ',ndxcollist,';') SelectQueryToLoadCache
    FROM
    (
        SELECT
            engine,table_schema db,table_name tb,
            index_name,GROUP_CONCAT(column_name ORDER BY seq_in_index) ndxcollist
        FROM
        (
            SELECT
                B.engine,A.table_schema,A.table_name,
                A.index_name,A.column_name,A.seq_in_index
            FROM
                information_schema.statistics A INNER JOIN
                (
                    SELECT engine,table_schema,table_name
                    FROM information_schema.tables WHERE
                    engine='InnoDB'
                ) B USING (table_schema,table_name)
            WHERE B.table_schema NOT IN ('information_schema','mysql')
            ORDER BY table_schema,table_name,index_name,seq_in_index
        ) A
        GROUP BY table_schema,table_name,index_name
    ) AA
ORDER BY db,tb
;

这是一个类似的查询，用于进行预加载 InnoDB 缓冲池和 MyISAM 密钥缓冲区的查询（我于 2011 年 11 月发布）

SELECT DISTINCT
    CONCAT('SELECT ',ndxcollist,' FROM ',
    db,'.',tb,' ORDER BY ',ndxcollist,';') SelectQueryToLoadCache
FROM (
    SELECT
        engine,table_schema db,table_name tb,index_name,
        GROUP_CONCAT(column_name ORDER BY seq_in_index) ndxcollist
    FROM (
        SELECT
            B.engine,A.table_schema,A.table_name,
            A.index_name,A.column_name,A.seq_in_index
        FROM
            information_schema.statistics A INNER JOIN
            (
                SELECT engine,table_schema,table_name
                FROM information_schema.tables
                WHERE engine IN ('InnoDB','MyISAM')
            ) B USING (table_schema,table_name)
        WHERE
            B.table_schema NOT IN ('information_schema','mysql')
            AND A.index_type <> 'FULLTEXT'
        ORDER BY
            table_schema,table_name,index_name,seq_in_index
        ) A
    GROUP BY
        table_schema,table_name,index_name
) AA
ORDER BY
    engine DESC,db,tb
;

如果您看到同一查询在显示中多次出现，则表明存在冗余索引。

试一试 ！！！

更新 2012-02-04 21:53 EDT

虽然可以通过如下方式创建专用于 MyISAM 的缓存：

SET GLOBAL authentication_cache.key_buffer_size = 1024 * 1024 * 8; 
CACHE INDEX mydb.users INTO authentication_cache; 
LOAD INDEX INTO CACHE mydb.users;

您仍然必须决定加载所有索引或特定索引。我提供的脚本只是向您展示了您可以加载的所有可能索引的列表。您没有义务加载所有索引，只需加载您知道使用最多的索引。如果您有硬件和预算，您可以将任意数量的内容加载到专用的 MyISAM 缓存中。

还有一点需要考虑：提到的所有查询实际上都在访问覆盖索引。运行这些查询只会访问 .MYI 文件的 MyISAM 页和 InnoDB 表的索引页。永远不会检索表数据。鉴于此，无论存储引擎如何，所有或选定的查询都会填充索引页。

更多关于覆盖索引原则的链接

• http://www.mysqlperformanceblog.com/2006/11/23/covering-index-and-prefix-indexes/
• http://ronaldbradford.com/blog/tag/covering-index/
• http://shallop.com/2011/04/covering-indexes-in-mysql/
• http://www.mysqlconf.com/mysql2009/public/schedule/detail/6796

更新 2012-02-04 22:05 EDT

关于 InnoDB 与 MyISAM 的快速说明。您可以缓存 InnoDB 的数据页。MyISAM 没有。