背景:
用innodb_table_monitor来查看表内部的存储信息和索引结构是一个好的办法。再之前的MySQL 字符串主键和整型主键分析中提到了一些内容,但没有细讲,现在来好好的分析下。
使用方法:
建立一张 innodb_table_monitor的表:
create table innodb_table_monitor(a int)engine=innodb;
表建立之后,会每隔1m20s间隔把监控到的信息写到error日志中。要是停止监控的话,只需要删除表就可以了。注意:要是一直开启的话,错误日志会变的非常大。
日志的具体信息:
=========================================== 121103 10:25:57 INNODB TABLE MONITOR OUTPUT =========================================== -------------------------------------- TABLE: name SYS_FOREIGN, id 0 11, flags 0, columns 7, indexes 3, appr.rows 8 COLUMNS: ID: DATA_VARCHAR prtype 524292 len 0; FOR_NAME: DATA_VARCHAR prtype 524292 len 0; REF_NAME: DATA_VARCHAR prtype 524292 len 0; N_COLS: DATA_INT len 4; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name ID_IND, id 0 11, fields 1/6, uniq 1, type 3 root page 46, appr.key vals 8, leaf pages 1, size pages 1 FIELDS: ID DB_TRX_ID DB_ROLL_PTR FOR_NAME REF_NAME N_COLS INDEX: name FOR_IND, id 0 12, fields 1/2, uniq 2, type 0 root page 47, appr.key vals 4, leaf pages 1, size pages 1 FIELDS: FOR_NAME ID INDEX: name REF_IND, id 0 13, fields 1/2, uniq 2, type 0 root page 48, appr.key vals 3, leaf pages 1, size pages 1 FIELDS: REF_NAME ID -------------------------------------- TABLE: name SYS_FOREIGN_COLS, id 0 12, flags 0, columns 7, indexes 1, appr.rows 8 COLUMNS: ID: DATA_VARCHAR prtype 524292 len 0; POS: DATA_INT len 4; FOR_COL_NAME: DATA_VARCHAR prtype 524292 len 0; REF_COL_NAME: DATA_VARCHAR prtype 524292 len 0; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name ID_IND, id 0 14, fields 2/6, uniq 2, type 3 root page 49, appr.key vals 8, leaf pages 1, size pages 1 FIELDS: ID POS DB_TRX_ID DB_ROLL_PTR FOR_COL_NAME REF_COL_NAME --------------------------------------
上面显示,其中输出结构的开始部分会包含2张内部数据字典表用于维护外键的信息,表名为SYS_FOREIGN、SYS_FOREIGN_COLS。看看用户创建表的信息:
1,有主键的表(有数据):
CREATE TABLE `test` ( `uid` char(36) NOT NULL DEFAULT ‘‘, `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, `status` tinyint(4) DEFAULT NULL, PRIMARY KEY (`uid`), KEY `idx_id` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 TABLE: name test/test, id 0 718, flags 1, columns 7, indexes 2, appr.rows 635787 2 COLUMNS: uid: DATA_MYSQL DATA_NOT_NULL len 108; id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4; name: DATA_VARMYSQL len 765; status: DATA_INT DATA_BINARY_TYPE len 1; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; 3 INDEX: name PRIMARY, id 0 1387, fields 1/6, uniq 1, type 3 4 root page 3, appr.key vals 635787, leaf pages 4056, size pages 4078 5 FIELDS: uid DB_TRX_ID DB_ROLL_PTR id name status /*主键包含所有列*/
6 INDEX: name idx_id, id 0 1388, fields 1/2, uniq 2, type 0 7 root page 4, appr.key vals 638241, leaf pages 1834, size pages 1896 8 FIELDS: id uid /*表中定义的二级索引包含主键uid列*/
第一部分(1):表信息:表名(test),表ID(718),列数(7),索引数(2),索性的基数<Cardinality>(625787,会变动);
第二部分(2):列信息:包括列名、列类型(DATA_XXXX)、是否NULL、以及列字段的长度。后面还有额外三列(主键ID,事务ID,回滚子指针) 总共7列;
• DATA_xxx(列类型): These symbols indicate the data type. There may be multiple DATA_xxx symbols for a given column. • prtype(列的数据类型的字符集编码,空性,符号性,以及是否它是一个二进制字符串): The column‘s “precise” type. This field includes information such as the column data type, character set code, nullability,signedness, and whether it is a binary string. This field is described in the innobase/include/data0type.h source file. • len(列字段的长度):The column length in bytes. • prec(类型的精确值):The precision of the type.
第三部分(3~5):索引信息:索引名、索引ID,fields m/n (m代表用户定义索引中的列数/n代表总的索引列数,其中包含附加的internal columns),由于没有显示的定义主键或者非空的唯一索引,InnoDB会建表的时候自动的创建名字为GEN_CLUST_INDEX的Clustered Index。如果显示的定义一个主键的话,这个时候INDEX中name的值是:PRIMARY。以及 一些page信息和索引的基数信息。最后则是被索引的列,和 fields m/n 里的n对应。
• type(索引类型:聚集索引1,唯一索引2,普通索引0,既聚集又唯一3): The index type. This is a bit field. For example, 1 indicates a clustered index and 2 indicates a unique index, so a clustered index (which always contains unique values), will have a type value of 3. An index with a type value of 0 is neither clustered nor unique. The flag values are defined in the innobase/include/dict0mem.h source file. • root page(索引节点:根节点): The index root page number. • appr. key vals(索引的基数): The approximate index cardinality. • leaf page(页节点大小): number of leaf pages in the index. • size pages(总页大小): The approximages: The approate total number of pages in the index. • FIELDS(被索引的列,主键包含所有列以及隐藏列,二级索引包含主键): The names of the fields in the index. For a clustered index that was generated automatically, the field list begins with the internal DB_ROW_ID (row ID) field. DB_TRX_ID and DB_ROLL_PTR are always added internally to the clustered index, following the fields that comprise the primary key. For a secondary index, the final fields are those from the primary key that are not part of the secondary index.
2,上面的表是有主键的,看看无主键的表(没有数据):
CREATE TABLE `test1` ( `uid` char(36) NOT NULL DEFAULT ‘‘, `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, `status` tinyint(4) DEFAULT NULL, KEY `idx_id` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 TABLE: name test/test1, id 0 820, flags 1, columns 7, indexes 2, appr.rows 0 2 COLUMNS: uid: DATA_MYSQL DATA_NOT_NULL len 108; id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4; name: DATA_VARMYSQL len 765; status: DATA_INT DATA_BINARY_TYPE len 1; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; 3 INDEX: name GEN_CLUST_INDEX, id 0 1524, fields 0/7, uniq 1, type 1 /*1 说明只是主键,不是唯一*/ 4 root page 3, appr.key vals 0, leaf pages 1, size pages 1 5 FIELDS: DB_ROW_ID DB_TRX_ID DB_ROLL_PTR uid id name status 6 INDEX: name idx_id, id 0 1525, fields 1/2, uniq 2, type 0 7 root page 4, appr.key vals 0, leaf pages 1, size pages 1 8 FIELDS: id DB_ROW_ID
1和2对比异同:
第一行和第二行他们的信息是一样的。
第三行出现不一致,因为1的表是有主键的,而2的表没有主键,2会自动生成一个Row_ID来代替,而导致第五行也不一致,因为2比1多了一个Row_ID(6个字节)。所以2的表中被索引的列有7个,而1只有6个,2没有定义索引列,而1定义了一个(fields)。因为二级索引包含主键列(第8行),主键不一样了,导致二级索引的列也会不一样。
3,测试有没有主键表大小问题:
CREATE TABLE `test2` ( `uid` char(36) NOT NULL DEFAULT ‘‘, `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, `status` tinyint(4) DEFAULT NULL, PRIMARY KEY `idx_id` (`id`) ) ENGINE=InnoDB; /*有自增主键*/ CREATE TABLE `test3` ( `uid` char(36) NOT NULL DEFAULT ‘‘, `id` int(11) NOT NULL, `name` varchar(255) DEFAULT NULL, `status` tinyint(4) DEFAULT NULL ) ENGINE=InnoDB; /*无主键*/ CREATE TABLE `test4` ( `uid` char(36) NOT NULL DEFAULT ‘‘, `id` int(11) NOT NULL, `name` varchar(255) DEFAULT NULL, `status` tinyint(4) DEFAULT NULL, PRIMARY KEY (`uid`) ) ENGINE=InnoDB; /*有字符串主键*/
-------------------------------------- TABLE: name test/test2, id 0 824, flags 1, columns 7, indexes 1, appr.rows 625647 COLUMNS: uid: DATA_MYSQL DATA_NOT_NULL len 108; id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4; name: DATA_VARMYSQL len 765; status: DATA_INT DATA_BINARY_TYPE len 1; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name PRIMARY, id 0 1532, fields 1/6, uniq 1, type 3 root page 3, appr.key vals 625647, leaf pages 4056, size pages 4070 FIELDS: id DB_TRX_ID DB_ROLL_PTR uid name status -------------------------------------- TABLE: name test/test3, id 0 825, flags 1, columns 7, indexes 1, appr.rows 617020 COLUMNS: uid: DATA_MYSQL DATA_NOT_NULL len 108; id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4; name: DATA_VARMYSQL len 765; status: DATA_INT DATA_BINARY_TYPE len 1; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name GEN_CLUST_INDEX, id 0 1533, fields 0/7, uniq 1, type 1 root page 3, appr.key vals 617020, leaf pages 4311, size pages 4326 FIELDS: DB_ROW_ID DB_TRX_ID DB_ROLL_PTR uid id name status -------------------------------------- TABLE: name test/test4, id 0 826, flags 1, columns 7, indexes 1, appr.rows 655560 COLUMNS: uid: DATA_MYSQL DATA_NOT_NULL len 108; id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4; name: DATA_VARMYSQL len 765; status: DATA_INT DATA_BINARY_TYPE len 1; DB_ROW_ID: DATA_SYS prtype 256 len 6; DB_TRX_ID: DATA_SYS prtype 257 len 6; DB_ROLL_PTR: DATA_SYS prtype 258 len 7; INDEX: name PRIMARY, id 0 1534, fields 1/6, uniq 1, type 3 root page 3, appr.key vals 655560, leaf pages 4056, size pages 4078 FIELDS: uid DB_TRX_ID DB_ROLL_PTR id name status --------------------------------------