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InnoDB中索引块的内部组织一直是大家比较感兴趣并且乐于研究的东西,我们从很多书籍和文章都不惜笔墨进行大量的描述比如<>中就能感受到作者用了大量篇幅描述什么是slot、什么是heap、记录的逻辑和物理顺序是怎么样的。
但是我们却很难直观的看到,因为数据文件是二进制文件。虽然我们可以通过例如LINUX的hexdump等类似命令进行查看,但是大量的16进制信息很难直观的提取出各种有用的信息,相信不少人和笔者一样都是通过肉眼进行查看,但是这显然是一种吃力又不讨好的方法。
在Oracle中我们可以通过dump block的方法查看block的信息,那么InnoDB是否也可以这样呢?
本着这种让大家更加直观的观察到底层索引块的信息的宗旨,笔者直接借用源码中的各种宏定义,使用C++和STL list容器实现了这样一个工具innblock。由于工作原因不能全身心投入代码编写,代码有些混乱。所以如果有bug还请大家见谅以及提出,笔者会尽快进行更新,感谢。
index page(索引页、索引块),InnoDB表是基于聚集索引的索引组织表,整个表其实不是聚集索引,就是普通索引。因此InnoDB表空间文件中,数据页其实也是索引页,所以下面我们统称为索引页,英文用page no表示;
本工具有2个功能。
第一个scan功能用于查找ibd文件中所有的索引页。
第二个analyze功能用于扫描数据块里的row data。
先看下 help 输出
------------------------------------------------------------------------ [Author]:gaopeng [Blog]:blog.itpub.net/7728585/abstract/1/ [QQ]:22389860 [Review]:yejinrong@zhishutang [Blog]:imysql.com [QQ]:4700963 -------USAGE:../innblock Datafile [scan/pageno] Blocksize [Datafile]:innodb data file! [scan]:physical scan data file to find index level and index block no [pageno]:which block you will parse [Blocksize](KB):block size of KB general is 16k only 4k/8k/16k/32k ------------------------------------------------------------------------
[root@test test]# ./innblock testblock.ibd scan 16
[root@test test]# ./innblock testblock.ibd 3 16
可以执行 innblock help 获得更详细的使用帮助信息。
首先,创建测试表,填充数据
mysql> create table testblock ( id1 int primary key, name varchar(30), id3 int, key(name), key(id3)); mysql> insert into testblock values(1,'gao',1),(2,'gao',2),(3,'gao',3),(4,'gao',4); mysql> delete from testblock where id1=1;
[root@test]# innblock testblock.ibd scan 16 ------------------------------------------------------------------------ Welcome to use this block analyze tool: [Author]:gaopeng [Blog]:blog.itpub.net/7728585/abstract/1/ [QQ]:22389860 [Review]:yejinrong@zhishutang [Blog]:imysql.com [QQ]:4700963 ------------------------------------------------------------------------ Datafile Total Size:131072 ===INDEX_ID:248 level0 total block is (1) block_no: 3,level: 0|*| ===INDEX_ID:249 level0 total block is (1) block_no: 4,level: 0|*| ===INDEX_ID:250 level0 total block is (1) block_no: 5,level: 0|*|
我们发现有3个索引,索引ID(INDEX_ID)分别是 248、249、250,查看数据字典确认
mysql> SELECT A.SPACE AS TBL_SPACEID, A.TABLE_ID, A.NAME AS TABLE_NAME, FILE_FORMAT, ROW_FORMAT, SPACE_TYPE, B.INDEX_ID , B.NAME AS INDEX_NAME, PAGE_NO, B.TYPE AS INDEX_TYPE FROM INNODB_SYS_TABLES A LEFT JOIN INNODB_SYS_INDEXES B ON A.TABLE_ID =B.TABLE_ID WHERE A.NAME = 'test/testblock’; +-------------+----------+----------------+-------------+------------+------------+----------+------------+---------+------------+ | TBL_SPACEID | TABLE_ID | TABLE_NAME | FILE_FORMAT | ROW_FORMAT | SPACE_TYPE | INDEX_ID | INDEX_NAME | PAGE_NO | INDEX_TYPE | +-------------+----------+----------------+-------------+------------+------------+----------+------------+---------+------------+ | 242 | 168 | test/testblock | Barracuda | Dynamic | Single | 248 | PRIMARY | 3 | 3 | | 242 | 168 | test/testblock | Barracuda | Dynamic | Single | 249 | name | 4 | 0 | | 242 | 168 | test/testblock | Barracuda | Dynamic | Single | 250 | id3 | 5 | 0 | +-------------+----------+----------------+-------------+------------+------------+----------+------------+---------+------------+
我们选取 pageno=3 那个索引页进行扫描,可见下面信息
[root@test test]# innblock testblock.ibd 3 16 ------------------------------------------------------------------------ Welcome to use this block analyze tool: [Author]:gaopeng [Blog]:blog.itpub.net/7728585/abstract/1/ [QQ]:22389860 [Review]:yejinrong@zhishutang [Blog]:imysql.com [QQ]:4700963 ------------------------------------------------------------------------ ==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:6 n_rows:3 heap_top:244 del_bytes:31 last_ins_offset:0 page_dir:2 page_n_dir:3 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510679871 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:5 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (5) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 -----Total used rows:5 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:1 del rows list(logic): (1) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0 -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:4 (2) INFIMUM slot offset:99 n_owned:1
我在工具的help文档中也有详细的解释,这里单独对analyze功能解析数据块的输出详解一番,并且我也会给出这些值来自源码的哪个宏定义。这部分知识点在<>中也有详细说明。
[block_no]:page offset no inside space,begin is 0(取自 FIL_PAGE_OFFSET)
索引页码(index page no),该页相对于表空间的偏移量,从0开始计数。如果page no = 3,则实际上是第4个index page。
[space_id]:this contains the space id of the page(FIL_PAGE_SPACE_ID)
本索引页所属的表空间ID,可以在 INNODB_SYS_TABLES、INNODB_SYS_TABLESPACES、INNODB_SYS_DATAFILES 等系统视图中查看。
[index_id]:index id where the page belongs.This field should not be written to after page creation. (PAGE_INDEX_ID)
本索引页所属的索引ID,可以在 INNODB_SYS_INDEXES 系统视图中查看。
[slot_nums]:number of slots in page directory(PAGE_N_DIR_SLOTS)
本索引页中所包含的slot(槽)的数量。
[heaps_rows]:number of records in the heap include delete rows after purge and INFIMUM/SUPREMUM(取自PAGE_N_HEAP)
本索引页中的全部记录数量,这其中包含了已经deleted且已被purged的记录(这种记录会被放到索引页的garbage队列中),以及两个伪记录INFIMUM/SUPREMUM。
[n_rows]:number of records not include delete rows after pruge and INFIMUM/SUPREMUM(PAGE_N_RECS)
本索引页中的记录数,不含deleted且已被purged的记录,以及两个伪记录INFIMUM、SUPREMUM。
[heap_top]:pointer offset to record heap top (PAGE_HEAP_TOP)
指向本索引页已分配的最大物理存储空间的偏移量。
[del_bytes]:number of bytes in deleted records after purge(PAGE_GARBAGE)
本索引页中所有deleted了的且已被purged的记录的总大小。
[last_ins_offset]:pointer to the last inserted record, or NULL if this info has been reset by a delete(PAGE_LAST_INSERT)
指向本索引页最后插入记录的位置偏移量,如果最后操作是delete,则这个偏移量为空。通过判断索引页内数据最后插入的方向,用于索引分裂判断。
[page_dir]:last insert direction: PAGE_LEFT, ...(PAGE_DIRECTION)
本索引页中数据最后插入的方向,同样用于索引分裂判断。
[page_n_dir]:number of consecutive inserts to the same direction(PAGE_N_DIRECTION)
向同一个方向插入数据的行数,同样用于索引分裂中进行判断
[leaf_inode_space leaf_inode_pag_no leaf_inode_offset]:leaf segment postion and in inode block offset,only root block(PAGE_BTR_SEG_LEAF开始 10字节)
[no_leaf_inode_space no_leaf_inode_pag_no no_leaf_inode_offset]:no_leaf segment postion and in inode block offset,only root block(取自PAGE_BTR_SEG_TOP 开始 10字节)
这6个值只在root节点会有信息,分别表示了叶子段和非叶子段的inode的位置和在inode块中的偏移量,其他块都为0。
[last_modify_lsn]:lsn of the end of the newest modification log record to the page(FIL_PAGE_LSN)
本块最后一次修改的LSN。
[page_type]:for this tool only B+_TREE(FIL_PAGE_TYPE)
对于本工具而言始终为B+ TREE,因为不支持其它page type。
[level]:level of the node in an index tree; the leaf level is the level 0(PAGE_LEVEL)
本索引页所处的B+ TREE的层级。注意,叶子结点的PAGE LEVEL为0。
Total used rows:5 used rows list(logic):
not delete purge rows and not delete logic sequence list(next offset list).
这个链表是逻辑有序链表,也是我们平时所说的块内数据有序的展示。它的顺序当然按照主键或者ROWID进行排列,因为是通过物理偏移量链表实现的,实际上就是逻辑上有序。我在实现的时候实际上是取了INFIMUM的偏移量开始进行扫描直到最后,但是注意被deleted且已经被purged的记录不在其中。
Total used rows:5 used rows list(phy):
not delete purge rows and not delete physics sequence list(sort by heap no).
这个链表是物理上的顺序,实际上就是heap no的顺序,我在实现的时候实际上就是将上面的逻辑链表按照heap no进行排序完成的,所以块内部是逻辑有序物理无序的,同样注意被deleted且已被purged的记录不在其中。
Total del rows:1 del rows list(logic):
purge delete logic sequence list(next offset list).
这个链表是逻辑上的,也就是被deleted且被purged后的记录都存在于这个链表中,通过读取块的PAGE_FREE获取链表信息。
Total slot:2 slot list:
slot physics sequence list.
这是slot(槽的)信息,通过扫描块尾部8字节以前信息进行分析得到,我们可以发现在slot中存储的是记录的偏移量。
在这里链表中包含一些信息,这里就用help中的解析给出了。
本节全部使用测试表如下:
mysql> create table testblock ( id1 int primary key, name varchar(30), id3 int, key(name), key(id3) );
初始化测试数据:
mysql> insert into testblock values(1,'gao',1),(2,'gao',2),(3,'gao',3),(4,'gao',4);
发起事务,先执行delete,暂不commit
mysql> begin; delete from testblock where id1=1;
分析结果:
[root@test]# innblock testblock.ibd 3 16 ==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:6 n_rows:4 heap_top:244 del_bytes:0 last_ins_offset:220 page_dir:2 page_n_dir:3 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510695376 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:6 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (6) SUPREMUM record offset:112 heapno:1 n_owned 5,delflag:N minflag:0 rectype:3 -----Total used rows:6 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 5,delflag:N minflag:0 rectype:3 (3) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0 (4) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (6) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:0 del rows list(logic): -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:5 (2) INFIMUM slot offset:99 n_owned:1
我们看到其中有一条记录是
(2) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0
其 delflag = Y,offset = 127,这条记录只是delete,但还没 commit,也还没被 purged,因此不会出现在 del rows list链表中。
同时注意到几个信息:
三个信息结合起来看,表示还没有真正被清除的数据。
接着上面的事务,继续执行commit
mysql> commit; Query OK, 0 rows affected (0.00 sec)
分析结果:
==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:6 n_rows:3 heap_top:244 del_bytes:31 last_ins_offset:0 page_dir:2 page_n_dir:3 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510695802 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:5 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (5) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 -----Total used rows:5 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:1 del rows list(logic): (1) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0 -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:4 (2) INFIMUM slot offset:99 n_owned:1
我们看到,执行commit,这条偏移量为127的记录被purged后入了del rows list链表
(1) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0
其delflag = Y,同时我们观察到
可见,commit且被purged的数据才是真正的删除(清除)。
上面删除的记录的heapno为2,接着插入新记录
insert into testblock values(5,'gaopeng',1);
显然它的长度大于删除记录的长度。
分析结果:
==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:7 n_rows:4 heap_top:279 del_bytes:31 last_ins_offset:251 page_dir:5 page_n_dir:0 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510695994 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:6 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:251 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0 (6) SUPREMUM record offset:112 heapno:1 n_owned 5,delflag:N minflag:0 rectype:3 -----Total used rows:6 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 5,delflag:N minflag:0 rectype:3 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (6) normal record offset:251 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:1 del rows list(logic): (1) normal record offset:127 heapno:2 n_owned 0,delflag:Y minflag:0 rectype:0 -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:5 (2) INFIMUM slot offset:99 n_owned:1
我们看到有一条新记录
(5) normal record offset:251 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0
这条记录的heapno = 6,而删除的旧记录 heapno=2,这表明它没有重用del rows list中的空间,因为删除记录的空间根本放不下这条新记录,所以只能重新分配。同时我们注意到 **heap_top = 279 ** ,这里也发生了变化,体现了实际为这行数据分配了新的heapno。
在上面的基础上,我们插入新记录
insert into testblock values(6,'gao',1);
分析结果:
==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:7 n_rows:5 heap_top:279 del_bytes:0 last_ins_offset:127 page_dir:2 page_n_dir:1 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510700272 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:7 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:251 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0 (6) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (7) SUPREMUM record offset:112 heapno:1 n_owned 6,delflag:N minflag:0 rectype:3 -----Total used rows:7 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 6,delflag:N minflag:0 rectype:3 (3) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (6) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (7) normal record offset:251 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:0 del rows list(logic): -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:6 (2) INFIMUM slot offset:99 n_owned:1
我们这次新写入的数据长度和删除的数据长度一致,我们发现heapno重用了del rows list中的记录没有了,而在数据逻辑顺序中多了一条
(6) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0
我们发现heapno=2的记录 delflag 不再是 Y了,同时 heap_top = 279 ** 也没有变化,del_bytes:31** 变成了 del_bytes:0,都充分说明了这块空间得到重用。
清空数据表后执行测试
mysql> insert into testblock values(1,'gao',1),(2,'gao',2),(3,'gao',3),(4,'gaopeng',4); mysql> delete from testblock where id1=4; mysql> delete from testblock where id1=3; mysql> insert into testblock values(5,'gaopeng',5);
在这里,我们先删除 [id1=4] 记录,后删除 [id1=3] 记录。
由于del list是头插法,所以后删除的 [id1=3] 的记录会放在del list链表的最头部,也就是[del list header] => [id1=3] => [id1=4]。虽然 [id=4] 的记录空间足以容下新记录 (5,'gaopeng’,5),但并没被重用。因为InnoDB只检测第一个 del list 中的第一个空位 [id1=3],显然这个记录空间不足以容下新记录 (5,’gaopeng',5),所以还是新开辟了heap。
分析结果:
==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:7 n_rows:3 heap_top:283 del_bytes:66 last_ins_offset:255 page_dir:5 page_n_dir:0 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510728551 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:5 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:255 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0 (5) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 -----Total used rows:5 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 (3) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:255 heapno:6 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:2 del rows list(logic): (1) normal record offset:189 heapno:4 n_owned 0,delflag:Y minflag:0 rectype:0 (2) normal record offset:220 heapno:5 n_owned 0,delflag:Y minflag:0 rectype:0 -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:4 (2) INFIMUM slot offset:99 n_owned:1
我们看到 del list 中共有2条记录(没被重用),却新增加了 heapno = 6 的记录。
从重组函数 btr_page_reorganize_low 来看,PAGE_GARBAGE确实包含了碎片空间。
清空数据表后执行测试
mysql> insert into testblock values(1,'gao',1),(2,'gao',2),(3,'gao',3),(4,'gaopeng',4); mysql> delete from testblock where id1=4;
分析结果:
==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:6 n_rows:3 heap_top:248 del_bytes:35 last_ins_offset:0 page_dir:2 page_n_dir:3 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510748484 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:5 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (5) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 -----Total used rows:5 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 4,delflag:N minflag:0 rectype:3 (3) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:1 del rows list(logic): (1) normal record offset:220 heapno:5 n_owned 0,delflag:Y minflag:0 rectype:0 -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:4 (2) INFIMUM slot offset:99 n_owned:1
注意这里 del_bytes:35 就是删除这条记录的空间的使用量。接下来执行SQL
mysql> insert into testblock values(5,'gao',5);
再次分析结果:
==== Block base info ==== block_no:3 space_id:242 index_id:248 slot_nums:2 heaps_rows:6 n_rows:4 heap_top:248 del_bytes:4 last_ins_offset:220 page_dir:5 page_n_dir:0 leaf_inode_space:242 leaf_inode_pag_no:2 leaf_inode_offset:242 no_leaf_inode_space:242 no_leaf_inode_pag_no:2 no_leaf_inode_offset:50 last_modify_lsn:510748643 page_type:B+_TREE level:0 ==== Block list info ==== -----Total used rows:6 used rows list(logic): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (3) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 (6) SUPREMUM record offset:112 heapno:1 n_owned 5,delflag:N minflag:0 rectype:3 -----Total used rows:6 used rows list(phy): (1) INFIMUM record offset:99 heapno:0 n_owned 1,delflag:N minflag:0 rectype:2 (2) SUPREMUM record offset:112 heapno:1 n_owned 5,delflag:N minflag:0 rectype:3 (3) normal record offset:127 heapno:2 n_owned 0,delflag:N minflag:0 rectype:0 (4) normal record offset:158 heapno:3 n_owned 0,delflag:N minflag:0 rectype:0 (5) normal record offset:189 heapno:4 n_owned 0,delflag:N minflag:0 rectype:0 (6) normal record offset:220 heapno:5 n_owned 0,delflag:N minflag:0 rectype:0 -----Total del rows:0 del rows list(logic): -----Total slot:2 slot list: (1) SUPREMUM slot offset:112 n_owned:5 (2) INFIMUM slot offset:99 n_owned:1
注意到 del_bytes:4,这个刚好就是 'gaopeng' 7字节减去 'gao' 3字节剩下的4字节,我们也看到了 [heapno=5] 这个记录被重用了(del list为空,heaono=5的记录 delflag 不为 Y)。
总之本工具可以按照你的想法进行各种测试和观察。
实际上本工具我并没有显示的分配内存,内存分配基本使用了STL LIST容器检测结果如下:
==11984== LEAK SUMMARY: ==11984== definitely lost: 0 bytes in 0 blocks ==11984== indirectly lost: 0 bytes in 0 blocks ==11984== possibly lost: 0 bytes in 0 blocks ==11984== still reachable: 568 bytes in 1 blocks ==11984== suppressed: 0 bytes in 0 blocks ==11984== Reachable blocks (those to which a pointer was found) are not shown. ==11984== To see them, rerun with: --leak-check=full --show-reachable=yes
本工具基本采集了InnoDB索引页全部固定信息,希望能够帮助大家更方便获得各种信息,效率显然高于肉眼看二进制文件,这是作者在分析InnoDB遇到的困境,也是写这个小工具的出发点。
最后再次感谢叶金荣对工具审核&建议,同时感谢 MySQL运维内参 三位作者周彦伟、王竹峰、强昌金对本工具的认可,这也是我个人最大的荣耀。
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