InnoDB文件物理结构解析6

InnoDB文件物理结构解析6 - FIL_PAGE_INDEX

本文讨论Secondary Key Page的解析，也就是表非主键索引的记录存储。与Clustered Key Page有相同的基本记录结构，也细分为Leaf Page和Non-Leaf Page，我们先看结构：

### Contents (Secondary Key - Leaf Page) ###
------------------------+------------------------+
Secondary Key Fields (k)| Cluster Key Fields (j) |
------------------------+------------------------+### Contents (Secondary Key - Non-Leaf Page) ###
-----------------------------------------+----------------------------------------+-----------------------+
Secondary Key Min. Key on Child Page (k) | Cluster Key Min. Key on Child Page (j) | Child Page Number (4) |
-----------------------------------------+----------------------------------------+-----------------------+

先看Leaf Page, 记录的基本结构都是一样的，有Extra Bytes, null-bitmap, variable-field-lengths部分，但是内容不同。InnoDB中，非主键索引(组合索引)字段是允许包含空值的。null-bitmap用于标记Secondary Key Fields中的空值。variable-field-lengths包含Secondary和Cluster Key的可变长字段的记录存储的长度。

记录内容中，最前面部分存放索引的字段，后面接着索引字段值对应的主键值，记录内容不包含DB_TRX_ID和DB_ROLL_PTR伪字段。以sakila.film表的idx_title(index_id = 597)索引为例，根据《InnoDB文件物理结构解析2》的IdxPage1案例的输出，idx_title索引的相关页为:

 PAGE       PAGE_TYPE LEVEL INDEX_ID   PAGE_PREV   PAGE_NEXT
----- --------------- ----- -------- ----------- -----------5     FIL_PAGE_INDEX     1      597  4294967295  4294967295 
16     FIL_PAGE_INDEX     0      597  4294967295          17 
17     FIL_PAGE_INDEX     0      597          16  4294967295

所以，page(5)是Secondary Key Non-Leaf Page，page(16)和page(17)为Secondary Key Leaf Page，我们写个案例分析page(16)的内容：

public class IdxPage6 {public static void main(String[] args) throws Exception {String fileName = "D:\\Data\\mysql\\8.0.18\\data\\sakila\\film.ibd";try (IbdFileParser parser = new IbdFileParser(fileName)) {IndexPage page = (IndexPage) parser.getPage(16);long indexId = page.getIndexHeader().getIndexId().longValueExact();TableMeta tableMeta = IdxPage3.getFilmTableMeta(); 定义索引的元数据(索引包含哪些列)tableMeta.setSecondaryKey(indexId, 1, "title");SecondaryKeyLeafPage leafPage = new SecondaryKeyLeafPage(page.getPageRaw(), page.getPageSize());List<SecondaryKeyLeafRecord> records = leafPage.getUserRecords(tableMeta);StringBuilder buff = new StringBuilder();buff.append("Secondary Key Fields             Cluster Key Fields      \n").append("-------------------------------- ------------------------\n");for (SecondaryKeyLeafRecord record : records) {List<RecordField> skFields = record.getSecondaryKeyFields();List<RecordField> ckFields = record.getClusterKeyFields();StringBuilder skValue = new StringBuilder();StringBuilder ckValue = new StringBuilder();for(RecordField field: skFields) {skValue.append(field.getName()).append(" = ").append(field.getContent()).append(" ");}buff.append(String.format("%-32s ", skValue));for(RecordField field: ckFields) {ckValue.append(field.getName()).append(" = ").append(field.getContent()).append(" ");}buff.append(String.format("%-24s\n", ckValue));}System.out.println(buff);}}
}
/*
程序输出:
Secondary Key Fields             Cluster Key Fields      
-------------------------------- ------------------------
title = ACADEMY DINOSAUR         film_id = 1             
title = ACE GOLDFINGER           film_id = 2             
title = ADAPTATION HOLES         film_id = 3             
title = AFFAIR PREJUDICE         film_id = 4             
title = AFRICAN EGG              film_id = 5             
title = AGENT TRUMAN             film_id = 6             
title = AIRPLANE SIERRA          film_id = 7             
title = AIRPORT POLLOCK          film_id = 8             
title = ALABAMA DEVIL            film_id = 9             
title = ALADDIN CALENDAR         film_id = 10            
title = ALAMO VIDEOTAPE          film_id = 11  
...      
*/

由输出可以看到，InnoDB索引，记录的是索引值对应的主键值，而不是行记录的地址，这与Oracle数据库的索引是不同的，或许与InnoDB是索引组织表有关，行记录存储在主键中。找条输出验证一下解析结果：

root@localhost [sakila]> select title from film where film_id=10;
+------------------+
| title            |
+------------------+
| ALADDIN CALENDAR | // film_id =10 <--> title = ALADDIN CALENDAR与预期的一样；
+------------------+
1 row in set (0.00 sec)

我们接下来通过案例解析page(5)， Non-Leaf页：

public class IdxPage7 {public static void main(String[] args) throws Exception {String fileName = "D:\\Data\\mysql\\8.0.18\\data\\sakila\\film.ibd";try (IbdFileParser parser = new IbdFileParser(fileName)) {IndexPage page = (IndexPage) parser.getPage(5);long indexId = page.getIndexHeader().getIndexId().longValueExact();TableMeta tableMeta = IdxPage3.getFilmTableMeta(); 定义索引的元数据(索引包含哪些列)tableMeta.setSecondaryKey(indexId, 1, "title");SecondaryKeyNonLeafPage rootPage = new SecondaryKeyNonLeafPage(page.getPageRaw(), page.getPageSize());List<SecondaryKeyNonLeafRecord> records = rootPage.getUserRecords(tableMeta);StringBuilder buff = new StringBuilder();buff.append("Secondary Key Min. Key on Child Page Cluster Key Min. Key on Child Page  Child Page Number \n").append("------------------------------------ ----------------------------------- ------------------\n");for(SecondaryKeyNonLeafRecord record : records) {List<RecordField> minSkFields = record.getMinSecondaryKeyOnChild();List<RecordField> minCkFields = record.getMinClusterKeyOnChild();long childPageNo = record.getChildPageNumber();StringBuilder skValue = new StringBuilder();StringBuilder ckValue = new StringBuilder();for(RecordField field: minSkFields) {skValue.append(field.getName()).append(" = ").append(field.getContent()).append(" ");}buff.append(String.format("%-36s ", skValue));for(RecordField field: minCkFields) {ckValue.append(field.getName()).append(" = ").append(field.getContent()).append(" ");}buff.append(String.format("%-35s ", ckValue));buff.append(String.format("%-15d\n", childPageNo));}System.out.println(buff);}}
}
/*
程序输出:
Secondary Key Min. Key on Child Page Cluster Key Min. Key on Child Page  Child Page Number 
------------------------------------ ----------------------------------- ------------------
title = ACADEMY DINOSAUR             film_id = 1                         16             
title = GILMORE BOILED               film_id = 358                       17             
*/