mysql源码阅读笔记 (1) 底层物理页面的数据结构

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Innodb数据页结构

单个页面的数据结构如下图所示：
这里写图片描述

1.1 文件头（fil0fil.h）

    /** The byte offsets on a file page for various variables @{ */#define FIL_PAGE_SPACE_OR_CHKSUM 0  /*!< in < MySQL-4.0.14 space id the                    page belongs to (== 0) but in later                    versions the 'new' checksum of the                    page */#define FIL_PAGE_OFFSET     4   /*!< page offset inside space */#define FIL_PAGE_PREV       8   /*!< if there is a 'natural'                    predecessor of the page, its                    offset.  Otherwise FIL_NULL.                    This field is not set on BLOB                    pages, which are stored as a                    singly-linked list.  See also                    FIL_PAGE_NEXT. */#define FIL_PAGE_NEXT       12  /*!< if there is a 'natural' successor                    of the page, its offset.                    Otherwise FIL_NULL.                    B-tree index pages                    (FIL_PAGE_TYPE contains FIL_PAGE_INDEX)                    on the same PAGE_LEVEL are maintained                    as a doubly linked list via                    FIL_PAGE_PREV and FIL_PAGE_NEXT                    in the collation order of the                    smallest user record on each page. */#define FIL_PAGE_LSN        16  /*!< lsn of the end of the newest                    modification log record to the page */#define FIL_PAGE_TYPE       24  /*!< file page type: FIL_PAGE_INDEX,...,                    2 bytes.                    The contents of this field can only                    be trusted in the following case:                    if the page is an uncompressed                    B-tree index page, then it is                    guaranteed that the value is                    FIL_PAGE_INDEX.                    The opposite does not hold.                    In tablespaces created by                    MySQL/InnoDB 5.1.7 or later, the                    contents of this field is valid                    for all uncompressed pages. */#define FIL_PAGE_FILE_FLUSH_LSN 26  /*!< this is only defined for the                    first page in a system tablespace                    data file (ibdata*, not *.ibd):                    the file has been flushed to disk                    at least up to this lsn */#define FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID  34 /*!< starting from 4.1.x this                    contains the space id of the page */#define FIL_PAGE_SPACE_ID  FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID

各个字段的说明：

名称大小（字节) 说明 FIL_PAGE_SPACE_OR_CHKSUM 4 页的checksum FIL_PAGE_OFFSET 4 表空间中页的偏移值 FIL_PAGE_PREV 4 B+树的链接,上一个叶子节点 FIL_PAGE_NEXT 4 B+树的链接下一个叶子节点 FIL_PAGE_LSN 8 该页最后被修改的日志序列位置LSN;
(Log Sequence Number) FIL_PAGE_TYPE 2 页的类型 FIL_PAGE_FILE_FLUSH_LSN 8 代表文件至少被更新到了改LSN FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID 4 version > 4.1开始，代表该页属于哪个表空间

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