file space

/* SPACE HEADER ============ File space header data structure: this data structure is contained in the first page of a space. The space for this header is reserved in every extent descriptor page, but used only in the first. */ /*-------------------------------------*/ #define FSP_SPACE_ID 0 /* space id */ #define FSP_NOT_USED 4 /* this field contained a value up to which we know that the modifications in the database have been flushed to the file space; not used now */ #define FSP_SIZE 8 /* Current size of the space in pages */ #define FSP_FREE_LIMIT 12 /* Minimum page number for which the free list has not been initialized: the pages >= this limit are, by definition, free; note that in a single-table tablespace where size < 64 pages, this number is 64, i.e., we have initialized the space about the first extent, but have not physically allocted those pages to the file */ #define FSP_SPACE_FLAGS 16 /* table->flags & ~DICT_TF_COMPACT */ #define FSP_FRAG_N_USED 20 /* number of used pages in the FSP_FREE_FRAG list */ #define FSP_FREE 24 /* list of free extents */ #define FSP_FREE_FRAG (24 + FLST_BASE_NODE_SIZE) /* list of partially free extents not belonging to any segment */ #define FSP_FULL_FRAG (24 + 2 * FLST_BASE_NODE_SIZE) /* list of full extents not belonging to any segment */ #define FSP_SEG_ID (24 + 3 * FLST_BASE_NODE_SIZE) /* 8 bytes which give the first unused segment id */ #define FSP_SEG_INODES_FULL (32 + 3 * FLST_BASE_NODE_SIZE) /* list of pages containing segment headers, where all the segment inode slots are reserved */ #define FSP_SEG_INODES_FREE (32 + 4 * FLST_BASE_NODE_SIZE) /* list of pages containing segment headers, where not all the segment header slots are reserved */ /*-------------------------------------*/ /* File space header size */ #define FSP_HEADER_SIZE (32 + 5 * FLST_BASE_NODE_SIZE) #define FSP_FREE_ADD 4 /* this many free extents are added to the free list from above FSP_FREE_LIMIT at a time */ /* FILE SEGMENT INODE ================== Segment inode which is created for each segment in a tablespace. NOTE: in purge we assume that a segment having only one currently used page can be freed in a few steps, so that the freeing cannot fill the file buffer with bufferfixed file pages. */ typedef byte fseg_inode_t; #define FSEG_INODE_PAGE_NODE FSEG_PAGE_DATA /* the list node for linking segment inode pages */ #define FSEG_ARR_OFFSET (FSEG_PAGE_DATA + FLST_NODE_SIZE) /*-------------------------------------*/ #define FSEG_ID 0 /* 8 bytes of segment id: if this is 0, it means that the header is unused */ #define FSEG_NOT_FULL_N_USED 8 /* number of used segment pages in the FSEG_NOT_FULL list */ #define FSEG_FREE 12 /* list of free extents of this segment */ #define FSEG_NOT_FULL (12 + FLST_BASE_NODE_SIZE) /* list of partially free extents */ #define FSEG_FULL (12 + 2 * FLST_BASE_NODE_SIZE) /* list of full extents */ #define FSEG_MAGIC_N (12 + 3 * FLST_BASE_NODE_SIZE) /* magic number used in debugging */ #define FSEG_FRAG_ARR (16 + 3 * FLST_BASE_NODE_SIZE) /* array of individual pages belonging to this segment in fsp fragment extent lists */ #define FSEG_FRAG_ARR_N_SLOTS (FSP_EXTENT_SIZE / 2) /* number of slots in the array for the fragment pages */ #define FSEG_FRAG_SLOT_SIZE 4 /* a fragment page slot contains its page number within space, FIL_NULL means that the slot is not in use */ /*-------------------------------------*/ #define FSEG_INODE_SIZE \ (16 + 3 * FLST_BASE_NODE_SIZE \ + FSEG_FRAG_ARR_N_SLOTS * FSEG_FRAG_SLOT_SIZE) #define FSP_SEG_INODES_PER_PAGE(zip_size) \ (((zip_size ? zip_size : UNIV_PAGE_SIZE) \ - FSEG_ARR_OFFSET - 10) / FSEG_INODE_SIZE) /* Number of segment inodes which fit on a single page */ #define FSEG_MAGIC_N_VALUE 97937874 #define FSEG_FILLFACTOR 8 /* If this value is x, then if the number of unused but reserved pages in a segment is less than reserved pages * 1/x, and there are at least FSEG_FRAG_LIMIT used pages, then we allow a new empty extent to be added to the segment in fseg_alloc_free_page. Otherwise, we use unused pages of the segment. */ #define FSEG_FRAG_LIMIT FSEG_FRAG_ARR_N_SLOTS /* If the segment has >= this many used pages, it may be expanded by allocating extents to the segment; until that only individual fragment pages are allocated from the space */ #define FSEG_FREE_LIST_LIMIT 40 /* If the reserved size of a segment is at least this many extents, we allow extents to be put to the free list of the extent: at most FSEG_FREE_LIST_MAX_LEN many */ #define FSEG_FREE_LIST_MAX_LEN 4 /* EXTENT DESCRIPTOR ================= File extent descriptor data structure: contains bits to tell which pages in the extent are free and which contain old tuple version to clean. */ /*-------------------------------------*/ #define XDES_ID 0 /* The identifier of the segment to which this extent belongs */ #define XDES_FLST_NODE 8 /* The list node data structure for the descriptors */ #define XDES_STATE (FLST_NODE_SIZE + 8) /* contains state information of the extent */ #define XDES_BITMAP (FLST_NODE_SIZE + 12) /* Descriptor bitmap of the pages in the extent */ /*-------------------------------------*/ //每一个extent的大小是1M,每个extent信息页面在数据文件的位置是固定的 /** File space extent size (one megabyte) in pages */ #define FSP_EXTENT_SIZE (1 << (20 - UNIV_PAGE_SIZE_SHIFT)) //对于每个extent里面的页面，用两bit来表示状态，就是下面的两个 #define XDES_BITS_PER_PAGE 2 /* How many bits are there per page */ #define XDES_FREE_BIT 0 /* Index of the bit which tells if the page is free */ #define XDES_CLEAN_BIT 1 /* NOTE: currently not used! Index of the bit which tells if there are old versions of tuples on the page */ /** @name The space low address page map The pages at FSP_XDES_OFFSET and FSP_IBUF_BITMAP_OFFSET are repeated every XDES_DESCRIBED_PER_PAGE pages in every tablespace. */ /* @{ */ /*--------------------------------------*/ //file space的前几个页面 #define FSP_XDES_OFFSET 0 /* !< extent descriptor */ #define FSP_IBUF_BITMAP_OFFSET 1 /* !< insert buffer bitmap */ /* The ibuf bitmap pages are the ones whose page number is the number above plus a multiple of XDES_DESCRIBED_PER_PAGE */ #define FSP_FIRST_INODE_PAGE_NO 2 /*!< in every tablespace */ /* The following pages exist in the system tablespace (space 0). */ #define FSP_IBUF_HEADER_PAGE_NO 3 /*!< insert buffer header page, in tablespace 0 */ #define FSP_IBUF_TREE_ROOT_PAGE_NO 4 /*!< insert buffer B-tree root page in tablespace 0 */ /* The ibuf tree root page number in tablespace 0; its fseg inode is on the page number FSP_FIRST_INODE_PAGE_NO */ #define FSP_TRX_SYS_PAGE_NO 5 /*!< transaction system header, in tablespace 0 */ #define FSP_FIRST_RSEG_PAGE_NO 6 /*!< first rollback segment page, in tablespace 0 */ #define FSP_DICT_HDR_PAGE_NO 7 /*!< data dictionary header page, in tablespace 0 */