Innodb系统表-结构解析

/** File page types (values of FIL_PAGE_TYPE) @{ */
#define FIL_PAGE_INDEX		17855	/*!< B-tree node */
#define FIL_PAGE_RTREE		17854	/*!< B-tree node */
#define FIL_PAGE_UNDO_LOG	2	/*!< Undo log page */
#define FIL_PAGE_INODE		3	/*!< Index node */
#define FIL_PAGE_IBUF_FREE_LIST	4	/*!< Insert buffer free list */
/* File page types introduced in MySQL/InnoDB 5.1.7 */
#define FIL_PAGE_TYPE_ALLOCATED	0	/*!< Freshly allocated page */
#define FIL_PAGE_IBUF_BITMAP	5	/*!< Insert buffer bitmap */
#define FIL_PAGE_TYPE_SYS	6	/*!< System page */
#define FIL_PAGE_TYPE_TRX_SYS	7	/*!< Transaction system data */
#define FIL_PAGE_TYPE_FSP_HDR	8	/*!< File space header */
#define FIL_PAGE_TYPE_XDES	9	/*!< Extent descriptor page */
...省略一些不太关注的类型

/* The offset of the dictionary header on the page */
#define	DICT_HDR		FSEG_PAGE_DATA       //38字节文件头部信息

/*-------------------------------------------------------------*/
/* Dictionary header offsets */
#define DICT_HDR_ROW_ID		0	/* The latest assigned row id */
#define DICT_HDR_TABLE_ID	8	/* The latest assigned table id */
#define DICT_HDR_INDEX_ID	16	/* The latest assigned index id */
#define DICT_HDR_MAX_SPACE_ID	24	/* The latest assigned space id,or 0*/
#define DICT_HDR_MIX_ID_LOW	28	/* Obsolete,always DICT_HDR_FIRST_ID*/
#define DICT_HDR_TABLES		32	/* Root of SYS_TABLES clust index */
#define DICT_HDR_TABLE_IDS	36	/* Root of SYS_TABLE_IDS sec index */
#define DICT_HDR_COLUMNS	40	/* Root of SYS_COLUMNS clust index */
#define DICT_HDR_INDEXES	44	/* Root of SYS_INDEXES clust index */
#define DICT_HDR_FIELDS		48	/* Root of SYS_FIELDS clust index */

#define DICT_HDR_FSEG_HEADER	56	/* Segment header for the tablespace
					segment into which the dictionary
					header is created */

#define	PAGE_N_HEAP	 4	/* number of records in the heap,
				bit 15=flag: new-style compact page format */

/* Offsets of the bit-fields in an old-style record. NOTE! In the table the
most significant bytes and bits are written below less significant.

	(1) byte offset		(2) bit usage within byte
	downward from
	origin ->	1	8 bits pointer to next record
			2	8 bits pointer to next record
			3	1 bit short flag
				7 bits number of fields
			4	3 bits number of fields
				5 bits heap number
			5	8 bits heap number
			6	4 bits n_owned
				4 bits info bi
*/

h.deleteFlag = (data[0] & 0x20) != 0
h.minRecFlag = (data[0] & 0x10) != 0
h.Owned = data[0] & 0x0f
h.heapNo |= uint16(data[1]) << 5
h.heapNo |= uint16(data[2]&0xf8) >> 3
h.nField |= uint16(data[2]&0x07) << 7
h.nField |= uint16(data[3]&0xfe) >> 1
h.sFlag = (data[3] & 0x1) != 0
h.nextRecorder = binary.BigEndian.Uint16(data[4:])

enum dict_fld_sys_tables_enum {
	DICT_FLD__SYS_TABLES__NAME		= 0,
	DICT_FLD__SYS_TABLES__DB_TRX_ID		= 1,
	DICT_FLD__SYS_TABLES__DB_ROLL_PTR	= 2,
	DICT_FLD__SYS_TABLES__ID		= 3,
	DICT_FLD__SYS_TABLES__N_COLS		= 4,
	DICT_FLD__SYS_TABLES__TYPE		= 5,
	DICT_FLD__SYS_TABLES__MIX_ID		= 6,
	DICT_FLD__SYS_TABLES__MIX_LEN		= 7,
	DICT_FLD__SYS_TABLES__CLUSTER_ID	= 8,
	DICT_FLD__SYS_TABLES__SPACE		= 9,
	DICT_NUM_FIELDS__SYS_TABLES		= 10
};

Convert a 32 bit integer from SYS_TABLES.TYPE to dict_table_t::flags
The following chart shows the translation of the low order bit.
Other bits are the same.
========================= Low order bit ==========================
                    | REDUNDANT | COMPACT | COMPRESSED and DYNAMIC
SYS_TABLES.TYPE     |     1     |    1    |     1
dict_table_t::flags |     0     |    1    |     1
==================================================================
@return ulint containing SYS_TABLES.TYPE */
UNIV_INLINE
ulint
dict_sys_tables_type_to_tf(
/*=======================*/
	ulint	type,	/*!< in: SYS_TABLES.TYPE field */
	ulint	n_cols)	/*!< in: SYS_TABLES.N_COLS field */
{
	ulint	flags;
	ulint	redundant = !(n_cols & DICT_N_COLS_COMPACT); // 判断是redundant还是COMPACT

	/* Adjust bit zero. */
	flags = redundant ? 0 : 1;

	/* ZIP_SSIZE, ATOMIC_BLOBS & DATA_DIR are the same. */  
	flags |= type & (DICT_TF_MASK_ZIP_SSIZE
			 | DICT_TF_MASK_ATOMIC_BLOBS
			 | DICT_TF_MASK_DATA_DIR
			 | DICT_TF_MASK_SHARED_SPACE); //除了最低位，用相应的标志位与type做 '&'运算，判断是否存在这些属性，最后存放在flags中

	ut_ad(!DICT_TF_GET_ZIP_SSIZE(flags) || DICT_TF_HAS_ATOMIC_BLOBS(flags));

	return(flags);
}

i_s_dict_fill_sys_tables(
/*=====================*/
	THD*		thd,		/*!< in: thread */
	dict_table_t*	table,		/*!< in: table */
	TABLE*		table_to_fill)	/*!< in/out: fill this table */
{
	Field**			fields;
	ulint			compact = DICT_TF_GET_COMPACT(table->flags); //获取compact标志位
	ulint			atomic_blobs = DICT_TF_HAS_ATOMIC_BLOBS(
								table->flags);  //获取atomic_blobs标志位，这个标志就代表了对于 blob or text field 做页外存储，也就代表file_format是Barracuda
	const page_size_t&	page_size = dict_tf_get_page_size(table->flags);
	const char*		file_format;
	const char*		row_format;
	const char*		space_type;

	file_format = trx_sys_file_format_id_to_name(atomic_blobs); //可以参考file_format_name_map，是一个指针数组，下标0代表Antelope，下标1代表Barracuda
    
    if (!compact) {
		row_format = "Redundant";
	} else if (!atomic_blobs) {
		row_format = "Compact";
	} else if (DICT_TF_GET_ZIP_SSIZE(table->flags)) {
		row_format = "Compressed";
	} else {
		row_format = "Dynamic";
	}

	if (is_system_tablespace(table->space)) {
		space_type = "System";
	} else if (DICT_TF_HAS_SHARED_SPACE(table->flags)) {
		space_type = "General";
	} else {
		space_type = "Single";
	}
//省略无用代码
}