Information Schema
为了和 MySQL 保持兼容，TiDB 支持很多 INFORMATION_SCHEMA 表，其中有不少表都支持相应的 SHOW 命令。查询 INFORMATION_SCHEMA 表也为表的连接操作提供了可能。
ANALYZE_STATUS 表
ANALYZE_STATUS 表提供正在执行的收集统计信息的任务以及有限条历史任务记录。
select * from `ANALYZE_STATUS`;
+--------------+------------+----------------+-------------------+----------------+---------------------+----------+
| TABLE_SCHEMA | TABLE_NAME | PARTITION_NAME | JOB_INFO | PROCESSED_ROWS | START_TIME | STATE |
+--------------+------------+----------------+-------------------+----------------+---------------------+----------+
| test | t | | analyze index idx | 2 | 2019-06-21 19:51:14 | finished |
| test | t | | analyze columns | 2 | 2019-06-21 19:51:14 | finished |
| test | t1 | p0 | analyze columns | 0 | 2019-06-21 19:51:15 | finished |
| test | t1 | p3 | analyze columns | 0 | 2019-06-21 19:51:15 | finished |
| test | t1 | p1 | analyze columns | 0 | 2019-06-21 19:51:15 | finished |
| test | t1 | p2 | analyze columns | 1 | 2019-06-21 19:51:15 | finished |
+--------------+------------+----------------+-------------------+----------------+---------------------+----------+
6 rows in set
CHARACTER_SETS 表
CHARACTER_SETS 表提供字符集相关的信息。TiDB 目前仅支持部分字符集。
SELECT * FROM character_sets;
+--------------------+----------------------+---------------+--------+
| CHARACTER_SET_NAME | DEFAULT_COLLATE_NAME | DESCRIPTION | MAXLEN |
+--------------------+----------------------+---------------+--------+
| utf8 | utf8_bin | UTF-8 Unicode | 3 |
| utf8mb4 | utf8mb4_bin | UTF-8 Unicode | 4 |
| ascii | ascii_bin | US ASCII | 1 |
| latin1 | latin1_bin | Latin1 | 1 |
| binary | binary | binary | 1 |
+--------------------+----------------------+---------------+--------+
5 rows in set (0.00 sec)
COLLATIONS 表
COLLATIONS 表提供了 CHARACTER_SETS 表中字符集对应的排序规则列表。TiDB 当前仅支持二进制排序规则，包含该表仅为兼容 MySQL。
SELECT * FROM collations WHERE character_set_name='utf8mb4';
+------------------------+--------------------+------+------------+-------------+---------+
| COLLATION_NAME | CHARACTER_SET_NAME | ID | IS_DEFAULT | IS_COMPILED | SORTLEN |
+------------------------+--------------------+------+------------+-------------+---------+
| utf8mb4_general_ci | utf8mb4 | 45 | Yes | Yes | 1 |
| utf8mb4_bin | utf8mb4 | 46 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 1 |
| utf8mb4_icelandic_ci | utf8mb4 | 225 | | Yes | 1 |
| utf8mb4_latvian_ci | utf8mb4 | 226 | | Yes | 1 |
| utf8mb4_romanian_ci | utf8mb4 | 227 | | Yes | 1 |
| utf8mb4_slovenian_ci | utf8mb4 | 228 | | Yes | 1 |
| utf8mb4_polish_ci | utf8mb4 | 229 | | Yes | 1 |
| utf8mb4_estonian_ci | utf8mb4 | 230 | | Yes | 1 |
| utf8mb4_spanish_ci | utf8mb4 | 231 | | Yes | 1 |
| utf8mb4_swedish_ci | utf8mb4 | 232 | | Yes | 1 |
| utf8mb4_turkish_ci | utf8mb4 | 233 | | Yes | 1 |
| utf8mb4_czech_ci | utf8mb4 | 234 | | Yes | 1 |
| utf8mb4_danish_ci | utf8mb4 | 235 | | Yes | 1 |
| utf8mb4_lithuanian_ci | utf8mb4 | 236 | | Yes | 1 |
| utf8mb4_slovak_ci | utf8mb4 | 237 | | Yes | 1 |
| utf8mb4_spanish2_ci | utf8mb4 | 238 | | Yes | 1 |
| utf8mb4_roman_ci | utf8mb4 | 239 | | Yes | 1 |
| utf8mb4_persian_ci | utf8mb4 | 240 | | Yes | 1 |
| utf8mb4_esperanto_ci | utf8mb4 | 241 | | Yes | 1 |
| utf8mb4_hungarian_ci | utf8mb4 | 242 | | Yes | 1 |
| utf8mb4_sinhala_ci | utf8mb4 | 243 | | Yes | 1 |
| utf8mb4_german2_ci | utf8mb4 | 244 | | Yes | 1 |
| utf8mb4_croatian_ci | utf8mb4 | 245 | | Yes | 1 |
| utf8mb4_unicode_520_ci | utf8mb4 | 246 | | Yes | 1 |
| utf8mb4_vietnamese_ci | utf8mb4 | 247 | | Yes | 1 |
+------------------------+--------------------+------+------------+-------------+---------+
26 rows in set (0.00 sec)
COLLATION_CHARACTER_SET_APPLICABILITY 表
COLLATION_CHARACTER_SET_APPLICABILITY 表将排序规则映射至适用的字符集名称。和 COLLATIONS 表一样，包含此表也是为了兼容 MySQL。
SELECT * FROM collation_character_set_applicability WHERE character_set_name='utf8mb4';
+------------------------+--------------------+
| COLLATION_NAME | CHARACTER_SET_NAME |
+------------------------+--------------------+
| utf8mb4_general_ci | utf8mb4 |
| utf8mb4_bin | utf8mb4 |
| utf8mb4_unicode_ci | utf8mb4 |
| utf8mb4_icelandic_ci | utf8mb4 |
| utf8mb4_latvian_ci | utf8mb4 |
| utf8mb4_romanian_ci | utf8mb4 |
| utf8mb4_slovenian_ci | utf8mb4 |
| utf8mb4_polish_ci | utf8mb4 |
| utf8mb4_estonian_ci | utf8mb4 |
| utf8mb4_spanish_ci | utf8mb4 |
| utf8mb4_swedish_ci | utf8mb4 |
| utf8mb4_turkish_ci | utf8mb4 |
| utf8mb4_czech_ci | utf8mb4 |
| utf8mb4_danish_ci | utf8mb4 |
| utf8mb4_lithuanian_ci | utf8mb4 |
| utf8mb4_slovak_ci | utf8mb4 |
| utf8mb4_spanish2_ci | utf8mb4 |
| utf8mb4_roman_ci | utf8mb4 |
| utf8mb4_persian_ci | utf8mb4 |
| utf8mb4_esperanto_ci | utf8mb4 |
| utf8mb4_hungarian_ci | utf8mb4 |
| utf8mb4_sinhala_ci | utf8mb4 |
| utf8mb4_german2_ci | utf8mb4 |
| utf8mb4_croatian_ci | utf8mb4 |
| utf8mb4_unicode_520_ci | utf8mb4 |
| utf8mb4_vietnamese_ci | utf8mb4 |
+------------------------+--------------------+
26 rows in set (0.00 sec)
COLUMNS 表
COLUMNS 表提供了表的所有列的信息。
CREATE TABLE test.t1 (a int);
1 row in set (0.01 sec)
SELECT * FROM information_schema.columns WHERE table_schema='test' AND TABLE_NAME='t1';
*************************** 1. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: test
TABLE_NAME: t1
COLUMN_NAME: a
ORDINAL_POSITION: 1
COLUMN_DEFAULT: NULL
IS_NULLABLE: YES
DATA_TYPE: int
CHARACTER_MAXIMUM_LENGTH: NULL
CHARACTER_OCTET_LENGTH: NULL
NUMERIC_PRECISION: 11
NUMERIC_SCALE: 0
DATETIME_PRECISION: NULL
CHARACTER_SET_NAME: NULL
COLLATION_NAME: NULL
COLUMN_TYPE: int(11)
COLUMN_KEY:
EXTRA:
PRIVILEGES: select,insert,update,references
COLUMN_COMMENT:
GENERATION_EXPRESSION:
1 row in set (0.01 sec)
COLUMNS 表中列的含义如下：
TABLE_CATALOG：包含列的表所属的目录的名称。该值始终为def。TABLE_SCHEMA：包含列的表所属的数据库的名称。TABLE_NAME：包含列的表的名称。COLUMN_NAME：列的名称。ORDINAL_POSITION：表中列的位置。COLUMN_DEFAULT：列的默认值。如果列的显式默认值为NULL，或者列定义中不包含default子句，则此值为NULL。IS_NULLABLE：列的可空性。如果列中可以存储空值，则该值为YES，则为NO。DATA_TYPE：列数据类型。CHARACTER_MAXIMUM_LENGTH：对于字符串列，以字符为单位的最大长度。CHARACTER_OCTET_LENGTH：对于字符串列，以字节为单位的最大长度。NUMERIC_PRECISION：对于数字列，为数字精度。NUMERIC_SCALE：对于数字列，为数字刻度。DATETIME_PRECISION：对于时间列，小数秒精度。CHARACTER_SET_NAME：对于字符串列，字符集名称。COLLATION_NAME：对于字符串列，排序规则名称。COLUMN_TYPE：列类型。COLUMN_KEY：该列是否被索引。具体显示如下:- 如果此值为空，则该列要么未被索引，要么被索引且是多列非唯一索引中的第二列。
- 如果此值是
PRI，则该列是主键，或者是多列主键中的一列。 - 如果此值是
UNI，则该列是唯一索引的第一列。 - 如果此值是
MUL，则该列是非唯一索引的第一列，在该列中允许给定值的多次出现。
EXTRA：关于给定列的任何附加信息。PRIVILEGES：当前用户对该列拥有的权限。目前在 TiDB 中，此值为定值，一直为select,insert,update,references。COLUMN_COMMENT：列定义中包含的注释。GENERATION_EXPRESSION：对于生成的列，显示用于计算列值的表达式。对于未生成的列为空。
对应的 SHOW 语句如下：
SHOW COLUMNS FROM t1 FROM test;
+-------+---------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+------+---------+-------+
| a | int(11) | YES | | NULL | |
+-------+---------+------+------+---------+-------+
1 row in set (0.00 sec)
ENGINES 表
ENGINES 表提供了关于存储引擎的信息。从和 MySQL 兼容性上考虑，TiDB 会一直将 InnoDB 描述为唯一支持的引擎。此外，ENGINES 表中其它列值也都是定值。
SELECT * FROM engines;
*************************** 1. row ***************************
ENGINE: InnoDB
SUPPORT: DEFAULT
COMMENT: Supports transactions, row-level locking, and foreign keys
TRANSACTIONS: YES
XA: YES
SAVEPOINTS: YES
1 row in set (0.00 sec)
ENGINES 表中列的含义如下：
ENGINE：存储引擎的名称。SUPPORT：服务器对存储引擎的支持级别，在 TiDB 中此值一直是DEFAULT。COMMENT：存储引擎的简要描述。TRANSACTIONS：存储引擎是否支持事务。XA：存储引擎是否支持 XA 事务。SAVEPOINTS：存储引擎是否支持savepoints。
KEY_COLUMN_USAGE 表
KEY_COLUMN_USAGE 表描述了列的键约束，比如主键约束。
SELECT * FROM key_column_usage WHERE table_schema='mysql' and table_name='user';
*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: PRIMARY
TABLE_CATALOG: def
TABLE_SCHEMA: mysql
TABLE_NAME: user
COLUMN_NAME: Host
ORDINAL_POSITION: 1
POSITION_IN_UNIQUE_CONSTRAINT: NULL
REFERENCED_TABLE_SCHEMA: NULL
REFERENCED_TABLE_NAME: NULL
REFERENCED_COLUMN_NAME: NULL
*************************** 2. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: PRIMARY
TABLE_CATALOG: def
TABLE_SCHEMA: mysql
TABLE_NAME: user
COLUMN_NAME: User
ORDINAL_POSITION: 2
POSITION_IN_UNIQUE_CONSTRAINT: NULL
REFERENCED_TABLE_SCHEMA: NULL
REFERENCED_TABLE_NAME: NULL
REFERENCED_COLUMN_NAME: NULL
2 rows in set (0.00 sec)
KEY_COLUMN_USAGE 表中列的含义如下：
CONSTRAINT_CATALOG：约束所属的目录的名称。该值始终为def。CONSTRAINT_SCHEMA：约束所属的数据库的名称。CONSTRAINT_NAME：约束名称。TABLE_CATALOG：表所属目录的名称。该值始终为def。TABLE_SCHEMA：表所属的架构数据库的名称。TABLE_NAME：具有约束的表的名称。COLUMN_NAME：具有约束的列的名称。ORDINAL_POSITION：列在约束中的位置，而不是列在表中的位置。列位置从 1 开始编号。POSITION_IN_UNIQUE_CONSTRAINT：唯一约束和主键约束为空。对于外键约束，此列是被引用的表的键的序号位置。REFERENCED_TABLE_SCHEMA：约束引用的数据库的名称。目前在 TiDB 中，除了外键约束，其它约束此列的值都为nil。REFERENCED_TABLE_NAME：约束引用的表的名称。目前在 TiDB 中，除了外键约束，其它约束此列的值都为nil。REFERENCED_COLUMN_NAME：约束引用的列的名称。目前在 TiDB 中，除了外键约束，其它约束此列的值都为nil。
PROCESSLIST 表
PROCESSLIST 和 show processlist 的功能一样，都是查看当前正在处理的请求。
PROCESSLIST 表会比 show processlist 多一个 MEM 列，MEM 是指正在处理的请求已使用的内存，单位是 byte。
+----+------+------+--------------------+---------+------+-------+---------------------------+-----+
| ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO | MEM |
+----+------+------+--------------------+---------+------+-------+---------------------------+-----+
| 1 | root | ::1 | INFORMATION_SCHEMA | Query | 0 | 2 | select * from PROCESSLIST | 0 |
+----+------+------+--------------------+---------+------+-------+---------------------------+-----+
SCHEMATA 表
SCHEMATA 表提供了关于数据库的信息。表中的数据与 SHOW DATABASES 语句的执行结果等价。
SELECT * FROM schemata;
+--------------+--------------------+----------------------------+------------------------+----------+
| CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
+--------------+--------------------+----------------------------+------------------------+----------+
| def | INFORMATION_SCHEMA | utf8mb4 | utf8mb4_bin | NULL |
| def | mynewdb | utf8mb4 | utf8mb4_bin | NULL |
| def | mysql | utf8mb4 | utf8mb4_bin | NULL |
| def | PERFORMANCE_SCHEMA | utf8mb4 | utf8mb4_bin | NULL |
| def | test | utf8mb4 | utf8mb4_bin | NULL |
+--------------+--------------------+----------------------------+------------------------+----------+
5 rows in set (0.00 sec)
SESSION_VARIABLES 表
SESSION_VARIABLES 表提供了关于 session 变量的信息。表中的数据跟 SHOW SESSION VARIABLES 语句执行结果类似。
SELECT * FROM session_variables LIMIT 10;
+----------------------------------+----------------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+----------------------------------+----------------------+
| max_write_lock_count | 18446744073709551615 |
| server_id_bits | 32 |
| net_read_timeout | 30 |
| innodb_online_alter_log_max_size | 134217728 |
| innodb_optimize_fulltext_only | OFF |
| max_join_size | 18446744073709551615 |
| innodb_read_io_threads | 4 |
| session_track_gtids | OFF |
| have_ssl | DISABLED |
| max_binlog_cache_size | 18446744073709547520 |
+----------------------------------+----------------------+
10 rows in set (0.00 sec)
SLOW_QUERY 表
SLOW_QUERY 表中提供了慢查询相关的信息，其内容通过解析 TiDB 慢查询日志而来，列名和慢日志中的字段名是一一对应。关于如何使用该表调查和改善慢查询请参考慢查询日志文档。
mysql> desc information_schema.slow_query;
+---------------+---------------------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------+---------------------+------+------+---------+-------+
| Time | timestamp unsigned | YES | | NULL | |
| Txn_start_ts | bigint(20) unsigned | YES | | NULL | |
| User | varchar(64) | YES | | NULL | |
| Host | varchar(64) | YES | | NULL | |
| Conn_ID | bigint(20) unsigned | YES | | NULL | |
| Query_time | double unsigned | YES | | NULL | |
| Process_time | double unsigned | YES | | NULL | |
| Wait_time | double unsigned | YES | | NULL | |
| Backoff_time | double unsigned | YES | | NULL | |
| Request_count | bigint(20) unsigned | YES | | NULL | |
| Total_keys | bigint(20) unsigned | YES | | NULL | |
| Process_keys | bigint(20) unsigned | YES | | NULL | |
| DB | varchar(64) | YES | | NULL | |
| Index_ids | varchar(100) | YES | | NULL | |
| Is_internal | tinyint(1) unsigned | YES | | NULL | |
| Digest | varchar(64) | YES | | NULL | |
| Stats | varchar(512) | YES | | NULL | |
| Cop_proc_avg | double unsigned | YES | | NULL | |
| Cop_proc_p90 | double unsigned | YES | | NULL | |
| Cop_proc_max | double unsigned | YES | | NULL | |
| Cop_proc_addr | varchar(64) | YES | | NULL | |
| Cop_wait_avg | double unsigned | YES | | NULL | |
| Cop_wait_p90 | double unsigned | YES | | NULL | |
| Cop_wait_max | double unsigned | YES | | NULL | |
| Cop_wait_addr | varchar(64) | YES | | NULL | |
| Mem_max | bigint(20) unsigned | YES | | NULL | |
| Succ | tinyint(1) unsigned | YES | | NULL | |
| Query | longblob unsigned | YES | | NULL | |
+---------------+---------------------+------+------+---------+-------+
STATISTICS 表
STATISTICS 表提供了关于表索引的信息。
desc statistics;
+---------------|---------------------|------|------|---------|-------+
| Field | Type | Null | Key | Default | Extra |
+---------------|---------------------|------|------|---------|-------+
| TABLE_CATALOG | varchar(512) | YES | | NULL | |
| TABLE_SCHEMA | varchar(64) | YES | | NULL | |
| TABLE_NAME | varchar(64) | YES | | NULL | |
| NON_UNIQUE | varchar(1) | YES | | NULL | |
| INDEX_SCHEMA | varchar(64) | YES | | NULL | |
| INDEX_NAME | varchar(64) | YES | | NULL | |
| SEQ_IN_INDEX | bigint(2) UNSIGNED | YES | | NULL | |
| COLUMN_NAME | varchar(21) | YES | | NULL | |
| COLLATION | varchar(1) | YES | | NULL | |
| CARDINALITY | bigint(21) UNSIGNED | YES | | NULL | |
| SUB_PART | bigint(3) UNSIGNED | YES | | NULL | |
| PACKED | varchar(10) | YES | | NULL | |
| NULLABLE | varchar(3) | YES | | NULL | |
| INDEX_TYPE | varchar(16) | YES | | NULL | |
| COMMENT | varchar(16) | YES | | NULL | |
| INDEX_COMMENT | varchar(1024) | YES | | NULL | |
+---------------|---------------------|------|------|---------|-------+
下列语句是等价的：
SELECT * FROM INFORMATION_SCHEMA.STATISTICS
WHERE table_name = 'tbl_name'
AND table_schema = 'db_name'
SHOW INDEX
FROM tbl_name
FROM db_name
TABLES 表
TABLES 表提供了数据库里面关于表的信息。
SELECT * FROM tables WHERE table_schema='mysql' AND table_name='user';
*************************** 1. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: mysql
TABLE_NAME: user
TABLE_TYPE: BASE TABLE
ENGINE: InnoDB
VERSION: 10
ROW_FORMAT: Compact
TABLE_ROWS: 0
AVG_ROW_LENGTH: 0
DATA_LENGTH: 0
MAX_DATA_LENGTH: 0
INDEX_LENGTH: 0
DATA_FREE: 0
AUTO_INCREMENT: 0
CREATE_TIME: 2019-03-29 09:17:27
UPDATE_TIME: NULL
CHECK_TIME: NULL
TABLE_COLLATION: utf8mb4_bin
CHECKSUM: NULL
CREATE_OPTIONS:
TABLE_COMMENT:
TIDB_TABLE_ID: 5
1 row in set (0.00 sec)
以下操作是等价的：
SELECT table_name FROM INFORMATION_SCHEMA.TABLES
WHERE table_schema = 'db_name'
[AND table_name LIKE 'wild']
SHOW TABLES
FROM db_name
[LIKE 'wild']
TABLE_CONSTRAINTS 表
TABLE_CONSTRAINTS 表记录了表的约束信息。
SELECT * FROM table_constraints WHERE constraint_type='UNIQUE';
*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: name
TABLE_SCHEMA: mysql
TABLE_NAME: help_topic
CONSTRAINT_TYPE: UNIQUE
*************************** 2. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: tbl
TABLE_SCHEMA: mysql
TABLE_NAME: stats_meta
CONSTRAINT_TYPE: UNIQUE
*************************** 3. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: tbl
TABLE_SCHEMA: mysql
TABLE_NAME: stats_histograms
CONSTRAINT_TYPE: UNIQUE
*************************** 4. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: tbl
TABLE_SCHEMA: mysql
TABLE_NAME: stats_buckets
CONSTRAINT_TYPE: UNIQUE
*************************** 5. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: delete_range_index
TABLE_SCHEMA: mysql
TABLE_NAME: gc_delete_range
CONSTRAINT_TYPE: UNIQUE
*************************** 6. row ***************************
CONSTRAINT_CATALOG: def
CONSTRAINT_SCHEMA: mysql
CONSTRAINT_NAME: delete_range_done_index
TABLE_SCHEMA: mysql
TABLE_NAME: gc_delete_range_done
CONSTRAINT_TYPE: UNIQUE
6 rows in set (0.00 sec)
其中：
CONSTRAINT_TYPE的取值可以是UNIQUE，PRIMARY KEY，或者FOREIGN KEY。UNIQUE和PRIMARY KEY信息与SHOW INDEX语句的执行结果类似。
TIDB_HOT_REGIONS 表
TIDB_HOT_REGIONS 表提供了关于热点 REGION 的相关信息。
desc TIDB_HOT_REGIONS;
+----------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------+---------------------+------+-----+---------+-------+
| TABLE_ID | bigint(21) unsigned | YES | | <null> | |
| INDEX_ID | bigint(21) unsigned | YES | | <null> | |
| DB_NAME | varchar(64) | YES | | <null> | |
| TABLE_NAME | varchar(64) | YES | | <null> | |
| INDEX_NAME | varchar(64) | YES | | <null> | |
| TYPE | varchar(64) | YES | | <null> | |
| MAX_HOT_DEGREE | bigint(21) unsigned | YES | | <null> | |
| REGION_COUNT | bigint(21) unsigned | YES | | <null> | |
| FLOW_BYTES | bigint(21) unsigned | YES | | <null> | |
+----------------+---------------------+------+-----+---------+-------+
TIDB_INDEXES 表
TIDB_INDEXES 记录了所有表中的 INDEX 信息。
desc TIDB_INDEXES;
+---------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------+---------------------+------+-----+---------+-------+
| TABLE_SCHEMA | varchar(64) | YES | | <null> | |
| TABLE_NAME | varchar(64) | YES | | <null> | |
| NON_UNIQUE | bigint(21) unsigned | YES | | <null> | |
| KEY_NAME | varchar(64) | YES | | <null> | |
| SEQ_IN_INDEX | bigint(21) unsigned | YES | | <null> | |
| COLUMN_NAME | varchar(64) | YES | | <null> | |
| SUB_PART | bigint(21) unsigned | YES | | <null> | |
| INDEX_COMMENT | varchar(2048) | YES | | <null> | |
| INDEX_ID | bigint(21) unsigned | YES | | <null> | |
+---------------+---------------------+------+-----+---------+-------+
TIDB_INDEXES 表中列的含义如下：
TABLE_SCHEMA：索引所在表的所属数据库的名称。TABLE_NAME：索引所在表的名称。NON_UNIQUE：如果索引是唯一的，则为0，否则为1。KEY_NAME：索引的名称。如果索引是主键，则名称为PRIMARY。SEQ_IN_INDEX：索引中列的顺序编号，从1开始。COLUMN_NAME：索引所在的列名。SUB_PART：索引前缀长度。如果列是部分被索引，则该值为被索引的字符数量，否则为NULL。INDEX_COMMENT：创建索引时以COMMENT标注的注释。INDEX_ID：索引的 ID。
TIKV_REGION_PEERS 表
TIKV_REGION_PEERS 表提供了所有 REGION 的 peer 信息。
desc TIKV_REGION_PEERS;
+--------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+---------------------+------+-----+---------+-------+
| REGION_ID | bigint(21) unsigned | YES | | <null> | |
| PEER_ID | bigint(21) unsigned | YES | | <null> | |
| STORE_ID | bigint(21) unsigned | YES | | <null> | |
| IS_LEARNER | tinyint(1) unsigned | YES | | <null> | |
| IS_LEADER | tinyint(1) unsigned | YES | | <null> | |
| STATUS | varchar(10) | YES | | <null> | |
| DOWN_SECONDS | bigint(21) unsigned | YES | | <null> | |
+--------------+---------------------+------+-----+---------+-------+
TIKV_REGION_STATUS 表
TIKV_REGION_STATUS 表提供了所有 REGION 的状态信息。
desc TIKV_REGION_STATUS;
+------------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------------------+------+-----+---------+-------+
| REGION_ID | bigint(21) unsigned | YES | | <null> | |
| START_KEY | text | YES | | <null> | |
| END_KEY | text | YES | | <null> | |
| EPOCH_CONF_VER | bigint(21) unsigned | YES | | <null> | |
| EPOCH_VERSION | bigint(21) unsigned | YES | | <null> | |
| WRITTEN_BYTES | bigint(21) unsigned | YES | | <null> | |
| READ_BYTES | bigint(21) unsigned | YES | | <null> | |
| APPROXIMATE_SIZE | bigint(21) unsigned | YES | | <null> | |
| APPROXIMATE_KEYS | bigint(21) unsigned | YES | | <null> | |
+------------------+---------------------+------+-----+---------+-------+
TIKV_STORE_STATUS 表
TIKV_STORE_STATUS 表提供了所有 TiKV Store 的状态信息。
desc TIKV_STORE_STATUS;
+-------------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+---------------------+------+-----+---------+-------+
| STORE_ID | bigint(21) unsigned | YES | | <null> | |
| ADDRESS | varchar(64) | YES | | <null> | |
| STORE_STATE | bigint(21) unsigned | YES | | <null> | |
| STORE_STATE_NAME | varchar(64) | YES | | <null> | |
| LABEL | json unsigned | YES | | <null> | |
| VERSION | varchar(64) | YES | | <null> | |
| CAPACITY | varchar(64) | YES | | <null> | |
| AVAILABLE | varchar(64) | YES | | <null> | |
| LEADER_COUNT | bigint(21) unsigned | YES | | <null> | |
| LEADER_WEIGHT | bigint(21) unsigned | YES | | <null> | |
| LEADER_SCORE | bigint(21) unsigned | YES | | <null> | |
| LEADER_SIZE | bigint(21) unsigned | YES | | <null> | |
| REGION_COUNT | bigint(21) unsigned | YES | | <null> | |
| REGION_WEIGHT | bigint(21) unsigned | YES | | <null> | |
| REGION_SCORE | bigint(21) unsigned | YES | | <null> | |
| REGION_SIZE | bigint(21) unsigned | YES | | <null> | |
| START_TS | datetime unsigned | YES | | <null> | |
| LAST_HEARTBEAT_TS | datetime unsigned | YES | | <null> | |
| UPTIME | varchar(64) | YES | | <null> | |
+-------------------+---------------------+------+-----+---------+-------+
USER_PRIVILEGES 表
USER_PRIVILEGES 表提供了关于全局权限的信息。该表的数据根据 mysql.user 系统表生成。
desc USER_PRIVILEGES;
+----------------|--------------|------|------|---------|-------+
| Field | Type | Null | Key | Default | Extra |
+----------------|--------------|------|------|---------|-------+
| GRANTEE | varchar(81) | YES | | NULL | |
| TABLE_CATALOG | varchar(512) | YES | | NULL | |
| PRIVILEGE_TYPE | varchar(64) | YES | | NULL | |
| IS_GRANTABLE | varchar(3) | YES | | NULL | |
+----------------|--------------|------|------|---------|-------+
4 rows in set (0.00 sec)
USER_PRIVILEGES 表中列的含义如下：
GRANTEE：被授权的用户名称，格式为'user_name'@'host_name'。TABLE_CATALOG：表所属的目录的名称。该值始终为def。PRIVILEGE_TYPE：被授权的权限类型，每行只列一个权限。IS_GRANTABLE：如果用户有GRANT OPTION的权限，则为YES，否则为NO。
VIEWS 表
VIEWS 表提供了关于 SQL 视图的信息。
create view test.v1 as select 1;
Query OK, 0 rows affected (0.00 sec)
select * from views;
*************************** 1. row ***************************
TABLE_CATALOG: def
TABLE_SCHEMA: test
TABLE_NAME: v1
VIEW_DEFINITION: select 1
CHECK_OPTION: CASCADED
IS_UPDATABLE: NO
DEFINER: root@127.0.0.1
SECURITY_TYPE: DEFINER
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
1 row in set (0.00 sec)
VIEWS 表中列的含义如下：
TABLE_CATALOG：视图所属的目录的名称。该值始终为def。TABLE_SCHEMA：视图所属的数据库的名称。TABLE_NAME：视图名称。VIEW_DEFINITION：视图的定义，由创建视图时SELECT部分的语句组成。CHECK_OPTION：CHECK_OPTION的值。取值为NONE、CASCADE或LOCAL。IS_UPDATABLE：UPDATE/INSERT/DELETE是否对该视图可用。在 TiDB，始终为NO。DEFINER：视图的创建者用户名称，格式为'user_name'@'host_name'。SECURITY_TYPE：SQL SECURITY的值，取值为DEFINER或INVOKER。CHARACTER_SET_CLIENT：在视图创建时 session 变量character_set_client的值。COLLATION_CONNECTION：在视图创建时 session 变量collation_connection的值。
不支持的 Information Schema 表
TiDB 包含以下 INFORMATION_SCHEMA 表，但仅会返回空行：
COLUMN_PRIVILEGESEVENTSFILESGLOBAL_STATUSGLOBAL_VARIABLESOPTIMIZER_TRACEPARAMETERSPARTITIONSPLUGINSPROFILINGREFERENTIAL_CONSTRAINTSROUTINESSCHEMA_PRIVILEGESSESSION_STATUSTABLESPACESTABLE_PRIVILEGESTRIGGERS