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Information Schema
Learn how to use Information Schema in TiDB.
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Information Schema

As part of MySQL compatibility, TiDB supports a number of INFORMATION_SCHEMA tables. Many of these tables also have a corresponding SHOW command. The benefit of querying INFORMATION_SCHEMA is that it is possible to join between tables.

Fully Supported Information Schema Tables

CHARACTER_SETS table

The CHARACTER_SETS table provides information about character sets. The default character set in TiDB is utf8mb4. Additional character sets in this table are included for compatibility with MySQL:

mysql> 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 table

The COLLATIONS table provides a list of collations that correspond to character sets in the CHARACTER_SETS table. Currently this table is included only for compatibility with MySQL, as TiDB only supports binary collation:

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 table

The COLLATION_CHARACTER_SET_APPLICABILITY table maps collations to the applicable character set name. Similar to the COLLATIONS table, it is included only for compatibility with MySQL:

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 table

The COLUMNS table provides detailed information about columns in tables:

mysql> CREATE TABLE test.t1 (a int);
1 row in set (0.01 sec)

mysql> SELECT * FROM information_schema.columns WHERE table_schema='test' AND TABLE_NAME='t1'\G
*************************** 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)

The corresponding SHOW statement is as follows:

mysql> 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 table

The ENGINES table provides information about storage engines. For compatibility, TiDB will always describe InnoDB as the only supported engine:

mysql> SELECT * FROM engines\G
*************************** 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)

KEY_COLUMN_USAGE table

The KEY_COLUMN_USAGE table describes the key constraints of the columns, such as the primary key constraint:

mysql> SELECT * FROM key_column_usage WHERE table_schema='mysql' and table_name='user'\G
*************************** 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)

SCHEMATA table

The SCHEMATA table provides information about databases. The table data is equivalent to the result of the SHOW DATABASES statement:

mysql> select * from SCHEMATA\G
*************************** 1. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: INFORMATION_SCHEMA
DEFAULT_CHARACTER_SET_NAME: utf8mb4
    DEFAULT_COLLATION_NAME: utf8mb4_bin
                  SQL_PATH: NULL
*************************** 2. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: mysql
DEFAULT_CHARACTER_SET_NAME: utf8mb4
    DEFAULT_COLLATION_NAME: utf8mb4_bin
                  SQL_PATH: NULL
*************************** 3. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: PERFORMANCE_SCHEMA
DEFAULT_CHARACTER_SET_NAME: utf8mb4
    DEFAULT_COLLATION_NAME: utf8mb4_bin
                  SQL_PATH: NULL
*************************** 4. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: test
DEFAULT_CHARACTER_SET_NAME: utf8mb4
    DEFAULT_COLLATION_NAME: utf8mb4_bin
                  SQL_PATH: NULL
4 rows in set (0.00 sec)

SESSION_VARIABLES table

The SESSION_VARIABLES table provides information about session variables. The table data is similar to the result of the SHOW SESSION VARIABLES statement:

mysql> 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 table

The SLOW_QUERY table provides the slow query information, which is the parsing result of the TiDB slow log file. The column names in the table are corresponding to the field names in the slow log. For how to use this table to identify problematic statements and improve query performance, see Slow Query Log Document.

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 table

The STATISTICS table provides information about table indexes:

mysql> 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    |       |
+---------------|---------------------|------|------|---------|-------+

The following statements are equivalent:

SELECT * FROM INFORMATION_SCHEMA.STATISTICS
  WHERE table_name = 'tbl_name'
  AND table_schema = 'db_name'

SHOW INDEX
  FROM tbl_name
  FROM db_name

TABLES table

The TABLES table provides information about tables in databases:

mysql> SELECT * FROM tables WHERE table_schema='mysql' AND table_name='user'\G
*************************** 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)

The following statements are equivalent:

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 table

The TABLE_CONSTRAINTS table describes which tables have constraints:

mysql> SELECT * FROM table_constraints WHERE constraint_type='UNIQUE'\G
*************************** 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)
  • The CONSTRAINT_TYPE value can be UNIQUE, PRIMARY KEY, or FOREIGN KEY.
  • The UNIQUE and PRIMARY KEY information is similar to the result of the SHOW INDEX statement.

USER_PRIVILEGES table

The USER_PRIVILEGES table provides information about global privileges. This information comes from the mysql.user system table:

mysql> 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)

VIEWS table

The VIEWS table provides information about SQL views:

mysql> create view test.v1 as select 1;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from views\G
*************************** 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)

Unsupported Information Schema Tables

The following INFORMATION_SCHEMA tables are present in TiDB, but will always return zero rows:

  • COLUMN_PRIVILEGES
  • EVENTS
  • FILES
  • GLOBAL_STATUS
  • GLOBAL_VARIABLES
  • OPTIMIZER_TRACE
  • PARAMETERS
  • PARTITIONS
  • PLUGINS
  • PROFILING
  • REFERENTIAL_CONSTRAINTS
  • ROUTINES
  • SCHEMA_PRIVILEGES
  • SESSION_STATUS
  • TABLESPACES
  • TABLE_PRIVILEGES
  • TRIGGERS
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