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Information Schema
Learn how to use Information Schema in TiDB.
/docs/dev/system-tables/system-table-information-schema/
/docs/dev/reference/system-databases/information-schema/

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

ANALYZE_STATUS table

The ANALYZE_STATUS table provides information about the running tasks that collect statistics and a limited number of history tasks.

{{< copyable "sql" >}}

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 table

The CHARACTER_SETS table provides information about character sets. Currently, TiDB only supports some of the character sets.

{{< copyable "sql" >}}

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:

{{< copyable "sql" >}}

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:

{{< copyable "sql" >}}

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:

{{< copyable "sql" >}}

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

{{< copyable "sql" >}}

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)

The description of columns in the COLUMNS table is as follows:

  • TABLE_CATALOG: The name of the catalog to which the table with the column belongs. The value is always def.
  • TABLE_SCHEMA: The name of the schema in which the table with the column is located.
  • TABLE_NAME: The name of the table with the column.
  • COLUMN_NAME: The name of the column.
  • ORDINAL_POSITION: The position of the column in the table.
  • COLUMN_DEFAULT: The default value of the column. If the explicit default value is NULL, or if the column definition does not include the default clause, this value is NULL.
  • IS_NULLABLE: Whether the column is nullable. If the column can store null values, this value is YES; otherwise, it is NO.
  • DATA_TYPE: The type of data in the column.
  • CHARACTER_MAXIMUM_LENGTH: For string columns, the maximum length in characters.
  • CHARACTER_OCTET_LENGTH: For string columns, the maximum length in bytes.
  • NUMERIC_PRECISION: The numeric precision of a number-type column.
  • NUMERIC_SCALE: The numeric scale of a number-type column.
  • DATETIME_PRECISION: For time-type columns, the fractional seconds precision.
  • CHARACTER_SET_NAME: The name of the character set of a string column.
  • COLLATION_NAME: The name of the collation of a string column.
  • COLUMN_TYPE: The column type.
  • COLUMN_KEY: Whether this column is indexed. This field might have the following values:
    • Empty: This column is not indexed, or this column is indexed and is the second column in a multi-column non-unique index.
    • PRI: This column is the primary key or one of multiple primary keys.
    • UNI: This column is the first column of the unique index.
    • MUL: The column is the first column of a non-unique index, in which a given value is allowed to occur for multiple times.
  • EXTRA: Any additional information of the given column.
  • PRIVILEGES: The privilege that the current user has on this column. Currently, this value is fixed in TiDB, and is always select,insert,update,references.
  • COLUMN_COMMENT: Comments contained in the column definition.
  • GENERATION_EXPRESSION: For generated columns, this value displays the expression used to calculate the column value. For non-generated columns, the value is empty.

The corresponding SHOW statement is as follows:

{{< copyable "sql" >}}

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. In addition, other column values in the ENGINES table are also fixed values.

{{< copyable "sql" >}}

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)

The description of columns in the ENGINES table is as follows:

  • ENGINES: The name of the storage engine.
  • SUPPORT: The level of support that the server has on the storage engine. In TiDB, the value is always DEFAULT.
  • COMMENT: The brief comment on the storage engine.
  • TRANSACTIONS：Whether the storage engine supports transactions.
  • XA: Whether the storage engine supports XA transactions.
  • SAVEPOINTS: Whether the storage engine supports savepoints.

KEY_COLUMN_USAGE table

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

{{< copyable "sql" >}}

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)

The description of columns in the KEY_COLUMN_USAGE table is as follows:

  • CONSTRAINT_CATALOG: The name of the catalog to which the constraint belongs. The value is always def.
  • CONSTRAINT_SCHEMA: The name of the schema to which the constraint belongs.
  • CONSTRAINT_NAME: The name of the constraint.
  • TABLE_CATALOG: The name of the catalog to which the table belongs. The value is always def.
  • TABLE_SCHEMA: The name of the schema to which the table belongs.
  • TABLE_NAME: The name of the table with constraints.
  • COLUMN_NAME: The name of the column with constraints.
  • ORDINAL_POSITION: The position of the column in the constraint, rather than in the table. The position number starts from 1.
  • POSITION_IN_UNIQUE_CONSTRAINT: The unique constraint and the primary key constraint are empty. For foreign key constraints, this column is the position of the referenced table's key.
  • REFERENCED_TABLE_SCHEMA: The name of the schema referenced by the constraint. Currently in TiDB, the value of this column in all constraints is nil, except for the foreign key constraint.
  • REFERENCED_TABLE_NAME: The name of the table referenced by the constraint. Currently in TiDB, the value of this column in all constraints is nil, except for the foreign key constraint.
  • REFERENCED_COLUMN_NAME: The name of the column referenced by the constraint. Currently in TiDB, the value of this column in all constraints is nil, except for the foreign key constraint.

PROCESSLIST table

PROCESSLIST, just like show processlist, is used to view the requests that are being handled.

The PROCESSLIST table has a MEM column that show processlist does not have. MEM means the occupied memory of the requests being handled, and its unit is byte.

+----+------+------+--------------------+---------+------+-------+---------------------------+-----+
| ID | USER | HOST | DB                 | COMMAND | TIME | STATE | INFO                      | MEM |
+----+------+------+--------------------+---------+------+-------+---------------------------+-----+
| 1  | root | ::1  | INFORMATION_SCHEMA | Query   | 0    | 2     | select * from PROCESSLIST | 0   |
+----+------+------+--------------------+---------+------+-------+---------------------------+-----+

SCHEMATA table

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

{{< copyable "sql" >}}

select * from SCHEMATA;
*************************** 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)

CLUSTER_PROCESSLIST

CLUSTER_PROCESSLIST is the cluster system table corresponding to PROCESSLIST. It is used to query the PROCESSLIST information of all TiDB nodes in the cluster. The table schema of CLUSTER_PROCESSLIST has one more column than PROCESSLIST, the INSTANCE column, which stores the address of the TiDB node this row of data is from.

{{< copyable "sql" >}}

SELECT * FROM information_schema.cluster_processlist;
+-----------------+-----+------+----------+------+---------+------+------------+------------------------------------------------------+-----+----------------------------------------+
| INSTANCE        | ID  | USER | HOST     | DB   | COMMAND | TIME | STATE      | INFO                                                 | MEM | TxnStart                               |
+-----------------+-----+------+----------+------+---------+------+------------+------------------------------------------------------+-----+----------------------------------------+
| 10.0.1.22:10080 | 150 | u1   | 10.0.1.1 | test | Query   | 0    | autocommit | select count(*) from usertable                       | 372 | 05-28 03:54:21.230(416976223923077223) |
| 10.0.1.22:10080 | 138 | root | 10.0.1.1 | test | Query   | 0    | autocommit | SELECT * FROM information_schema.cluster_processlist | 0   | 05-28 03:54:21.230(416976223923077220) |
| 10.0.1.22:10080 | 151 | u1   | 10.0.1.1 | test | Query   | 0    | autocommit | select count(*) from usertable                       | 372 | 05-28 03:54:21.230(416976223923077224) |
| 10.0.1.21:10080 | 15  | u2   | 10.0.1.1 | test | Query   | 0    | autocommit | select max(field0) from usertable                    | 496 | 05-28 03:54:21.230(416976223923077222) |
| 10.0.1.21:10080 | 14  | u2   | 10.0.1.1 | test | Query   | 0    | autocommit | select max(field0) from usertable                    | 496 | 05-28 03:54:21.230(416976223923077225) |
+-----------------+-----+------+----------+------+---------+------+------------+------------------------------------------------------+-----+----------------------------------------+

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:

{{< copyable "sql" >}}

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 of the current node, 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.

{{< copyable "sql" >}}

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>  |       |
| Parse_time                | double unsigned     | YES  |     | <null>  |       |
| Compile_time              | double unsigned     | YES  |     | <null>  |       |
| Prewrite_time             | double unsigned     | YES  |     | <null>  |       |
| Wait_prewrite_binlog_time | double unsigned     | YES  |     | <null>  |       |
| Commit_time               | double unsigned     | YES  |     | <null>  |       |
| Get_commit_ts_time        | double unsigned     | YES  |     | <null>  |       |
| Commit_backoff_time       | double unsigned     | YES  |     | <null>  |       |
| Backoff_types             | varchar(64)         | YES  |     | <null>  |       |
| Resolve_lock_time         | double unsigned     | YES  |     | <null>  |       |
| Local_latch_wait_time     | double unsigned     | YES  |     | <null>  |       |
| Write_keys                | bigint(22) unsigned | YES  |     | <null>  |       |
| Write_size                | bigint(22) unsigned | YES  |     | <null>  |       |
| Prewrite_region           | bigint(22) unsigned | YES  |     | <null>  |       |
| Txn_retry                 | bigint(22) unsigned | YES  |     | <null>  |       |
| Process_time              | double unsigned     | YES  |     | <null>  |       |
| Wait_time                 | double unsigned     | YES  |     | <null>  |       |
| Backoff_time              | double unsigned     | YES  |     | <null>  |       |
| LockKeys_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_names               | 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>  |       |
| Plan_from_cache           | tinyint(1)          | YES  |     | <null>  |       |
| Plan                      | longblob unsigned   | YES  |     | <null>  |       |
| Plan_digest               | varchar(128)        | YES  |     | <null>  |       |
| Prev_stmt                 | longblob unsigned   | YES  |     | <null>  |       |
| Query                     | longblob unsigned   | YES  |     | <null>  |       |
+---------------------------+---------------------+------+-----+---------+-------+

CLUSTER_SLOW_QUERY table

The CLUSTER_SLOW_QUERY table provides the slow query information of all nodes in the cluster, which is the parsing result of the TiDB slow log files. You can use the CLUSTER_SLOW_QUERY table the way you do with SLOW_QUERY. The table schema of the CLUSTER_SLOW_QUERY table differs from that of the SLOW_QUERY table in that an INSTANCE column is added to CLUSTER_SLOW_QUERY. The INSTANCE column represents the TiDB node address of the row information on the slow query. For how to use this table to identify problematic statements and improve query performance, see Slow Query Log Document.

{{< copyable "sql" >}}

desc information_schema.cluster_slow_query;
+---------------------------+---------------------+------+-----+---------+-------+
| Field                     | Type                | Null | Key | Default | Extra |
+---------------------------+---------------------+------+-----+---------+-------+
| INSTANCE                  | varchar(64)         | YES  |     | <null>  |       |
| 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>  |       |
| Parse_time                | double unsigned     | YES  |     | <null>  |       |
| Compile_time              | double unsigned     | YES  |     | <null>  |       |
| Prewrite_time             | double unsigned     | YES  |     | <null>  |       |
| Wait_prewrite_binlog_time | double unsigned     | YES  |     | <null>  |       |
| Commit_time               | double unsigned     | YES  |     | <null>  |       |
| Get_commit_ts_time        | double unsigned     | YES  |     | <null>  |       |
| Commit_backoff_time       | double unsigned     | YES  |     | <null>  |       |
| Backoff_types             | varchar(64)         | YES  |     | <null>  |       |
| Resolve_lock_time         | double unsigned     | YES  |     | <null>  |       |
| Local_latch_wait_time     | double unsigned     | YES  |     | <null>  |       |
| Write_keys                | bigint(22) unsigned | YES  |     | <null>  |       |
| Write_size                | bigint(22) unsigned | YES  |     | <null>  |       |
| Prewrite_region           | bigint(22) unsigned | YES  |     | <null>  |       |
| Txn_retry                 | bigint(22) unsigned | YES  |     | <null>  |       |
| Process_time              | double unsigned     | YES  |     | <null>  |       |
| Wait_time                 | double unsigned     | YES  |     | <null>  |       |
| Backoff_time              | double unsigned     | YES  |     | <null>  |       |
| LockKeys_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_names               | 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>  |       |
| Plan_from_cache           | tinyint(1)          | YES  |     | <null>  |       |
| Plan                      | longblob unsigned   | YES  |     | <null>  |       |
| Plan_digest               | varchar(128)        | YES  |     | <null>  |       |
| Prev_stmt                 | longblob unsigned   | YES  |     | <null>  |       |
| Query                     | longblob unsigned   | YES  |     | <null>  |       |
+---------------------------+---------------------+------+-----+---------+-------+

When the cluster system table is queried, TiDB does not obtain data from all nodes, but pushes down the related calculation to other nodes. The execution plan is as follows:

{{< copyable "sql" >}}

desc select count(*) from information_schema.cluster_slow_query where user = 'u1';
+--------------------------+----------+-----------+--------------------------+------------------------------------------------------+
| id                       | estRows  | task      | access object            | operator info                                        |
+--------------------------+----------+-----------+--------------------------+------------------------------------------------------+
| StreamAgg_20             | 1.00     | root      |                          | funcs:count(Column#53)->Column#51                    |
| └─TableReader_21         | 1.00     | root      |                          | data:StreamAgg_9                                     |
|   └─StreamAgg_9          | 1.00     | cop[tidb] |                          | funcs:count(1)->Column#53                            |
|     └─Selection_19       | 10.00    | cop[tidb] |                          | eq(information_schema.cluster_slow_query.user, "u1") |
|       └─TableFullScan_18 | 10000.00 | cop[tidb] | table:CLUSTER_SLOW_QUERY | keep order:false, stats:pseudo                       |
+--------------------------+----------+-----------+--------------------------+------------------------------------------------------+

In the above execution plan, the user = u1 condition is pushed down to other (cop) TiDB nodes, and the aggregate operator is also pushed down (the StreamAgg operator in the graph).

Currently, because statistics of the system tables are not collected, sometimes some aggregation operators cannot be pushed down, which results in slow execution. In this case, you can manually specify the SQL HINT to push down the aggregation operators. For example:

{{< copyable "sql" >}}

select /*+ AGG_TO_COP() */ count(*) from information_schema.cluster_slow_query group by user;

STATISTICS table

The STATISTICS table provides information about table indexes:

{{< copyable "sql" >}}

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)     | YES  |      | NULL    |       |
| COLUMN_NAME   | varchar(21)   | YES  |      | NULL    |       |
| COLLATION     | varchar(1)    | YES  |      | NULL    |       |
| CARDINALITY   | bigint(21)    | YES  |      | NULL    |       |
| SUB_PART      | bigint(3)     | 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    |       |
| IS_VISIBLE    | varchar(3)    | YES  |      | NULL    |       |
| Expression    | varchar(64)   | 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:

{{< copyable "sql" >}}

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
TIDB_ROW_ID_SHARDING_INFO: NULL
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']

Most of the information in the table is the same as MySQL. Only two columns are newly defined by TiDB:

  • TIDB_TABLE_ID: to indicate the internal ID of a table. This ID is unique in a TiDB cluster.
  • TIDDB_ROW_ID_SHARDING_INFO: to indicate the sharding type of a table. The possible values are as follows:
    • "NOT_SHARDED": the table is not sharded.
    • "NOT_SHARDED(PK_IS_HANDLE)": the table that defines an integer Primary Key as its row id is not sharded.
    • "PK_AUTO_RANDOM_BITS={bit_number}": the table that defines an integer Primary Key as its row id is sharded because the Primary Key is assigned with AUTO_RANDOM attribute.
    • "SHARD_BITS={bit_number}": the table is sharded using SHARD_ROW_ID_BITS={bit_number}.
    • NULL: the table is a system table or view, and thus cannot be sharded.

TABLE_CONSTRAINTS table

The TABLE_CONSTRAINTS table describes which tables have constraints:

{{< copyable "sql" >}}

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)
  • 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.

TIDB_HOT_REGIONS table

The TIDB_HOT_REGIONS table provides information about hotspot Regions.

{{< copyable "sql" >}}

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 table

The TIDB_INDEXES table provides the INDEX information of all tables.

{{< copyable "sql" >}}

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

TIKV_REGION_PEERS table

The TIKV_REGION_PEERS table provides the peer information of all Regions.

{{< copyable "sql" >}}

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 table

The TIKV_REGION_STATUS table provides the status information of all Regions.

{{< copyable "sql" >}}

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 table

The TIKV_STORE_STATUS table provides the status information of all TiKV Stores.

{{< copyable "sql" >}}

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 table

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

{{< copyable "sql" >}}

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:

{{< copyable "sql" >}}

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

{{< copyable "sql" >}}

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)

TIDB_INDEXES table

The TIDB_INDEXES table provides index-related information.

{{< copyable "sql" >}}

desc tidb_indexes\G
*************************** 1. row ***************************
       Table: TIDB_INDEXES
Create Table: CREATE TABLE `TIDB_INDEXES` (
  `TABLE_SCHEMA` varchar(64) DEFAULT NULL,
  `TABLE_NAME` varchar(64) DEFAULT NULL,
  `NON_UNIQUE` bigint(21) unsigned DEFAULT NULL,
  `KEY_NAME` varchar(64) DEFAULT NULL,
  `SEQ_IN_INDEX` bigint(21) unsigned DEFAULT NULL,
  `COLUMN_NAME` varchar(64) DEFAULT NULL,
  `SUB_PART` bigint(21) unsigned DEFAULT NULL,
  `INDEX_COMMENT` varchar(2048) DEFAULT NULL,
  `INDEX_ID` bigint(21) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.00 sec)

INDEX_ID is the unique ID that TiDB allocates for each index. It can be used to do a join operation with INDEX_ID obtained from another table or API.

For example, you can obtain TABLE_ID and INDEX_ID that are involved in some slow query in the SLOW_QUERY table and then obtain the specific index information using the following SQL statements:

select
   tidb_indexes.*
from
   tidb_indexes,
   tables
where
   tidb_indexes.table_schema = tables.table_schema
   and tidb_indexes.table_name = tidb_indexes.table_name
   and tables.tidb_table_id = ?
   and index_id = ?

TIDB_HOT_REGIONS table

The TIDB_HOT_REGIONS table provides the hot Region information in the current TiKV instance.

{{< copyable "sql" >}}

desc tidb_hot_regions\G
*************************** 1. row ***************************
       Table: TIDB_HOT_REGIONS
Create Table: CREATE TABLE `TIDB_HOT_REGIONS` (
  `TABLE_ID` bigint(21) unsigned DEFAULT NULL,
  `INDEX_ID` bigint(21) unsigned DEFAULT NULL,
  `DB_NAME` varchar(64) DEFAULT NULL,
  `TABLE_NAME` varchar(64) DEFAULT NULL,
  `INDEX_NAME` varchar(64) DEFAULT NULL,
  `TYPE` varchar(64) DEFAULT NULL,
  `MAX_HOT_DEGREE` bigint(21) unsigned DEFAULT NULL,
  `REGION_COUNT` bigint(21) unsigned DEFAULT NULL,
  `FLOW_BYTES` bigint(21) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.00 sec)
  • TABLE_ID and INDEX_ID are IDs generated for the corresponding table and index in TiDB.
  • TYPE is the type for a hot Region. Its value can be READ or WRITE.

TIKV_STORE_STATUS table

The TIKV_STORE_STATUS table shows some basic information of TiKV nodes via PD's API, like the ID allocated in the cluster, address and port, and status, capacity, and the number of Region leaders of the current node.

{{< copyable "sql" >}}

desc tikv_store_status\G
*************************** 1. row ***************************
       Table: TIKV_STORE_STATUS
Create Table: CREATE TABLE `TIKV_STORE_STATUS` (
  `STORE_ID` bigint(21) unsigned DEFAULT NULL,
  `ADDRESS` varchar(64) DEFAULT NULL,
  `STORE_STATE` bigint(21) unsigned DEFAULT NULL,
  `STORE_STATE_NAME` varchar(64) DEFAULT NULL,
  `LABEL` json unsigned DEFAULT NULL,
  `VERSION` varchar(64) DEFAULT NULL,
  `CAPACITY` varchar(64) DEFAULT NULL,
  `AVAILABLE` varchar(64) DEFAULT NULL,
  `LEADER_COUNT` bigint(21) unsigned DEFAULT NULL,
  `LEADER_WEIGHT` bigint(21) unsigned DEFAULT NULL,
  `LEADER_SCORE` bigint(21) unsigned DEFAULT NULL,
  `LEADER_SIZE` bigint(21) unsigned DEFAULT NULL,
  `REGION_COUNT` bigint(21) unsigned DEFAULT NULL,
  `REGION_WEIGHT` bigint(21) unsigned DEFAULT NULL,
  `REGION_SCORE` bigint(21) unsigned DEFAULT NULL,
  `REGION_SIZE` bigint(21) unsigned DEFAULT NULL,
  `START_TS` datetime unsigned DEFAULT NULL,
  `LAST_HEARTBEAT_TS` datetime unsigned DEFAULT NULL,
  `UPTIME` varchar(64) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.01 sec)

TIKV_REGION_STATUS table

The TIKV_REGION_STATUS table shows some basic information of TiKV Regions via PD's API, like the Region ID, starting and ending key-values, and read and write traffic.

{{< copyable "sql" >}}

desc tikv_region_status\G
*************************** 1. row ***************************
       Table: TIKV_REGION_STATUS
Create Table: CREATE TABLE `TIKV_REGION_STATUS` (
  `REGION_ID` bigint(21) unsigned DEFAULT NULL,
  `START_KEY` text DEFAULT NULL,
  `END_KEY` text DEFAULT NULL,
  `EPOCH_CONF_VER` bigint(21) unsigned DEFAULT NULL,
  `EPOCH_VERSION` bigint(21) unsigned DEFAULT NULL,
  `WRITTEN_BYTES` bigint(21) unsigned DEFAULT NULL,
  `READ_BYTES` bigint(21) unsigned DEFAULT NULL,
  `APPROXIMATE_SIZE` bigint(21) unsigned DEFAULT NULL,
  `APPROXIMATE_KEYS` bigint(21) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.00 sec)

You can implement the top confver, top read and top write operations in pd-ctl via the ORDER BY X LIMIT Y operation on the EPOCH_CONF_VER, WRITTEN_BYTES and READ_BYTES columns.

You can query the top 3 Regions with the most write data using the following SQL statement:

select * from tikv_region_status order by written_bytes desc limit 3;

TIKV_REGION_PEERS table

The TIKV_REGION_PEERS table shows detailed information of a single Region node in TiKV, like whether it is a learner or leader.

{{< copyable "sql" >}}

desc tikv_region_peers\G
*************************** 1. row ***************************
       Table: TIKV_REGION_PEERS
Create Table: CREATE TABLE `TIKV_REGION_PEERS` (
  `REGION_ID` bigint(21) unsigned DEFAULT NULL,
  `PEER_ID` bigint(21) unsigned DEFAULT NULL,
  `STORE_ID` bigint(21) unsigned DEFAULT NULL,
  `IS_LEARNER` tinyint(1) unsigned DEFAULT NULL,
  `IS_LEADER` tinyint(1) unsigned DEFAULT NULL,
  `STATUS` varchar(10) DEFAULT NULL,
  `DOWN_SECONDS` bigint(21) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.00 sec)

For example, you can query the specific TiKV addresses for the top 3 Regions with the maximum value of WRITTEN_BYTES using the following SQL statement:

select
   address,
   tikv.address,
   region.region_id,
from
   tikv_store_status tikv,
   tikv_region_peers peer,
   (
      select
         *
      from
         tikv_region_status region
      order by
         written_bytes desc limit 3
   )
   region
where
   region.region_id = peer.region_id
   and peer.is_leader = 1
   and peer.store_id = tikv.region_id

ANALYZE_STATUS table

The ANALYZE_STATUS table shows the execution status of the ANALYZE command in the current cluster.

{{< copyable "sql" >}}

desc analyze_status\G
*************************** 1. row ***************************
       Table: ANALYZE_STATUS
Create Table: CREATE TABLE `ANALYZE_STATUS` (
  `TABLE_SCHEMA` varchar(64) DEFAULT NULL,
  `TABLE_NAME` varchar(64) DEFAULT NULL,
  `PARTITION_NAME` varchar(64) DEFAULT NULL,
  `JOB_INFO` varchar(64) DEFAULT NULL,
  `PROCESSED_ROWS` bigint(20) unsigned DEFAULT NULL,
  `START_TIME` datetime unsigned DEFAULT NULL,
  `STATE` varchar(64) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.00 sec)

The STATE column shows the execution status of a specific ANALYZE task. Its value can be pending, running,finished or failed.

SLOW_QUERY table

The SLOW_QUERY table maps slow query logs. Its column names and field names of slow query logs have an one-to-one corresponse relationship. For details, see Identify Slow Queries.

{{< copyable "sql" >}}

desc slow_query\G
*************************** 1. row ***************************
       Table: SLOW_QUERY
Create Table: CREATE TABLE `SLOW_QUERY` (
  `Time` timestamp unsigned NULL DEFAULT NULL,
  `Txn_start_ts` bigint(20) unsigned DEFAULT NULL,
  `User` varchar(64) DEFAULT NULL,
  `Host` varchar(64) DEFAULT NULL,
  `Conn_ID` bigint(20) unsigned DEFAULT NULL,
  `Query_time` double unsigned DEFAULT NULL,
  `Process_time` double unsigned DEFAULT NULL,
  `Wait_time` double unsigned DEFAULT NULL,
  `Backoff_time` double unsigned DEFAULT NULL,
  `Request_count` bigint(20) unsigned DEFAULT NULL,
  `Total_keys` bigint(20) unsigned DEFAULT NULL,
  `Process_keys` bigint(20) unsigned DEFAULT NULL,
  `DB` varchar(64) DEFAULT NULL,
  `Index_ids` varchar(100) DEFAULT NULL,
  `Is_internal` tinyint(1) unsigned DEFAULT NULL,
  `Digest` varchar(64) DEFAULT NULL,
  `Stats` varchar(512) DEFAULT NULL,
  `Cop_proc_avg` double unsigned DEFAULT NULL,
  `Cop_proc_p90` double unsigned DEFAULT NULL,
  `Cop_proc_max` double unsigned DEFAULT NULL,
  `Cop_proc_addr` varchar(64) DEFAULT NULL,
  `Cop_wait_avg` double unsigned DEFAULT NULL,
  `Cop_wait_p90` double unsigned DEFAULT NULL,
  `Cop_wait_max` double unsigned DEFAULT NULL,
  `Cop_wait_addr` varchar(64) DEFAULT NULL,
  `Mem_max` bigint(20) unsigned DEFAULT NULL,
  `Query` varchar(4096) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
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