Doc Menu

TiDB Specific Functions

This document introduces the functions that are specific to TiDB.

TIDB_BOUNDED_STALENESS

The TIDB_BOUNDED_STALENESS function is an internal function of TiDB.

TIDB_DECODE_KEY

The TIDB_DECODE_KEY function can be used to decode a TiDB-encoded key entry into a JSON structure containing _tidb_rowid and table_id. These encoded keys can be found in some system tables and in logging outputs.

Synopsis

TableStmt
TIDB_DECODE_KEY(STR)

Example

SELECT START_KEY, TIDB_DECODE_KEY(START_KEY) FROM information_schema.tikv_region_status WHERE table_name='t1' AND REGION_ID=2\G
*************************** 1. row ***************************
                 START_KEY: 7480000000000000FF3B5F728000000000FF1DE3F10000000000FA
TIDB_DECODE_KEY(START_KEY): {"_tidb_rowid":1958897,"table_id":"59"}
1 row in set (0.00 sec)

MySQL compatibility

The TIDB_DECODE_KEY function is TiDB-specific and not compatible with MySQL.

TIDB_DECODE_PLAN

The TIDB_DECODE_PLAN function can be used to decode a TiDB execution plan. These plans can be found in the slow query log.

Synopsis

TableStmt
TIDB_DECODE_PLAN(STR)

Example

SELECT tidb_decode_plan('8QIYMAkzMV83CQEH8E85LjA0CWRhdGE6U2VsZWN0aW9uXzYJOTYwCXRpbWU6NzEzLjHCtXMsIGxvb3BzOjIsIGNvcF90YXNrOiB7bnVtOiAxLCBtYXg6IDU2OC41wgErRHByb2Nfa2V5czogMCwgcnBjXxEpAQwFWBAgNTQ5LglZyGNvcHJfY2FjaGVfaGl0X3JhdGlvOiAwLjAwfQkzLjk5IEtCCU4vQQoxCTFfNgkxXzAJMwm2SGx0KHRlc3QudC5hLCAxMDAwMCkNuQRrdgmiAHsFbBQzMTMuOMIBmQnEDDk2MH0BUgEEGAoyCTQzXzUFVwX1oGFibGU6dCwga2VlcCBvcmRlcjpmYWxzZSwgc3RhdHM6cHNldWRvCTk2ISE2aAAIMTUzXmYA')\G
*************************** 1. row ***************************
  tidb_decode_plan('8QIYMAkzMV83CQEH8E85LjA0CWRhdGE6U2VsZWN0aW9uXzYJOTYwCXRpbWU6NzEzLjHCtXMsIGxvb3BzOjIsIGNvcF90YXNrOiB7bnVtOiAxLCBtYXg6IDU2OC41wgErRHByb2Nfa2V5czogMCwgcnBjXxEpAQwFWBAgNTQ5LglZyGNvcHJfY2FjaGVfaGl0X3JhdGlvOiAwLjAwfQkzLjk5IEtCCU4vQQoxCTFfNgkxXz:     id                     task         estRows    operator info                              actRows    execution info                                                                                                                         memory     disk
    TableReader_7          root         319.04     data:Selection_6                           960        time:713.1µs, loops:2, cop_task: {num: 1, max: 568.5µs, proc_keys: 0, rpc_num: 1, rpc_time: 549.1µs, copr_cache_hit_ratio: 0.00}    3.99 KB    N/A
    └─Selection_6          cop[tikv]    319.04     lt(test.t.a, 10000)                        960        tikv_task:{time:313.8µs, loops:960}                                                                                                   N/A        N/A
      └─TableFullScan_5    cop[tikv]    960        table:t, keep order:false, stats:pseudo    960        tikv_task:{time:153µs, loops:960}                                                                                                     N/A        N/A

MySQL compatibility

The TIDB_DECODE_PLAN function is TiDB-specific and not compatible with MySQL.

TIDB_IS_DDL_OWNER

The TIDB_IS_DDL_OWNER function can be used to check whether or not the TiDB instance you are connected to is the one that is the DDL Owner. The DDL Owner is the TiDB instance that is tasked with executing DDL statements on behalf of all other nodes in the cluster.

Synopsis

TableStmt
TIDB_IS_DDL_OWNER())

Example

SELECT tidb_is_ddl_owner();
+---------------------+
| tidb_is_ddl_owner() |
+---------------------+
|                   1 |
+---------------------+
1 row in set (0.00 sec)

MySQL compatibility

The TIDB_IS_DDL_OWNER function is TiDB-specific and not compatible with MySQL.

See also

TIDB_PARSE_TSO

The TIDB_PARSE_TSO function can be used to extract the physical timestamp from a TiDB TSO timestamp.

TSO stands for Time Stamp Oracle and is a monotonically increasing timestamp given out by PD (Placement Driver) for every transaction.

A TSO is a number that consists of two parts:

  • A physical timestamp
  • A logical counter

Synopsis

TableStmt
TIDB_PARSE_TSO(NUM)

Example

BEGIN;
SELECT TIDB_PARSE_TSO(@@tidb_current_ts);
ROLLBACK;
+-----------------------------------+
| TIDB_PARSE_TSO(@@tidb_current_ts) |
+-----------------------------------+
| 2021-05-26 11:33:37.776000        |
+-----------------------------------+
1 row in set (0.0012 sec)

Here TIDB_PARSE_TSO is used to extract the physical timestamp from the timestamp number that is available in the tidb_current_ts session variable. Because timestamps are given out per transaction, this function is running in a transaction.

MySQL compatibility

The TIDB_PARSE_TSO function is TiDB-specific and not compatible with MySQL.

See also

TIDB_VERSION

The TIDB_VERSION function can be used to get the version and build details of the TiDB server that you are connected to. You can use this function when reporting issues on GitHub.

Synopsis

TableStmt
TIDB_VERSION()

Example

SELECT TIDB_VERSION()\G
*************************** 1. row ***************************
TIDB_VERSION(): Release Version: v5.1.0-alpha-13-gd5e0ed0aa-dirty
Edition: Community
Git Commit Hash: d5e0ed0aaed72d2f2dfe24e9deec31cb6cb5fdf0
Git Branch: master
UTC Build Time: 2021-05-24 14:39:20
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false
1 row in set (0.00 sec)

MySQL compatibility

The TIDB_VERSION function is TiDB-specific and not compatible with MySQL. If MySQL compatibility is required, you can also use VERSION to get version information, but the result does not contain build details.