---
sidebar_label: Statistics
title: Performance_Schema Database
---

TDengine includes a built-in database named `PERFORMANCE_SCHEMA` to provide access to database performance statistics. This document introduces the tables of PERFORMANCE_SCHEMA and their structure.

## PERF_APP

Provides information about clients (such as applications) that connect to the cluster. Similar to SHOW APPS.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :----------: | ------------ | ------------------------------- |
| 1   |    app_id    | UBIGINT      | Client ID                       |
| 2   |      ip      | BINARY(16)   | Client IP address                      |
| 3   |     pid      | INT          | Client process                   |
| 4   |     name     | BINARY(24)   | Client name                      |
| 5   |  start_time  | TIMESTAMP    | Time when client was started                  |
| 6   |  insert_req  | UBIGINT      | Insert requests                |
| 7   |  insert_row  | UBIGINT      | Rows inserted                 |
| 8   | insert_time  | UBIGINT      | Time spent processing insert requests in microseconds |
| 9   | insert_bytes | UBIGINT      | Size of data inserted in byted           |
| 10  | fetch_bytes  | UBIGINT      | Size of query results in bytes                  |
| 11  |  query_time  | UBIGINT      | Time spend processing query requests                |
| 12  |  slow_query  | UBIGINT      | Number of slow queries (greater than or equal to 3 seconds)  |
| 13  |  total_req   | UBIGINT      | Total requests                        |
| 14  | current_req  | UBIGINT      | Requests currently being processed          |
| 15  | last_access  | TIMESTAMP    | Last update time                    |

## PERF_CONNECTIONS

Provides information about connections to the database. Similar to SHOW CONNECTIONS.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | -------------------------------------------------- |
| 1   |   conn_id   | INT          | Connection ID                                            |
| 2   |    user     | BINARY(24)   | User name                                             |
| 3   |     app     | BINARY(24)   | Client name                                         |
| 4   |     pid     | UINT         | Client process ID on client device that initiated the connection |
| 5   |  end_point  | BINARY(128)  | Client endpoint                                         |
| 6   | login_time  | TIMESTAMP    | Login time                                           |
| 7   | last_access | TIMESTAMP    | Last update time                                       |

## PERF_QUERIES

Provides information about SQL queries currently running. Similar to SHOW QUERIES.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :----------: | ------------ | ---------------------------- |
| 1   |   kill_id    | UBIGINT      | ID used to stop the query            |
| 2   |   query_id   | INT          | Query ID                      |
| 3   |   conn_id    | UINT         | Connection ID                      |
| 4   |     app      | BINARY(24)   | Client name                     |
| 5   |     pid      | INT          | Client process ID on client device |
| 6   |     user     | BINARY(24)   | User name                       |
| 7   |  end_point   | BINARY(16)   | Client endpoint                   |
| 8   | create_time  | TIMESTAMP    | Creation time                     |
| 9   |  exec_usec   | BIGINT       | Elapsed time                   |
| 10  | stable_query | BOOL         | Whether the query is on a supertable             |
| 11  |   sub_num    | INT          | Number of subqueries                   |
| 12  |  sub_status  | BINARY(1000) | Subquery status                   |
| 13  |     sql      | BINARY(1024) | SQL statement                     |

## PERF_CONSUMERS

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :------------: | ------------ | ----------------------------------------------------------- |
| 1   |  consumer_id   | BIGINT       | Consumer ID                                             |
| 2   | consumer_group | BINARY(192)  | Consumer group                                                    |
| 3   |   client_id    | BINARY(192)  | Client ID (user-defined) |
| 4   |     status     | BINARY(20)   | Consumer status                                              |
| 5   |     topics     | BINARY(204)  | Subscribed topic. Returns one row for each topic.              |
| 6   |    up_time     | TIMESTAMP    | Time of first connection to TDengine Server                                     |
| 7   | subscribe_time | TIMESTAMP    | Time of first subscription                                        |
| 8   | rebalance_time | TIMESTAMP    | Time of first rebalance triggering                                 |

## PERF_TRANS

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :--------------: | ------------ | -------------------------------------------------------------- |
| 1   |        id        | INT          | ID of the transaction currently running                                           |
| 2   |   create_time    | TIMESTAMP    | Creation time                                                 |
| 3   |      stage       | BINARY(12)   | Transaction stage (redoAction, undoAction, or commit) |
| 4   |       db1        | BINARY(64)   | First database having a conflict with the transaction                               |
| 5   |       db2        | BINARY(64)   | Second database having a conflict with the transaction                               |
| 6   |   failed_times   | INT          | Times the transaction has failed                                           |
| 7   |  last_exec_time  | TIMESTAMP    | Previous time the transaction was run                                             |
| 8   | last_action_info | BINARY(511)  | Reason for failure on previous run                                     |

## PERF_SMAS

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | ------------------------------------------- |
| 1   |  sma_name   | BINARY(192)  | Time-range-wise SMA name |
| 2   | create_time | TIMESTAMP    | Creation time                                |
| 3   | stable_name | BINARY(192)  | Supertable name                        |
| 4   |  vgroup_id  | INT          | Dedicated vgroup name                      |