22-meta.md

---
sidebar_label: Metadata
title: Information_Schema Database
---

TDengine includes a built-in database named `INFORMATION_SCHEMA` to provide access to database metadata, system information, and status information. This information includes database names, table names, and currently running SQL statements. All information related to TDengine maintenance is stored in this database. It contains several read-only tables. These tables are more accurately described as views, and they do not correspond to specific files. You can query these tables but cannot write data to them. The INFORMATION_SCHEMA database is intended to provide a unified method for SHOW commands to access data. However, using SELECT ... FROM INFORMATION_SCHEMA.tablename offers several advantages over SHOW commands:

1. You can use a USE statement to specify the INFORMATION_SCHEMA database as the current database.
2. You can use the familiar SELECT syntax to access information, provided that you know the table and column names.
3. You can filter and order the query results. More generally, you can use any SELECT syntax that TDengine supports to query the INFORMATION_SCHEMA database.
4. Future versions of TDengine can add new columns to INFORMATION_SCHEMA tables without affecting existing business systems.
5. It is easier for users coming from other database management systems. For example, Oracle users can query data dictionary tables.

Note: SHOW statements are still supported for the convenience of existing users.

This document introduces the tables of INFORMATION_SCHEMA and their structure.

## INS_DNODES

Provides information about dnodes. Similar to SHOW DNODES.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :------------: | ------------ | ------------------------- |
| 1   |     vnodes     | SMALLINT     | Current number of vnodes on the dnode |
| 2   |     vnodes     | SMALLINT     | Maximum number of vnodes on the dnode |
| 3   |     status     | BINARY(10)   | Current status                  |
| 4   |      note      | BINARY(256)  | Reason for going offline or other information            |
| 5   |       id       | SMALLINT     | Dnode ID                  |
| 6   |    endpoint    | BINARY(134)  | Dnode endpoint              |
| 7   |     create     | TIMESTAMP    | Creation time                  |

## INS_MNODES

Provides information about mnodes. Similar to SHOW MNODES.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | ------------------ |
| 1   |       id       | SMALLINT     | Mnode ID                  |
| 2   |    endpoint    | BINARY(134)  | Mnode endpoint              |
| 3   |    role     | BINARY(10)   | Current role           |
| 4   |  role_time  | TIMESTAMP    | Time at which the current role was assumed |
| 5   | create_time | TIMESTAMP    | Creation time           |

## INS_MODULES

Provides information about modules. Similar to SHOW MODULES.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :------: | ------------ | ---------- |
| 1   |       id       | SMALLINT     | Module ID                  |
| 2   |    endpoint    | BINARY(134)  | Module endpoint              |
| 3   |  module  | BINARY(10)   | Module status   |

## INS_QNODES

Provides information about qnodes. Similar to SHOW QNODES.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | ------------ |
| 1   |       id       | SMALLINT     | Qnode ID                  |
| 2   |    endpoint    | BINARY(134)  | Qnode endpoint              |
| 3   | create_time | TIMESTAMP    | Creation time           |

## INS_CLUSTER

Provides information about the cluster.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | ---------- |
| 1   |     id      | BIGINT       | Cluster ID |
| 2   |    name     | BINARY(134)  | Cluster name   |
| 3   | create_time | TIMESTAMP    | Creation time           |

## INS_DATABASES

Provides information about user-created databases. Similar to SHOW DATABASES.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :------------------: | ---------------- | ------------------------------------------------ |
| 1| name| BINARY(32)| Database name |
| 2   | create_time | TIMESTAMP    | Creation time           |
| 3   |       ntables        | INT              | Number of standard tables and subtables (not including supertables) |
| 4   |       vgroups        | INT              | Number of vgroups                           |
| 6   |       replica        | INT              | Number of replicas                                           |
| 7   |        quorum        | BINARY(3)        | Strong consistency                                         |
| 8   |       duration       | INT              | Duration for storage of single files                         |
| 9   |         keep         | INT              | Data retention period                                     |
| 10  |        buffer        | INT              | Write cache size per vnode, in MB           |
| 11  |       pagesize       | INT              | Page size for vnode metadata storage engine, in KB   |
| 12  |        pages         | INT              | Number of pages per vnode metadata storage engine            |
| 13  |       minrows        | INT              | Maximum number of records per file block                           |
| 14  |       maxrows        | INT              | Minimum number of records per file block                           |
| 15  |         comp         | INT              | Compression method                                     |
| 16  |      precision       | BINARY(2)        | Time precision                                      |
| 17  |        status        | BINARY(10)       | Current database status                                       |
| 18  |      retention       | BINARY (60)      | Aggregation interval and retention period                         |
| 19  |    single_stable     | BOOL             | Whether the database can contain multiple supertables           |
| 20  |      cachemodel      | BINARY(60)       | Caching method for the newest data               |
| 21  |      cachesize       | INT              | Memory per vnode used for caching the newest data  |
| 22  |      wal_level       | INT              | WAL level                                     |
| 23  |   wal_fsync_period   | INT              | Interval at which WAL is written to disk  |
| 24  | wal_retention_period | INT              | WAL retention period                                   |
| 25  |  wal_retention_size  | INT              | Maximum WAL size                                   |
| 26  |   wal_roll_period    | INT              | WAL rotation period                                 |
| 27  |   wal_segment_size   | WAL file size |

## INS_FUNCTIONS

Provides information about user-defined functions.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | -------------- |
| 1   |    name     | BINARY(64)   | Function name         |
| 2   |   comment   | BINARY(255)  | Function description       |
| 3   |  aggregate  | INT          | Whether the UDF is an aggregate function |
| 4   | output_type | BINARY(31)   | Output data type       |
| 5   | create_time | TIMESTAMP    | Creation time       |
| 6   |  code_len   | INT          | Length of the source code       |
| 7   |   bufsize   | INT          | Buffer size    |

## INS_INDEXES

Provides information about user-created indices. Similar to SHOW INDEX.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :--------------: | ------------ | ---------------------------------------------------------------------------------- |
| 1   |     db_name      | BINARY(32)   | Database containing the table with the specified index                                                       |
| 2   |     table_name      | BINARY(192)   | Table containing the specified index                                                       |
| 3   |    index_name    | BINARY(192)  | Index name                                                                             |
| 4   |     db_name      | BINARY(64)   | Index column                                                       |
| 5   |    index_type    | BINARY(10)   | SMA or FULLTEXT index                                                             |
| 6   | index_extensions | BINARY(256)  | Other information For SMA indices, this shows a list of functions. For FULLTEXT indices, this is null. |

## INS_STABLES

Provides information about supertables.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :-----------: | ------------ | ------------------------ |
| 1   |  stable_name  | BINARY(192)  | Supertable name               |
| 2   |    db_name    | BINARY(64)   | All databases in the supertable |
| 3   |  create_time  | TIMESTAMP    | Creation time                 |
| 4   |    columns    | INT          | Number of columns                   |
| 5   |     tags      | INT          | Number of tags                |
| 6   |  last_update  | TIMESTAMP    | Last updated time             |
| 7   | table_comment | BINARY(1024) | Table description                   |
| 8   |   watermark   | BINARY(64)   | Window closing time           |
| 9   |   max_delay   | BINARY(64)   | Maximum delay for pushing stream processing results  |
| 10  |    rollup     | BINARY(128)  | Rollup aggregate function          |

## INS_TABLES

Provides information about standard tables and subtables.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :-----------: | ------------ | ---------------- |
| 1   |  table_name   | BINARY(192)  | Table name             |
| 2   |    db_name    | BINARY(64)   | Database name         |
| 3   |  create_time  | TIMESTAMP    | Creation time         |
| 4   |    columns    | INT          | Number of columns           |
| 5   |  stable_name  | BINARY(192)  | Supertable name |
| 6   |      uid      | BIGINT       | Table ID            |
| 7   |   vgroup_id   | INT          | Vgroup ID        |
| 8   |      ttl      | INT          | Table time-to-live    |
| 9   | table_comment | BINARY(1024) | Table description           |
| 10  |     type      | BINARY(20)   | Table type           |

## INS_TAGS

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------- | ---------------------- |
| 1   | table_name  | BINARY(192)   | Table name                   |
| 2   |   db_name   | BINARY(64)    | Database name |
| 3   | stable_name | BINARY(192)   | Supertable name       |
| 4   |  tag_name   | BINARY(64)    | Tag name             |
| 5   |  tag_type   | BINARY(64)    | Tag type             |
| 6   |  tag_value  | BINARY(16384) | Tag value               |

## INS_USERS

Provides information about TDengine users.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | -------- |
| 1   |  user_name  | BINARY(23)   | User name   |
| 2   |  privilege  | BINARY(256)  | User permissions     |
| 3   | create_time | TIMESTAMP    | Creation time |

## INS_GRANTS

Provides information about TDengine Enterprise Edition permissions.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :---------: | ------------ | -------------------------------------------------- |
| 1   |   version   | BINARY(9)    | Whether the deployment is a licensed or trial version |
| 2   |  cpu_cores  | BINARY(9)    | CPU cores included in license                           |
| 3   |   dnodes    | BINARY(10)   | Dnodes included in license                         |
| 4   |   streams   | BINARY(10)   | Streams included in license                                   |
| 5   |    users    | BINARY(10)   | Users included in license                                 |
| 6   |   streams   | BINARY(10)   | Accounts included in license                                   |
| 7   |   storage   | BINARY(21)   | Storage space included in license                             |
| 8   | connections | BINARY(21)   | Client connections included in license                           |
| 9   |  databases  | BINARY(11)   | Databases included in license                               |
| 10  |    speed    | BINARY(9)    | Write speed specified in license (data points per second)                       |
| 11  |  querytime  | BINARY(9)    | Total query time specified in license                               |
| 12  | timeseries  | BINARY(21)   | Number of metrics included in license                                 |
| 13  |   expired   | BINARY(5)    | Whether the license has expired                |
| 14  | expire_time | BINARY(19)   | When the trial period expires                                     |

## INS_VGROUPS

Provides information about vgroups.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :-------: | ------------ | ------------------------------------------------------ |
| 1   | vgroup_id | INT          | Vgroup ID                                              |
| 2   |  db_name  | BINARY(32)   | Database name                                               |
| 3   |  tables   | INT          | Tables in vgroup                                  |
| 4   |  status   | BINARY(10)   | Vgroup status                                       |
| 5   | v1_dnode  | INT          | Dnode ID of first vgroup member                           |
| 6   | v1_status | BINARY(10)   | Status of first vgroup member                                       |
| 7   | v2_dnode  | INT          | Dnode ID of second vgroup member                           |
| 8   | v2_status | BINARY(10)   | Status of second vgroup member                                       |
| 9   | v3_dnode  | INT          | Dnode ID of third vgroup member                          |
| 10  | v3_status | BINARY(10)   | Status of third vgroup member                                       |
| 11  |  nfiles   | INT          | Number of data and metadata files in the vgroup                      |
| 12  | file_size | INT          | Size of the data and metadata files in the vgroup                      |
| 13  |   tsma    | TINYINT      | Whether time-range-wise SMA is enabled. 1 means enabled; 0 means disabled. |

## INS_CONFIGS

Provides system configuration information.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :------: | ------------ | ------------ |
| 1   |    name     | BINARY(32)  | Parameter   |
| 2   |  value   | BINARY(64)   | Value |

## INS_DNODE_VARIABLES

Provides dnode configuration information.

| #   |    **Column**    | **Data Type** | **Description**                  |
| --- | :------: | ------------ | ------------ |
| 1   | dnode_id | INT          | Dnode ID |
| 2   |   name   | BINARY(32)   | Parameter   |
| 3   |  value   | BINARY(64)   | Value |