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# System Tables

IoTDB has a built-in system database called `INFORMATION_SCHEMA`, which contains a series of system tables for storing IoTDB runtime information (such as currently executing SQL statements, etc.). Currently, the `INFORMATION_SCHEMA` database only supports read operations.

## 1. System Database

* ​**Name**​: `INFORMATION_SCHEMA`
* ​**Commands**​: Read-only, only supports `Show databases (DETAILS)` / `Show Tables (DETAILS)` / `Use`. Other operations will result in an error: `"The database 'information_schema' can only be queried."`
* ​**Attributes**​:` TTL=INF`, other attributes default to `null  `
* ​**SQL Example**​:

```sql
IoTDB> show databases
+------------------+-------+-----------------------+---------------------+---------------------+
|          Database|TTL(ms)|SchemaReplicationFactor|DataReplicationFactor|TimePartitionInterval|
+------------------+-------+-----------------------+---------------------+---------------------+
|information_schema|    INF|                   null|                 null|                 null|
+------------------+-------+-----------------------+---------------------+---------------------+

IoTDB> show tables from information_schema
+-----------------------+-------+
|              TableName|TTL(ms)|
+-----------------------+-------+
|                columns|    INF|
|           config_nodes|    INF|
|         configurations|    INF|
|            connections|    INF|
|        current_queries|    INF|
|             data_nodes|    INF|
|              databases|    INF|
|              functions|    INF|
|               keywords|    INF|
|                  nodes|    INF|
|           pipe_plugins|    INF|
|                  pipes|    INF|
|                queries|    INF|
|queries_costs_histogram|    INF|
|                regions|    INF|
|               services|    INF|
|          subscriptions|    INF|
|       table_disk_usage|    INF|
|                 tables|    INF|
|                 topics|    INF|
|                  views|    INF|
+-----------------------+-------+
```

## 2. System Tables

* ​**Names**​: `DATABASES`, `TABLES`, `REGIONS`, `QUERIES`, `COLUMNS`, `PIPES`, `PIPE_PLUGINS`, `SUBSCRIPTION`, `TOPICS`, `VIEWS`, `MODELS`, `FUNCTIONS`, `CONFIGURATIONS`, `KEYWORDS`, `NODES`, `CONFIG_NODES`, `DATA_NODES` , `CONNECTIONS`, `CURRENT_QUERIES`, `QUERIES_COSTS_HISTOGRAM`, `SERVICES`, `TABLE_DISK_USAGE` (detailed descriptions in later sections)
* ​**Operations**​: Read-only, only supports `SELECT`, `COUNT/SHOW DEVICES`, `DESC`. Any modifications to table structure or content are not allowed and will result in an error: `"The database 'information_schema' can only be queried."  `
* ​**Column Names**​: System table column names are all lowercase by default and separated by underscores (`_`).

### 2.1 DATABASES

* Contains information about all databases in the cluster.
* Table structure is as follows:

| Column Name                     | Data Type | Column Type | Description                    |
| --------------------------------- | ----------- | ------------- | -------------------------------- |
| `database`                  | STRING    | TAG         | Database name                  |
| `ttl(ms)`                   | STRING    | ATTRIBUTE   | Data retention time            |
| `schema_replication_factor` | INT32     | ATTRIBUTE   | Schema replica count           |
| `data_replication_factor`   | INT32     | ATTRIBUTE   | Data replica count             |
| `time_partition_interval`   | INT64     | ATTRIBUTE   | Time partition interval        |
| `schema_region_group_num`   | INT32     | ATTRIBUTE   | Number of schema region groups |
| `data_region_group_num`     | INT32     | ATTRIBUTE   | Number of data region groups   |

* The query results only display the collection of databases for which you have any permission on the database itself or any table within the database.
* Query Example:

```sql
IoTDB> select * from information_schema.databases
+------------------+-------+-------------------------+-----------------------+-----------------------+-----------------------+---------------------+
|          database|ttl(ms)|schema_replication_factor|data_replication_factor|time_partition_interval|schema_region_group_num|data_region_group_num|
+------------------+-------+-------------------------+-----------------------+-----------------------+-----------------------+---------------------+
|information_schema|    INF|                     null|                   null|                   null|                   null|                 null|
|         database1|    INF|                        1|                      1|              604800000|                      0|                    0|
+------------------+-------+-------------------------+-----------------------+-----------------------+-----------------------+---------------------+
```

### 2.2 TABLES

* Contains information about all tables in the cluster.
* Table structure is as follows:

| Column Name      | Data Type | Column Type | Description         |
| ------------------ | ----------- | ------------- | --------------------- |
| `database`   | STRING    | TAG         | Database name       |
| `table_name` | STRING    | TAG         | Table name          |
| `ttl(ms)`    | STRING    | ATTRIBUTE   | Data retention time |
| `status`     | STRING    | ATTRIBUTE   | Status              |
| `comment`    | STRING    | ATTRIBUTE   | Description/comment |

* Note:  Possible values for `status`: `USING`, `PRE_CREATE`, `PRE_DELETE`.  For details, refer to the [View Tables](../Basic-Concept/Table-Management_apache.md#12-view-tables) in Table Management documentation
* The query results only display the collection of tables for which you have any permission.
* Query Example:

```sql
IoTDB> select * from information_schema.tables
+------------------+--------------+-----------+------+-------+-----------+
|          database|    table_name|    ttl(ms)|status|comment| table_type|
+------------------+--------------+-----------+------+-------+-----------+
|information_schema|     databases|        INF| USING|   null|SYSTEM VIEW|
|information_schema|        models|        INF| USING|   null|SYSTEM VIEW|
|information_schema| subscriptions|        INF| USING|   null|SYSTEM VIEW|
|information_schema|       regions|        INF| USING|   null|SYSTEM VIEW|
|information_schema|     functions|        INF| USING|   null|SYSTEM VIEW|
|information_schema|      keywords|        INF| USING|   null|SYSTEM VIEW|
|information_schema|       columns|        INF| USING|   null|SYSTEM VIEW|
|information_schema|        topics|        INF| USING|   null|SYSTEM VIEW|
|information_schema|configurations|        INF| USING|   null|SYSTEM VIEW|
|information_schema|       queries|        INF| USING|   null|SYSTEM VIEW|
|information_schema|        tables|        INF| USING|   null|SYSTEM VIEW|
|information_schema|  pipe_plugins|        INF| USING|   null|SYSTEM VIEW|
|information_schema|         nodes|        INF| USING|   null|SYSTEM VIEW|
|information_schema|    data_nodes|        INF| USING|   null|SYSTEM VIEW|
|information_schema|         pipes|        INF| USING|   null|SYSTEM VIEW|
|information_schema|         views|        INF| USING|   null|SYSTEM VIEW|
|information_schema|  config_nodes|        INF| USING|   null|SYSTEM VIEW|
|         database1|        table1|31536000000| USING|   null| BASE TABLE|
+------------------+--------------+-----------+------+-------+-----------+
```

### 2.3 REGIONS

* Contains information about all regions in the cluster.
* Table structure is as follows:

| Column Name             | Data Type | Column Type | Description                                                                                                                                                       |
| ------------------------- | ----------- | ------------- |-------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `region_id`         | INT32     | TAG         | Region ID                                                                                                                                                         |
| `datanode_id`       | INT32     | TAG         | DataNode ID                                                                                                                                                       |
| `type`              | STRING    | ATTRIBUTE   | Type (`SchemaRegion`/`DataRegion`)                                                                                                                                |
| `status`            | STRING    | ATTRIBUTE   | Status (`Running`,`Unknown`, etc.)                                                                                                                                |
| `database`          | STRING    | ATTRIBUTE   | Database name                                                                                                                                                     |
| `series_slot_num`   | INT32     | ATTRIBUTE   | Number of series slots                                                                                                                                            |
| `time_slot_num`     | INT64     | ATTRIBUTE   | Number of time slots                                                                                                                                              |
| `rpc_address`       | STRING    | ATTRIBUTE   | RPC address                                                                                                                                                       |
| `rpc_port`          | INT32     | ATTRIBUTE   | RPC port                                                                                                                                                          |
| `internal_address`  | STRING    | ATTRIBUTE   | Internal communication address                                                                                                                                    |
| `role`              | STRING    | ATTRIBUTE   | Role (`Leader`/`Follower`)                                                                                                                                        |
| `create_time`       | TIMESTAMP | ATTRIBUTE   | Creation time                                                                                                                                                     |
| `tsfile_size_bytes` | INT64     | ATTRIBUTE   | - For​**DataRegion with statistics ​**​: Total file size of TsFiles. <br>- For**DataRegion without statistics**(Unknown):`-1`.<br>- For​**SchemaRegion**​:`null`. |

* Only administrators are allowed to perform query operations.
* Query Example:

```SQL
IoTDB> select * from information_schema.regions
+---------+-----------+------------+-------+---------+---------------+-------------+-----------+--------+----------------+------+-----------------------------+-----------------+
|region_id|datanode_id|        type| status| database|series_slot_num|time_slot_num|rpc_address|rpc_port|internal_address|  role|                  create_time|tsfile_size_bytes|
+---------+-----------+------------+-------+---------+---------------+-------------+-----------+--------+----------------+------+-----------------------------+-----------------+
|        0|          1|SchemaRegion|Running|database1|             12|            0|    0.0.0.0|    6667|       127.0.0.1|Leader|2025-03-31T11:19:08.485+08:00|             null|
|        1|          1|  DataRegion|Running|database1|              6|            6|    0.0.0.0|    6667|       127.0.0.1|Leader|2025-03-31T11:19:09.156+08:00|             3985|
|        2|          1|  DataRegion|Running|database1|              6|            6|    0.0.0.0|    6667|       127.0.0.1|Leader|2025-03-31T11:19:09.156+08:00|             3841|
+---------+-----------+------------+-------+---------+---------------+-------------+-----------+--------+----------------+------+-----------------------------+-----------------+
```

### 2.4 QUERIES

* Contains information about all currently executing queries in the cluster. Can also be queried using the `SHOW QUERIES` syntax.
* Table structure is as follows:

| Column Name        | Data Type | Column Type | Description                                                |
| -------------------- | ----------- | ------------- | ------------------------------------------------------------ |
| `query_id`     | STRING    | TAG         | Query ID                                                   |
| `start_time`   | TIMESTAMP | ATTRIBUTE   | Query start timestamp (precision matches system precision) |
| `datanode_id`  | INT32     | ATTRIBUTE   | DataNode ID that initiated the query                       |
| `elapsed_time` | FLOAT     | ATTRIBUTE   | Query execution duration (in seconds)                      |
| `statement`    | STRING    | ATTRIBUTE   | SQL statement of the query                                 |
| `user`         | STRING    | ATTRIBUTE   | User who initiated the query                               |

* For regular users, the query results only display the queries executed by themselves; for administrators, all queries are displayed.
* Query Example:

```SQL
IoTDB> select * from information_schema.queries
+-----------------------+-----------------------------+-----------+------------+----------------------------------------+----+
|               query_id|                   start_time|datanode_id|elapsed_time|                               statement|user|
+-----------------------+-----------------------------+-----------+------------+----------------------------------------+----+
|20250331_023242_00011_1|2025-03-31T10:32:42.360+08:00|          1|       0.025|select * from information_schema.queries|root|
+-----------------------+-----------------------------+-----------+------------+----------------------------------------+----+
```

### 2.5 COLUMNS

* Contains information about all columns in tables across the cluster
* Table structure is as follows:

| Column Name       | Data Type | Column Type | Description        |
| ------------------- | ----------- | ------------- | -------------------- |
| `database`    | STRING    | TAG         | Database name      |
| `table_name`  | STRING    | TAG         | Table name         |
| `column_name` | STRING    | TAG         | Column name        |
| `datatype`    | STRING    | ATTRIBUTE   | Column data type   |
| `category`    | STRING    | ATTRIBUTE   | Column category    |
| `status`      | STRING    | ATTRIBUTE   | Column status      |
| `comment`     | STRING    | ATTRIBUTE   | Column description |

Notes: 
* Possible values for `status`: `USING`, `PRE_DELETE`. For details, refer to [Viewing Table Columns](../Basic-Concept/Table-Management_apache.html#13-view-table-columns) in Table Management documentation.
* The query results only display the column information of tables for which you have any permission.

* Query Example:

```SQL
IoTDB> select * from information_schema.columns where database = 'database1'
+---------+----------+------------+---------+---------+------+-------+
| database|table_name| column_name| datatype| category|status|comment|
+---------+----------+------------+---------+---------+------+-------+
|database1|    table1|        time|TIMESTAMP|     TIME| USING|   null|
|database1|    table1|      region|   STRING|      TAG| USING|   null|
|database1|    table1|    plant_id|   STRING|      TAG| USING|   null|
|database1|    table1|   device_id|   STRING|      TAG| USING|   null|
|database1|    table1|    model_id|   STRING|ATTRIBUTE| USING|   null|
|database1|    table1| maintenance|   STRING|ATTRIBUTE| USING|   null|
|database1|    table1| temperature|    FLOAT|    FIELD| USING|   null|
|database1|    table1|    humidity|    FLOAT|    FIELD| USING|   null|
|database1|    table1|      status|  BOOLEAN|    FIELD| USING|   null|
|database1|    table1|arrival_time|TIMESTAMP|    FIELD| USING|   null|
+---------+----------+------------+---------+---------+------+-------+
```

### 2.6 PIPES

* Contains information about all pipes in the cluster
* Table structure is as follows:

| Column Name                       | Data Type | Column Type | Description                                              |
| ----------------------------------- | ----------- | ------------- | ---------------------------------------------------------- |
| `id`                          | STRING    | TAG         | Pipe name                                                |
| `creation_time`               | TIMESTAMP | ATTRIBUTE   | Creation time                                            |
| `state`                       | STRING    | ATTRIBUTE   | Pipe status (`RUNNING`/`STOPPED`)                |
| `pipe_source`                 | STRING    | ATTRIBUTE   | Source plugin parameters                                 |
| `pipe_processor`              | STRING    | ATTRIBUTE   | Processor plugin parameters                              |
| `pipe_sink`                   | STRING    | ATTRIBUTE   | Sink plugin parameters                                   |
| `exception_message`           | STRING    | ATTRIBUTE   | Exception message                                        |
| `remaining_event_count`       | INT64     | ATTRIBUTE   | Remaining event count (`-1`if Unknown)               |
| `estimated_remaining_seconds` | DOUBLE    | ATTRIBUTE   | Estimated remaining time in seconds (`-1`if Unknown) |

* Only administrators are allowed to perform operations.
* Query Example:

```SQL
select * from information_schema.pipes
+----------+-----------------------------+-------+--------------------------------------------------------------------------+--------------+-----------------------------------------------------------------------+-----------------+---------------------+---------------------------+
|        id|                creation_time|  state|                                                               pipe_source|pipe_processor|                                                              pipe_sink|exception_message|remaining_event_count|estimated_remaining_seconds|
+----------+-----------------------------+-------+--------------------------------------------------------------------------+--------------+-----------------------------------------------------------------------+-----------------+---------------------+---------------------------+
|tablepipe1|2025-03-31T12:25:24.040+08:00|RUNNING|{__system.sql-dialect=table, source.password=******, source.username=root}|            {}|{format=hybrid, node-urls=192.168.xxx.xxx:6667, sink=iotdb-thrift-sink}|                 |                    0|                        0.0|
+----------+-----------------------------+-------+--------------------------------------------------------------------------+--------------+-----------------------------------------------------------------------+-----------------+---------------------+---------------------------+
```

### 2.7 PIPE\_PLUGINS

* Contains information about all PIPE plugins in the cluster
* Table structure is as follows:

| Column Name       | Data Type | Column Type | Description                                         |
| ------------------- | ----------- | ------------- | ----------------------------------------------------- |
| `plugin_name` | STRING    | TAG         | Plugin name                                         |
| `plugin_type` | STRING    | ATTRIBUTE   | Plugin type (`Builtin`/`External`)          |
| `class_name`  | STRING    | ATTRIBUTE   | Plugin's main class name                            |
| `plugin_jar`  | STRING    | ATTRIBUTE   | Plugin's JAR file name (`null`for builtin type) |

* Query Example:

```SQL
IoTDB> select * from information_schema.pipe_plugins
+---------------------+-----------+-------------------------------------------------------------------------------------------------+----------+
|          plugin_name|plugin_type|                                                                                       class_name|plugin_jar|
+---------------------+-----------+-------------------------------------------------------------------------------------------------+----------+
|IOTDB-THRIFT-SSL-SINK|    Builtin|org.apache.iotdb.commons.pipe.agent.plugin.builtin.connector.iotdb.thrift.IoTDBThriftSslConnector|      null|
|   IOTDB-AIR-GAP-SINK|    Builtin|   org.apache.iotdb.commons.pipe.agent.plugin.builtin.connector.iotdb.airgap.IoTDBAirGapConnector|      null|
|      DO-NOTHING-SINK|    Builtin|        org.apache.iotdb.commons.pipe.agent.plugin.builtin.connector.donothing.DoNothingConnector|      null|
| DO-NOTHING-PROCESSOR|    Builtin|        org.apache.iotdb.commons.pipe.agent.plugin.builtin.processor.donothing.DoNothingProcessor|      null|
|    IOTDB-THRIFT-SINK|    Builtin|   org.apache.iotdb.commons.pipe.agent.plugin.builtin.connector.iotdb.thrift.IoTDBThriftConnector|      null|
|         IOTDB-SOURCE|    Builtin|                org.apache.iotdb.commons.pipe.agent.plugin.builtin.extractor.iotdb.IoTDBExtractor|      null|
+---------------------+-----------+-------------------------------------------------------------------------------------------------+----------+
```

### 2.8 SUBSCRIPTIONS

* Contains information about all data subscriptions in the cluster
* Table structure is as follows:

| Column Name                | Data Type | Column Type | Description             |
| ---------------------------- | ----------- | ------------- | ------------------------- |
| `topic_name`           | STRING    | TAG         | Subscription topic name |
| `consumer_group_name`  | STRING    | TAG         | Consumer group name     |
| `subscribed_consumers` | STRING    | ATTRIBUTE   | Subscribed consumers    |

* Only administrators are allowed to perform operations.
* Query Example:

```SQL
IoTDB> select * from information_schema.subscriptions where topic_name = 'topic_1'
+----------+-------------------+--------------------------------+
|topic_name|consumer_group_name|            subscribed_consumers|
+----------+-------------------+--------------------------------+
|   topic_1|                cg1|[c3, c4, c5, c6, c7, c0, c1, c2]|
+----------+-------------------+--------------------------------+
```

### 2.9 TOPICS

* Contains information about all data subscription topics in the cluster
* Table structure is as follows:

| Column Name         | Data Type | Column Type | Description                    |
| --------------------- | ----------- | ------------- | -------------------------------- |
| `topic_name`    | STRING    | TAG         | Subscription topic name        |
| `topic_configs` | STRING    | ATTRIBUTE   | Topic configuration parameters |

* Only administrators are allowed to perform operations.
* Query Example:

```SQL
IoTDB> select * from information_schema.topics
+----------+----------------------------------------------------------------+
|topic_name|                                                   topic_configs|
+----------+----------------------------------------------------------------+
|     topic|{__system.sql-dialect=table, start-time=2025-01-10T17:05:38.282}|
+----------+----------------------------------------------------------------+
```

### 2.10 VIEWS

> This system table is available starting from version V2.0.5.

* Contains information about all table views in the database.
* The table structure is as follows:

| Column Name      | Data Type | Column Category | Description                     |
| ------------------ | ----------- | ----------------- | --------------------------------- |
| database         | STRING    | TAG             | Database name                   |
| table\_name      | STRING    | TAG             | View name                       |
| view\_definition | STRING    | ATTRIBUTE       | SQL statement for view creation |

* The query results only display the collection of views for which you have any permission.
* Query example:

```SQL
IoTDB> select * from information_schema.views
+---------+----------+---------------------------------------------------------------------------------------------------------------------------------------+
| database|table_name|                                                                                                                        view_definition|
+---------+----------+---------------------------------------------------------------------------------------------------------------------------------------+
|database1|        ln|CREATE VIEW "ln" ("device" STRING TAG,"model" STRING TAG,"status" BOOLEAN FIELD,"hardware" STRING FIELD) WITH (ttl='INF') AS root.ln.**|
+---------+----------+---------------------------------------------------------------------------------------------------------------------------------------+
```


### 2.11 MODELS

> This system table is available starting from version V 2.0.5 and has been discontinued since version V 2.0.8.

* Contains information about all models in the database.
* The table structure is as follows:

| Column Name | Data Type | Column Category | Description                                                                                    |
| ------------- | ----------- | ----------------- | ------------------------------------------------------------------------------------------------ |
| model\_id   | STRING    | TAG             | Model name                                                                                     |
| model\_type | STRING    | ATTRIBUTE       | Model type (Forecast, Anomaly Detection, Custom)                                               |
| state       | STRING    | ATTRIBUTE       | Model status (Available/Unavailable)                                                           |
| configs     | STRING    | ATTRIBUTE       | String format of model hyperparameters, consistent with the output of the `show` command   |
| notes       | STRING    | ATTRIBUTE       | Model description\* Built-in model: Built-in model in IoTDB\* User-defined model: Custom model |

* Query example:

```SQL
-- Find all built-in forecast models
IoTDB> select * from information_schema.models where model_type = 'BUILT_IN_FORECAST'
+---------------------+-----------------+------+-------+-----------------------+
|             model_id|       model_type| state|configs|                  notes|
+---------------------+-----------------+------+-------+-----------------------+
|       _STLForecaster|BUILT_IN_FORECAST|ACTIVE|   null|Built-in model in IoTDB|
|     _NaiveForecaster|BUILT_IN_FORECAST|ACTIVE|   null|Built-in model in IoTDB|
|               _ARIMA|BUILT_IN_FORECAST|ACTIVE|   null|Built-in model in IoTDB|
|_ExponentialSmoothing|BUILT_IN_FORECAST|ACTIVE|   null|Built-in model in IoTDB|
|         _HoltWinters|BUILT_IN_FORECAST|ACTIVE|   null|Built-in model in IoTDB|
|             _sundial|BUILT_IN_FORECAST|ACTIVE|   null|Built-in model in IoTDB|
+---------------------+-----------------+------+-------+-----------------------+
```


### 2.12 FUNCTIONS

> This system table is available starting from version V2.0.5.

* Contains information about all functions in the database.
* The table structure is as follows:

| Column Name      | Data Type | Column Category | Description                                                              |
| ------------------ | ----------- | ----------------- | -------------------------------------------------------------------------- |
| function\_name   | STRING    | TAG             | Function name                                                            |
| function\_type   | STRING    | ATTRIBUTE       | Function type (Built-in/User-defined, Scalar/Aggregation/Table Function) |
| class\_name(udf) | STRING    | ATTRIBUTE       | Class name if it is a UDF, otherwise null (tentative)                    |
| state            | STRING    | ATTRIBUTE       | Availability status                                                      |

* Query example:

```SQL
IoTDB> select * from information_schema.functions where function_type='built-in table function'
+--------------+-----------------------+---------------+---------+
|function_name |          function_type|class_name(udf)|    state|
+--------------+-----------------------+---------------+---------+
|      CUMULATE|built-in table function|           null|AVAILABLE|
|       SESSION|built-in table function|           null|AVAILABLE|
|           HOP|built-in table function|           null|AVAILABLE|
|        TUMBLE|built-in table function|           null|AVAILABLE|
|      FORECAST|built-in table function|           null|AVAILABLE|
|     VARIATION|built-in table function|           null|AVAILABLE|
|      CAPACITY|built-in table function|           null|AVAILABLE|
+--------------+-----------------------+---------------+---------+
```


### 2.13 CONFIGURATIONS

> This system table is available starting from version V2.0.5.

* Contains all configuration properties of the database.
* The table structure is as follows:

| Column Name | Data Type | Column Category | Description                  |
| ------------- | ----------- | ----------------- | ------------------------------ |
| variable    | STRING    | TAG             | Configuration property name  |
| value       | STRING    | ATTRIBUTE       | Configuration property value |

* Only administrators are allowed to perform operations on this table.
* Query example:

```SQL
IoTDB> select * from information_schema.configurations
+----------------------------------+-----------------------------------------------------------------+
|                          variable|                                                            value|
+----------------------------------+-----------------------------------------------------------------+
|                       ClusterName|                                                   defaultCluster|
|             DataReplicationFactor|                                                                1|
|           SchemaReplicationFactor|                                                                1|
|  DataRegionConsensusProtocolClass|                      org.apache.iotdb.consensus.iot.IoTConsensus|
|SchemaRegionConsensusProtocolClass|                  org.apache.iotdb.consensus.ratis.RatisConsensus|
|  ConfigNodeConsensusProtocolClass|                  org.apache.iotdb.consensus.ratis.RatisConsensus|
|               TimePartitionOrigin|                                                                0|
|             TimePartitionInterval|                                                        604800000|
|              ReadConsistencyLevel|                                                           strong|
|           SchemaRegionPerDataNode|                                                                1|
|             DataRegionPerDataNode|                                                                0|
|                     SeriesSlotNum|                                                             1000|
|           SeriesSlotExecutorClass|org.apache.iotdb.commons.partition.executor.hash.BKDRHashExecutor|
|         DiskSpaceWarningThreshold|                                                             0.05|
|                TimestampPrecision|                                                               ms|
+----------------------------------+-----------------------------------------------------------------+
```


### 2.14 KEYWORDS

> This system table is available starting from version V2.0.5.

* Contains all keywords in the database.
* The table structure is as follows:

| Column Name | Data Type | Column Category | Description                                     |
| ------------- | ----------- | ----------------- | ------------------------------------------------- |
| word        | STRING    | TAG             | Keyword                                         |
| reserved    | INT32     | ATTRIBUTE       | Whether it is a reserved word (1 = Yes, 0 = No) |

* Query example:

```SQL
IoTDB> select * from information_schema.keywords limit 10
+----------+--------+
|      word|reserved|
+----------+--------+
|    ABSENT|       0|
|ACTIVATION|       1|
|  ACTIVATE|       1|
|       ADD|       0|
|     ADMIN|       0|
|     AFTER|       0|
|   AINODES|       1|
|       ALL|       0|
|     ALTER|       1|
|   ANALYZE|       0|
+----------+--------+
```


### 2.15 NODES

> This system table is available starting from version V2.0.5.

* Contains information about all nodes in the database cluster.
* The table structure is as follows:

| Column Name                                | Data Type | Column Category | Description          |
| -------------------------------------------- | ----------- | ----------------- | ---------------------- |
| node\_id                                   | INT32     | TAG             | Node ID              |
| node\_type                                 | STRING    | ATTRIBUTE       | Node type            |
| status                                     | STRING    | ATTRIBUTE       | Node status          |
| internal\_address                          | STRING    | ATTRIBUTE       | Internal RPC address |
| internal\_port                             | INT32     | ATTRIBUTE       | Internal port        |
| version                                    | STRING    | ATTRIBUTE       | Version number       |
| build\_info                                | STRING    | ATTRIBUTE       | Commit ID            |

* Only administrators are allowed to perform operations on this table.
* Query example:

```SQL
IoTDB> select * from information_schema.nodes 
+-------+----------+-------+----------------+-------------+-------+----------+
|node_id| node_type| status|internal_address|internal_port|version|build_info|
+-------+----------+-------+----------------+-------------+-------+----------+
|      0|ConfigNode|Running|       127.0.0.1|        10710|2.0.5.1|   58d685e|
|      1|  DataNode|Running|       127.0.0.1|        10730|2.0.5.1|   58d685e|
+-------+----------+-------+----------------+-------------+-------+----------+
```


### 2.16 CONFIG\_NODES

> This system table is available starting from version V2.0.5.

* Contains information about all ConfigNodes in the cluster.
* The table structure is as follows:

| Column Name             | Data Type | Column Category | Description               |
| ------------------------- | ----------- | ----------------- | --------------------------- |
| node\_id                | INT32     | TAG             | Node ID                   |
| config\_consensus\_port | INT32     | ATTRIBUTE       | ConfigNode consensus port |
| role                    | STRING    | ATTRIBUTE       | ConfigNode role           |

* Only administrators are allowed to perform operations on this table.
* Query example:

```SQL
IoTDB> select * from information_schema.config_nodes 
+-------+---------------------+------+
|node_id|config_consensus_port|  role|
+-------+---------------------+------+
|      0|                10720|Leader|
+-------+---------------------+------+
```


### 2.17 DATA\_NODES

> This system table is available starting from version V2.0.5.

* Contains information about all DataNodes in the cluster.
* The table structure is as follows:

| Column Name             | Data Type | Column Category | Description                 |
| ------------------------- | ----------- | ----------------- | ----------------------------- |
| node\_id                | INT32     | TAG             | Node ID                     |
| data\_region\_num       | INT32     | ATTRIBUTE       | Number of DataRegions       |
| schema\_region\_num     | INT32     | ATTRIBUTE       | Number of SchemaRegions     |
| rpc\_address            | STRING    | ATTRIBUTE       | RPC address                 |
| rpc\_port               | INT32     | ATTRIBUTE       | RPC port                    |
| mpp\_port               | INT32     | ATTRIBUTE       | MPP communication port      |
| data\_consensus\_port   | INT32     | ATTRIBUTE       | DataRegion consensus port   |
| schema\_consensus\_port | INT32     | ATTRIBUTE       | SchemaRegion consensus port |

* Only administrators are allowed to perform operations on this table.
* Query example:

```SQL
IoTDB> select * from information_schema.data_nodes 
+-------+---------------+-----------------+-----------+--------+--------+-------------------+---------------------+
|node_id|data_region_num|schema_region_num|rpc_address|rpc_port|mpp_port|data_consensus_port|schema_consensus_port|
+-------+---------------+-----------------+-----------+--------+--------+-------------------+---------------------+
|      1|              4|                4|    0.0.0.0|    6667|   10740|              10760|                10750|
+-------+---------------+-----------------+-----------+--------+--------+-------------------+---------------------+
```

### 2.18 CONNECTIONS

> This system table is available starting from version V 2.0.8

* Contains all connections in the cluster.
* The table structure is as follows:

| **Column Name** | **Data Type** | **Column Type** | **Description**        |
|-----------------|---------------|-----------------|------------------------|
| datanode_id     | STRING        | TAG             | DataNode ID           |
| user_id         | STRING        | TAG             | User ID               |
| session_id      | STRING        | TAG             | Session ID            |
| user_name       | STRING        | ATTRIBUTE       | Username              |
| last_active_time| TIMESTAMP     | ATTRIBUTE       | Last active time      |
| client_ip       | STRING        | ATTRIBUTE       | Client IP address     |

* Query example:

```SQL
IoTDB> select * from information_schema.connections;
+-----------+-------+----------+---------+-----------------------------+---------+
|datanode_id|user_id|session_id|user_name|             last_active_time|client_ip|
+-----------+-------+----------+---------+-----------------------------+---------+
|          1|      0|         2|     root|2026-01-21T16:28:54.704+08:00|127.0.0.1|
+-----------+-------+----------+---------+-----------------------------+---------+
```

### 2.19 CURRENT_QUERIES

> This system table is available starting from version V 2.0.8

* Contains all queries whose execution end time falls within the range `[now() - query_cost_stat_window, now())`, including currently executing queries. The `query_cost_stat_window` parameter represents the query cost statistics window. Its default value is 0 and can be configured via the `iotdb-system.properties` configuration file.
* The table structure is as follows:

| Column Name  | Data Type | Column Type | Description                                                                 |
|--------------|-----------|-------------|-----------------------------------------------------------------------------|
| query_id     | STRING    | TAG         | Query statement ID                                                         |
| state        | STRING    | FIELD       | Query state: RUNNING indicates executing, FINISHED indicates completed     |
| start_time   | TIMESTAMP | FIELD       | Query start timestamp (precision matches system timestamp precision)       |
| end_time     | TIMESTAMP | FIELD       | Query end timestamp (precision matches system timestamp precision). NULL if query is not yet finished |
| datanode_id  | INT32     | FIELD       | DataNode from which the query was initiated                                |
| cost_time    | FLOAT     | FIELD       | Query execution time in seconds. If query is not finished, shows elapsed time |
| statement    | STRING    | FIELD       | Query SQL / concatenated query request SQL                                |
| user         | STRING    | FIELD       | User who initiated the query                                               |
| client_ip    | STRING    | FIELD       | Client IP address that initiated the query                                 |

* Regular users can only view their own queries; administrators can view all queries.
* Query example:

```SQL
IoTDB> select * from information_schema.current_queries;
+-----------------------+-------+-----------------------------+--------+-----------+---------+------------------------------------------------+----+---------+
|               query_id|  state|                   start_time|end_time|datanode_id|cost_time|                                       statement|user|client_ip|
+-----------------------+-------+-----------------------------+--------+-----------+---------+------------------------------------------------+----+---------+
|20260121_085427_00013_1|RUNNING|2026-01-21T16:54:27.019+08:00|    null|          1|      0.0|select * from information_schema.current_queries|root|127.0.0.1|
+-----------------------+-------+-----------------------------+--------+-----------+---------+------------------------------------------------+----+---------+
```

### 2.20 QUERIES_COSTS_HISTOGRAM

> This system table is available starting from version V 2.0.8

* Contains a histogram of query execution times within the past `query_cost_stat_window` period (only statistics for completed SQL queries). The `query_cost_stat_window` parameter represents the query cost statistics window. Its default value is 0 and can be configured via the `iotdb-system.properties` configuration file.
* The table structure is as follows:

| Column Name  | Data Type | Column Type | Description                                                                 |
|--------------|-----------|-------------|-----------------------------------------------------------------------------|
| bin          | STRING    | TAG         | Bucket name: 61 buckets total - [0, 1), [1, 2), [2, 3), ..., [59, 60), 60+ |
| nums         | INT32     | FIELD       | Number of SQL queries in the bucket                                        |
| datanode_id  | INT32     | FIELD       | DataNode to which this bucket belongs                                      |

* Only administrators can execute operations on this table.
* Query example:

```SQL
IoTDB> select * from information_schema.queries_costs_histogram limit 10
+------+----+-----------+
|   bin|nums|datanode_id|
+------+----+-----------+
| [0,1)|   0|          1|
| [1,2)|   0|          1|
| [2,3)|   0|          1|
| [3,4)|   0|          1|
| [4,5)|   0|          1|
| [5,6)|   0|          1|
| [6,7)|   0|          1|
| [7,8)|   0|          1|
| [8,9)|   0|          1|
|[9,10)|   0|          1|
+------+----+-----------+
```

### 2.21 SERVICES

> This system table is available starting from version V 2.0.8

* Displays services (MQTT service, REST service) on all active DataNodes (with RUNNING or READ-ONLY status).
* Table structure:

| Column Name   | Data Type | Column Type | Description                     |
|---------------|-----------|-------------|---------------------------------|
| service_name  | STRING    | TAG         | Service Name                    |
| datanode_id   | INT32     | ATTRIBUTE   | DataNode ID where service runs  |
| state         | STRING    | ATTRIBUTE   | Service status: RUNNING/STOPPED |


* Query example:

```sql
IoTDB> SELECT * FROM information_schema.services
+------------+-----------+---------+
|service_name|datanode_id|state    |
+------------+-----------+---------+
|MQTT        |1          |STOPPED  |
|REST        |1          |RUNNING  |
+------------+-----------+---------+
```

### 2.22 TABLE_DISK_USAGE
> This system table is available since version V2.0.9-beta

Used to display the disk space usage of specified tables (excluding views), including the size of ChunkGroups and the size of Metadata.

Note: Statistics are based on the actual size of data in TsFiles; therefore, deletions made via mods are not considered.

The table structure is shown below:

| Column Name     | Data Type | Column Type | Description                      |
|-----------------|-----------|-------------|----------------------------------|
| database        | string    | Field       | Database name                    |
| table_name      | string    | Field       | Table name                       |
| datanode_id     | int32     | Field       | DataNode node ID                 |
| region_id       | int32     | Field       | Region ID                        |
| time_partition  | int64     | Field       | Time partition ID                |
| size_in_bytes   | int64     | Field       | Disk space occupied (in bytes)    |

**Query Examples**:

```SQL
-- Query all data;
select * from information_schema.table_disk_usage;
```

```Bash
+---------+-------------------+-----------+---------+--------------+-------------+
| database|         table_name|datanode_id|region_id|time_partition|size_in_bytes|
+---------+-------------------+-----------+---------+--------------+-------------+
|database1|             table1|          1|        3|          2864|          867|
|database1|            table11|          1|        3|          2864|            0|
|database1|             table3|          1|        3|          2864|            0|
|database1|             table1|          1|        3|          2865|         1411|
|database1|            table11|          1|        3|          2865|            0|
|database1|             table3|          1|        3|          2865|            0|
|database1|             table1|          1|        3|          2925|          590|
|database1|            table11|          1|        3|          2925|            0|
|database1|             table3|          1|        3|          2925|            0|
|database1|             table1|          1|        4|          2864|          883|
|database1|            table11|          1|        4|          2864|            0|
|database1|             table3|          1|        4|          2864|            0|
|database1|             table1|          1|        4|          2865|         1224|
|database1|            table11|          1|        4|          2865|            0|
|database1|             table3|          1|        4|          2865|            0|
|database1|             table1|          1|        4|          2888|            0|
|database1|            table11|          1|        4|          2888|            0|
|database1|             table3|          1|        4|          2888|          205|
|     etth|   tab_cov_forecast|          1|        8|             0|            0|
|     etth|           tab_real|          1|        8|             0|          963|
|     etth|tab_target_forecast|          1|        8|             0|            0|
|     etth|   tab_cov_forecast|          1|        9|             0|          448|
|     etth|           tab_real|          1|        9|             0|            0|
|     etth|tab_target_forecast|          1|        9|             0|            0|
+---------+-------------------+-----------+---------+--------------+-------------+
```

```SQL
-- Specify query conditions;
select * from information_schema.table_disk_usage where region_id = 4 and table_name like '%1';
```

```Bash
+---------+----------+-----------+---------+--------------+-------------+
| database|table_name|datanode_id|region_id|time_partition|size_in_bytes|
+---------+----------+-----------+---------+--------------+-------------+
|database1|    table1|          1|        4|          2864|          883|
|database1|   table11|          1|        4|          2864|            0|
|database1|    table1|          1|        4|          2865|         1224|
|database1|   table11|          1|        4|          2865|            0|
|database1|    table1|          1|        4|          2888|            0|
|database1|   table11|          1|        4|          2888|            0|
+---------+----------+-----------+---------+--------------+-------------+
```


## 3. Permission Description

* GRANT/REVOKE operations are not supported for the `information_schema` database or any of its tables.
* All users can view `information_schema` database details via the `SHOW DATABASES` statement.
* All users can list system tables via `SHOW TABLES FROM information_schema`.
* All users can inspect system table structures using the `DESC` statement.