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​:

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:

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 in Table Management documentation
• The query results only display the collection of tables for which you have any permission.
• Query Example:

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. - ForDataRegion without statistics(Unknown):-1. - For​SchemaRegion​:null.

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

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
wait_time_in_server	FLOAT	ATTRIBUTE	Cumulative time that the client request waits in the server for results to be returned, in seconds (supported since V2.0.10)
client_ip	STRING	ATTRIBUTE	IP address of the client that initiated the query (supported since V2.0.10)
timeout	INT64	ATTRIBUTE	Timeout of the query, in ms (supported since V2.0.10)

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

IoTDB> select * from information_schema.queries
+-----------------------+-----------------------------+-----------+------------+----------------------------------------+----+-------------------+---------+-------+
|               query_id|                   start_time|datanode_id|elapsed_time|                               statement|user|wait_time_in_server|client_ip|timeout|
+-----------------------+-----------------------------+-----------+------------+----------------------------------------+----+-------------------+---------+-------+
|20260601_032216_00018_1|2026-06-01T11:22:16.815+08:00|          1|       0.014|select * from information_schema.queries|root|          0.0158324|127.0.0.1|  60000|
+-----------------------+-----------------------------+-----------+------------+----------------------------------------+----+-------------------+---------+-------+

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 in Table Management documentation.

• The query results only display the column information of tables for which you have any permission.

• Query Example:

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 (-1if Unknown)
estimated_remaining_seconds	DOUBLE	ATTRIBUTE	Estimated remaining time in seconds (-1if Unknown)

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

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 (nullfor builtin type)

• Query Example:

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:

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:

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:

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:

-- 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:

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:

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:

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:

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:

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:

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:

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:

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:

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:

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 V2.0.10

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:

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

+---------+-------------------+-----------+---------+--------------+-------------+
| 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|
+---------+-------------------+-----------+---------+--------------+-------------+

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

+---------+----------+-----------+---------+--------------+-------------+
| 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.