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Metadata /tdengine-reference/sql-manual/metadata

TDengine has a built-in database called INFORMATION_SCHEMA, which provides access to database metadata, system information, and status, such as the names of databases or tables, the SQL statements currently being executed, etc. This database stores information about all other databases maintained by TDengine. It contains multiple read-only tables. In fact, these tables are views, not base tables, so there are no files associated with them. Therefore, you can only query these tables, and cannot perform write operations like INSERT. The INFORMATION_SCHEMA database is designed to provide access to the information provided by various SHOW statements supported by TDengine (such as SHOW TABLES, SHOW DATABASES) in a more consistent way. Compared to SHOW statements, using SELECT ... FROM INFORMATION_SCHEMA.tablename has the following advantages:

  1. You can use the USE statement to set INFORMATION_SCHEMA as the default database
  2. You can use the familiar syntax of the SELECT statement, only needing to learn some table names and column names
  3. You can filter, sort, and perform other operations on the query results. In fact, you can use any SELECT statement supported by TDengine to query the tables in INFORMATION_SCHEMA
  4. TDengine can flexibly add columns to the existing tables in INFORMATION_SCHEMA in future evolutions without worrying about impacting existing business systems
  5. More interoperable with other database systems. For example, Oracle database users are familiar with querying tables in the Oracle data dictionary

:::info

  • Since SHOW statements are already familiar and widely used by developers, they are still retained.
  • Some columns in the system tables may be keywords, and need to use the escape character '`' when querying, for example, to query how many VGROUPs the database test has:
   select `vgroups` from ins_databases where name = 'test';

:::

This chapter will detail the tables and table structures in the built-in metadata database INFORMATION_SCHEMA.

INS_DNODES

Provides information about dnodes. You can also use SHOW DNODES to query this information. Users with SYSINFO set to 0 cannot view this table.

# Column Name Data Type Description
1 vnodes SMALLINT The actual number of vnodes in the dnode. Note, vnodes is a TDengine keyword, and needs to be escaped with ` when used as a column name.
2 support_vnodes SMALLINT Maximum number of supported vnodes
3 status BINARY(10) Current status
4 note BINARY(256) Information such as the reason for being offline
5 id SMALLINT dnode id
6 endpoint BINARY(134) Address of the dnode
7 create TIMESTAMP Creation time

INS_MNODES

Provides information about mnodes. You can also use SHOW MNODES to query this information. Users with SYSINFO set to 0 cannot view this table.

# Column Name Data Type Description
1 id SMALLINT mnode id
2 endpoint BINARY(134) address of the mnode
3 role BINARY(10) current role
4 role_time TIMESTAMP time when current role was assumed
5 create_time TIMESTAMP creation time

INS_QNODES

Information about QNODEs in the current system. You can also use SHOW QNODES to query this information. Users with SYSINFO set to 0 cannot view this table.

# Column Name Data Type Description
1 id SMALLINT qnode id
2 endpoint VARCHAR(134) address of the qnode
3 create_time TIMESTAMP creation time

INS_SNODES

Information about SNODEs in the current system. You can also use SHOW SNODES to query this information. Users with SYSINFO set to 0 cannot view this table.

# Column Name Data Type Description
1 id SMALLINT snode id
2 endpoint VARCHAR(134) address of the snode
3 create_time TIMESTAMP creation time

INS_CLUSTER

Stores cluster-related information. Users with SYSINFO set to 0 cannot view this table.

# Column Name Data Type Description
1 id BIGINT cluster id
2 name VARCHAR(134) cluster name
3 create_time TIMESTAMP creation time

INS_DATABASES

Provides information about database objects created by users. You can also use SHOW DATABASES to query this information.

# Column Name Data Type Description
1 name VARCHAR(64) database name
2 create_time TIMESTAMP creation time
3 ntables INT number of tables in the database, including subtables and basic tables but excluding supertables
4 vgroups INT number of vgroups in the database. Note, vgroups is a TDengine keyword and must be escaped with ` when used as a column name.
6 replica INT number of replicas. Note, replica is a TDengine keyword and must be escaped with ` when used as a column name.
7 strict VARCHAR(4) deprecated parameter
8 duration VARCHAR(10) time span for storing data in a single file. Note, duration is a TDengine keyword and must be escaped with ` when used as a column name. Internally stored in minutes, may be displayed in days or hours when queried
9 keep VARCHAR(32) data retention duration. Note, keep is a TDengine keyword and must be escaped with ` when used as a column name. Internally stored in minutes, may be displayed in days or hours when queried
10 buffer INT size of the write cache memory block for each vnode, in MB. Note, buffer is a TDengine keyword and must be escaped with ` when used as a column name.
11 pagesize INT page size for the metadata storage engine in each VNODE, in KB. Note, pagesize is a TDengine keyword and must be escaped with ` when used as a column name.
12 pages INT number of cache pages for the metadata storage engine in each vnode. Note, pages is a TDengine keyword and must be escaped with ` when used as a column name.
13 minrows INT minimum number of records in a file block. Note, minrows is a TDengine keyword and must be escaped with ` when used as a column name.
14 maxrows INT maximum number of records in a file block. Note, maxrows is a TDengine keyword and must be escaped with ` when used as a column name.
15 comp INT data compression method. Note, comp is a TDengine keyword and must be escaped with ` when used as a column name.
16 precision VARCHAR(2) time resolution. Note, precision is a TDengine keyword and must be escaped with ` when used as a column name.
17 status VARCHAR(10) database status
18 retentions VARCHAR(60) data aggregation period and retention duration. Note, retentions is a TDengine keyword and must be escaped with ` when used as a column name.
19 single_stable BOOL indicates whether only one supertable can be created in this database. Note, single_stable is a TDengine keyword and must be escaped with ` when used as a column name.
20 cachemodel VARCHAR(60) indicates whether to cache recent data of subtables in memory. Note, cachemodel is a TDengine keyword and must be escaped with ` when used as a column name.
21 cachesize INT size of memory used to cache recent data of subtables in each vnode. Note, cachesize is a TDengine keyword and must be escaped with ` when used as a column name.
22 wal_level INT WAL level. Note, wal_level is a TDengine keyword and must be escaped with ` when used as a column name.
23 wal_fsync_period INT data write-to-disk period. Note, wal_fsync_period is a TDengine keyword and must be escaped with ` when used as a column name.
24 wal_retention_period INT WAL retention duration, in seconds. Note, wal_retention_period is a TDengine keyword and must be escaped with ` when used as a column name.
25 wal_retention_size INT WAL retention limit. Note, wal_retention_size is a TDengine keyword and must be escaped with ` when used as a column name.
26 stt_trigger SMALLINT number of disk files that trigger file merging. Note, stt_trigger is a TDengine keyword and must be escaped with ` when used as a column name.
27 table_prefix SMALLINT length of the prefix to ignore when the internal storage engine allocates a VNODE to store data for a table based on its name. Note, table_prefix is a TDengine keyword and must be escaped with ` when used as a column name.
28 table_suffix SMALLINT length of the suffix to ignore when the internal storage engine allocates a VNODE to store data for a table based on its name. Note, table_suffix is a TDengine keyword and must be escaped with ` when used as a column name.
29 tsdb_pagesize INT page size in the time-series data storage engine. Note, tsdb_pagesize is a TDengine keyword and must be escaped with ` when used as a column name.

INS_FUNCTIONS

Information about user-created custom functions.

# Column Name Data Type Description
1 name VARCHAR(64) Function name
2 comment VARCHAR(255) Additional explanation. Note that comment is a TDengine keyword and needs to be escaped with ``.
3 aggregate INT Whether it is an aggregate function. Note that aggregate is a TDengine keyword and needs to be escaped with ``.
4 output_type VARCHAR(31) Output type
5 create_time TIMESTAMP Creation time
6 code_len INT Code length
7 bufsize INT Buffer size
8 func_language VARCHAR(31) Programming language of the custom function
9 func_body VARCHAR(16384) Function body definition
10 func_version INT Function version number. Initial version is 0, and the version number increases by 1 with each update.

INS_INDEXES

Provides information about indexes created by the user. You can also use SHOW INDEX to query this information.

# Column Name Data Type Description
1 db_name VARCHAR(32) Database name containing the table with this index
2 table_name VARCHAR(192) Name of the table containing this index
3 index_name VARCHAR(192) Index name
4 column_name VARCHAR(64) Column name on which the index is built
5 index_type VARCHAR(10) Currently includes SMA and tag
6 index_extensions VARCHAR(256) Additional information about the index. For SMA/tag types of indexes, it is a list of function names.

INS_STABLES

Provides information about supertables created by users.

# Column Name Data Type Description
1 stable_name VARCHAR(192) Supertable name
2 db_name VARCHAR(64) Name of the database containing the supertable
3 create_time TIMESTAMP Creation time
4 columns INT Number of columns
5 tags INT Number of tags. Note, tags is a TDengine keyword, use ` to escape when using it as a column name.
6 last_update TIMESTAMP Last update time
7 table_comment VARCHAR(1024) Table comment
8 watermark VARCHAR(64) Window closing time. Note, watermark is a TDengine keyword, use ` to escape when using it as a column name.
9 max_delay VARCHAR(64) Maximum delay for pushing calculation results. Note, max_delay is a TDengine keyword, use ` to escape when using it as a column name.
10 rollup VARCHAR(128) rollup aggregation function. Note, rollup is a TDengine keyword, use ` to escape when using it as a column name.

INS_TABLES

Provides information about basic tables and subtables created by users

# Column Name Data Type Description
1 table_name VARCHAR(192) Table name
2 db_name VARCHAR(64) Database name
3 create_time TIMESTAMP Creation time
4 columns INT Number of columns
5 stable_name VARCHAR(192) Name of the supertable it belongs to
6 uid BIGINT Table ID
7 vgroup_id INT vgroup ID
8 ttl INT Table's time to live. Note, ttl is a TDengine keyword, use ` to escape when using it as a column name.
9 table_comment VARCHAR(1024) Table comment
10 type VARCHAR(21) Table type

INS_TAGS

# Column Name Data Type Description
1 table_name VARCHAR(192) Table name
2 db_name VARCHAR(64) Name of the database the table belongs to
3 stable_name VARCHAR(192) Name of the supertable
4 tag_name VARCHAR(64) Name of the tag
5 tag_type VARCHAR(64) Type of the tag
6 tag_value VARCHAR(16384) Value of the tag

INS_COLUMNS

# Column Name Data Type Description
1 table_name VARCHAR(192) Table name
2 db_name VARCHAR(64) Name of the database the table belongs to
3 table_type VARCHAR(21) Table type
4 col_name VARCHAR(64) Name of the column
5 col_type VARCHAR(32) Type of the column
6 col_length INT Length of the column
7 col_precision INT Precision of the column
8 col_scale INT Scale of the column
9 col_nullable INT Whether the column can be null

INS_USERS

Provides information about users created in the system. Users with SYSINFO attribute as 0 cannot view this table.

# Column Name Data Type Description
1 name VARCHAR(24) Username
2 super TINYINT Whether the user is a superuser, 1: Yes, 0: No
3 enable TINYINT Whether the user is enabled, 1: Yes, 0: No
4 sysinfo TINYINT Whether the user can view system information, 1: Yes, 0: No
5 create_time TIMESTAMP Creation time
6 allowed_host VARCHAR(49152) IP whitelist

INS_GRANTS

Provides information about enterprise edition licenses. Users with SYSINFO attribute as 0 cannot view this table.

# Column Name Data Type Description
1 version VARCHAR(9) Enterprise license description: official (officially licensed)/trial (trial)
2 cpu_cores VARCHAR(9) Number of CPU cores licensed for use
3 dnodes VARCHAR(10) Number of dnode nodes licensed for use. Note, dnodes is a TDengine keyword, use ` to escape when used as a column name.
4 streams VARCHAR(10) Number of streams licensed for creation. Note, streams is a TDengine keyword, use ` to escape when used as a column name.
5 users VARCHAR(10) Number of users licensed for creation. Note, users is a TDengine keyword, use ` to escape when used as a column name.
6 accounts VARCHAR(10) Number of accounts licensed for creation. Note, accounts is a TDengine keyword, use ` to escape when used as a column name.
7 storage VARCHAR(21) Amount of storage space licensed for use. Note, storage is a TDengine keyword, use ` to escape when used as a column name.
8 connections VARCHAR(21) Number of client connections licensed for use. Note, connections is a TDengine keyword, use ` to escape when used as a column name.
9 databases VARCHAR(11) Number of databases licensed for use. Note, databases is a TDengine keyword, use ` to escape when used as a column name.
10 speed VARCHAR(9) Number of data points per second licensed for writing
11 querytime VARCHAR(9) Total duration of queries licensed for use
12 timeseries VARCHAR(21) Number of time-series licensed for use
13 expired VARCHAR(5) Whether expired, true: expired, false: not expired
14 expire_time VARCHAR(19) Trial period expiration time

INS_VGROUPS

Information on all vgroups in the system. Users with SYSINFO property set to 0 cannot view this table.

# Column Name Data Type Description
1 vgroup_id INT vgroup id
2 db_name VARCHAR(32) Database name
3 tables INT Number of tables in this vgroup. Note that tables is a TDengine keyword and must be escaped with ` when used as a column name.
4 status VARCHAR(10) Status of this vgroup
5 v1_dnode INT ID of the dnode of the first member
6 v1_status VARCHAR(10) Status of the first member
7 v2_dnode INT ID of the dnode of the second member
8 v2_status VARCHAR(10) Status of the second member
9 v3_dnode INT ID of the dnode of the third member
10 v3_status VARCHAR(10) Status of the third member
11 nfiles INT Number of data/metadata files in this vgroup
12 file_size INT Size of data/metadata files in this vgroup
13 tsma TINYINT Whether this vgroup is dedicated to Time-range-wise SMA, 1: Yes, 0: No

INS_CONFIGS

System configuration parameters.

# Column Name Data Type Description
1 name VARCHAR(32) Configuration item name
2 value VARCHAR(64) Value of the configuration item. Note that value is a TDengine keyword and must be escaped with ` when used as a column name.

INS_DNODE_VARIABLES

Configuration parameters for each dnode in the system. Users with SYSINFO attribute 0 cannot view this table.

# Column Name Data Type Description
1 dnode_id INT ID of the dnode
2 name VARCHAR(32) Configuration item name
3 value VARCHAR(64) The value of the configuration item. Note, value is a TDengine keyword, use ` to escape when used as a column name.

INS_TOPICS

# Column Name Data Type Description
1 topic_name VARCHAR(192) Name of the topic
2 db_name VARCHAR(64) DB associated with the topic
3 create_time TIMESTAMP Creation time of the topic
4 sql VARCHAR(1024) SQL statement used to create the topic

INS_SUBSCRIPTIONS

# Column Name Data Type Description
1 topic_name VARCHAR(204) Subscribed topic
2 consumer_group VARCHAR(193) Consumer group of the subscriber
3 vgroup_id INT vgroup id assigned to the consumer
4 consumer_id BIGINT Unique id of the consumer
5 user VARCHAR(24) Username of the consumer logging in
6 fqdn VARCHAR(128) fqdn of the consumer's machine
7 offset VARCHAR(64) Consumption progress of the consumer
8 rows BIGINT Number of data rows consumed by the consumer

INS_STREAMS

# Column Name Data Type Description
1 stream_name VARCHAR(64) Stream computing name
2 create_time TIMESTAMP Creation time
3 sql VARCHAR(1024) SQL statement provided for creating stream computing
4 status VARCHAR(20) Current status of the stream
5 source_db VARCHAR(64) Source database
6 target_db VARCHAR(64) Destination database
7 target_table VARCHAR(192) Target table for stream computing output
8 watermark BIGINT Watermark, see SQL manual for stream computing. Note, watermark is a TDengine keyword, use ` to escape when used as a column name.
9 trigger INT Mode of pushing computation results, see SQL manual for stream computing. Note, trigger is a TDengine keyword, use ` to escape when used as a column name.

INS_USER_PRIVILEGES

Note: Users with SYSINFO property set to 0 cannot view this table.

# Column Name Data Type Description
1 user_name VARCHAR(24) Username
2 privilege VARCHAR(10) Permission description
3 db_name VARCHAR(65) Database name
4 table_name VARCHAR(193) Table name
5 condition VARCHAR(49152) Subtable permission filter condition

INS_DISK_USAGE

# Column Name Data type Description
1 db_name VARCHAR(32) Database name
2 vgroup_id INT vgroup ID
3 wal BIGINT WAL file size, in KB
4 data1 BIGINT Data file size on primary storage, in KB
5 data2 BIGINT Data file size on secondary storage, in KB
6 data3 BIGINT Data file size on tertiary storage, in KB
7 cache_rdb BIGINT Size of last/last_row files, in KB
8 table_meta BIGINT Size of meta files, in KB
9 s3 BIGINT Size occupied on S3, in KB
10 raw_data BIGINT Estimated size of raw data, in KB

note:

INS_FILESETS

Provides information about file sets.

| # | Column | Data Type | Description | ** | | --- | :-----------: | ------------- | ---------------------------------------------------- | | 1 | db_name | VARCHAR(65) | Database name | | 2 | vgroup_id | INT | Vgroup ID | | 3 | fileset_id | INT | File set ID | | 4 | start_time | TIMESTAMP | Start time of the time range covered by the file set | | 5 | end_time | TIMESTAMP | End time of the time range covered by the file set | | 6 | total_size | BIGINT | Total size of the file set | | 7 | last_compact | TIMESTAMP | Time of the last compaction | | 8 | shold_compact | bool | Whether the file set should be compacted |