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Metadata The INFORMATION_SCHEMA database stores all metadata information in the system. /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, and currently executed SQL statements. This database stores information about all other databases maintained by TDengine. It contains several read-only tables. In fact, these tables are views rather than base tables, so there are no associated files with them. Therefore, you can only query these tables and cannot perform write operations such as INSERT. The INFORMATION_SCHEMA database is designed to provide access to information supported by various SHOW statements (like SHOW TABLES, SHOW DATABASES) in a more consistent manner. 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 SELECT statement syntax, 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 existing tables in INFORMATION_SCHEMA in future versions without worrying about affecting existing business systems.
  5. It is more interoperable with other database systems. For example, Oracle database users are familiar with querying the Oracle data dictionary tables.

:::info

  • Since SHOW statements have already been familiar and widely used by developers, they are still retained.

  • Some columns in system tables may be keywords, and you need to use the escape character '`' when querying, for example, to query how many VGROUPs 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 related to 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 that vnodes is a TDengine keyword and needs to be escaped with `.
2 support_vnodes SMALLINT The maximum number of supported vnodes
3 status BINARY(10) The current status
4 note BINARY(256) Reason for offline and other information
5 id SMALLINT dnode id
6 endpoint BINARY(134) The address of the dnode
7 create TIMESTAMP Creation time

INS_MNODES

Provides information related to 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) The address of the mnode
3 role BINARY(10) Current role
4 role_time TIMESTAMP The time when it became the current role
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) The 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) The 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 user-created database objects. 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 that vgroups is a TDengine keyword and needs to be escaped with `.
5 replica INT Number of replicas. Note that replica is a TDengine keyword and needs to be escaped with `.
6 strict VARCHAR(4) Deprecated parameter
7 duration VARCHAR(10) Duration of time data is stored in a single file. Note that duration is a TDengine keyword and needs to be escaped with `. The internal storage unit is minutes, and it may be converted to days or hours during queries.
8 keep VARCHAR(32) Data retention duration. Note that keep is a TDengine keyword and needs to be escaped with `. The internal storage unit is minutes, and it may be converted to days or hours during queries.
9 buffer INT Size of the memory block for writing caches per vnode, in MB. Note that buffer is a TDengine keyword and needs to be escaped with `.
10 pagesize INT Page size of the metadata storage engine in each VNODE, in KB. Note that pagesize is a TDengine keyword and needs to be escaped with `.
11 pages INT Number of cached pages for metadata storage engine in each vnode. Note that pages is a TDengine keyword and needs to be escaped with `.
12 minrows INT Minimum number of records in a file block. Note that minrows is a TDengine keyword and needs to be escaped with `.
13 maxrows INT Maximum number of records in a file block. Note that maxrows is a TDengine keyword and needs to be escaped with `.
14 comp INT Data compression method. Note that comp is a TDengine keyword and needs to be escaped with `.
15 precision VARCHAR(2) Time resolution. Note that precision is a TDengine keyword and needs to be escaped with `.
16 status VARCHAR(10) Database status
17 retentions VARCHAR(60) Data aggregation cycle and retention duration. Note that retentions is a TDengine keyword and needs to be escaped with `.
18 single_stable BOOL Indicates whether only one supertable can be created in this database. Note that single_stable is a TDengine keyword and needs to be escaped with `.
19 cachemodel VARCHAR(60) Indicates whether to cache the most recent data of subtables in memory. Note that cachemodel is a TDengine keyword and needs to be escaped with `.
20 cachesize INT Size of memory used for caching the most recent data of subtables in each vnode. Note that cachesize is a TDengine keyword and needs to be escaped with `.
21 wal_level INT WAL level. Note that wal_level is a TDengine keyword and needs to be escaped with `.
22 wal_fsync_period INT Data persistence period. Note that wal_fsync_period is a TDengine keyword and needs to be escaped with `.
23 wal_retention_period INT WAL retention duration, in seconds. Note that wal_retention_period is a TDengine keyword and needs to be escaped with `.
24 wal_retention_size INT WAL retention limit. Note that wal_retention_size is a TDengine keyword and needs to be escaped with `.
25 stt_trigger SMALLINT Number of persistent files that trigger file merging. Note that stt_trigger is a TDengine keyword and needs to be escaped with `.
26 table_prefix SMALLINT Length of prefix to ignore when assigning storage of table data by table name in the internal storage engine. Note that table_prefix is a TDengine keyword and needs to be escaped with `.
27 table_suffix SMALLINT Length of suffix to ignore when assigning storage of table data by table name in the internal storage engine. Note that table_suffix is a TDengine keyword and needs to be escaped with `.
28 tsdb_pagesize INT Page size in the time-series data storage engine. Note that tsdb_pagesize is a TDengine keyword and needs to be escaped with `.

INS_FUNCTIONS

Information about user-created custom functions.

# Column Name Data Type Description
1 name VARCHAR(64) Function name
2 comment VARCHAR(255) Additional description. Note that comment is a TDengine keyword and needs to be escaped with `.
3 aggregate INT Indicates 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 each update increments the version number.

INS_INDEXES

Provides information related to indexes created by users. You can also use SHOW INDEX to query this information.

# Column Name Data Type Description
1 db_name VARCHAR(32) Database name containing 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) Name of the column indexed
5 index_type VARCHAR(10) Currently, there are SMA and tag
6 index_extensions VARCHAR(256) Additional information about the index. For SMA/tag indexes, this 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 where the supertable is located
3 create_time TIMESTAMP Creation time
4 columns INT Number of columns
5 tags INT Number of tags. Note that tags is a TDengine keyword and needs to be escaped with `.
6 last_update TIMESTAMP Last update time
7 table_comment VARCHAR(1024) Table comment
8 watermark VARCHAR(64) Window closing time. Note that watermark is a TDengine keyword and needs to be escaped with `.
9 max_delay VARCHAR(64) Maximum delay for pushing computation results. Note that max_delay is a TDengine keyword and needs to be escaped with `.
10 rollup VARCHAR(128) Rollup aggregation function. Note that rollup is a TDengine keyword and needs to be escaped with `.

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) Name of the database where the table is located
3 create_time TIMESTAMP Creation time
4 columns INT Number of columns
5 stable_name VARCHAR(192) Name of the supertable to which it belongs
6 uid BIGINT Table id
7 vgroup_id INT vgroup id
8 ttl INT Lifecycle of the table. Note that ttl is a TDengine keyword and needs to be escaped with `.
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 where this table is located
3 stable_name VARCHAR(192) Name of the supertable to which it belongs
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 where this table is located
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 Indicates whether the column can be null

INS_USERS

Provides information about users created in the system. Users with SYSINFO set to 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 authorizations. Users with SYSINFO set to 0 cannot view this table.

# Column Name Data Type Description
1 version VARCHAR(9) Enterprise edition authorization description: official (officially authorized) / trial (trial version)
2 cpu_cores VARCHAR(9) Number of CPU cores authorized for use
3 dnodes VARCHAR(10) Number of dnode nodes authorized for use. Note that dnodes is a TDengine keyword and needs to be escaped with `.
4 streams VARCHAR(10) Number of streams authorized for creation. Note that streams is a TDengine keyword and needs to be escaped with `.
5 users VARCHAR(10) Number of users authorized for creation. Note that users is a TDengine keyword and needs to be escaped with `.
6 accounts VARCHAR(10) Number of accounts authorized for creation. Note that accounts is a TDengine keyword and needs to be escaped with `.
7 storage VARCHAR(21) Size of storage space authorized for use. Note that storage is a TDengine keyword and needs to be escaped with `.
8 connections VARCHAR(21) Number of client connections authorized for use. Note that connections is a TDengine keyword and needs to be escaped with `.
9 databases VARCHAR(11) Number of databases authorized for use. Note that databases is a TDengine keyword and needs to be escaped with `.
10 speed VARCHAR(9) Number of data points per second authorized for use
11 querytime VARCHAR(9) Total duration for queries authorized for use
12 timeseries VARCHAR(21) Number of measurement points authorized for use
13 expired VARCHAR(5) Whether it has expired, true: expired, false: not expired
14 expire_time VARCHAR(19) Trial expiration date

INS_VGROUPS

Information about all vgroups in the system. Users with SYSINFO 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 needs to be escaped with `.
4 status VARCHAR(10) Status of this vgroup
5 v1_dnode INT ID of the dnode where the first member is located
6 v1_status VARCHAR(10) Status of the first member
7 v2_dnode INT ID of the dnode where the second member is located
8 v2_status VARCHAR(10) Status of the second member
9 v3_dnode INT ID of the dnode where the third member is located
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 Indicates whether this vgroup is specifically for 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 needs to be escaped with `.

INS_DNODE_VARIABLES

Configuration parameters for each dnode in the system. Users with SYSINFO set to 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) Value of the configuration item. Note that value is a TDengine keyword and needs to be escaped with `.

INS_TOPICS

# Column Name Data Type Description
1 topic_name VARCHAR(192) Topic name
2 db_name VARCHAR(64) Database related to the topic
3 create_time TIMESTAMP Creation time of the topic
4 sql VARCHAR(1024) SQL statement used to create this topic

INS_SUBSCRIPTIONS

# Column Name Data Type Description
1 topic_name VARCHAR(204) Subscribed topic
2 consumer_group VARCHAR(193) Subscriber's consumer group
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
6 fqdn VARCHAR(128) FQDN of the machine where the consumer is located
7 offset VARCHAR(64) Consumer's consumption progress
8 rows BIGINT Number of data records consumed

INS_STREAMS

# Column Name Data Type Description
1 stream_name VARCHAR(64) Stream calculation name
2 create_time TIMESTAMP Creation time
3 sql VARCHAR(1024) SQL statement provided when creating the stream calculation
4 status VARCHAR(20) Current status of the stream
5 source_db VARCHAR(64) Source database
6 target_db VARCHAR(64) Target database
7 target_table VARCHAR(192) Target table where the stream calculation writes results
8 watermark BIGINT Watermark, see SQL manual for stream calculations. Note that watermark is a TDengine keyword and needs to be escaped with `.
9 trigger INT Push result computation mode, see SQL manual for stream calculations. Note that trigger is a TDengine keyword and needs to be escaped with `.

INS_USER_PRIVILEGES

Note: Users with SYSINFO 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