System connector

The System connector provides information and metrics about the currently running Trino cluster. It makes this available via normal SQL queries.

Configuration

The System connector doesn't need to be configured: it is automatically available via a catalog named system.

Using the System connector

List the available system schemas:

SHOW SCHEMAS FROM system;

List the tables in one of the schemas:

SHOW TABLES FROM system.runtime;

Query one of the tables:

SELECT * FROM system.runtime.nodes;

Kill a running query:

CALL system.runtime.kill_query(query_id => '20151207_215727_00146_tx3nr', message => 'Using too many resources');

System connector tables

metadata.catalogs

The catalogs table contains the list of available catalogs.

metadata.schema_properties

The schema properties table contains the list of available properties that can be set when creating a new schema.

metadata.table_properties

The table properties table contains the list of available properties that can be set when creating a new table.

(system-metadata-materialized-views)=

metadata.materialized_views

The materialized views table contains the following information about all {ref}materialized views <sql-materialized-view-management>:

:::{list-table} Metadata for materialized views :widths: 30, 70 :header-rows: 1

• • Column
  • Description
• • catalog_name
  • Name of the catalog containing the materialized view.
• • schema_name
  • Name of the schema in catalog_name containing the materialized view.
• • name
  • Name of the materialized view.
• • storage_catalog
  • Name of the catalog used for the storage table backing the materialized view.
• • storage_schema
  • Name of the schema in storage_catalog used for the storage table backing the materialized view.
• • storage_table
  • Name of the storage table backing the materialized view.
• • freshness
  • Freshness of data in the storage table. Queries on the materialized view access the storage table if not STALE, otherwise the definition is used to access the underlying data in the source tables.
• • last_fresh_time
  • Date and time of the last refresh of the materialized view.
• • comment
  • User supplied text about the materialized view.
• • definition
  • SQL query that defines the data provided by the materialized view. :::

metadata.materialized_view_properties

The materialized view properties table contains the list of available properties that can be set when creating a new materialized view.

metadata.table_comments

The table comments table contains the list of table comment.

runtime.nodes

The nodes table contains the list of visible nodes in the Trino cluster along with their status.

(optimizer-rule-stats)=

runtime.optimizer_rule_stats

The optimizer_rule_stats table contains the statistics for optimizer rule invocations during the query planning phase. The statistics are aggregated over all queries since the server start-up. The table contains information about invocation frequency, failure rates and performance for optimizer rules. For example, you can look at the multiplication of columns invocations and average_time to get an idea about which rules generally impact query planning times the most.

runtime.queries

The queries table contains information about currently and recently running queries on the Trino cluster. From this table you can find out the original query SQL text, the identity of the user who ran the query, and performance information about the query, including how long the query was queued and analyzed.

runtime.tasks

The tasks table contains information about the tasks involved in a Trino query, including where they were executed, and how many rows and bytes each task processed.

runtime.transactions

The transactions table contains the list of currently open transactions and related metadata. This includes information such as the create time, idle time, initialization parameters, and accessed catalogs.

System connector procedures

:::{function} runtime.kill_query(query_id, message)

Kill the query identified by query_id. The query failure message includes the specified message. message is optional.

:::

(system-type-mapping)=

Type mapping

Trino supports all data types used within the System schemas so no mapping is required.

(system-sql-support)=

SQL support

The connector provides {ref}globally available <sql-globally-available> and {ref}read operation <sql-read-operations> statements to access Trino system data and metadata.