================ System Connector

The System connector provides information and metrics about the currently running Presto 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. The columns in metadata.catalogs are:

======================================= ====================================================================== Column Name Description ======================================= ====================================================================== catalog_name The value of this column is derived from the names of catalog.properties files present under etc/catalog path under presto installation directory. Everything except the suffix .properties is treated as the catalog name. For example, if there is a file named my_catalog.properties, then my_catalog will be listed as the value for this column.

connector_id The values in this column are a duplicate of the values in the catalog_name column.

connector_name This column represents the actual name of the underlying connector that a particular catalog is using. This column contains the value of connector.name property from the catalog.properties file. ======================================= ======================================================================

Example:

Suppose a user configures a single catalog by creating a file named my_catalog.properties with the below contents::

connector.name=hive-hadoop2
hive.metastore.uri=thrift://localhost:9083

metadata.catalogs table will show below output::

presto> select * from system.metadata.catalogs;
 catalog_name | connector_id | connector_name
--------------+--------------+----------------
 my_catalog   | my_catalog   | hive-hadoop2

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.

runtime.nodes ^^^^^^^^^^^^^^^^^

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

runtime.queries ^^^^^^^^^^^^^^^^^^^

The queries table contains information about currently and recently running queries on the Presto cluster. From this table you can find out the original query text (SQL), 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 Presto 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
will include the specified ``message``.