Presto 0.100 Documentation

4.8. 系统连接器

4.8. 系统连接器

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;

System Connector Tables

metadata.catalog

The catalogs table contains the list of available catalogs.

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 and how many rows and bytes each task processed.