12.18. PostgreSQL Connector

The PostgreSQL connector allows querying and creating tables in an external PostgreSQL database. This can be used to join data between different systems like PostgreSQL and Hive, or between two different PostgreSQL instances.

Configuration

To configure the PostgreSQL connector, create a catalog properties file in etc/catalog named, for example, postgresql.properties, to mount the PostgreSQL connector as the postgresql catalog. Create the file with the following contents, replacing the connection properties as appropriate for your setup:

connector.name=postgresql
connection-url=jdbc:postgresql://example.net:5432/database
connection-user=root
connection-password=secret

Multiple PostgreSQL Databases or Servers

The PostgreSQL connector can only access a single database within a PostgreSQL server. Thus, if you have multiple PostgreSQL databases, or want to connect to multiple PostgreSQL servers, you must configure multiple instances of the PostgreSQL connector.

To add another catalog, simply add another properties file to etc/catalog with a different name (making sure it ends in .properties). For example, if you name the property file sales.properties, Presto will create a catalog named sales using the configured connector.

Querying PostgreSQL

The PostgreSQL connector provides a schema for every PostgreSQL schema. You can see the available PostgreSQL schemas by running SHOW SCHEMAS:

SHOW SCHEMAS FROM postgresql;

If you have a PostgreSQL schema named web, you can view the tables in this schema by running SHOW TABLES:

SHOW TABLES FROM postgresql.web;

You can see a list of the columns in the clicks table in the web database using either of the following:

DESCRIBE postgresql.web.clicks;
SHOW COLUMNS FROM postgresql.web.clicks;

Finally, you can access the clicks table in the web schema:

SELECT * FROM postgresql.web.clicks;

If you used a different name for your catalog properties file, use that catalog name instead of postgresql in the above examples.

User Impersonation

PostgreSQL connector supports user impersonation. Please see User Impersonation for more details.

User impersonation can be turned with:

postgresql.impersonation.enabled=true

User impersonation in PostgreSQL connector is based on SET ROLE. For more details please visit: www.postgresql.org/docs.

Table Statistics

PostgreSQL connector supports table and column statistics. The statistics are collected by PostgreSQL Database and retrieved by the connector. To collect statistics for a table, execute the following statement in PostgreSQL Database.

ANALYZE table_schema.table_name;

Please refer to PostgreSQL documentation for additional ANALYZE options.

The table and column statistics can be viewed in Presto using SHOW STATS and are used for Cost based optimizations.

Table Statistics Configuration Properties

Property Name Description Default
statistics.enabled Enables table and column statistics. true
statistics.cache-ttl Duration for which table and column statistics are cached. 0s
statistics.cache-missing Cache the fact that table statistics were not available. false

PostgreSQL Connector Limitations

The following SQL statements are not yet supported: