5.16. PostgreSQL Connector

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

Configuration

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

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

Multiple PostgreSQL Databases or Servers

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

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

  1. SHOW SCHEMAS FROM postgresql;

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

  1. SHOW TABLES FROM postgresql.web;

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

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

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

  1. SELECT * FROM postgresql.web.clicks;

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

PostgreSQL Connector Limitations

The following SQL statements are not yet supported: