11.5. 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.
PostgreSQL Connector Limitations
The following SQL statements are not yet supported:
- INSERT
- DELETE
- ALTER TABLE
- CREATE TABLE (CREATE TABLE AS is supported)