psql Commands for Managing PostgreSQL Extensions

• PostgreSQL extensions are add-on modules that provide additional functionality to the database server.
• They can offer new data types, functions, operators, or even foreign data wrappers for interacting with external systems.

psql

• psql is the command-line interface (CLI) tool for interacting with PostgreSQL databases.
• It allows you to execute SQL statements, manage databases and objects, and perform various administrative tasks.

Listing Installed Extensions

To see a list of extensions currently installed in your PostgreSQL database, use the following command within psql:

\dx

• The backslash (\) prefix indicates that this is a psql-specific command, not a standard SQL statement.
• dx is a shorthand for the command \d extensions.

Output Interpretation

The \dx command will typically display information about each installed extension in a tabular format, including:

• name: The name of the extension.
• type: The type of the extension (usually p), indicating a procedural language extension.
• owner: The database user who owns the extension.
• default_version: The default version of the extension that was installed.
• installed_version: The actual version of the extension that is currently installed.
• schema: The schema where the extension's objects are installed (often public).

Example Output

        name        | type  | owner | default_version | installed_version | schema
-------------------+-------+-------+------------------+--------------------+---------
 plpgsql             | p     | postgres | 11                | 11                | public
 uuid-ossp           | p     | postgres | 1.1                | 1.1                | public

In this example:

• plpgsql and uuid-ossp are the names of the installed extensions.
• Both are procedural language extensions (p).
• They are owned by the default user postgres.
• Their default and installed versions are the same (11 and 1.1, respectively).
• Their objects are installed in the public schema.

Additional Considerations

• If you want to see more detailed information about a specific extension, you can use the \d [extension_name] command.
• To see extensions that are available for installation but not yet installed, use the pg_available_extensions system view within SQL queries.

\dx

This code snippet will display a list of all extensions currently installed in your PostgreSQL database.

Getting Details of a Specific Extension:

\d plpgsql  -- Replace 'plpgsql' with the actual extension name

This code retrieves detailed information about a particular extension, such as its functions, operators, and data types. Replace plpgsql with the name of the extension you're interested in.

Checking Available Extensions (Using SQL Query):

SELECT name, version
FROM pg_available_extensions;

PostgreSQL provides a system catalog named pg_extension that stores information about installed extensions. You can query this catalog to retrieve a list of extensions. Here's an example SQL query:

SELECT extname AS name, extversion AS version, pg_catalog.pg_namespace.nspname AS schema
FROM pg_catalog.pg_extension
JOIN pg_catalog.pg_namespace ON pg_catalog.pg_extension.extnamespace = pg_catalog.pg_namespace.oid;

This query retrieves the following information:

• extname: The name of the extension (same as name in \dx output).
• extversion: The version of the extension (same as installed_version in \dx).

Using pgAdmin (if applicable):

If you're using a graphical administration tool like pgAdmin, you can visualize installed extensions:

• Open pgAdmin and connect to your PostgreSQL server.
• In the object tree, navigate to the server you're connected to.
• Expand the server node and locate the "Extensions" node.
• This node will list all installed extensions with details like name, version, and owner.

Choosing the Right Method:

• For a quick overview from the command line, \dx is the simplest approach.
• If you need more flexibility and want to filter or manipulate the extension data using SQL, the pg_extension system catalog query is suitable.
• If you prefer a visual interface and are already using pgAdmin, that option can be convenient.