Goal Find foreign data wrappers that do not have any associated foreign servers.
Type Problem detection (Each row in the result could represent a flaw in the design)
Reliability High (Few or no false-positive results)
License MIT License
Fixing Suggestion Drop the foreign data wrapper or start to use it.
Data Source INFORMATION_SCHEMA only
SQL Query
SELECT foreign_data_wrapper_name
FROM INFORMATION_SCHEMA.foreign_data_wrappers AS fdw
WHERE NOT EXISTS (SELECT 1
FROM INFORMATION_SCHEMA.foreign_servers AS fs
WHERE fdw.foreign_data_wrapper_name=fs.foreign_data_wrapper_name)
ORDER BY foreign_data_wrapper_name;

SQL statements that help generate fixes for the identified problem.

SQL Query to Generate FixDescription
SELECT format('DROP FOREIGN DATA WRAPPER %1$I;', foreign_data_wrapper_name) AS statements
FROM INFORMATION_SCHEMA.foreign_data_wrappers AS fdw
WHERE NOT EXISTS (SELECT 1
FROM INFORMATION_SCHEMA.foreign_servers AS fs
WHERE fdw.foreign_data_wrapper_name=fs.foreign_data_wrapper_name)
ORDER BY foreign_data_wrapper_name;
Drop the foreign data wrapper.
Collections

This query belongs to the following collections:

NameDescription
Find problems automaticallyQueries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not .
Categories

This query is classified under the following categories:

NameDescription
Distributed databaseQueries of this category provide information about the foreign table mechanism.
Unused implementation elementsQueries of this catergory provide information about the database objects that are not used.

Further reading and related materials:

Reference
https://wiki.postgresql.org/wiki/Foreign_data_wrappers