The list of all the queries

Installed extensions

Query goal: Try to use as much the possibilities of the DBMS as possible. On the other hand, do not install extensions that are not needed in order not to overcomplicate the database.
Query type: General (Overview of some aspect of the database.)
Query license: MIT License
Fixing suggestion: If you do not need an extension, then drop it.
Data source: system catalog only
SQL query: Click on query to copy it

SELECT name, installed_version, comment
FROM pg_catalog.pg_available_extensions
WHERE installed_version IS NOT NULL
ORDER BY name;

SQL statements for generating SQL statements that help us to fix the problem

SQL queryDescription
SELECT format('DROP EXTENSION %1$I;', name) AS statements
FROM pg_catalog.pg_available_extensions
WHERE installed_version IS NOT NULL
ORDER BY name;
Drop the extension.

Collections where the query belongs to

Collection nameCollection description
Find problems by overviewQueries that results point to different aspects of database that might have problems. A human reviewer has to decide based on the results as to whether there are problems or not .

Categories where the query belongs to

Category nameCategory description
Comfortability of data managementQueries of this category provide information about the means that have been used to make the use or management of database more comfortable and thus, more efficient.
ExtensionsQueries of this category provide information about extensions in the database.
SecurityQueries of this category provide information about the security measures.

Reference materials for further reading

Reference
There are quite a lot of extensions that are shipped together with the PostgreSQL source code.
Anyone can create an extension and there are many examples: https://pgxn.org/

The list of all the queries