Goal Find enumerated types that are not used in case of any base table column, domain, and routine (input or otput) parameter (as their type). Do not keep in your database elements that are not needed by anybody. These should be put in use or dropped, otherwise these are dead code.
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 (opens in new tab)
Fixing Suggestion Use the type at least once or drop it. It is possible that an enumerated type is used as the type of a variable in a routine. In this case dropping the type succeeds although it invalidates the routine.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
WITH input_parameters AS (SELECT unnest(proargtypes) AS parameter_type
FROM pg_proc),
enumeration_types AS (SELECT t.oid, nspname AS type_schema, typname, array_agg(enumlabel ORDER BY enumsortorder) AS values
FROM pg_catalog.pg_type t LEFT JOIN pg_catalog.pg_enum e ON t.oid=e.enumtypid
INNER JOIN pg_catalog.pg_namespace n ON n.oid=t.typnamespace
WHERE nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL) 
AND t.typtype='e'
GROUP BY t.oid, nspname, typname)
SELECT  type_schema, typname, values
FROM enumeration_types AS et
WHERE NOT EXISTS (SELECT 1
FROM pg_attribute 
WHERE pg_attribute.atttypid=et.oid)
AND NOT EXISTS (SELECT 1
FROM pg_proc 
WHERE pg_proc.prorettype=et.oid)
AND NOT EXISTS (SELECT 1
FROM input_parameters 
WHERE input_parameters.parameter_type=et.oid)
AND NOT EXISTS (SELECT 1
FROM pg_type
WHERE pg_type.typbasetype =et.oid)
ORDER BY type_schema, typname;

SQL statements that help generate fixes for the identified problem.

Fix Action #1
WITH input_parameters AS (SELECT unnest(proargtypes) AS parameter_type
FROM pg_proc),
enumeration_types AS (SELECT t.oid, n.nspname AS type_schema,
t.typname AS type_name
FROM pg_type AS t INNER JOIN pg_namespace AS n ON n.oid=t.typnamespace
INNER JOIN pg_authid AS a ON n.nspowner=a.oid
WHERE (n.nspname='public' OR rolname<>'postgres')
AND t.typtype='e'),
unused_types AS (SELECT  type_schema, type_name
FROM enumeration_types AS et
WHERE NOT EXISTS (SELECT 1
FROM pg_attribute 
WHERE pg_attribute.atttypid=et.oid)
AND NOT EXISTS (SELECT 1
FROM pg_proc 
WHERE pg_proc.prorettype=et.oid)
AND NOT EXISTS (SELECT 1
FROM input_parameters 
WHERE input_parameters.parameter_type=et.oid)
AND NOT EXISTS (SELECT 1
FROM pg_type
WHERE pg_type.typbasetype =et.oid))
SELECT format('DROP TYPE %1$I.%2$I RESTRICT;', type_schema, type_name) AS statements
FROM unused_types
ORDER BY type_schema, type_name;

Drop the enumerated type.

SQL Query to Generate FixDescription
WITH input_parameters AS (SELECT unnest(proargtypes) AS parameter_type
FROM pg_proc),
enumeration_types AS (SELECT t.oid, n.nspname AS type_schema,
t.typname AS type_name
FROM pg_type AS t INNER JOIN pg_namespace AS n ON n.oid=t.typnamespace
INNER JOIN pg_authid AS a ON n.nspowner=a.oid
WHERE (n.nspname='public' OR rolname<>'postgres')
AND t.typtype='e'),
unused_types AS (SELECT  type_schema, type_name
FROM enumeration_types AS et
WHERE NOT EXISTS (SELECT 1
FROM pg_attribute 
WHERE pg_attribute.atttypid=et.oid)
AND NOT EXISTS (SELECT 1
FROM pg_proc 
WHERE pg_proc.prorettype=et.oid)
AND NOT EXISTS (SELECT 1
FROM input_parameters 
WHERE input_parameters.parameter_type=et.oid)
AND NOT EXISTS (SELECT 1
FROM pg_type
WHERE pg_type.typbasetype =et.oid))
SELECT format('DROP TYPE %1$I.%2$I RESTRICT;', type_schema, type_name) AS statements
FROM unused_types
ORDER BY type_schema, type_name;
Drop the enumerated type.

Collections

This query belongs to the following collections:

Find problems automatically

Queries, 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 .

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:

Comfortability of database evolution

Queries of this category provide information about the means that influence database evolution.

Data types

Queries of this category provide information about the data types and their usage.

Unused implementation elements

Queries of this catergory provide information about the database objects that are not used.

User-defined types

Queries of this category provide information about user-defined types in the database.

NameDescription
Comfortability of database evolutionQueries of this category provide information about the means that influence database evolution.
Data typesQueries of this category provide information about the data types and their usage.
Unused implementation elementsQueries of this catergory provide information about the database objects that are not used.
User-defined typesQueries of this category provide information about user-defined types in the database.

Further reading and related materials:

https://en.wikipedia.org/wiki/Dead_code
The corresponding code smells in case of cleaning code are "F4: Dead Function" and "G9: Dead Code". (Robert C. Martin, Clean Code)
Reference
https://en.wikipedia.org/wiki/Dead_code
The corresponding code smells in case of cleaning code are "F4: Dead Function" and "G9: Dead Code". (Robert C. Martin, Clean Code)