Very similar (but not equal) routine names

CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;
WITH routines AS (SELECT routine_schema, routine_name, specific_name, routine_type
FROM INFORMATION_SCHEMA.routines AS r
WHERE routine_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
AND NOT EXISTS (SELECT 1
FROM pg_catalog.pg_depend d inner join pg_catalog.pg_proc pc ON d.objid=pc.oid
WHERE EXISTS (SELECT 1 FROM pg_catalog.pg_extension e WHERE d.refobjid=e.oid) AND
pc.proname || '_' || pc.oid = r.specific_name))
SELECT r1.routine_schema AS routine1_schema, r1.routine_name AS routine1_name, r1.routine_type AS routine1_type, 
r2.routine_schema AS routine2_schema, r2.routine_name AS routine2_name, r2.routine_type AS routine1_type
FROM routines AS r1, routines AS r2
WHERE r1.specific_name<>r2.specific_name
AND r1.routine_name<>r2.routine_name
AND levenshtein(r1.routine_name,r2.routine_name)=1
ORDER BY routine1_name, routine2_name;

DROP EXTENSION IF EXISTS fuzzystrmatch;