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WITH routines AS (SELECT 
  pg_namespace.nspname AS specific_schema, 
  pg_proc.proname || '_' || pg_proc.oid AS specific_name
FROM 
  pg_catalog.pg_proc, 
  pg_catalog.pg_namespace,
  pg_catalog.pg_type
WHERE 
  pg_proc.pronamespace = pg_namespace.oid
  AND pg_proc.prorettype=pg_type.oid
  AND pg_type.typname<>'trigger'
  AND pg_proc.proname NOT IN ('f_assume_you_must_use_files', 'f_check_format_comma_separated_list', 'f_check_password', 'f_default_value_with_no_match') 
AND pg_namespace.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 NOT EXISTS (SELECT 1
FROM pg_catalog.pg_depend d 
WHERE EXISTS (SELECT 1 FROM pg_catalog.pg_extension e WHERE d.refobjid=e.oid) AND
d.objid=pg_proc.oid)),
in_params AS (SELECT specific_schema, specific_name
FROM information_schema.parameters 
WHERE parameter_mode='IN'),
parameters_stats AS (SELECT specific_schema, specific_name, Count(in_params.specific_name) AS nr_of_parameters
FROM routines LEFT JOIN in_params USING (specific_schema, specific_name)
GROUP BY specific_schema, specific_name)
SELECT nr_of_parameters, Count(*) AS nr_of_routines
FROM parameters_stats
GROUP BY nr_of_parameters
ORDER BY nr_of_routines DESC;