Goal Find routines with multiple raise exception commands. Perhaps it has multiple tasks and it violates the separation of concerns and single responsibilities principles.
Notes Refers to the column pg_proc.prokind and thus works starting from PostgreSQL 11. In the returned body of routine the query replaces each newline character with the line break (br) tag for the better readability in case the query result is displayed in a web browser. There could be multiple routines with the same name but with different parameters in the same schema (overloading). Thus, for the unique identification of the routine it is necessary to present also its parameters in addition to the schema name and routine name.
Type Problem detection (Each row in the result could represent a flaw in the design)
Reliability Low (Many false-positive results)
License MIT (opens in new tab)
Fixing Suggestion Create multiple triggers where each has a WHEN clause.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
SELECT 
  pg_namespace.nspname AS routine_schema, 
  pg_proc.proname AS routine_name, 
  pg_get_function_identity_arguments(pg_proc.oid) AS parameters,
  CASE WHEN pg_proc.prokind='f' THEN 'FUNCTION'
  WHEN pg_proc.prokind='p' THEN 'PROCEDURE'
  WHEN pg_proc.prokind='w' THEN 'WINDOW FUNCTION' END AS routine_type,
  regexp_replace(pg_get_functiondef(pg_proc.oid),'[\r\n]','<br>','g')  AS routine_src
FROM 
  pg_catalog.pg_proc, 
  pg_catalog.pg_namespace,
  pg_catalog.pg_language
WHERE 
  pg_proc.pronamespace = pg_namespace.oid 
  AND pg_proc.prolang = pg_language.oid 
  AND pg_language.lanname='plpgsql' 
  AND pg_proc.prokind<>'a' 
  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_get_functiondef(pg_proc.oid)~*'raise[[:space:]]+exception[[:space:]].+raise[[:space:]]+exception[[:space:]]'
 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)
ORDER BY routine_schema, routine_name, parameters;

Categories

This query is classified under the following categories:

Does not work in some earlier PostgreSQL version

Queries of this category provide information that was not available in some earlier PostgreSQL version

Triggers and rules

Queries of this category provide information about triggers and rules in a database.

NameDescription
Does not work in some earlier PostgreSQL versionQueries of this category provide information that was not available in some earlier PostgreSQL version
Triggers and rulesQueries of this category provide information about triggers and rules in a database.

Further reading and related materials:

https://en.wikipedia.org/wiki/Separation_of_concerns
The corresponding code smell in case of cleaning code is "G23: Prefer Polymorphism to If/Else or Switch/Case". (Robert C. Martin, Clean Code)
Reference
https://en.wikipedia.org/wiki/Separation_of_concerns
The corresponding code smell in case of cleaning code is "G23: Prefer Polymorphism to If/Else or Switch/Case". (Robert C. Martin, Clean Code)