Goal Use SQL language instead of PL/pgSQL where possible. Instead of using an IF statement, you can check as to whether the data modification succeeded or not by using the RETURNING clause in the data modification statement.
Notes Refers to the column pg_proc.prokind and thus works starting from PostgreSQL 11. 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. 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.
Type Problem detection Each row in the result could represent a flaw in the design
Reliability Medium Medium number of false-positive results
License MIT (opens in new tab)
Fixing Suggestion Instead of using conditionals to determine the returned value, one can check as to whether the data modification succeeded or not by using the RETURNING clause in the data modification statement. In this case it might be possible the routine written in PL/pgSQL with the routine written in SQL.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
SELECT 
  pg_namespace.nspname AS function_schema, 
  pg_proc.proname AS function_name, 
  pg_get_function_identity_arguments(pg_proc.oid) AS parameters,
  regexp_replace(pg_get_functiondef(pg_proc.oid),'[\r\n]','<br>','g')  AS function_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='f' 
  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)~*'(INSERT|UPDATE|DELETE)[^;]+;[[:space:]]+IF([[:space:]]+|[[:space:]]+NOT[[:space:]]+)FOUND[[:space:]]+THEN[[:space:]]*RETURN[[:space:]]+(TRUE|FALSE)[[:space:]]*;[[:space:]]*ELSE[[:space:]]*RETURN[[:space:]]+(TRUE|FALSE)[[:space:]]*;[[:space:]]*END[[:space:]]+IF'
 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 function_schema, function_name, parameters;

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:

Does not work in some earlier PostgreSQL version

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

User-defined routines

Queries of this category provide information about the user-defined routines

NameDescription
Does not work in some earlier PostgreSQL versionQueries of this category provide information that was not available in some earlier PostgreSQL version
User-defined routinesQueries of this category provide information about the user-defined routines