There is no reason to use PL/pgSQL to write table functions

Query goal:

Using PL/pgSQL may cause context switching between declarative SQL and procedural PL/pgSQL. Thus use PL/pgSQL only if you truly need some of its constructs. You can create table functions by using SQL.

Notes about the query:

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.

Query type:

Problem detection (Each row in the result could represent a flaw in the design)

Query reliability:

High (Few or no false-positive results)

Query license:

MIT License

Fixing suggestion:

Use SQL language to write a table function.

Data source:

INFORMATION_SCHEMA+system catalog

SQL query:

Click on query to copy it

SELECT 
  pg_namespace.nspname AS routine_schema, 
  pg_proc.proname AS routine_name,
  pg_get_function_identity_arguments(pg_proc.oid) AS parameters,
  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,
  pg_catalog.pg_type
WHERE 
  pg_proc.pronamespace = pg_namespace.oid 
  AND pg_proc.prolang = pg_language.oid 
  AND pg_type.oid=pg_proc.prorettype 
  AND pg_language.lanname='plpgsql' 
  AND pg_proc.prokind='f'  
  AND pg_proc.proretset=true 
  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)
ORDER BY routine_schema, routine_name, parameters;

Collections where the query belongs to

Collection name	Collection description
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 .

Collection name

Collection description

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 .

Categories where the query belongs to

Category name	Category description
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

Category name

Category description

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

Reference materials for further reading

Reference
https://www.postgresql.org/docs/current/xfunc-sql.html#XFUNC-SQL-FUNCTIONS-RETURNING-TABLE

Reference

https://www.postgresql.org/docs/current/xfunc-sql.html#XFUNC-SQL-FUNCTIONS-RETURNING-TABLE