Routine for reading data uses another routine to read some data

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Goal Find routines that only read data but invoke some other routine to read some more data.
Notes The query only considers routines that have SQL-standard body. 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 License
Fixing Suggestion In terms of performance it might be better to have one query instead of a query that invokes a function to read data from some other table.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
WITH select_routines AS (SELECT 
  pg_namespace.nspname AS specific_schema, 
  pg_proc.proname AS routine_name, 
  pg_proc.proname || '_' || pg_proc.oid AS specific_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]','
','g')  AS routine_src,
  pg_language.lanname AS routine_language
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_proc.prokind<>'a'  
  AND pg_get_functiondef(pg_proc.oid)~*'([[:space:]]*SELECT[[:space:]]|[[:space:]]*PERFORM[[:space:]]).+[[:space:]]FROM[[:space:]]'
  AND pg_get_functiondef(pg_proc.oid)!~*'(insert|update[^;]+set[[:space:]]|delete)'
  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))

SELECT r.specific_schema AS user_schema, r.routine_name AS user_name, r.parameters AS user_parametes, r.routine_type AS user_type, r.routine_src AS user_src,
r2.specific_schema AS used_schema, r2.routine_name AS used_name, r2.parameters AS used_parametes, r2.routine_type AS used_type, r2.routine_src AS used_src
FROM select_routines AS r INNER JOIN INFORMATION_SCHEMA.routine_routine_usage AS rru USING (specific_schema, specific_name)
INNER JOIN select_routines AS r2 ON rru.routine_schema=r2.specific_schema AND rru.routine_name=r2.specific_name
ORDER BY r.specific_schema, r.routine_name, r.parameters;
Categories

This query is classified under the following categories:

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