This query identifies potential null-propagation defects in user-defined routines and views. It targets subqueries utilizing the standard concatenation operator (||) where operands are not protected by a coalesce() function. In PostgreSQL, the operation string || NULL yields NULL, causing the entire result to vanish if any component is missing. This behavior is often unintentional. The query flags these risky patterns, suggesting remediation via explicit null handling or the adoption of null-safe alternatives like concat(), concat_ws(), or format().
Notes
Refers to the column pg_proc.prokind and thus works starting from PostgreSQL 11. The query uses system information function pg_get_viewdef to get the view subquery pretty printed, i.e., without excessive brackets. The query does not consider the routines that are a part of an extension. In the returned body of subquery of view/materialized view/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)
For instance, let us assume that columns given_name and surname in table Person are both optional, i.e., permit NULLs. Instead of writing SELECT given_name || ' ' || surname FROM Person;, one should write SELECT Trim(coalesce(given_name,'') || ' ' || coalesce(surname,'')) AS person_name FROM Person; or SELECT concat_ws(' ', given_name, surname) AS person_name FROM Person;
Data Source
INFORMATION_SCHEMA+system catalog
SQL Query
WITH derived_tables AS (SELECT n.nspname AS schema_name,
c.relname AS object_name,
CASE WHEN c.relkind='v' THEN 'VIEW'
WHEN c.relkind='m' THEN 'MATERIALIZED VIEW'
END AS object_type,
pg_get_viewdef(c.oid, true) AS object_definition,
regexp_replace(pg_get_viewdef(c.oid, true),'[\r\n]',' ','g') AS object_def
FROM pg_namespace AS n INNER JOIN pg_authid AS a ON n.nspowner=a.oid
INNER JOIN pg_class AS c ON n.oid=c.relnamespace
WHERE (n.nspname='public' OR a.rolname<>'postgres')
AND relkind IN ('v','m')),
routines AS (SELECT
pg_namespace.nspname AS schema_name,
pg_proc.proname || '(' || pg_get_function_identity_arguments(pg_proc.oid) || ')' AS object_name,
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 object_type,
pg_get_functiondef(pg_proc.oid) AS object_definition,
regexp_replace( regexp_replace(pg_get_functiondef(pg_proc.oid),'<','<','g'),'[\r\n]',' ','g') AS object_def
FROM
pg_catalog.pg_proc,
pg_catalog.pg_namespace
WHERE
pg_proc.pronamespace = pg_namespace.oid
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_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)),
checked_elements AS (SELECT schema_name, object_name, object_type, object_definition, object_def
FROM derived_tables
UNION SELECT schema_name, object_name, object_type, object_definition, object_def
FROM routines)
SELECT schema_name, object_name, object_type, object_def
FROM checked_elements
WHERE object_definition ~*'[|][|]'
AND object_definition !~*'coalesce[[:space:]]*[(].+[|][|].+coalesce[[:space:]]*[(]'
ORDER BY schema_name, object_type, object_name;
Categories
This query is classified under the following categories:
Name
Description
Derived tables
Queries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer.
Does not work in some earlier PostgreSQL version
Queries of this category provide information that was not available in some earlier PostgreSQL version
Missing data
Queries of this category provide information about missing data (NULLs) in a database.
System-defined functions
Queries of this category provide information about the use of system-defined functions.
User-defined routines
Queries of this category provide information about the user-defined routines