Goal Find derived tables (views and materialized views) that sort rows based on random values. This can be used to find a random subset of rows. It is a computationally expensive operation.
Notes In the returned subquery of view/materialized view 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 Bill Karwin in his book of SQL database design antipatterns offers various alternatives for finding a random subset of rows.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
SELECT
table_schema,
table_name,
type,
regexp_replace(view_definition,'[\r\n]','<br>','g') AS view_definition
FROM (SELECT 
views.table_schema, 
views.table_name, 
'VIEW' AS type,
views.view_definition
FROM 
information_schema.views
WHERE table_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
UNION SELECT schemaname, matviewname, 'MATERIALIZED VIEW' AS type, regexp_replace(definition,'[\r\n]','<br>','g') AS definition
FROM pg_catalog.pg_matviews) AS foo
WHERE view_definition ~*'order[[:space:]]+by[[:space:]]+[(]random[(][)][)]'
ORDER BY table_schema, table_name;

Categories

This query is classified under the following categories:

Derived tables

Queries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer.

Performance

Queries of this category provide information about indexes in a database.

NameDescription
Derived tablesQueries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer.
PerformanceQueries of this category provide information about indexes in a database.

Further reading and related materials:

This is one of the antipatterns from the Bill Karwin's book of SQL antipatterns. See Chapter 16: Random Selection.
Reference
This is one of the antipatterns from the Bill Karwin's book of SQL antipatterns. See Chapter 16: Random Selection.