Goal This query assesses the extent of active logic implementation within the database schema. It verifies that there are at least 3 user-defined triggers or rewrite rules present in the database. These objects represent automated tasks that for example enforce complex integrity constraints. Meeting this threshold indicates a baseline competency in utilizing PostgreSQL's event-driven capabilities.
Notes This query implements a requirement that might occur in a learning situation. The condition in the query ensures that if the requirement is not fulfilled, then the query returns one row, otherwise it does not return a row. The result is achieved by using a PostgreSQL feature that permits SELECT statements without the FROM clause. The number of triggers+rules (three in this case) serves here as an example. It could be replaced with some other threshold. Rules are specific to PostgreSQL and thus it is not possible to get information about these from the INFORMATION_SCHEMA views.
Type Problem detection (Each row in the result could represent a flaw in the design)
Reliability High (Few or no false-positive results)
License MIT (opens in new tab)
Fixing Suggestion Create additional triggers or rules.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
WITH activedb AS (SELECT trigger_schema, trigger_name, 'TRIGGER' AS type
FROM information_schema.triggers
WHERE trigger_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 r.schemaname,  r.rulename, 'RULE' AS type
FROM 
  pg_catalog.pg_rules r, 
  pg_catalog.pg_namespace n, 
  pg_catalog.pg_authid u
WHERE 
  r.schemaname = n.nspname AND
  n.nspowner = u.oid AND (n.nspname = 'public' OR u.rolname <> 'postgres'))
SELECT 'Too few triggers and/or rules, must be at least three' As comment, (SELECT Count(*) AS cnt FROM activedb) AS the_number_of_triggers_rules
WHERE (SELECT Count(*) AS cnt FROM activedb)<3;

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:

Assessment

Queries of this category could be used specifically in the learning environment to assess as to whether student projects have filled certain criteria.

Triggers and rules

Queries of this category provide information about triggers and rules in a database.

NameDescription
AssessmentQueries of this category could be used specifically in the learning environment to assess as to whether student projects have filled certain criteria.
Triggers and rulesQueries of this category provide information about triggers and rules in a database.