Find simple check constraints, i.e., check constraints that cover one column that seem to have multiple tasks. The corresponding code smell in case of cleaning code is "G30: Functions Should Do One Thing". (Robert C. Martin, Clean Code)
Notes
The query finds CHECK constraints that are associated with a base table directly as well as CHECK constraints that are associated with domains that are used to define at least one column. The query does not find CHECK constraints of domains that are not associated with any table.
Type
Problem detection (Each row in the result could represent a flaw in the design)
WITH all_simple_checks AS (SELECT
(SELECT nspname FROM pg_namespace WHERE oid=c.relnamespace) AS object_schema,
c.relname || '.' || a.attname AS target,
COALESCE(basetype.typname, t.typname) AS data_type,
o.conname AS constraint_name,
pg_get_constraintdef(o.oid) AS check_clause,
'TABLE CHECK' AS check_type
FROM pg_constraint o
INNER JOIN pg_class c ON c.oid = o.conrelid
INNER JOIN pg_attribute a ON a.attrelid = o.conrelid AND a.attnum = o.conkey[1]
INNER JOIN pg_type t ON a.atttypid = t.oid
LEFT JOIN pg_type basetype ON t.typtype = 'd' AND t.typbasetype = basetype.oid
WHERE o.contype = 'c' AND cardinality(o.conkey) = 1
UNION SELECT
ns.nspname AS object_schema,
t.typname AS target,
basetype.typname AS data_type,
c.conname AS constraint_name,
pg_get_constraintdef(c.oid) AS check_clause,
'DOMAIN CHECK' AS check_type
FROM pg_constraint c
INNER JOIN pg_type t ON c.contypid = t.oid
INNER JOIN pg_namespace ns ON t.typnamespace = ns.oid
INNER JOIN pg_type basetype ON t.typbasetype = basetype.oid
WHERE
c.contype = 'c'
AND c.contypid <> 0
AND pg_get_constraintdef(c.oid) <> 'CHECK ((VALUE IS NOT NULL))')
SELECT object_schema, target, check_clause, check_type, constraint_name
FROM all_simple_checks
WHERE check_clause~*'[[:space:]]AND[[:space:]]'
AND check_clause!~*'[[:space:]]OR[[:space:]]'
AND check_clause~*'[[:space:]](=|<>|~|!~|~\*|!~\*|~~|~~\*|!~~|!~~*)[[:space:]]'
ORDER BY check_type, object_schema, target;
Collections
This query belongs to the following collections:
Name
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
This query is classified under the following categories:
Name
Description
CHECK constraints
Queries of this category provide information about CHECK constraints.
Comfortability of database evolution
Queries of this category provide information about the means that influence database evolution.