Using system-defined names of constraints (constraints that involve one column)

WITH pkey_constraint_names AS (
select 
'PRIMARY KEY' AS type,
o.conname AS constraint_name,
n.nspname as schema_name,
c.relname as table_name, 
(select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name
from pg_constraint o inner join pg_class c on c.oid = o.conrelid 
inner join pg_namespace AS n on n.oid=c.relnamespace
inner join pg_authid AS a ON n.nspowner=a.oid
where (n.nspname='public' OR a.rolname<>'postgres')
and o.contype ='p'  and cardinality(o.conkey)=1),

ukey_constraint_names AS (
select 
'UNIQUE' AS type,
o.conname AS constraint_name,
n.nspname as schema_name,
c.relname as table_name, 
(select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name
from pg_constraint o inner join pg_class c on c.oid = o.conrelid 
inner join pg_namespace AS n on n.oid=c.relnamespace
inner join pg_authid AS a ON n.nspowner=a.oid
where (n.nspname='public' OR a.rolname<>'postgres')
and o.contype ='u'  and cardinality(o.conkey)=1),

chk_constraint_names AS (select 
'CHECK' AS type,
o.conname AS constraint_name,
(select nspname from pg_namespace where oid=c.relnamespace) as schema_name,
c.relname as table_name, 
(select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name
from pg_constraint o inner join pg_class c on c.oid = o.conrelid 
inner join pg_namespace AS n on n.oid=c.relnamespace
inner join pg_authid AS a ON n.nspowner=a.oid
where (n.nspname='public' OR a.rolname<>'postgres')
and o.contype ='c'  and cardinality(o.conkey)=1),

fk_constraint_names AS (select 
'FOREIGN KEY' AS type,
o.conname AS constraint_name,
n.nspname as schema_name,
c.relname as table_name, 
(select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name
from pg_constraint o inner join pg_class c on c.oid = o.conrelid 
inner join pg_namespace AS n on n.oid=c.relnamespace
inner join pg_authid AS a ON n.nspowner=a.oid
where (n.nspname='public' OR a.rolname<>'postgres')
and o.contype ='f'  and cardinality(o.conkey)=1),

exclude_constraint_names AS (select 
'EXCLUDE' AS type,
o.conname AS constraint_name,
n.nspname as schema_name,
c.relname as table_name, 
(select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name
from pg_constraint o inner join pg_class c on c.oid = o.conrelid 
inner join pg_namespace AS n on n.oid=c.relnamespace
inner join pg_authid AS a ON n.nspowner=a.oid
where (n.nspname='public' OR a.rolname<>'postgres')
and o.contype ='x'  and cardinality(o.conkey)=1),

stats AS (SELECT type, Count(*) AS cnt_total, 
Count(*) FILTER (WHERE lower(constraint_name) = lower(table_name) || '_pkey') AS cnt_system_generated
FROM pkey_constraint_names
GROUP BY type

UNION SELECT type, Count(*) AS cnt_total, 
Count(*) FILTER (WHERE lower(constraint_name) = lower(table_name) || '_' || lower(column_name) || '_key') AS cnt_system_generated
FROM ukey_constraint_names
GROUP BY type

UNION SELECT type, Count(*) AS cnt_total, 
Count(*) FILTER (WHERE regexp_like(constraint_name, '^' || table_name || '_' || column_name || '_check[[:digit:]]*$','i')) AS cnt_system_generated
FROM chk_constraint_names
GROUP BY type

UNION SELECT type, Count(*) AS cnt_total, 
Count(*) FILTER (WHERE regexp_like(constraint_name, '^' || table_name || '_' || column_name || '_fkey[[:digit:]]*$','i')) AS cnt_system_generated
FROM fk_constraint_names
GROUP BY type

UNION SELECT type, Count(*) AS cnt_total, 
Count(*) FILTER (WHERE lower(constraint_name) = lower(table_name) || '_' || lower(column_name) || '_excl') AS cnt_system_generated
FROM exclude_constraint_names
GROUP BY type
)
SELECT type AS constraint_type, cnt_total AS number_of_constraints, cnt_system_generated AS number_of_constraints_with_system_generated_names, cnt_total - cnt_system_generated AS number_of_constraints_with_user_defined_names
FROM stats
WHERE cnt_system_generated>0
ORDER BY cnt_system_generated DESC, constraint_type;

Query goal:	Find the constraint types in case of which there exists system-defined names.
Notes about the query:	The query considers only constraints that involve one column. PostgreSQL 14 added primary keys, unique constraints, and foreign keys to system catalogs. Thus the query was modified to exclude the results from the system catalog. The query uses regexp_like() function that was added to PostgreSQL 15.
Query type:	Problem detection (Each row in the result could represent a flaw in the design)
Query reliability:	Medium (Medium number of false-positive results)
Query license:	MIT License
Fixing suggestion:	Give names to constraints explicitly. Use a uniform style.
Data source:	system catalog only
SQL query:	Click on query to copy it WITH pkey_constraint_names AS ( select 'PRIMARY KEY' AS type, o.conname AS constraint_name, n.nspname as schema_name, c.relname as table_name, (select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name from pg_constraint o inner join pg_class c on c.oid = o.conrelid inner join pg_namespace AS n on n.oid=c.relnamespace inner join pg_authid AS a ON n.nspowner=a.oid where (n.nspname='public' OR a.rolname<>'postgres') and o.contype ='p' and cardinality(o.conkey)=1), ukey_constraint_names AS ( select 'UNIQUE' AS type, o.conname AS constraint_name, n.nspname as schema_name, c.relname as table_name, (select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name from pg_constraint o inner join pg_class c on c.oid = o.conrelid inner join pg_namespace AS n on n.oid=c.relnamespace inner join pg_authid AS a ON n.nspowner=a.oid where (n.nspname='public' OR a.rolname<>'postgres') and o.contype ='u' and cardinality(o.conkey)=1), chk_constraint_names AS (select 'CHECK' AS type, o.conname AS constraint_name, (select nspname from pg_namespace where oid=c.relnamespace) as schema_name, c.relname as table_name, (select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name from pg_constraint o inner join pg_class c on c.oid = o.conrelid inner join pg_namespace AS n on n.oid=c.relnamespace inner join pg_authid AS a ON n.nspowner=a.oid where (n.nspname='public' OR a.rolname<>'postgres') and o.contype ='c' and cardinality(o.conkey)=1), fk_constraint_names AS (select 'FOREIGN KEY' AS type, o.conname AS constraint_name, n.nspname as schema_name, c.relname as table_name, (select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name from pg_constraint o inner join pg_class c on c.oid = o.conrelid inner join pg_namespace AS n on n.oid=c.relnamespace inner join pg_authid AS a ON n.nspowner=a.oid where (n.nspname='public' OR a.rolname<>'postgres') and o.contype ='f' and cardinality(o.conkey)=1), exclude_constraint_names AS (select 'EXCLUDE' AS type, o.conname AS constraint_name, n.nspname as schema_name, c.relname as table_name, (select a.attname from pg_attribute a where a.attrelid = c.oid and a.attnum = o.conkey[1] and a.attisdropped = false) as column_name from pg_constraint o inner join pg_class c on c.oid = o.conrelid inner join pg_namespace AS n on n.oid=c.relnamespace inner join pg_authid AS a ON n.nspowner=a.oid where (n.nspname='public' OR a.rolname<>'postgres') and o.contype ='x' and cardinality(o.conkey)=1), stats AS (SELECT type, Count() AS cnt_total, Count() FILTER (WHERE lower(constraint_name) = lower(table_name) \|\| '_pkey') AS cnt_system_generated FROM pkey_constraint_names GROUP BY type UNION SELECT type, Count() AS cnt_total, Count() FILTER (WHERE lower(constraint_name) = lower(table_name) \|\| '_' \|\| lower(column_name) \|\| '_key') AS cnt_system_generated FROM ukey_constraint_names GROUP BY type UNION SELECT type, Count() AS cnt_total, Count() FILTER (WHERE regexp_like(constraint_name, '^' \|\| table_name \|\| '_' \|\| column_name \|\| '_check[[:digit:]]$','i')) AS cnt_system_generated FROM chk_constraint_names GROUP BY type UNION SELECT type, Count() AS cnt_total, Count() FILTER (WHERE regexp_like(constraint_name, '^' \|\| table_name \|\| '_' \|\| column_name \|\| '_fkey[[:digit:]]$','i')) AS cnt_system_generated FROM fk_constraint_names GROUP BY type UNION SELECT type, Count() AS cnt_total, Count() FILTER (WHERE lower(constraint_name) = lower(table_name) \|\| '_' \|\| lower(column_name) \|\| '_excl') AS cnt_system_generated FROM exclude_constraint_names GROUP BY type ) SELECT type AS constraint_type, cnt_total AS number_of_constraints, cnt_system_generated AS number_of_constraints_with_system_generated_names, cnt_total - cnt_system_generated AS number_of_constraints_with_user_defined_names FROM stats WHERE cnt_system_generated>0 ORDER BY cnt_system_generated DESC, constraint_type;

Category name	Category description
CHECK constraints	Queries of this category provide information about CHECK constraints.
Naming	Queries of this category provide information about the style of naming.
Relationships between tables	Queries of this category provide information about how database tables are connected to each other and whether such connections have been explicitly defined and whether it has been done correctly.
Uniqueness	Queries of this category provide information about uniqueness constraints (PRIMARY KEY, UNIQUE, EXCLUDE) as well as unique indexes.

Using system-defined names of constraints (constraints that involve one column)

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Reference materials for further reading