Goal This query identifies foreign key constraints that use ON DELETE CASCADE in a non-identifying relationship. A relationship is considered non-identifying if the foreign key columns in the child table are not part of the child table's candidate key. In such cases, the child entity has its own independent identity, and using ON DELETE CASCADE is often a design flaw that can lead to unexpected and catastrophic data loss.
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 Remove ON DELETE CASCADE. If the foreign key columns are mandatory, then ON DELETE NO ACTION is probably the best replacement.
Data Source system catalog only
SQL Query 
WITH fk as (select
o.conname,
(select nspname from pg_namespace where oid=f.relnamespace) as foreign_schema,
f.relname as foreign_table,
f.oid as foreign_table_oid,
o.confkey AS foreign_col,
(select nspname from pg_namespace where oid=c.relnamespace) as target_schema,
c.relname as target_table,
c.oid as target_table_oid,
o.conkey AS target_col,
CASE WHEN o.confupdtype='a' THEN 'NO ACTION'
WHEN o.confupdtype='r' THEN 'RESTRICT'
WHEN o.confupdtype='c' THEN 'CASCADE'
WHEN o.confupdtype='n' THEN 'SET NULL'
WHEN o.confupdtype='d' THEN 'SET DEFAULT' END AS on_update,
CASE WHEN o.confdeltype='a' THEN 'NO ACTION'
WHEN o.confdeltype='r' THEN 'RESTRICT'
WHEN o.confdeltype='c' THEN 'CASCADE'
WHEN o.confdeltype='n' THEN 'SET NULL'
WHEN o.confdeltype='d' THEN 'SET DEFAULT' END AS on_delete
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
inner join pg_class f on f.oid = o.confrelid
where o.contype = 'f'),
fk_unnest as (select conname, foreign_schema, foreign_table,  foreign_table_oid, foreign_col, foreign_col_num, target_schema, target_table, target_table_oid, target_col, target_col_num, ordin, on_update, on_delete
from fk, unnest(fk.foreign_col, fk. target_col) with ordinality as f(foreign_col_num, target_col_num, ordin)),
fk_with_names as (select conname, foreign_schema, foreign_table, array_agg(a_foreign.attname order by ordin) as foreign_col, target_schema, target_table, array_agg(a_target.attname order by ordin) as target_col, on_update, on_delete
from fk_unnest fk inner join pg_attribute a_foreign on fk.foreign_col_num = a_foreign.attnum and fk.foreign_table_oid = a_foreign.attrelid and a_foreign.attisdropped = false
inner join pg_attribute a_target on fk.target_col_num = a_target.attnum and fk.target_table_oid = a_target.attrelid and a_target.attisdropped = false
group by conname, foreign_schema, foreign_table, target_schema, target_table,on_update, on_delete, target_col),

key as (select
(select nspname from pg_namespace where oid=c.relnamespace) as target_schema,
c.relname as target_table,
c.oid as target_table_oid,
o.conkey AS target_col
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
where o.contype in ('p','u','x')),
key_unnest as (select target_schema, target_table, target_table_oid, target_col, target_col_num, ordin
from key, unnest(key.target_col) with ordinality as f(target_col_num, ordin)),
key_with_names as (select target_schema, target_table, array_agg(a_target.attname order by ordin) as target_col
from key_unnest key inner join pg_attribute a_target on key.target_col_num = a_target.attnum and key.target_table_oid = a_target.attrelid and a_target.attisdropped = false and a_target.attnotnull=true
group by target_schema, target_table)

select fk.conname, fk.foreign_schema, fk.foreign_table, fk.foreign_col, fk.target_schema, fk.target_table, fk.target_col, fk.on_update, fk.on_delete, key.target_col as target_key_col
from fk_with_names as fk, key_with_names as key
where fk.target_schema=key.target_schema
and fk.target_table=key.target_table
and not (fk.target_col <@ key.target_col)
and fk.on_delete='CASCADE'
order by fk.target_schema, fk.target_table, fk.target_col, fk.foreign_schema, fk.foreign_table, fk.foreign_col;

Collections

This query belongs to the following collections:

Find problems about integrity constraints

A selection of queries that return information about the state of integrity constraints in the datadabase. Contains all the types of queries - problem detection, software measure, and general overview

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 about integrity constraintsA selection of queries that return information about the state of integrity constraints in the datadabase. Contains all the types of queries - problem detection, software measure, and general overview
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:

Comfortability of data management

Queries of this category provide information about the means that have been used to make the use or management of database more comfortable and thus, more efficient.

Compensating actions

Queries of this category provide information about compensating actions of foreign key constraints.

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.

NameDescription
Comfortability of data managementQueries of this category provide information about the means that have been used to make the use or management of database more comfortable and thus, more efficient.
Compensating actionsQueries of this category provide information about compensating actions of foreign key constraints.
Relationships between tablesQueries 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.