Find foreign key constraints that completely overlap with a candidate key constraint (primary key or unique constraint) but the foreign key constraint does not have the ON DELETE CASCADE compensating action. In this case there is a foreign key that implements a relationship type between a strong entity type and a weak entity type (1-1 relationship type). Therefore, in this case ON DELETE CASCADE is an appropriate compensating action.
Notes
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Type
Problem detection (Each row in the result could represent a flaw in the design)
Drop the foreign key constraint and recreate with ON DELETE CASCADE compensating action.
Data Source
system catalog only
SQL Query
with keys as (select
o.conname,
(select nspname from pg_namespace where oid=c.relnamespace) as key_schema,
c.relname as key_table,
c.oid as key_table_oid,
o.conkey AS key_col
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
where o.contype in ('u', 'p')),
keys_unnest as (select conname, key_schema, key_table, key_table_oid, key_col, key_col_num, ordin
from keys, unnest(keys.key_col) with ordinality as k(key_col_num, ordin)),
keys_with_names AS (select key_schema, key_table, array_agg(a_key.attname order by ordin) as key_col
from keys_unnest k inner join pg_attribute a_key on k.key_col_num = a_key.attnum and k.key_table_oid = a_key.attrelid and a_key.attisdropped = false
group by conname, key_schema, key_table
),
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 foreign_col_num) as foreign_col, target_schema, target_table, array_agg(a_target.attname order by target_col_num) 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)
SELECT f.*
FROM fk_with_names AS f, keys_with_names AS k
WHERE f.target_schema=k.key_schema
AND f.target_table=k.key_table
AND f.target_col = k.key_col
AND f.on_delete<>'CASCADE'
ORDER BY target_table, target_schema, target_col, foreign_schema, foreign_table, foreign_col;
SQL statements that help generate fixes for the identified problem.
SQL Query to Generate Fix
Description
WITH fk AS (SELECT
o.conname,
(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
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' and o.confdeltype<>'c'),
ck AS (SELECT
o.conname,
(SELECT nspname FROM pg_namespace WHERE oid=c.relnamespace) AS target_schema,
c.relname AS target_table,
o.conkey
FROM pg_constraint o INNER JOIN pg_class c on c.oid = o.conrelid
WHERE o.contype in ('p','u')),
one_to_one AS (SELECT fk.conname, fk.target_schema, fk.target_table, unnest(fk.conkey) AS target_column, fk.target_table_oid
FROM fk,ck
WHERE fk.target_schema=ck.target_schema AND fk.target_table=ck.target_table AND fk.conkey <@ ck.conkey AND fk.conkey @> ck.conkey)
SELECT format('ALTER TABLE %1$I.%2$I DROP CONSTRAIN %3$I;', target_schema, target_table, conname) AS statements
FROM one_to_one o INNER JOIN pg_attribute a on o.target_column = a.attnum and o.target_table_oid = a.attrelid
GROUP BY conname, target_schema, target_table
ORDER BY target_schema, target_table, conname;
Drop the foreign key constraint.
Collections
This query belongs to the following collections:
Name
Description
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 .
Categories
This query is classified under the following categories:
Name
Description
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.
Validity and completeness
Queries of this category provide information about whether database design represents the world (domain) correctly (validity) and whether database design captures all the information about the world (domain) that is correct and relevant (completeness).