Find composite foreign keys with a mix of mandatory and optional columns. In case of a composite foreign keys all the columns should either optional or mandatory in order to avoid problems with NULLs.
Type
Problem detection (Each row in the result could represent a flaw in the design)
If possible, then declare to all the foreign key columns NOT NULL constraint. If there indeed must be a mix of mandatory and optional columns in the foreign key, then make sure that the match type is FULL in this case in order to avoid problems with NULLs.
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,
unnest(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,
unnest(o.conkey) AS target_col,
CASE WHEN o.confmatchtype='f' THEN 'FULL'
WHEN o.confmatchtype='p' THEN 'PARTIAL'
WHEN o.confmatchtype='s' THEN 'SIMPLE' END AS match_type
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 cardinality(o.confkey)>1),
fk_grouped as (
select fk.conname, fk.foreign_schema, array_agg(fk.foreign_table || '.' || a_foreign.attname order by a_foreign.attnum) as foreign_col, fk.target_schema, array_agg(fk.target_table || '.' || a_target.attname order by a_target.attnum) as target_col,
array_agg(a_target.attnotnull order by a_target.attnum) as target_not_null, match_type
from fk inner join pg_attribute a_foreign on fk.foreign_col = 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 = a_target.attnum and fk.target_table_oid = a_target.attrelid and a_target.attisdropped = false
group by fk.conname, fk.foreign_schema, fk.target_schema, match_type)
select conname, foreign_schema, foreign_col, target_schema, target_col, target_not_null, match_type
from fk_grouped
where target_not_null @> array['f']::boolean[] and target_not_null @> array['t']::boolean[]
order by conname, target_schema, target_col, match_type;
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
Missing data
Queries of this category provide information about missing data (NULLs) in a database.
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.