This query identifies base tables with a potentially redundant key structure. It specifically targets those having more than one PRIMARY KEY or UNIQUE constraint defined on a single integer-type column whose name matches the surrogate key naming convention (id_* or *_id). This pattern is a strong indicator of multiple surrogate keys for the same entity, which can indicate an overcomplicated data model. A single entity should typically have only one system-generated identifier to maintain schema clarity, simplify join logic, and avoid redundancy. The presence of multiple such keys warrants a review to determine if one is superfluous.
Type
Problem detection (Each row in the result could represent a flaw in the design)
with simple_keys as (select
n.nspname as table_schema,
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 n on c.relnamespace=n.oid
where o.contype in ('u', 'p')
and c.relkind = 'r'
and cardinality(o.conkey)=1
and n.nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)),
integer_columns AS (SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.columns
WHERE data_type IN ('smallint', 'integer', 'bigint')
AND (table_schema, table_name) IN (SELECT table_schema, table_name
FROM INFORMATION_SCHEMA.tables
WHERE table_type IN ('BASE TABLE'))
AND table_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL))
SELECT table_schema, table_name, Count(*) AS number_of_simple_int_keys, string_agg (column_name, '; ' ORDER BY column_name) AS simple_int_keys
FROM simple_keys
WHERE (table_schema, table_name, column_name) IN (SELECT table_schema, table_name, column_name
FROM integer_columns)
AND (column_name~*'_id$'
OR column_name~*'^id_')
GROUP BY table_schema, table_name
HAVING Count(*) >1
ORDER BY Count(*) DESC, table_schema, table_name;
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
Duplication of implementation elements
Queries of this catergory provide information about the duplication of the database objects.
Result quality depends on names
Queries of this category use names (for instance, column names) to try to guess the meaning of a database object. Thus, the goodness of names determines the number of false positive and false negative results.
Uniqueness
Queries of this category provide information about uniqueness constraints (PRIMARY KEY, UNIQUE, EXCLUDE) as well as unique indexes.
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).