Goal Find where a hierarchical structure is implemented in a base table by adding a foreign key that refers to a candidate key of the same table. Find only cases where the candidate key and foreign key column names are very similar (Levenshtein distance shorter than four).
Type Problem detection (Each row in the result could represent a flaw in the design)
Reliability Low (Many false-positive results)
License MIT License
Fixing Suggestion Rename the foreign key column to provide better meaning.
Data Source system catalog only
SQL Query
CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;
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
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_columns as (
select fk.conname, fk.foreign_schema, fk.foreign_table, a_foreign.attname as foreign_col, fk.target_schema, fk.target_table, a_target.attname as target_col
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)
select *
from fk_columns
where (foreign_schema=target_schema and foreign_table=target_table) 
and foreign_col<>target_col 
and length(foreign_col)<>1
and length(target_col)<>1
and levenshtein(foreign_col,target_col) <4
order by target_schema, target_table, conname;

DROP EXTENSION IF EXISTS fuzzystrmatch;
Categories

This query is classified under the following categories:

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.
Hierarchical dataQueries of this catergory provide information about storing hierarchical data in the database.
NamingQueries of this category provide information about the style of naming.
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.