BOOLEAN base table and foreign table columns with a PRIMARY KEY, UNIQUE, or FOREIGN KEY constraint that involves olnly this column

Query goal:

Find base table columns with the Boolean type that has a PRIMARY KEY, UNIQUE, or FOREIGN KEY constraint that involves only this column. Avoid unnecessary constraints. It is quite improbable that there must be such constraints. For instance, a table with PRIMARY KEY () or UNIQUE () constraint can have at most two rows.

Query type:

Problem detection (Each row in the result could represent a flaw in the design)

Query reliability:

Medium (Medium number of false-positive results)

Query license:

MIT License

Fixing suggestion:

Drop the unnecessary constraints.

Data source:

INFORMATION_SCHEMA+system catalog

SQL query:

Click on query to copy it

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,
o.conname AS constraint_name,
CASE WHEN o.contype='p' THEN 'PRIMARY KEY'
WHEN o.contype='u' THEN 'UNIQUE'
ELSE 'FOREIGN KEY' END AS constraint_type
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', 'f')
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)),
boolean_columns AS (SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.columns
WHERE data_type='boolean' 
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, column_name, constraint_name, constraint_type
FROM simple_keys
WHERE (table_schema, table_name, column_name) IN (SELECT table_schema, table_name, column_name
FROM boolean_columns)
ORDER BY table_schema, table_name, column_name;

SQL statements for generating SQL statements that help us to fix the problem

SQL query	Description
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, o.conname AS constraint_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', 'f') 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)), boolean_columns AS (SELECT table_schema, table_name, column_name FROM INFORMATION_SCHEMA.columns WHERE data_type='boolean' 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 format('ALTER TABLE %1$I.%2$I DROP CONSTRAINT %3$I CASCADE;', table_schema, table_name, constraint_name) AS statements FROM simple_keys WHERE (table_schema, table_name, column_name) IN (SELECT table_schema, table_name, column_name FROM boolean_columns) ORDER BY table_schema, table_name, column_name;	Drop the constraints.

SQL query

Description

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,
o.conname AS constraint_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', 'f')
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)),
boolean_columns AS (SELECT table_schema, table_name, column_name
FROM INFORMATION_SCHEMA.columns
WHERE data_type='boolean' 
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 format('ALTER TABLE %1$I.%2$I DROP CONSTRAINT %3$I CASCADE;', table_schema, table_name, constraint_name) AS statements
FROM simple_keys
WHERE (table_schema, table_name, column_name) IN (SELECT table_schema, table_name, column_name
FROM boolean_columns)
ORDER BY table_schema, table_name, column_name;

Drop the constraints.

Collections where the query belongs to

Collection name	Collection 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 .

Collection name

Collection 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 where the query belongs to

Category name	Category description
Boolean data	Queries of this category provide information about truth-values data that is kept in the 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.
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).

Category name

Category description

Boolean data

Queries of this category provide information about truth-values data that is kept in the 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.

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).