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.
Type Problem detection (Each row in the result could represent a flaw in the design)
Reliability Medium (Medium number of false-positive results)
License MIT (opens in new tab)
Fixing Suggestion Drop the unnecessary constraints.
Data Source INFORMATION_SCHEMA+system catalog
SQL Query 
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 that help generate fixes for the identified problem.

Fix Action #1
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 to Generate FixDescription
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

This query belongs to the following collections:

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 .

NameDescription
Find problems automaticallyQueries, 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:

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).

NameDescription
Boolean dataQueries of this category provide information about truth-values data that is kept in the database.
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.
UniquenessQueries of this category provide information about uniqueness constraints (PRIMARY KEY, UNIQUE, EXCLUDE) as well as unique indexes.
Validity and completenessQueries 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).