Duplicate DEFAULT values of base table columns

Query goal:	Find base table columns that have both default value determined through a domain and default value that is directly attached to the column. Do not duplicate specifications of default values to avoid confusion and surprises. If column and domain both have a default value, then in case of inserting data the default value that is associated directly with the column is used.
Query type:	Problem detection (Each row in the result could represent a flaw in the design)
Query reliability:	High (Few or no false-positive results)
Query license:	MIT License
Fixing suggestion:	Drop either the default value of the domain or the default value that is directly associated with the column. If you drop the default value of the domain, then do not forget that the domain could be used in case of different columns.
Data source:	INFORMATION_SCHEMA only
SQL query:	Click on query to copy it SELECT c.table_schema, c.table_name, c.column_name, c.data_type, c.domain_schema, c.domain_name, c.column_default, domain_default FROM information_schema.columns AS c INNER JOIN information_schema.domains d USING (domain_schema, domain_name) WHERE c.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) AND column_default IS NOT NULL AND domain_default IS NOT NULL ORDER BY c.table_schema, c.table_name, c.column_name;

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

SQL query	Description
WITH duplicate_defaults AS (SELECT c.table_schema, c.table_name, c.column_name, c.data_type, c.domain_schema, c.domain_name, c.column_default, domain_default FROM information_schema.columns AS c INNER JOIN information_schema.domains d USING (domain_schema, domain_name) WHERE c.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) AND column_default IS NOT NULL AND domain_default IS NOT NULL) SELECT DISTINCT format('ALTER DOMAIN %1$I.%2$I DROP DEFAULT;', domain_schema, domain_name) AS statements FROM duplicate_defaults ORDER BY statements;	Drop the domain default.
WITH duplicate_defaults AS (SELECT c.table_schema, c.table_name, c.column_name, c.data_type, c.domain_schema, c.domain_name, c.column_default, domain_default FROM information_schema.columns AS c INNER JOIN information_schema.domains d USING (domain_schema, domain_name) WHERE c.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) AND column_default IS NOT NULL AND domain_default IS NOT NULL) SELECT DISTINCT format('ALTER TABLE %1$I.%2$I ALTER COLUMN %3$I DROP DEFAULT;', table_schema, table_name, column_name) AS statements FROM duplicate_defaults ORDER BY statements;	Drop the column default.

SQL query

Description

WITH duplicate_defaults AS (SELECT c.table_schema, c.table_name, c.column_name,  c.data_type, c.domain_schema, c.domain_name, c.column_default, domain_default
FROM information_schema.columns AS c INNER JOIN information_schema.domains d USING (domain_schema, domain_name)
WHERE c.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) 
AND column_default IS NOT NULL 
AND domain_default IS NOT NULL)
SELECT DISTINCT format('ALTER DOMAIN %1$I.%2$I DROP DEFAULT;', domain_schema, domain_name) AS statements
FROM duplicate_defaults 
ORDER BY statements;

Drop the domain default.

WITH duplicate_defaults AS (SELECT c.table_schema, c.table_name, c.column_name,  c.data_type, c.domain_schema, c.domain_name, c.column_default, domain_default
FROM information_schema.columns AS c INNER JOIN information_schema.domains d USING (domain_schema, domain_name)
WHERE c.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) 
AND column_default IS NOT NULL 
AND domain_default IS NOT NULL)
SELECT DISTINCT format('ALTER TABLE %1$I.%2$I ALTER COLUMN %3$I DROP DEFAULT;', table_schema, table_name, column_name) AS statements
FROM duplicate_defaults 
ORDER BY statements;

Drop the column default.

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 .

Categories where the query belongs to

Category name	Category description
Comfortability of database evolution	Queries of this category provide information about the means that influence database evolution.
Comfortability of data management	Queries 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.
Default value	Queries of this catergory provide information about the use of default values.
Domains	Queries of this category provide information about reusable specifications of column properties.
Duplication of implementation elements	Queries of this catergory provide information about the duplication of the database objects.

Reference materials for further reading

Reference
https://en.wikipedia.org/wiki/Duplicate_code
The corresponding code smell in case of cleaning code is "G5: Duplication". (Robert C. Martin, Clean Code)

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