Duplicate stored generated base table columns

Query goal:

Find base tables that have more than one stored generated column with the same expression. The support of generated columns was added to PostgreSQL 12. Do remember that the same task can be solved in SQL usually in multiple different ways. Thus, the exact copies are not the only possible duplication.

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:

All but one are redundant. Drop the redundant stored generated columns.

Data source:

INFORMATION_SCHEMA only

SQL query:

Click on query to copy it

SELECT table_schema, table_name, generation_expression, Count(*) AS number_of_occurrences, string_agg(column_name, ';<br>' ORDER BY column_name) AS columns
FROM INFORMATION_SCHEMA.columns
WHERE (table_schema, table_name) IN (SELECT table_schema, table_name
FROM INFORMATION_SCHEMA.tables WHERE table_type='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) 
AND is_generated='ALWAYS'
GROUP BY table_schema, table_name, generation_expression
HAVING Count(*)>1
ORDER BY Count(*)>1 DESC, table_schema, table_name;

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

SQL query	Description
WITH duplicate_columns AS (SELECT table_schema, table_name, generation_expression, array_agg(column_name) AS columns FROM INFORMATION_SCHEMA.columns WHERE (table_schema, table_name) IN (SELECT table_schema, table_name FROM INFORMATION_SCHEMA.tables WHERE table_type='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) AND is_generated='ALWAYS' GROUP BY table_schema, table_name, generation_expression HAVING Count(*)>1) SELECT DISTINCT format('ALTER TABLE %1$I.%2$I DROP COLUMN %3$I;', table_schema, table_name, unnest(columns)) AS statements FROM duplicate_columns ORDER BY statements;	Drop the column. One of the columns must stay in place.

SQL query

Description

WITH duplicate_columns AS (SELECT table_schema, table_name, generation_expression, array_agg(column_name) AS columns
FROM INFORMATION_SCHEMA.columns
WHERE (table_schema, table_name) IN (SELECT table_schema, table_name
FROM INFORMATION_SCHEMA.tables WHERE table_type='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) 
AND is_generated='ALWAYS'
GROUP BY table_schema, table_name, generation_expression
HAVING Count(*)>1)
SELECT DISTINCT format('ALTER TABLE %1$I.%2$I DROP COLUMN %3$I;', table_schema, table_name, unnest(columns)) AS statements
FROM duplicate_columns 
ORDER BY statements;

Drop the column. One of the columns must stay in place.

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
Duplication of implementation elements	Queries of this catergory provide information about the duplication of the database objects.
Generated columns	Queries of this category provide information about generated stored base table columns.

Category name

Category description

Duplication of implementation elements

Queries of this catergory provide information about the duplication of the database objects.

Generated columns

Queries of this category provide information about generated stored base table columns.