Query goal: | Find views with exactly the same subquery. There should not be multiple views with exactly the same subquery. 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. |
Notes about the query: | In the returned subquery of view the query replaces each newline character with the line break (br) tag for the better readability in case the query result is displayed in a web browser. In case of the string_agg function, the line break (br) tag is used as a part of the separator for the better readability in case the query result is displayed in a web browser. |
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 views. |
Data source: | INFORMATION_SCHEMA only |
SQL query: | Click on query to copy it
SELECT regexp_replace(view_definition,'[\r\n]','<br>','g') AS view_definition, views, number_of_views FROM (SELECT view_definition, string_agg(table_schema || '.'|| table_name,';<br>' ORDER BY table_schema || '.'|| table_name) AS views, Count(*) AS number_of_views FROM information_schema.views WHERE 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) GROUP BY view_definition HAVING Count(*)>1) AS duplicate_views ORDER BY number_of_views DESC; |
SQL query | Description |
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WITH duplicate_views AS (SELECT view_definition, array_agg(table_schema || '.' || table_name) AS view_array FROM information_schema.views WHERE 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) GROUP BY view_definition HAVING Count(*)>1) SELECT format('DROP VIEW %1$s;', unnest(view_array)) AS statements FROM duplicate_views ORDER BY view_definition; | Drop the view. One of the views must stay in place. |
Collection name | Collection description |
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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 . |
Category name | Category description |
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Comfortability of database evolution | Queries of this category provide information about the means that influence database evolution. |
Derived tables | Queries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer. |
Duplication of implementation elements | Queries of this catergory provide information about the duplication of the database objects. |
Reference |
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https://refactoring.guru/smells/alternative-classes-with-different-interfaces |
https://refactoring.guru/smells/duplicate-code |
The corresponding code smell in case of cleaning code is "G5: Duplication". (Robert C. Martin, Clean Code) |