Query goal: | Depth of relational tree of a table T (DRT(T)) is defined by Piattini et al. (2001) as "the longest referential path between tables, from the table T to any other table in the schema". The result may help to classify the data. If the depth is 0, then probably the table contains classifers. Tables with the largest depth probably contain some extra information about main entities. |
Notes about the query: | The query finds transitive closure of tables. In other words it finds all possible paths between tables where it is possible to reach from one table to another based on parent-child relationships. The query assumes that these relationships have been enforced in the database by declaring foreign key (referential) constraints. |
Query type: | Sofware measure (Numeric values (software measures) about the database) |
Query license: | MIT License |
Data source: | system catalog only |
SQL query: | Click on query to copy it
WITH RECURSIVE transitive_closure AS ( WITH foo AS (SELECT conrelid AS child, confrelid AS parent FROM pg_constraint WHERE contype='f') SELECT child, parent, 1 AS distance, child || '.' || parent || '.' AS path_string FROM foo UNION ALL SELECT tc.child, e.parent, tc.distance + 1, tc.path_string || e.parent || '.' AS path_string FROM foo AS e INNER JOIN transitive_closure AS tc ON e.child = tc.parent WHERE tc.path_string NOT LIKE '%' || e.parent || '.%'), biggest_distance AS (SELECT child, Max(distance) AS depth FROM transitive_closure GROUP BY child) SELECT nc.nspname AS table_schema, c.relname AS table_name, depth FROM biggest_distance AS o INNER JOIN pg_class AS c ON o.child=c.oid INNER JOIN pg_namespace AS nc ON c.relnamespace=nc.oid INNER JOIN pg_authid AS a ON nc.nspowner=a.oid WHERE (nc.nspname='public' OR rolname<>'postgres') UNION SELECT nc.nspname AS table_schema, c.relname AS table_name, 0 AS depth FROM pg_class AS c INNER JOIN pg_namespace AS nc ON c.relnamespace=nc.oid INNER JOIN pg_authid AS a ON nc.nspowner=a.oid WHERE (nc.nspname='public' OR rolname<>'postgres') AND c.relkind='r' AND NOT EXISTS (SELECT * FROM pg_constraint WHERE contype='f' AND pg_constraint.conrelid=c.oid) ORDER BY depth DESC, table_schema, table_name; |
Collection name | Collection description |
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Find problems by overview | Queries that results point to different aspects of database that might have problems. A human reviewer has to decide based on the results as to whether there are problems or not . |
Find quick numeric overview of the database | Queries that return numeric values showing mostly the number of different types of database objects in the database |
Category name | Category description |
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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. |
Reference |
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Piattini, M., Calero, C., Sahraoui, H. A., & Lounis, H. (2001). Object-relational database metrics. L'Objet, 7(4), 477-496. |