Find for each base table the list of derived tables (both views and materialized views) that refer to the base table. If the database is used through the public database interface (virtual data layer), then, ideally, each table is referred from the subquery of at least one derived table.
Notes
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.
Type
General (Overview of some aspect of the database.)
WITH derived_tables AS (SELECT t.table_schema, t.table_name, vtu.view_schema, vtu.view_name, 'VIEW' AS type
FROM
information_schema.tables AS t LEFT JOIN information_schema.view_table_usage AS vtu
ON
t.table_schema = vtu.table_schema AND
t.table_name = vtu.table_name
WHERE t.table_type = 'BASE TABLE' AND t.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)
UNION SELECT DISTINCT
source_ns.nspname as source_schema,
source_table.relname as source_table,
dependent_ns.nspname as dependent_schema,
dependent_view.relname as dependent_view,
'MATERIALIZED VIEW' AS type
FROM pg_depend
JOIN pg_rewrite ON pg_depend.objid = pg_rewrite.oid
JOIN pg_class as dependent_view ON pg_rewrite.ev_class = dependent_view.oid
JOIN pg_class as source_table ON pg_depend.refobjid = source_table.oid
JOIN pg_namespace dependent_ns ON dependent_ns.oid = dependent_view.relnamespace
JOIN pg_namespace source_ns ON source_ns.oid = source_table.relnamespace
WHERE dependent_view.relkind='m'
AND dependent_ns.nspname NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL) AND
(dependent_ns.nspname ||'.'|| dependent_view.relname<>source_ns.nspname||'.'||source_table.relname))
SELECT table_schema,
table_name,
string_agg('(' || type || ') ' || view_schema || '.'|| view_name,', ') AS list_of_derived_tables,
Count(view_name) AS number_of_derived_tables,
Count(view_name) FILTER (WHERE type='VIEW') AS number_of_views,
Count(view_name) FILTER (WHERE type='MATERIALIZED VIEW') AS number_of_mat_views
FROM derived_tables
GROUP BY table_schema, table_name
ORDER BY Count(view_name) DESC, table_schema, table_name;
Collections
This query belongs to the following collections:
Name
Description
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 .
Categories
This query is classified under the following categories:
Name
Description
Derived tables
Queries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer.