Find dependent objects for a table or view - postgresql

Question

Background
When dropping (or replacing) objects in PostgreSQL, if there are dependencies, the drop will fail (without specifying CASCADE).
Problem
The error message returned by the database does not list the dependent objects.
Example Solution
The query might look something like:
SELECT * FROM information_schema i, pg_depend pd WHERE
i.object_id = pd.object_id AND
i.object_type = 'TABLE' AND
i.object_schema = 'public' AND
i.object_name = 'table_with_dependents';
The objid is missing.
Related
http://postgresql.1045698.n5.nabble.com/information-schema-problem-td2144069.html
http://www.alberton.info/postgresql_meta_info.html
Question
How do you generate a list of dependent objects by name and type?

Answer 1

The suggested solution didn't work for me with postgresql 9.1.4
this worked:
SELECT dependent_ns.nspname as dependent_schema
, dependent_view.relname as dependent_view
, source_ns.nspname as source_schema
, source_table.relname as source_table
, pg_attribute.attname as column_name
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_attribute ON pg_depend.refobjid = pg_attribute.attrelid
AND pg_depend.refobjsubid = pg_attribute.attnum
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
source_ns.nspname = 'my_schema'
AND source_table.relname = 'my_table'
AND pg_attribute.attnum > 0
AND pg_attribute.attname = 'my_column'
ORDER BY 1,2;

Answer 2

The easy way is:
BEGIN;
DROP TABLE tablename CASCADE;
DROP VIEW viewname CASCADE;
ROLLBACK;

Answer 3

For PostgreSQL 9.3 onward use the following view and functions to show any user object dependency. I also updated https://wiki.postgresql.org/wiki/Pg_depend_display.
/**** Usage Examples ****
-- Examine the entire object hierarchy
SELECT report.dependency_tree('');
-- Dependencies for any relations with names containing match (in regular expression)
SELECT report.dependency_tree('match');
-- Dependencies for relations person & address
SELECT report.dependency_tree('{person,address}'::text[]);
-- Dependencies for function slice
SELECT report.dependency_tree(ARRAY['slice'::regproc]);
-- Dependencies for type hstore
SELECT report.dependency_tree(ARRAY['hstore'::regtype]);
-- Dependencies for triggers by the name updated
SELECT report.dependency_tree(ARRAY(
SELECT oid FROM pg_trigger WHERE tgname ~ 'updated'
));
-- Dependencies for foreign key constraint names starting with product
SELECT report.dependency_tree(ARRAY(
SELECT oid FROM pg_constraint
WHERE conname ~ '^product.*_fk'
));
*/
DROP VIEW IF EXISTS report.dependency;
CREATE OR REPLACE VIEW report.dependency AS
WITH RECURSIVE preference AS (
SELECT 10 AS max_depth
, 16384 AS min_oid -- user objects only
, '^(londiste|pgq|pg_toast)'::text AS schema_exclusion
, '^pg_(conversion|language|ts_(dict|template))'::text AS class_exclusion
, '{"SCHEMA":"00", "TABLE":"01", "TABLE CONSTRAINT":"02", "DEFAULT VALUE":"03",
"INDEX":"05", "SEQUENCE":"06", "TRIGGER":"07", "FUNCTION":"08",
"VIEW":"10", "MATERIALIZED VIEW":"11", "FOREIGN TABLE":"12"}'::json AS type_sort_orders
)
, dependency_pair AS (
SELECT objid
, array_agg(objsubid ORDER BY objsubid) AS objsubids
, upper(obj.type) AS object_type
, coalesce(obj.schema, substring(obj.identity, E'(\\w+?)\\.'), '') AS object_schema
, obj.name AS object_name
, obj.identity AS object_identity
, refobjid
, array_agg(refobjsubid ORDER BY refobjsubid) AS refobjsubids
, upper(refobj.type) AS refobj_type
, coalesce(CASE WHEN refobj.type='schema' THEN refobj.identity
ELSE refobj.schema END
, substring(refobj.identity, E'(\\w+?)\\.'), '') AS refobj_schema
, refobj.name AS refobj_name
, refobj.identity AS refobj_identity
, CASE deptype
WHEN 'n' THEN 'normal'
WHEN 'a' THEN 'automatic'
WHEN 'i' THEN 'internal'
WHEN 'e' THEN 'extension'
WHEN 'p' THEN 'pinned'
END AS dependency_type
FROM pg_depend dep
, LATERAL pg_identify_object(classid, objid, 0) AS obj
, LATERAL pg_identify_object(refclassid, refobjid, 0) AS refobj
, preference
WHERE deptype = ANY('{n,a}')
AND objid >= preference.min_oid
AND (refobjid >= preference.min_oid OR refobjid = 2200) -- need public schema as root node
AND coalesce(obj.schema, substring(obj.identity, E'(\\w+?)\\.'), '') !~ preference.schema_exclusion
AND coalesce(CASE WHEN refobj.type='schema' THEN refobj.identity
ELSE refobj.schema END
, substring(refobj.identity, E'(\\w+?)\\.'), '') !~ preference.schema_exclusion
GROUP BY objid, obj.type, obj.schema, obj.name, obj.identity
, refobjid, refobj.type, refobj.schema, refobj.name, refobj.identity, deptype
)
, dependency_hierarchy AS (
SELECT DISTINCT
0 AS level,
refobjid AS objid,
refobj_type AS object_type,
refobj_identity AS object_identity,
--refobjsubids AS objsubids,
NULL::text AS dependency_type,
ARRAY[refobjid] AS dependency_chain,
ARRAY[concat(preference.type_sort_orders->>refobj_type,refobj_type,':',refobj_identity)] AS dependency_sort_chain
FROM dependency_pair root
, preference
WHERE NOT EXISTS
(SELECT 'x' FROM dependency_pair branch WHERE branch.objid = root.refobjid)
AND refobj_schema !~ preference.schema_exclusion
UNION ALL
SELECT
level + 1 AS level,
child.objid,
child.object_type,
child.object_identity,
--child.objsubids,
child.dependency_type,
parent.dependency_chain || child.objid,
parent.dependency_sort_chain || concat(preference.type_sort_orders->>child.object_type,child.object_type,':',child.object_identity)
FROM dependency_pair child
JOIN dependency_hierarchy parent ON (parent.objid = child.refobjid)
, preference
WHERE level < preference.max_depth
AND child.object_schema !~ preference.schema_exclusion
AND child.refobj_schema !~ preference.schema_exclusion
AND NOT (child.objid = ANY(parent.dependency_chain)) -- prevent circular referencing
)
SELECT * FROM dependency_hierarchy
ORDER BY dependency_chain ;
-- Procedure to report depedency tree using regexp search pattern (relation-only)
CREATE OR REPLACE FUNCTION report.dependency_tree(search_pattern text)
RETURNS TABLE(dependency_tree text)
SECURITY DEFINER LANGUAGE SQL
AS $function$
WITH target AS (
SELECT objid, dependency_chain
FROM report.dependency
WHERE object_identity ~ search_pattern
)
, list AS (
SELECT
format('%*s%s %s', -4*level
, CASE WHEN object_identity ~ search_pattern THEN '*' END
, object_type, object_identity
) AS dependency_tree
, dependency_sort_chain
FROM target
JOIN report.dependency report
ON report.objid = ANY(target.dependency_chain) -- root-bound chain
OR target.objid = ANY(report.dependency_chain) -- leaf-bound chain
WHERE length(search_pattern) > 0
-- Do NOT waste search time on blank/null search_pattern.
UNION
-- Query the entire dependencies instead.
SELECT
format('%*s%s %s', 4*level, '', object_type, object_identity) AS depedency_tree
, dependency_sort_chain
FROM report.dependency
WHERE length(coalesce(search_pattern,'')) = 0
)
SELECT dependency_tree FROM list
ORDER BY dependency_sort_chain;
$function$ ;
-- Procedure to report depedency tree by specific relation name(s) (in text array)
CREATE OR REPLACE FUNCTION report.dependency_tree(object_names text[])
RETURNS TABLE(dependency_tree text)
SECURITY DEFINER LANGUAGE SQL
AS $function$
WITH target AS (
SELECT objid, dependency_chain
FROM report.dependency
JOIN unnest(object_names) AS target(objname) ON objid = objname::regclass
)
, list AS (
SELECT DISTINCT
format('%*s%s %s', -4*level
, CASE WHEN object_identity = ANY(object_names) THEN '*' END
, object_type, object_identity
) AS dependency_tree
, dependency_sort_chain
FROM target
JOIN report.dependency report
ON report.objid = ANY(target.dependency_chain) -- root-bound chain
OR target.objid = ANY(report.dependency_chain) -- leaf-bound chain
)
SELECT dependency_tree FROM list
ORDER BY dependency_sort_chain;
$function$ ;
-- Procedure to report depedency tree by oid
CREATE OR REPLACE FUNCTION report.dependency_tree(object_ids oid[])
RETURNS TABLE(dependency_tree text)
SECURITY DEFINER LANGUAGE SQL
AS $function$
WITH target AS (
SELECT objid, dependency_chain
FROM report.dependency
JOIN unnest(object_ids) AS target(objid) USING (objid)
)
, list AS (
SELECT DISTINCT
format('%*s%s %s', -4*level
, CASE WHEN report.objid = ANY(object_ids) THEN '*' END
, object_type, object_identity
) AS dependency_tree
, dependency_sort_chain
FROM target
JOIN report.dependency report
ON report.objid = ANY(target.dependency_chain) -- root-bound chain
OR target.objid = ANY(report.dependency_chain) -- leaf-bound chain
)
SELECT dependency_tree FROM list
ORDER BY dependency_sort_chain;
$function$ ;

Answer 4

Include nested views in the query as follows:
WITH RECURSIVE view_deps AS (
SELECT DISTINCT dependent_ns.nspname as dependent_schema
, dependent_view.relname as dependent_view
, source_ns.nspname as source_schema
, source_table.relname as source_table
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 NOT (dependent_ns.nspname = source_ns.nspname AND dependent_view.relname = source_table.relname)
UNION
SELECT DISTINCT dependent_ns.nspname as dependent_schema
, dependent_view.relname as dependent_view
, source_ns.nspname as source_schema
, source_table.relname as source_table
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
INNER JOIN view_deps vd
ON vd.dependent_schema = source_ns.nspname
AND vd.dependent_view = source_table.relname
AND NOT (dependent_ns.nspname = vd.dependent_schema AND dependent_view.relname = vd.dependent_view)
)
SELECT *
FROM view_deps
ORDER BY source_schema, source_table;
If you care about specific table attributes add this to the top portion of the recursive CTE:
JOIN pg_attribute ON pg_depend.refobjid = pg_attribute.attrelid
AND pg_depend.refobjsubid = pg_attribute.attnum
...
WHERE
source_ns.nspname = 'my_schema'
AND source_table.relname = 'my_table'
AND pg_attribute.attnum > 0
AND pg_attribute.attname = 'my_column'

Answer 5

pg_constraint contains all constrains in the database you can list the oid of dependent tables using confrelid and conrelid from all all the foreign key constraints
query looks like this
select confrelid,conrelid from pg_constraint where contype='f';