Check if table inherits from other table in PostgreSQL

Question

In PostgreSQL for these tables

CREATE TABLE cities (
    name            text,
    population      float,
    altitude        int     -- in feet
);

CREATE T         


        

Answer 1

From Postgresql AutoDoc I found this SQL:

SELECT parnsp.nspname AS par_schemaname
    , parcla.relname AS par_tablename
    , chlnsp.nspname AS chl_schemaname
    , chlcla.relname AS chl_tablename
 FROM pg_catalog.pg_inherits
 JOIN pg_catalog.pg_class AS chlcla ON (chlcla.oid = inhrelid)
 JOIN pg_catalog.pg_namespace AS chlnsp ON (chlnsp.oid = chlcla.relnamespace)
 JOIN pg_catalog.pg_class AS parcla ON (parcla.oid = inhparent)
 JOIN pg_catalog.pg_namespace AS parnsp ON (parnsp.oid = parcla.relnamespace)

This is helpful as you can test in both directions with one query.

Answer 2

There is a catalog table for that: pg_inherits.

The catalog pg_inherits records information about table inheritance hierarchies. There is one entry for each direct child table in the database. (Indirect inheritance can be determined by following chains of entries.)

Here's a query that fits your question:

SELECT EXISTS (
   SELECT 1
   FROM   pg_catalog.pg_inherits
   WHERE  inhrelid = 'public.cities_capitals'::regclass
   );

TRUE if table cities_capitals inherits from somewhere, else FALSE.
Schema-qualify the name to be sure.

Answer 3

The following statement will retrieve the tables that cities inherits from. If the table does not inherit from another table, the result will be empty:

select bt.relname as table_name, bns.nspname as table_schema 
from pg_class ct 
    join pg_namespace cns on ct.relnamespace = cns.oid and cns.nspname = 'public' 
    join pg_inherits i on i.inhrelid = ct.oid and ct.relname = 'cities ' 
    join pg_class bt on i.inhparent = bt.oid 
    join pg_namespace bns on bt.relnamespace = bns.oid