Find disk size of Postgres materialized view

GetMaterializedViewSize.sql

/*
https://dba.stackexchange.com/questions/96534/postgres-check-disk-space-taken-by-materialized-view?newreg=6b1d58604fce4a1fbe3033ddbb52d7ca

relkind:
r = ordinary table,
i = index,
S = sequence,
v = view,
m = materialized view,
c = composite type,
t = TOAST table,
f = foreign table
*/
SELECT relname   AS objectname
     , relkind   AS objecttype
     , reltuples AS entries
     , pg_size_pretty(pg_table_size(oid)) AS size  -- depending - see below
FROM   pg_class
WHERE  relkind IN ('m')
ORDER  BY pg_table_size(oid) DESC;