CREATE TABLESPACE mvtbl_test_tblspace LOCATION '/tmp/tsttblsp';
CREATE TABLE test AS SELECT i as a, i as b , i as c FROM generate_series(1,1e6) i;
CREATE INDEX ON test(a);
CREATE INDEX ON test(a,b);
CREATE INDEX ON test(c);
SELECT pg_size_pretty(mvtbl('test','mvtbl_test_tblspace'));
 pg_size_pretty 
----------------
 123 MB
(1 row)

SELECT pg_size_pretty(mvtbl('test','pg_default'));
 pg_size_pretty 
----------------
 123 MB
(1 row)

DROP TABLESPACE mvtbl_test_tblspace;