[ADMIN] Strange size of pg_largeobject

Hi all,

I found that my pg_largeobject table is bigger than it should be:

Size:
mybase=# SELECT pg_size_pretty(pg_total_relation_size('pg_largeobject'));
 18 GB
mybase=# SELECT pg_size_pretty(pg_total_relation_size('pg_largeobject_loid_pn_index'));
 162 MB

Rows count and large objects count:
mybase=# select count(*) from pg_largeobject
38406
mybase=# select count(*) from pg_largeobject where pageno = 0;
778

The largest objects:
mybase=# select loid, count(pageno) from pg_largeobject group by loid order by count(pageno) limit 5 desc;
   loid    | count
-----------+-------
 406485914 |  2188
 167710689 |  1114
 412765517 |   996
 307045064 |   842
 167714441 |   645

I write the largest lo to the file system and check their sizes:
select lo_export(167710689, '/tmp/1');
select lo_export(406485914, '/tmp/2');
ls -lh /tmp/
-rw-r--r-- 1 postgres postgres 4,3M июл 20 15:22 123
-rw-r--r-- 1 postgres postgres 2,2M июл 20 15:23 1234

therefore, maximum size of my table should be 2.2*777 + 4.3 = 1713.7 mb (size2*[large objects count] + size1).

Before I execute queries, that i mentioned above, I run vacuum full. But it does not effect. Now table bloating factor about 20%.


Please, help me, if you have any suggestions about my problem.

--
Best regards,
Vladimir Yanchenko
Tech support engineer
Naumen