lo_import() of an empty file

I have just discovered if you try to lo_import() an empty file, and oid
is returned, but nothing is added to pg_largeobject:

$ > /rtmp/a
$ psql test

SELECT lo_import('/rtmp/a');
lo_import
-----------
16385

SELECT * from pg_largeobject;
loid | pageno | data
------+--------+------

However, the oid is incremented for each call:

SELECT lo_import('/rtmp/a');
lo_import
-----------
16386

SELECT lo_import('/rtmp/a');
lo_import
-----------
16387

SELECT lo_import('/rtmp/a');
lo_import
-----------
16388

An lo_export() of a non-existant oid does create an empty file. I guess
this is an optimization of allowing empty file imports to consume no
space in pg_largeobject, but it does seem odd.

I am asking hackers in case someone can see an error here, or something
that should be documented.

--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +