Obtaining the size of lobject in PostgreSQL

Question

I wonder why is there no function to directly obtain the size of large object in PostgreSQL. I believe one can seek() the end of object and then tell()

Answer 1

This function has been efficient enough for me, you may want to try it with you data:

CREATE OR REPLACE FUNCTION lo_size(oid) RETURNS integer 
AS $$ 
declare 
 fd integer; 
 sz integer; 
begin 
 fd = lo_open($1, 262144);
 if (fd<0) then
   raise exception 'Failed to open large object %', $1;
 end if;
 sz=lo_lseek(fd,0,2);
 if (lo_close(fd)!=0) then
   raise exception 'Failed to close large object %', $1;
 end if;
 return sz;
end; 
$$ LANGUAGE 'plpgsql'; 

Another option is select sum(length(data)) from pg_largeobject where loid=the_oid but it requires read access to pg_largeobject which I think has been suppressed in pg 9.0+ for non-superusers