Обсуждение: more blob questions

Hi List;

Suppose I have a table with say an integer key, a char column and a large
object column.

can I simply delete a row from the table (delete from bigtable where...), then
run a vacuum (or vacuum full) ? If so, in this scenario will postgres release
the space back to the OS or must I first remove the large object with
lo_unlink() ?

also, does the contrib vacuumlo perform tasks I cannot do via vacuum and
lo_unlink ?

Thanks in advance..

/Kevin

Kevin Kempter <kevin@kevinkempterllc.com> writes:
> Suppose I have a table with say an integer key, a char column and a large
> object column.

> can I simply delete a row from the table (delete from bigtable where...), then
> run a vacuum (or vacuum full) ? If so, in this scenario will postgres release
> the space back to the OS or must I first remove the large object with
> lo_unlink() ?

That would release only the row's space, not the large object's.  You
need to do the lo_unlink().

> also, does the contrib vacuumlo perform tasks I cannot do via vacuum and
> lo_unlink ?

It doesn't do any magic.  You might want to read the latest cleaned-up
documentation for it:
http://developer.postgresql.org/pgdocs/postgres/vacuumlo.html
The contrib/lo module is also worth reading about.

            regards, tom lane