Thread

Re: [HACKERS] New pg_type for large object

Peter T Mount <psqlhack@maidast.demon.co.uk> — 1998-04-10T18:48:29Z

On Fri, 10 Apr 1998, Kent S. Gordon wrote:

[snip]

>     > The first is, that when we update the OID which points to the
>     > large object, the large object is orphaned.  I realize that at
>     > the time of the update, we could select the old OID and
>     > subsequently drop the large object.  The problem is that general
>     > purpose tools such as MS Access do not provide an clean
>     > framework for invoking such a query.  Specifically, UPDATE
>     > statements would have to be torn apart to build such a SELECT
>     > statement.  In the short term I can build a separate daemon to
>     > track down the orphans.  I hope VACUUM will eventually handle
>     > these.
> 
> You should be able to use triggers to fix the problem at the time that 
> the update statement is run.

Yes that is one possibility, which I have done here, but this is a
generic problem, rather than one unique to a single application.

For triggers to work, you would have to add the trigger to each table, and
to each column that may contain a large object. Also, triggers are not
inherited.

Creating a new lo/blob data type would make this transparent to the user,
and would permit already written JDBC or ODBC based applications for other
databases to work without modification.

-- 
Peter T Mount  petermount@earthling.net or pmount@maidast.demon.co.uk
Main Homepage: http://www.demon.co.uk/finder
Work Homepage: http://www.maidstone.gov.uk Work EMail: peter@maidstone.gov.uk