Re: problem with LargeObject and commit - Mailing list pgsql-jdbc

Hi,

I'm having the following problem: I need to stream a LOB to a web client, without consuming
a lot of memory. So I am returning getInputStream() to the caller.

This works perfectly, except that I have to keep a transaction open to return the large object
stream, and I have (or found) no way of closing the transaction when the filestream is closed.

So of course, if I did that, I would get a lot of IDLE in transaction sessions...

So the logical way seemed to me to extend LargeObjectManager and LargeObject to have a
close method on my LargeObject that closes the transaction, meaning that my LargeObject
should have a connection attribute. So I wanted to do something like this (not working,
it's just for the sake of explanation):


public class StreamLargeObjectManager extends LargeObjectManager{

           public StreamLargeObject openStreamLargeObject(long oid, int mode)
             throws SQLException
           {
             LargeObject lo = super.open(oid, mode);
             StreamLargeObject so = new StreamLargeObject(lo, super.getConn()); //cannot be done because no access to connection
             return so;
           }
}


and

public class StreamLargeObject extends org.postgresql.largeobject.LargeObject{


        Connection conn;

        LargeObject lobj;


        public StreamLargeObject(LargeObject lg, BaseConnection conn) throws SQLException {
                this.lobj = lg;
                this.conn = conn;
        }


        @Override
        public void close() throws SQLException {

                lobj.close();
                this.conn.commit();

        }


       public getInputStream() throws SQLException
    {
        return lobj.getInputStream();
    }
}


As the comment says it all, I cannot do this: conn is private in LargeObjectManager. For now, the problem has been
worked around by duplicating all the LargeObjectManager code, but this is obviously ugly and not
maintainable. So my question is: have I missed some obvious solution ? Could a getter be added to
the LargeObjectManager's connection ?

Regards,

Marc


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