Re: problem with LargeObject and commit

Marc,

Sorry I have been travelling. Just looked at it, It's fine albeit more than
just changing the visibility of the function.

Dave Cramer

dave.cramer(at)credativ(dot)ca
http://www.credativ.ca

On Mon, Oct 14, 2013 at 10:38 AM, Marc Cousin <cousinmarc(at)gmail(dot)com> wrote:

> Hi,
>
> Did you give it a look ?
>
> Regards
>
> Marc
>
> On Sunday 06 October 2013 19:14:41 Marc Cousin wrote:
> > Hi,
> >
> > Attached is an attempt to do this (git diff on head).
> >
> > The code seems to work. It has been tested on the program we are
> migrating
> > from SQL Server, we can now stream LOBs directly to web browsers...
> >
> > Please note that I am not usually a Java developper. I did my best to do
> > this correctly, and the Java way (as far as I know :) ). If some things
> are
> > not done the right way, or there is a smarter solution, tell me, I'll
> > improve this.
> >
> > Regards,
> >
> > Marc
> >
> > On Tuesday 01 October 2013 08:11:21 Dave Cramer wrote:
> > > Well I don't see any reason not to open up the LOM class to allow you
> to
> > > extend it.
> > >
> > > Can you send a git pull?
> > >
> > > Dave Cramer
> > >
> > > dave.cramer(at)credativ(dot)ca
> > > http://www.credativ.ca
> > >
> > > On Tue, Oct 1, 2013 at 3:52 AM, Marc Cousin <cousinmarc(at)gmail(dot)com>
> wrote:
> > > > Sorry, I don't think I get it, so please correct me below if I
> didn't.
> > > >
> > > > I currently use getInputStream() on my large object. How could I
> provide
> > > > a
> > > > connection to the extended InputStream ? I am calling a LargeObject
> > > > method.
> > > >
> > > > Or maybe extend LargeObject to have a new getInputStream method with
> a
> > > > connection provided, and then provide this connection to the extended
> > > > InputStream ?
> > > >
> > > > My initial idea was to not have to provide the connection as a
> > > > parameter,
> > > > so I
> > > > wanted to use the Lob Manager.
> > > >
> > > > Anyway, shouldn't streaming a large object in this special case be
> > > > easier
> > > > to
> > > > do ? The original code (from SQL Server) didn't have to do all these
> > > > workarounds, and I'll get this objection from people that will have
> to
> > > > use
> > > > this code :)
> > > >
> > > > Just having conn as protected instead of private in the
> > > > LargeObjectManager
> > > > would have made it possible to me to do it simply: I could have
> provided
> > > > the
> > > > connection to my extended LargeObject, and from there end the
> > > > transaction
> > > > on
> > > > close().
> > > >
> > > > Regards.
> > > >
> > > > On Monday 30 September 2013 17:08:18 Dave Cramer wrote:
> > > > > Marc,
> > > > >
> > > > > You required the connection to create the LargeObjectManager, so
> why
> > > > > not
> > > > > just extend the InputStream and add the connection to that object.
> > > > > When you close the input stream, close the connection ????
> > > > >
> > > > > Dave Cramer
> > > > >
> > > > > dave.cramer(at)credativ(dot)ca
> > > > > http://www.credativ.ca
> > > > >
> > > > > On Mon, Sep 30, 2013 at 11:18 AM, Marc Cousin <
> cousinmarc(at)gmail(dot)com>
> > > >
> > > > wrote:
> > > > > > 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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>
>