[Velosurf-devel] Re: Oracle jdbc driver specificities (was : Re: velosurf 0.8 - changes)

[Asar K. <asa...@in...>]

Claude,

Unfortunatley, oracle's implementation if isOpen() does not work (unless it is 
has been fixed in the latest flavours - which I doubt - maybe someone else 
knows...) so it would cause a problem. If you do not want to introduce another 
parameter I suggest that you also code in "select 1 from dual" for oracle for 
backward compatibility if nothing else.

Best Regards
Asar Khan


On Mon, 23 Feb 2004 16:56:12 +0100, Claude Brisson wrote
> (Since this thread is becoming quite informative, I respond in the 
> mailing list)
> 
> (my initial post)
> > On Mon, 23 Feb 2004 01:17:35 +0100, Claude Brisson wrote
> > > Hi Asar,
> > >
> > > I am currently reviewing your changes, and I noticed the following one :
> > >
> > >   int concur = (mDBConnection.mDefaultReadOnly) ?
> > > ResultSet.CONCUR_READ_ONLY : ResultSet.CONCUR_UPDATABLE;  statement = new
> > > PooledStatement(mDBConnection,mDBConnection.getConnection()
> > > .createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,concur));
> > >
> > > I don't really understand it :
> > >
> > > 1. we don't need ResultSet.CONCUR_UPDATABLE since changes are made
> > > using separate queries.
> > >
> > > 2. we don't need ResultSet.TYPE_SCROLL_INSENSITIVE either, since we're
> > > only scrolling forward.
> > >
> > > So I'm not gonna include those changes, unless you can convince me I
> > > missed something.
> > >
> > > Other changes are fine, except that I'd like to try to determine
> > > automatically how to check the connection.
> > >
> > > CloD
> 
> Asar Khan wrote :
> > Hi Claude,
> >
> > Unfortunately its probably the most non-standard driver! And can be very
> > frustrating to work with.
> >
> > The reason why we need ResultSet.TYPE_SCROLL_INSENSITIVE (or you could use
> > ResultSet.TYPE_SCROLL_SENSITIVE) is that your code does not work with the
> > default ResultSet.FORWARD_ONLY. The isLast() method is not compatible with
> > FORWARD_ONLY and fails with the error:
> >
> > java.sql.SQLException: Invalid operation for forward only resultset : isLast
> 
> ok I see - so I'll keep ResultSet.TYPE_SCROLL_INSENSITIVE - no other 
> driver should be disturbed by that
> 
> >
> > IF YOU REMOVE THIS VELOSURF WILL NOT WORK WITH ORACLE.
> 
> I've installed an oracle instance for testing purposes ; don't worry,
>  I'll try not to let out something broken.
> 
> >
> > As for the code to set concur to ResultSet.CONCUR_READ_ONLY /
> > ResultSet.CONCUR_UPDATABLE i agree with your statement and it can be 
removed.
> > But you will have to specify ResultSet.CONCUR_READ_ONLY as the method 
requires
> > this as a minimum.
> >
> > I'm not too sure what you mean by your final statement about checking
> > automatically for the connection. If you're referring to the the 
checkConnection
> > () method in DBConnection.java then this had a hard-coded sql check "select 
1"
> > which again is incomaptible with oracle and causes a failure and a
> > reconnection - ultimatley it works but you have the overhead of a 
reconnection
> > and unecessary error logging.
> >
> > By allowing the user to specify a check query (which for most jdbc drivers 
will
> > not be required) the isOpen() will do the same thing when a query is not
> > supplied in the xml file.
> 
> Since the database driver can be deduced from the url 
> (mysql/oracle/...), I can call "select 1" in the case of mysql and 
> just isOpen( ) for others for now (untill someone discover that such 
> or such other driver also needs a special query).
> 
> >
> > I hope all this makes sense! If you have any further questions drop me a 
note.
> >
> > Regards
> > Asar Khan
> 
> > I'm not too sure what you mean by your final statement about checking
> > automatically for the connection. If you're referring to the the 
checkConnection
> > () method in DBConnection.java then this had a hard-coded sql check "select 
1"
> > which again is incomaptible with oracle and causes a failure and a
> > reconnection - ultimatley it works but you have the overhead of a 
reconnection
> > and unecessary error logging.
> >
> > By allowing the user to specify a check query (which for most jdbc drivers 
will
> > not be required) the isOpen() will do the same thing when a query is not
> > supplied in the xml file.
> 
> I just don't want to introduce a parameter that will look obscure to many.
> 
> Since the database driver can be deduced from the url 
> (mysql/oracle/...), I can call "select 1" in the case of mysql and 
> just isOpen( ) for others (untill someone discover that such or such 
> other driver also needs a special query because isOpen( ) ).
> 
> > I hope all this makes sense! If you have any further questions drop me a 
note.
> >
> > Regards
> > Asar Khan
> 
> Thanks,
> 
> CloD


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