Evan,
The row is locked between the select and update :)
Well, you could still argue that the update still performs better and I have to agree
with you!
Thank you
Regards
Sachin
Evan Ireland wrote:
> Sachin Hardas wrote:
> >
> > Evan,
> > We already do something of that sort. I don't know which is more efficient.
> > When an update is issued, we fetch the record from the database and compare it with
> > the original state we have with us.
>
> There is a small window between your select and update in which time
> the underlying data can be changed. I suggest the modified update syntax
> as it doesn't have any 'windows' where problems can arise.
>
> > A rollback is done if the states don't match.
> >
> > Thank you
> > Regards
> > Sachin
> >
> > Evan Ireland wrote:
> >
> > > Sachin Hardas wrote:
> > > >
> > > > Kristofer,
> > > > The solution you suggested would work only if you can modify the database.
> > > > We are not so lucky and cannot in any way update the database schema.
> > >
> > > Say you have table T, key column K, and data columns X, Y and Z. In your
> > > entity bean for T, save the original values of X, Y and Z. When you issue
> > > an update, use SQL of the form:
> > >
> > > update T set X = newX, Y = newY, Z = newZ
> > > where K = theK and X = oldX and Y = oldY and Z = oldZ
> > >
> > > Check the row count for this update. If it is zero, then rollback the
> > > transaction.
> > > ________________________________________________________________________________
> > >
> > > Evan Ireland Sybase EAServer Engineering [EMAIL PROTECTED]
> > > Wellington, New Zealand +64 4 934-5856
> > >
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> --
> ________________________________________________________________________________
>
> Evan Ireland Sybase EAServer Engineering [EMAIL PROTECTED]
> Wellington, New Zealand +64 4 934-5856
>
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