Subject Re: [firebird-support] wait/nowait transaction settings
Author Nick Upson
On 18/06/07, Ann W. Harrison <aharrison@...> wrote:
> Nick Upson wrote:
> > I have 2 processes which may both try to update the same row in a
> > table, currently when this happens I get "update conflict ...", so I
> > though I would change them both to having a wait transaction, which
> > would do what I need.
> >
> Unfortunately, no. Waiting doesn't change the fact that another
> concurrent transaction changed a record that you're planning to
> change. In theory, read-committed transactions could refetch
> the record, getting the new version and allow you to change it,
> but that's not how Firebird works now. And, of course, if the
> application has previously read the record and made decisions
> about the change based on old values, you wouldn't want to refetch
> the record and apply changes based on bad information.
> The purpose of 'wait' is to avoid live-lock, a situation in
> which two transactions modify the same two records in reverse
> order, each fails and immediately retries, fails again, and
> so on. It's not intended to allow a transaction to modify
> a record when it cannot read the most recent changes.

so I can't let A wait until B commits and then A will proceed?

There isn't actually a conflict as they are updating different fields
in a single-row table