On Thu, Apr 10, 2014 at 10:44 AM, Rajeev rastogi <rajeev.rast...@huawei.com>wrote:
> On 09 April 2014 12:14, Pavan Deolasee Wrote: > > >Whenever I was asked to have a look at implementing this feature, I > always wondered about the great amount of global state that a backend > maintains which is normally tied to a single top transaction. Since AT will > have same characteristics as a top level transaction, I > > >wonder how do you plan to separate those global state variables ? Sure, > we can group them in a structure and put them on a stack when an AT starts > and pop them off when the original top transaction becomes active again, > finding all such global state variables is > > >going to be tricky. > > > > I could think of few global variables like transaction properties > related(i.e. read-only mode, isolation level etc). As I plan to keep > transaction properties of autonomous transaction same as main transaction, > so there is no need to have these global variables separately. > > Apart from this there are global variables like with-in transaction > counters, GUC, xactStartTimeStamp. I think there is no need to maintain > these variables also separately. They can continue from previous value for > autonomous transaction also similar to as sub-transaction does. > > > Hmm. Is that in line with what other databases do ? I would have preferred AT to run like a standalone transaction without any influence of the starting transaction, managing its own resources/locks/visibility/triggers etc. > In-case of autonomous transaction, only specific global variables > initialized are related to resources (similar to sub-transaction), which > anyway gets stored in current transaction state. > > > > Please let me know if I am missing something or if you have some specific > global variables related issue. > > > No, I don't have any specific issues in mind. Mostly all such global state is managed through various AtStart/AtEOX and related routines. So a careful examination of all those routines will give a good idea what needs to be handled. You probably will require to write AtATStart/AtATEOX and similar routines to manage the state at AT start/commit/rollback. Sorry, I haven't looked at your WIP patch yet. Thanks, Pavan -- Pavan Deolasee http://www.linkedin.com/in/pavandeolasee
