On 2010-06-01 16:07 +0300, David Fetter wrote: > On Sat, May 29, 2010 at 08:21:46PM -0700, Richard Broersma wrote: >> On Sat, May 29, 2010 at 6:25 PM, David Fetter <david@xxxxxxxxxx> wrote: >> >>>> I wondering if write-able CTE's will be the silver bullet that >>>> will make rule based update-able views based multiple vertically >>>> partitioned table robust. By robust, I mean to elimination the >>>> update anomalies that can occur from the view point client side >>>> optimistic locking where the virtual row appears to be >>>> inconsistently updated. >>> >>> I'm not sure I understand. >> >> Sorry about that, unreadable text is was happens when I don't proof >> read before sending. >> >>> When the concurrency issues in writeable CTEs get fixed, they >>> could become a mechanism for doing what you describe, but I >>> suspect there would be significant work involved in harnessing >>> them to that task. >> >> Actually I wasn't aware of the concurrency issue of write-able >> CTE's. > > The concern, as I understand it, has to do with modifications to the > current snapshot. I'm sure someone who knows the code better can go > into more detail. Marko? There were some issues with the previous design, but they will all be gone if it ever gets committed. >> The concern I have specifically relates to update-able views that >> were based upon joined tables (using these views was an attempt to >> hide the complexity of Generalization Hierarchies from the client >> side application). Updates to these kinds of views can give the >> appearance of non-atom updates on the view's virtual row. Also, if >> the view's reported row update count doesn't match what the client >> side software expects, the client automatically rolls back the >> transaction and reports a concurrent update error. However, when >> this happens some of the underlying rule's update statements were in >> fact processed, so the refreshed row in the view appears to have an >> non-atomic update even though the client rolls back the transaction. >> >> The following email was my first discovery that these kinds of >> update-able view were not get-along well with client side optimistic >> locking. >> >> http://archives.postgresql.org/pgsql-odbc/2006-12/msg00029.php There are major problems with updateable views in postgres, and writeable CTEs can't make them go away. Regards, Marko Tiikkaja -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
