On Wed, Jun 28, 2017 at 4:54 PM, Rob Nikander <rob.nikan...@gmail.com> wrote:
> Hi, > > I'm reading about MVCC here: https://www.postgresql. > org/docs/current/static/mvcc.html. > > In some cases I can use these transaction isolation modes, but in other > cases, I may want to manage the versions and concurrency manually. Is there > a way to select the “version” of a row, or is that data hidden to ordinary > SQL statements? > > I’m thinking about a sequence of actions, which are logically a > transaction, but start on one thread and complete later on another thread. > I don’t think I can tie up a JDBC database connection for that long. I can > add a `version bigint` column to my table, and the final update will look > like: > > update ... where id = ? and version = the_version_selected_earlier_ > in_a_different_thread > > … and if that gets 0 rows, it can handle the conflict. > For that, you could use xmin. That tracks the transaction where the row first became visible. Best Wishes, Chris Travers > > Rob > > > -- Best Wishes, Chris Travers Efficito: Hosted Accounting and ERP. Robust and Flexible. No vendor lock-in. http://www.efficito.com/learn_more
