On 7 November 2015 at 16:53, Konstantin Knizhnik <k.knizh...@postgrespro.ru> wrote:
> On 11/07/2015 05:11 PM, Amit Kapila wrote: > > > Today, while studying your proposal and related material, I noticed > that in both the approaches DTM and tsDTM, you are talking about > committing a transaction and acquiring the snapshot consistently, but > not touched upon the how the locks will be managed across nodes and > how deadlock detection across nodes will work. This will also be one > of the crucial points in selecting one of the approaches. > > > Lock manager is one of the tasks we are currently working on. > There are still a lot of open questions: > 1. Should distributed lock manager (DLM) do something else except > detection of distributed deadlock? > 2. Should DLM be part of XTM API or it should be separate API? > 3. Should DLM be implemented by separate process or should it be part of > arbiter (dtmd). > 4. How to globally identify resource owners (0transactions) in global lock > graph. In case of DTM we have global (shared) XIDs, > and in tsDTM - global transactions IDs, assigned by application (which is > not so clear how to retrieve). > In other cases we may need to have local->global transaction id mapping, > so looks like DLM should be part of DTM... > Yes, we need a Distributed Lock Manager, but I think its a separate thing from the DTM. (I'm loath to use the phase DLM, which was used within Oracle Parallel server for a buffer lock manager, which is not what is being discussed). -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
