On 31 October 2015 at 10:22, konstantin knizhnik <k.knizh...@postgrespro.ru> wrote:
> Hi, > > PostgresPro cluster team wants to announce proposal for eXtensible > Transaction Manager API and reference implementation of distributed > transaction manager (pg_dtm). > pg_dtm is just a standard PostgreSQL extension which should be installed > in normal way. > > Source of pg_dtm and PostgreSQL patches are available here: > https://github.com/postgrespro/pg_dtm > WiKi page: https://wiki.postgresql.org/wiki/DTM Very interesting work. > xtm.patch patches PostgreSQL core by replacing direct calls of 7 TM > functions with indirect calls and At first I was concerned about recovery, but that looks to be covered. PostgreSQL assumes that top-level xid commit is atomic, along with all of its subtransactions. So the API having access to only Get/Set at the xid level would not work. We would need TransactionIdSetTreeStatus() rather than just SetStatus. GetStatus is not atomic. > adding 3 addition events to transaction commit callbacks: > Those look uncontentious, so we should add those anyway in a sub-patch. > We have also pgDTM implementation which is using timestamps (system time) > as CSNs. > It is also based on the same XTM transaction API. > We will publish it later once we clarify problems with recovery and > performance with this approach. > That is most interesting part, so it needs to be published. At present, I can't tell whether you need subtrans and multixact calls in the API as well. I would imagine we probably do, though we might imagine an implementation that didn't support those concepts. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
