> > > At PGCon we agreed to have such meeting in Vienna at least. But I think we > should be prepared and try to clean all our issues before. It looks like we > already out of time,but probably we could meet in Hong Kong ? > > Honestly, I still don't know which approach is better, we already played > with XL (ported to 9.4) and identified some very strong issues with > inconsistency, which scared us, especially taking into account how easy we > found them. XC people have fixed them, but I'm not sure if they were > fundamental and if we could construct more sophisticated tests and find > more issues in XC/XL. We also a bit disappointed by Huawei position about > CSN patch, we hoped to use for our XTM. FDW approach has been actively > criticized by pg_shard people and that's also made me a bit suspicious. It > looks like we are doomed to continue several development forks, so we > decided to work on very important common project, XTM, which we hoped could > be accepted by all parties and eventually committed to 9.6. Now I see we > were right, unfortunately. >
Distributed transaction manager should support at least three things 1. Atomic commit 2. Atomic visibility 3. Consistent snapshots (e.g. required for repeatable reads and higher isolation levels). I have submitted patch for implementing first for FDWs. The patch adds infrastructure to be used by all FDWs including postgres_fdw. It also adds postgres_fdw code to use this infrastructure. The same can be used to achieve atomic commit in postgres_fdw based sharding. Please see if XTM can benefit from it. If there are things that are required by XTM, please post the requirements on that thread and I will work on those. You can find the latest patch at http://www.postgresql.org/message-id/CAFjFpRfANWL53+x2HdM9TCNe5pup=opkqssj-kgfr-d2efj...@mail.gmail.com > > Again, could we organize meeting somewhere in September ? US is not good > for us, but other places should be ok. I want to have an agreement at > least on XTM. We still are testing various approaches, though. We could > present results of our experiments and are open to discussion. It's not > easy project, but it's something we could do for 9.6. > > I'm very glad Bruce started this discussion in -hackers, since it's silly > to me to participate in both threads :) Let's meet in September ! > > > >> -- >> Simon Riggs http://www.2ndQuadrant.com/ >> <http://www.2ndquadrant.com/> >> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services >> > > -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company
