On Sat, Mar 16, 2024 at 4:26 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Fri, Mar 15, 2024 at 7:50 PM Alexander Korotkov <aekorot...@gmail.com> > wrote: > > > > I went through this patch another time, and made some minor > > adjustments. Now it looks good, I'm going to push it if no > > objections. > > > > I have a question related to usability, if the regular reads (say a > Select statement or reads via function/procedure) need a similar > guarantee to see the changes on standby then do they also always need > to first do something like "BEGIN AFTER '0/3F0FF791' WITHIN 1000;"? Or > in other words, shouldn't we think of something for implicit > transactions?
+1 to have support for implicit txns. A strawman solution I can think of is to let primary send its current insert LSN to the standby every time it sends a bunch of WAL, and the standby waits for that LSN to be replayed on it at the start of every implicit txn automatically. The new BEGIN syntax requires application code changes. This led me to think how one can achieve read-after-write consistency today in a primary - standby set up. All the logic of this patch, that is, waiting for the standby to pass a given primary LSN needs to be done in the application code (or in proxy or in load balancer?). I believe there might be someone doing this already, it's good to hear from them. > In general, it seems this patch has been stuck for a long time on the > decision to choose an appropriate UI (syntax), and we thought of > moving it further so that the other parts of the patch can be > reviewed/discussed. So, I feel before pushing this we should see > comments from a few (at least two) other senior members who earlier > shared their opinion on the syntax. I know we don't have much time > left but OTOH pushing such a change (where we didn't have a consensus > on syntax) without much discussion at this point of time could lead to > discussions after commit. +1 to gain consensus first on the syntax changes. With this, we might be violating the SQL standard for explicit txn commands (I stand for correction about the SQL standard though). -- Bharath Rupireddy PostgreSQL Contributors Team RDS Open Source Databases Amazon Web Services: https://aws.amazon.com
