On Thu, Oct 26, 2017 at 11:14 AM, Ashutosh Bapat <ashutosh.ba...@enterprisedb.com> wrote: > In a nearby thread, we are discussing about atomic commit of > transactions involving foreign transactions. For maintaining > consistency, atomicity of transactions writing to foreign server, we > will need to create local transactions. Will that be possible on > standby? Obviously, we could add a restriction that no consistency and > atomic commit is guaranteed when foreign servers are written from a > standby. I am not sure how easy would be to impose such a restriction > and whether such a restriction would be practical.
Yeah, that feature definitely can't work on a standby. But we could probably allow writes when that feature is not in use. One thing that bothers me about Alexander's patch is that there wouldn't be any way to distinguish between those two cases. Maybe we need a callback to ask the FDW "given the configured options, could you work on a standby?" However, as Michael also points out, it's arguably wrong to allow a nominally read-only transaction to write data regardless of whether it works. In the case of a standby it could be argued that your transaction is only read-only because you had no other choice, but nonetheless that's how it is marked. I have a feeling that if we extend the definition of "read only" to mean "sometimes allow writes", we may regret it. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
