[PostgreSQL-Hackers] A few user-level questions on Streaming Replication and pg_upgrade

Hi,

Here are a few questions that were asked by a customer, who are trying
to assess the pros and cons of using Postgres and its SR feature. I would
like to get an opinion of someone more involved with the community than me.

.) Will Postgres support Streaming Replication from 9.0.x to 9.1.x; i.e.
across major releases.

I am pretty sure the answer is "no, it won't", but just double-checking
with the community.

.) Is Streaming Replication supported across minor releases, in reverse
direction; e.g. 9.0.3 to 9.0.1

I think the answer is "it depends", since it would depend upon whether
any SR related bug has been fixed in the 'greater' of the minor releases.

I am assuming that smaller minor release to bigger minor release will
always be supported (e.g. 9.0.1 to 9.0.3)

.) How reliable is `pg_upgrade -c` (dry run) currently; that is, how
accurate is pg_upgrade at predicting any potential problem with the eventual
in-place upgrade.

I'd say it is as reliable as it gets since this is the official tool
supported by the project, and it should not contain any known bugs. One has
to use the latest and greatest 'minor' version of the tool for the major
release they are upgrading to, though.

I'd also like to mention a piece of information that may be surprising
to some. Per Tom at a PGCon dinner, Postgres project does not promise
continued guarantee of in-place upgrades across future major releases.
Although the project will try hard to avoid having to make any changes that
may affect in-place upgrade capability, but if a case can be made that a
feature would give a significant improvement at the cost of compromising
this capability, then the in-place upgrade capability may be forgone for
that release.

Thanks in advance,