Re: Libpq support to connect to standby server as priority

On Fri, Nov 16, 2018 at 11:35 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Oh! The reason I assumed it wasn't doing that is that such a behavior
> seems completely insane. If the point is to keep down the load on your
> master server, then connecting only to immediately disconnect is not
> a friendly way to do that --- even without counting the fact that you
> might later come back and connect again.

That seems like a really weak argument. Opening a connection to the
master surely isn't free, but it must be vastly cheaper than the cost
of the queries you intend to run. I mean, no reasonable production
user of PostgreSQL opens a connection, runs one or two short queries,
and then closes the connection. You open a connection and keep it
open for minutes, hours, days, or longer, running hundreds, thousands,
or millions of queries. The cost of checking whether you've got a
master or a standby is a drop in the bucket.

And, I mean, if there's some scenario where what I just said isn't
true, well then don't use this feature in that particular case.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company