On Fri, Nov 16, 2018 at 11:35 AM Tom Lane <tgl@sss.pgh.pa.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.
And to enforce Robert's argument even further almost every pool implementation I am aware of
has a keep alive query. So why not use the opportunity to check to see if is a primary or standby at the same time