Random "SELECT 1" query in all requests on rails

Question

I'm profiling my rails 3.2 app with miniprofiler, and it shows me a

SELECT 1

query at the beginning of each page load or ajax call. It only takes 0.4ms, but it is still a seemingly unnecessary database query.

Anyone know why this query is happening or how to get rid of it?

Answer 1

SELECT 1 is like a ping - the cheapest query to test whether the session is alive and kicking. Various clients use it for that purpose. It may be useless in your case ...

Answer 2

For Postgres you can find it in this line on Github.

Or, if you using MySQL, you can see the solution in this groupon engineering blog.