SET extra_float_digits = 3 in postgresql

Question

Whenever I start Postgresql DB engine, I have almost 7-8 queries running in the background SET extra_float_digits = 3

I am not sure why these are running al

Answer 1

The queries aren't really running. As Nick says in the comments, the connections will be in idle state. pg_stat_activity shows the last statement that finished running when a query is idle.

As for the other part: I'd say you're using PgJDBC. SET extra_float_digits ensures that PgJDBC doesn't lose precision when it gets floating point values from the database. It's part of the initial connection conversation. It's normal and you can ignore it. If you're on a recent PgJDBC, send the additional connection parameter assumeMinServerVersion=9.0 and it'll go away.

So what you have there is a bunch of new, idle connections.

Look into your application / application server's configuration. Your connection pool probably doesn't have reasonable limits set.