Some of you might be familiar with pgBouncer project. Some are not. Some understand what/how/why it does, others do not.
This blog post is to have a place where I can point people who have question about how it works, why, and when it makes sense to use it (pgBouncer that is).
(disclaimer: all the data and examples in here are on Linux – the same data can be probably obtained on other systems too, it's just that I work on Linux and don't know other systems well).
This question pops occasionally in various places – PostgreSQL is using too much memory, why is that, and how can it be mitigated?
Before we can go to “optimizing", we should understand the problem. But do we? Both standard tools – ps and top – lie. How/why? Let's see.