PostgreSQL query planner's internals

How to understand why my query is so slow? Is it because of unoptimal plan ? Reading "explain" command output. Ways to extract and join data. Everything that affects query plan. Examples of wrong plans. Ways to rewrite queries.

The same query could be executed in different ways and sometimes difference in execution time could be in orders of magnitude. The task of planner/optimizer is to create some optimal plan within a reasonable time which expected to run the fastest. Usually it deals with it pretty well but sometimes problem with bad plan occurs and it's useful to know how it's working.

In this talk I'd like to tell about internals of query planner/optimizer, show different ways of how to change query plan and demonstrate known problems and solutions.