UPDATE Sept. 2023: For more recent information about planner statistics, see the PostgreSQL documentation about extended statistics, or this blog about CREATE STATISTICS. You can also find out more recent info in this blog about Improving Group By with Create Statistics. The blog post below about cross correlation has been preserved for reference. Planner estimates […]

In 99% of all cases the PostgreSQL planner does a perfect job to optimize your queries and to make sure that you enjoy high performance and low response times. The infrastructure ensuring this is both sophisticated as well as robust. However, there are some corner cases which can turn out to be quite nasty. In […]

The goal of the PostgreSQL optimizer is to provide you with a plan, which executes as fast as possible and returns all the data as rapidly as possible. In short: The game is about overall execution time of queries. However, there are cases in which you are not interested in receiving the entire result as […]

PostgreSQL knows a parameter called effective_cache_size. To many this is one of the most mysterious settings in the entire PostgreSQL config. Maybe this is the core reason why many people just completely ignore this setting – in many cases this is not the best idea of all. effective_cache_size can have a serious impact on execution […]