October 13th, 2015 by depesz | Tags: , , , | Comments Off on explain.depesz.com changes and new stats

Some time ago I was contacted by Adam Smith - he pointed out that subquery names in "Subquery Scan" nodes were not properly anonymized. Now, they are, which you can see in here: normal version anonymized version While working on it, I also added ...

In previous posts in this series, I talked about how to read EXPLAIN output, and what each line (operation/node) means. Now, in the final post, I will try to explain how it happens that Pg chooses "Operation X" over "Operation Y".

In this, hopefully 2nd to last, post in the series, I will cover the rest of usually happening operations that you can see in your explain outputs.

In previous post in the series I wrote about how to interpret single line in explain analyze output, it's structure, and later on described all basic data-getting operations (nodes in explain tree). Today, we'll move towards more complicated operations.

Last time I wrote about what explain output shows. Now I'd like to talk more about various types of "nodes" / operations that you might see in explain plans.

One of the first things new DBA hears is "Use the EXPLAIN". And upon first try he/she is greeted with incomprehensible: ...