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.