At the moment I have a view that is running very slow. It takes about 3 minutes to execute. This suddenly happened.
To debug what was going on I used an old dataset and compared both queries. On the old dataset the view returns the data within a second.
I noticed one difference: the current dataset runs on "nested loops" while my old dataset runs with a Hash Match.
You can see that in the picture:
I'm aware of the fact that you simply cannot "force" it to use Hash Match as I saw in other topics, yet I'm having a really hard time finding out why its going for a nested loop.
Is this because something in my dataset is not unique?
How can I fix my current dataset to start using this Hash Match again?