The mongodb regex parser cannot create accurate bounds to allow indexed lookups when the regex includes the "|" character. This was allowed previously, but could lead to incorrect results.
I've got a database with 14 mio rows representing an imaginary "file system". There are (amongst others) the fields "type" (only "folder" or "file"), "folder" and "filename".
I now try this:
Very fast, too. No results again - as expected.
Now, I try this:
This query never returns. The whole database becomes horribly slow to the point of being unusable. I cannot even run any other queries. This used to work on 2.4.x. Why?