Database performance issues related to OR operator

Hi everyone!   It's about solving the database performance issues that I believe are mainly because of the OR queries which are not supported by Postgres SQL - Similar topics have been discussed here before, but I just have more questions that I haven't found an answer to. I opened up the special search in Mendix pro and to my surprise I found that even Mendix own system module uses the same OR operator in xpaths for access rules. But xpath access rules are still the same xpaths used for making database retrieves. Right?   So here are few questions that I am looking for an answer: Is there actual difference between db retrieval xpath and access rules xpath? For access rules xpath the OR operator seems to be quite critical - even Mendix own module uses them. How do they actually hurt the performance? Where should I start looking? Is it only the OR operator that just ruins the whole thing or what are the other variables that can affect the performance of the query?
1 answers

What I would do initially is to check if splitting into two separate access rules with two separate XPaths is faster. Just like it happens, for example, when retrieving a list, where a faster solution is to retrieve two separate lists and then merge them into one, than using "or" operator.

Here is example in one of academy path: Mendix Academy - 4.3 XPath Optimizations