[Documentation] Document why N+1 Cached queries are considered bad
Problem to solve
The cached queries help with reducing DB load, but they still:
- consume memory
- require as to re-instantiate each AR object
- require as to re-instantiate each relation of the object
- makes us spend additional CPU-cycles to look into a list of cached queries.
We should treat the CACHE
the same as N+1
queries. They are cheaper, but they are not cheap at all from ~memory perspective.
Proposal
We should document why N+1 Cached
queries are considered bad form ~memory perspective, and update documentation https://docs.gitlab.com/ee/development/merge_request_performance_guidelines.html#query-counts.
Edited by Nikola Milojevic