DB Analyzer: Sort unused indexes by some heuristics

[ankush]

Framework auto indexes a few things. Some of these indexes are unused because the user isn't actually using those doctypes OR usage is not that frequent (like closing balance).

Currently, I have 1000+ index removal recommendations. IMO most of these recommendations are not actionable.

Simplest fix:

• Use table schema information, don't recommend index that are < 16MB in size.
• If index size isn't easy to fetch then use table size as a proxy, don't recommend tables that have <256MB size.
• Limit recommendations to 100 max after sorting.
• Those numbers are made up, but assuming modern machines with 20-60MB L3 cache, that data size is peanuts and not worth optimizing.

[ankush]

@tanmoysrt

[ankush]

Apply similar heuristics on redundant index too, sort by "impact"