Implement heuristic CE for SargableNode that takes into account the actual predicates (or equivalent intervals).

That is, compute specific

• equality (or point intervals): [c,c]
• closed-range inequality: [c1, c2]
• one-sided inequality: (minKey, c]
• inequalities (interval ends) can be either open or closed

Each of the cases above will have a different default selectivity, which also depends on the actual collection cardinality.

Consider using metadata for estimation (if already not used):

• multikey info
• unique info (_id field)
• anything else?