Re: Hash-based MCV matching for large IN-lists

Hi Chengpeng,

Thanks for your review!

* Treat NULL array elements as zero selectivity for ALL:

Agreed. For ALL/AND semantics the function now returns selectivity = 0.0 as soon as a NULL element is encountered.

* Fix cross-type equality argument order in `mcvs_in_equal`:

Agreed. Added 'op_is_reserved' flag MCVInHashContext, same as in MCVHashContext.

* Include non-MCV IN-list constants in non-disjoint selectivity:

This is not applicable to v3.

* Avoid double-negating inequality estimates for non-Const elements:

Agreed. var_eq_non_const() is now always with negate = false, not to call negation twice.

Attached v4 patch with above fixes.

-- 
Best regards,
Ilia Evdokimov,
Tantor Labs LLC,
https://tantorlabs.com/