Now, I got the point of three state consistent: we can keep only one consistent in opclasses that support new interface. exact true and exact false values will be passed in the case of current patch consistent; exact false and unknown will be passed in the case of current patch preConsistent. That's reasonable.
I'm going to mark this as "returned with feedback". For the next version, I'd like to see the API changed per above. Also, I'd like us to do something about the tidbitmap overhead, as a separate patch before this, so that we can assess the actual benefit of this patch. And a new test case that demonstrates the I/O benefits.
Revised version of patch is attached.
Changes are so:
1) Patch rebased against packed posting lists, not depends on additional information now.