Rowid Filter check is just like Index Condition Pushdown check: before
we check the filter, we must check if we have walked out of the range
we are scanning. (If we did, we should return, and not continue the scan).
Consequences of this:
- Rowid filtering doesn't work for keys that have partially-covered
blob columns (just like Index Condition Pushdown)
- The rowid filter function has three return values: CHECK_POS (passed)
CHECK_NEG (filtered out), CHECK_OUT_OF_RANGE.
All of the above is implemented in this patch
8d85715d50