These changes mean that the resultant view is now non-mergeable allowing semi or anti joins to be contemplated.
这些变化意味着结果视图现在是不可合并的,也就是不用考虑半连接和反连接了。
2
A region can be removed from the mergeable state through the MADV_UNMERGEABLE parameter (which immediately un-merges any merged pages from that region).