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Combined mutation reader produces range tombstones which do not overlap with the query range in some cases #3093
Since: 1.4, but impacts cache reads only since 2.0
When we get two range tombstones with the same lower bound from different data sources (e.g. two sstable), which need to be combined into a single stream, e.g. when populating cache, they need to be de-overlapped, because each mutation fragment in the stream must have a different position. If we have range tombstones
One effect of this may be that a reader will miss rows which are in the range
I'm in favor of doing 2, because it would simplify combining readers, which wouldn't need to accumulate and trim range tombstones. That includes the cache reader.
I don't like solution 3, because it makes combining readers more complicated, slower, and harder to properly construct (currently combining readers don't need to know restrictions of the leaf streams).
Solution 4 is confined to implementations of leaf readers, but also has disadvantage of making those more complicated and slower.