Sylvain Lebresne created CASSANDRA-8906:
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Summary: Experiment with optimizing partition merging when we can
prove that some sources don't overlap
Key: CASSANDRA-8906
URL: https://issues.apache.org/jira/browse/CASSANDRA-8906
Project: Cassandra
Issue Type: Improvement
Reporter: Sylvain Lebresne
When we merge a partition from two sources and it turns out that those 2
sources don't overlap for that partition, we still end up doing one comparison
by row in the first source. However, if we can prove that the 2 sources don't
overlap, for example by using the sstable min/max clustering values that we
store, we could speed this up. Note that it practice it's little bit more hairy
because we need to deal with N sources, but that's probably not too hard either.
I'll note that using the sstable min/max clustering values is not terribly
precise. We could do better if we were to push the same reasoning inside the
merge iterator, by for instance using the sstable per-partition index, which
can in theory tell use things like "don't bother comparing rows until the end
of this row block". This is quite a bit more involved though so maybe note
worth the complexity.
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