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Jonathan Ellis updated CASSANDRA-8906: -------------------------------------- Assignee: Ariel Weisberg > 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 > Assignee: Ariel Weisberg > Labels: compaction, performance > Fix For: 3.x > > > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)