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Tyler Hobbs commented on CASSANDRA-8833:
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bq. see if we can solve the index summary redistribution some other way (only
do it on compaction?) to be able to make SSTableReader totally immutable again,
got any insight here Tyler Hobbs?
We could switch to doing it on compaction only. I suppose we would determine
the new summary interval based on the read rates for SSTables participating in
the compaction. The main downside is that it would be less responsive to
changes. For example, if a new SSTable is flushed that shadows most of the
entries in an old SSTable, the old SSTable may keep its existing (and possibly
expensive) summary interval until the next compaction.
> Stop opening compaction results early
> -------------------------------------
>
> Key: CASSANDRA-8833
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8833
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Marcus Eriksson
> Fix For: 2.1.4
>
>
> We should simplify the code base by not doing early opening of compaction
> results. It makes it very hard to reason about sstable life cycles since they
> can be in many different states, "opened early", "starts moved", "shadowed",
> "final", instead of as before, basically just one (tmp files are not really
> 'live' yet so I don't count those). The ref counting of shared resources
> between sstables in these different states is also hard to reason about. This
> has caused quite a few issues since we released 2.1
> I think it all boils down to a performance vs code complexity issue, is
> opening compaction results early really 'worth it' wrt the performance gain?
> The results in CASSANDRA-6916 sure look like the benefits are big enough, but
> the difference should not be as big for people on SSDs (which most people who
> care about latencies are)
> WDYT [~benedict] [~jbellis] [~iamaleksey] [~JoshuaMcKenzie]?
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