Benedict created CASSANDRA-7819:
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Summary: In progress compactions should not prevent deletion of
stale sstables
Key: CASSANDRA-7819
URL: https://issues.apache.org/jira/browse/CASSANDRA-7819
Project: Cassandra
Issue Type: Improvement
Components: Core
Reporter: Benedict
Priority: Minor
Compactions retain references to potentially many sstables that existed when
they were started but that are now obsolete; many concurrent compactions can
compound this dramatically, and with very large files in size tiered compaction
it is possible to inflate disk utilisation dramatically beyond what is
necessary.
I propose, during compaction, periodically checking which sstables are obsolete
and simply replacing them with the sstable that replaced it. These sstables are
by definition only used for lookup, since we are in the process of obsoleting
the sstables we're compacting, they're only used to reference overlapping
ranges which may be covered by tombstones.
A simplest solution might even be to simply detect obsoletion and recalculate
our overlapping tree afresh. This is a pretty quick operation in the grand
scheme of things, certainly wrt compaction, so nothing lost to do this at the
rate we obsolete sstables.
See CASSANDRA-7139 for original discussion of the problem.
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