After incremental compaction, new sstables may have already replaced old
sstables at any point. Meaning that a new sstable is in-use by table and
a old sstable is already deleted when compaction itself is UNFINISHED.
Therefore, we should *NEVER* delete a new sstable unconditionally for an
interrupted compaction, or data loss could happen.
To fix it, we'll only delete new sstables that didn't replace anything
in the table, meaning they are unused.
Found the problem while auditting the code.
Fixes#4479.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20190506134723.16639-1-raphaelsc@scylladb.com>
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