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Björn Hegerfors commented on CASSANDRA-7272: -------------------------------------------- I don't understand why major compaction for STCS isn't already optimal. I do see why one might want to compact some but not all SSTables in a multi-tombstone compaction (CASSANDRA-7019) (though DTCS should be a better fit for anyone wanting this). But if every single SSTable is being rewritten to disk, why not write them into one file? As far as I understand, the ultimate goal of STCS is to be one SSTable. STCS only gets there, the natural way, once in a blue moon. But that's the most optimal state that it can be in. Am I wrong? The only explanation I can see for splitting the result of compacting all SSTables into fragments, is if those fragments are: 1. Partitioned smartly. For example into separate token ranges (à la LCS), timestamp ranges (à la DTCS) or clustering column ranges (which would be interesting). Or a combination of these. 2. The structure upheld by the resulting fragments is not subsequently demolished by the running compaction strategy going on with its usual business. > Add "Major" Compaction to LCS > ------------------------------ > > Key: CASSANDRA-7272 > URL: https://issues.apache.org/jira/browse/CASSANDRA-7272 > Project: Cassandra > Issue Type: Improvement > Components: Core > Reporter: T Jake Luciani > Assignee: Marcus Eriksson > Priority: Minor > Labels: compaction > Fix For: 3.0 > > > LCS has a number of minor issues (maybe major depending on your perspective). > LCS is primarily used for wide rows so for instance when you repair data in > LCS you end up with a copy of an entire repaired row in L0. Over time if you > repair you end up with multiple copies of a row in L0 - L5. This can make > predicting disk usage confusing. > Another issue is cleaning up tombstoned data. If a tombstone lives in level > 1 and data for the cell lives in level 5 the data will not be reclaimed from > disk until the tombstone reaches level 5. > I propose we add a "major" compaction for LCS that forces consolidation of > data to level 5 to address these. -- This message was sent by Atlassian JIRA (v6.3.4#6332)