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From Stefano Ortolani <>
Subject Leveled Compaction Strategy with a really intensive delete workload
Date Sun, 24 May 2015 17:50:57 GMT
Hi all,

I have a question re leveled compaction strategy that has been bugging me
quite a lot lately. Based on what I understood, a compaction takes place
when the SSTable gets to a specific size (10 times the size of its previous
generation). My question is about an edge case where, due to a really
intensive delete workloads, the SSTable is promoted to the next level (say
L1) and its size, because of the many evicted tombstones, fall back to 1/10
of its size (hence to a size compatible to the previous generation, L0).

What happens in this case? If the next major compaction is set to happen
when the SSTable is promoted to L2, well, that might take too long and too
many tobmstones could then appear in the meanwhile (and queries might
subsequently fail). Wouldn't be more correct to flag the SStable's
generation to its previous value (namely, not changing it even if a major
compaction took place)?

Stefano Ortolani

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