rocksdb::CompactRangeOptions.change_level is not compatible with level_compaction_dynamic_level_bytes

[hotpxl]

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• I had searched in the issues and found no similar issues.

Version

6b23c5a

Minimal reproduce step

Default configuration but with stats_dump_period_sec set (so you can see compaction stats) , redis-cli set a b, redis-cli compact.

What did you expect to see?

Because of how level_compaction_dynamic_level_bytes works, there should be only 1 compaction to L6 (the default bottom-most layer)

What did you see instead?

1 compaction on each layer and 2 compactions to L6

Anything Else?

I instrumented rocksdb code and this is because rocksdb::CompactRangeOptions.change_level is not compatible with level_compaction_dynamic_level_bytes.

When level_compaction_dynamic_level_bytes is set, set a b and compact will not compact to L1, it'll jump directly to the last layer (L6). And when change_level is set, it then moves this SST file from L6 back to L1.

Now when another periodic compaction comes along, it tries to move this file from L1->L2, L2->L3, ... This is why every layer has 1 compaction and the last layer has 2 compactions.

If you run a manual compaction at this time, since change_level is set, it'll move the SST file to L1 again, resulting in the same churn happening.

Obviously this is quite efficiently since these 2 options are trying to undo each other's work..

Are you willing to submit a PR?

• I'm willing to submit a PR!