storage/metamorphic: Add MVCC delete range using tombstone #83945
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It's a bit unclear to me how these tests verify the correctness of operations. Are we only testing that they don't crash or error?
I think what we really need is a set of randomized tests that verify that MVCC operations (including iterators) give the expected results, since there are far more edge cases than we can reasonably cover with explicit test cases.
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MVCC range tombstones can't be transactional, since we don't have ranged intents yet. Is this a required artifact of the test harness? If not, I think I'd prefer to avoid involving transactions.
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Good catch. I removed the transactional code; I figured we needed it in place to be able to fake latching in the operation generator, but turns out it's not necessary just yet.
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It's basically a determinism test. We spin up Pebble instances with different options, throw in some random store restarts in and random other mvcc operations (including MVCC Puts, CPuts, Gets, iterators, etc) and ensure that the result of those operations is consistent across different runs and instances of Pebble with different options. If, say, a compaction is corrupting a key somewhere or is leading to lack of determinism or consistent results, it'd show up here. Errors don't fail the test if every instance of Pebble returned the same error when the same set of operations is run. |
This change adds MVCCDeleteRangeUsingTombstone to the MVCC metamorphic tests. MVCCDeleteRange had already existed in this test suite, so this ended up being a relatively simple addition. One part of cockroachdb#82545, with possibly more parts to follow as other MVCC-level operations are added that utilize `writer.{Put,Clear}{MVCC,Engine}RangeKey`. Release note: None.
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Nice!
Reviewed 3 of 3 files at r2, all commit messages.
Reviewable status:complete! 1 of 0 LGTMs obtained (waiting on @erikgrinaker)
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TFTRs! bors r=erikgrinaker |
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To improve coverage, I'm wondering if we some runs should perform the delete range as a scan with point deletes, in order to test equivalence between MVCCDeleteRange and MVCC point deletes?
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They're not equivalent e.g. to an MVCC iterator, which will see range tombstones rather than point tombstones. They're only equivalent to an MVCC scan/get without tombstones. |
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Yeah, makes sense. I wonder if we'd get more value out of MVCC metamorphic tests that perform equivalent operations adding abstractions on top, when necessary. Varying Pebble options is great for surfacing bugs in Pebble, but it seems unlikely to surface new MVCC bugs. |
This change adds MVCCDeleteRangeUsingTombstone to the MVCC
metamorphic tests. MVCCDeleteRange had already existed in
this test suite, so this ended up being a relatively simple
addition.
One part of #82545, with possibly more parts to follow
as other MVCC-level operations are added that utilize
writer.{Put,Clear}{MVCC,Engine}RangeKey.Release note: None.