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storage: Update MVCC on {Rocks,Pebble} to support ignored seqnum ranges and rollbacks #42582

Merged
merged 3 commits into from
Jan 11, 2020
Merged

storage: Update MVCC on {Rocks,Pebble} to support ignored seqnum ranges and rollbacks #42582

merged 3 commits into from
Jan 11, 2020

Commits on Jan 11, 2020

  1. libroach,storage: extend MVCC to support ignored seqnum ranges 

    The MVCC code already had rudimentary understanding of sequence
numbers to allow reads to ignore writes at greater seqnums.

To implement SQL savepoint rollbacks, we must also support
ignoring writes that fall in ignored ranges of seqnums.

To achieve this, this commit extends the `mvccScanner` for
RocksDB (Pebble code remains to be done) to account for
ignored seqnum ranges, and also extends `MVCCResolveWriteIntent`
to collapse an intent to the last write that has not been marked
to be ignored by a savepoint rollback.

Release note: None
    @knz @itsbilal
    knz authored and itsbilal committed Jan 11, 2020
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  2. engine: Implement ignoreSeqNum on pebble, streamline resolveWriteIntent 

    This commit implements ignoreSeqNums functionality in the pebble
MVCC scanner to mimic that found in the RocksDB one. In addition,
it also restructures code and comments in mvccResolveWriteIntent
to allow for it to be called in cases where just a rollback is
happening (but not a timestamp push or a commit) and the intent
history could be cleaned up for better performance.

There's also a small bugfix in mvccRewriteIntentHistory that
ensures it rewrites the correct value in cases where the
intent timestamp is being pushed forward, and the latest
value is ignored.

Release note: None
    @itsbilal
    itsbilal committed Jan 11, 2020
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  3. engine: Add more test cases to test mvccResolveIntentHistory 

    The previous change made mvccResolveIntentHistory more complex
in some subtle ways, such as the larger variety of cases where
they can expect to be called (such as around cleaning up intent
histories).

This change tests those cases and ensures that the resolution
code does the appropriate thing in all expected combinations of
those conditions.

Release note: None
    @itsbilal
    itsbilal committed Jan 11, 2020
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