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https://issues.apache.org/jira/browse/IGNITE-9590?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vladimir Ozerov closed IGNITE-9590.
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> MVCC: Cleanup old rows in the vacuum thread.
> --------------------------------------------
>
> Key: IGNITE-9590
> URL: https://issues.apache.org/jira/browse/IGNITE-9590
> Project: Ignite
> Issue Type: Improvement
> Components: mvcc
> Reporter: Roman Kondakov
> Priority: Major
> Labels: performance
>
> When updating writer thread should iterate over the set of the last versions
> in order to find an appropriate version for its MVCC snapshot. During this
> iteration it collects invisible to anybody versions (their xid_max version is
> less than cleanup). When all outdated versions found, writer thread cleanups
> these rows - removes it from indexes and from pagestore.
> It would be more efficient if writer thread does not cleanup old rows by
> itself, but rather delegate it to vacuum workers: instead of cleaning just
> put it to cleanup queue.
> in case of significant backpressure during active updates, when cleanup
> workers can't keep up with removing outdated rows and cleanup queue is too
> big, writer threads can cleanup this rows by itself to prevent memory and
> performance problems.
> Upd: Also we can acquire checkpointReadLock for a fix-sized batch of cleaning
> versions Vacuum.cleanup() rather than for every single remove or rather than
> removing all outdated version at once. See TxLog.removeUntil() method.
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