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https://issues.apache.org/jira/browse/IGNITE-7998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16406312#comment-16406312
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Roman Kondakov commented on IGNITE-7998:
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There is a very raw prototype with a bunch of unsolved issues with persistence
in professional/ignite-5936-proto-with-persistence branch.
> SQL: Improve MVCC vacuum performance by iterating over data pages instead of
> cache tree.
> -----------------------------------------------------------------------------------------
>
> Key: IGNITE-7998
> URL: https://issues.apache.org/jira/browse/IGNITE-7998
> Project: Ignite
> Issue Type: Improvement
> Components: sql
> Reporter: Roman Kondakov
> Priority: Major
> Labels: iep-3
>
> At the moment vacuum process uses cache trees to find outdated (dead) entries
> and cache and index trees to cleanup them. It is not efficient due to several
> reasons. For example, we should lock a datapage for each cache tree entry to
> find out if entry is dead.
> We can consider a direct iteration over datapages as a possible improvement
> of the vacuum process. Data page iteration prototype demonstrated 5-10 times
> time improvement over the tree iteration.
> At first stage we need to implement direct datapages iteration only for
> collecting dead entries links.
> At the second stage we need to consider removing links to dead entries from
> index pages directly. In other words, we need to efficiently remove batches
> of dead links from indexes without traversing cache and index tree one dead
> link by one.
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