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https://issues.apache.org/jira/browse/KUDU-483?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon updated KUDU-483:
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Priority: Minor (was: Major)
> Non-ordered MRS scanning for better performance
> -----------------------------------------------
>
> Key: KUDU-483
> URL: https://issues.apache.org/jira/browse/KUDU-483
> Project: Kudu
> Issue Type: Improvement
> Components: perf, tablet
> Affects Versions: Backlog
> Reporter: Todd Lipcon
> Priority: Minor
>
> Here's a performance improvement I was thinking about recently:
> Currently, scanning the MRS is fairly expensive due to cache misses and the
> per-leaf iteration code. Each leaf node has a pointer to its adjacent leaf,
> but that may be somewhere fairly random in memory. Despite our best effort to
> prefetch, we see a lot of cache misses in this code.
> For short (non fault-tolerant) scans, we don't need to yield rows in key
> order. So, we could reorganize the memory layout of the MRS such that all
> leaf nodes were allocated from a single arena-like structure. Then, iterating
> could proceed in memory order rather than key order, and likely be a lot
> faster. For fault tolerant (ordered) scans, we'd still have to use the btree
> traversal.
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