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https://issues.apache.org/jira/browse/SOLR-15109?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Smiley reassigned SOLR-15109:
-----------------------------------
Component/s: SolrCloud
Assignee: David Smiley
Summary: Optimize shard splitByPrefix logic to reduce number of splits
required (was: Optimize splitByPrefix logic to reduce number of splits
required)
> Optimize shard splitByPrefix logic to reduce number of splits required
> ----------------------------------------------------------------------
>
> Key: SOLR-15109
> URL: https://issues.apache.org/jira/browse/SOLR-15109
> Project: Solr
> Issue Type: Improvement
> Security Level: Public(Default Security Level. Issues are Public)
> Components: SolrCloud
> Reporter: Megan Carey
> Assignee: David Smiley
> Priority: Major
> Attachments: Split 1 (1).png, Split 2 (1).png, Split 3 (1).png
>
>
> The goal of SplitByPrefix logic is to identify "buckets" within a shard that
> contain documents that should be co-located (according to their doc prefix),
> and split such that those buckets are preserved. One issue that we have found
> with splitByPrefix in practice is that it often takes several splits to
> isolate a particularly large bucket within the hash range.
> [~dsmiley] came up with a simple optimization that will reduce the number of
> splits needed to isolate such a bucket:
> {quote}Loop over all RangeCounts... does it intersect the middle third of the
> input? If not, move on. If so, track the biggest. When this loop finishes,
> you will have the biggest that also intersects the middle third. Then simply
> choose the side of this biggest RangeCount that is closest to the middle of
> the input range.{quote}
> This should be clearer with the following diagrams:
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