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https://issues.apache.org/jira/browse/LUCENE-10660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17571369#comment-17571369
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Adrien Grand commented on LUCENE-10660:
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The change made sense to me and I merged it, thank you [~tangdh]!
> precompute the max level in LogMergePolicy
> ------------------------------------------
>
> Key: LUCENE-10660
> URL: https://issues.apache.org/jira/browse/LUCENE-10660
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/index
> Affects Versions: 9.2
> Reporter: tang donghai
> Priority: Minor
> Time Spent: 20m
> Remaining Estimate: 0h
>
> I notice LogMergePolicy#findMerges will always calculate max level on the
> right side when find the next segments to merge.
>
> I think we could calculate the max levels only once, and when we need the max
> level, we could simply
> {code:java}
> float maxLevel = maxLevels[start];
> {code}
> and the precomputed code looks like below, compare each level in levels from
> right to left
> {code:java}
> float[] maxLevels = new float[numMergeableSegments + 1];
> maxLevels[numMergeableSegments] = -1.0f;
> for (int i = numMergeableSegments - 1; i >= 0; i--) {
> maxLevels[i] = Math.max(levels.get(i).level, maxLevels[i + 1]);
> }
> {code}
>
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