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Posted to dev@lucene.apache.org by "Robert Muir (JIRA)" <ji...@apache.org> on 2018/03/26 07:03:00 UTC

[jira] [Commented] (LUCENE-8221) MoreLikeThis.setMaxDocFreqPct can easily int-overflow on larger indexes

    [ https://issues.apache.org/jira/browse/LUCENE-8221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16413467#comment-16413467 ] 

Robert Muir commented on LUCENE-8221:
-------------------------------------

Its also confusing and inconsistent that it uses numDocs() in the percentage calculation, which excludes deleted documents, when docFreq() does not. It should really use maxDoc() here.

> MoreLikeThis.setMaxDocFreqPct can easily int-overflow on larger indexes
> -----------------------------------------------------------------------
>
>                 Key: LUCENE-8221
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8221
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Dawid Weiss
>            Assignee: Dawid Weiss
>            Priority: Minor
>         Attachments: LUCENE-8221.patch
>
>
> {code}
>   public void setMaxDocFreqPct(int maxPercentage) {
>     this.maxDocFreq = maxPercentage * ir.numDocs() / 100;
>   }
> {code}
> The above overflows integer range into negative numbers on even fairly small indexes (for maxPercentage = 75, it happens for just over 28 million documents.
> We should make the computations on long range so that it doesn't overflow and have a more strict argument validation.



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