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https://issues.apache.org/jira/browse/LUCENE-3325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13066630#comment-13066630
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Paul Elschot commented on LUCENE-3325:
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Currently positions are stored in this order (see the index file formats for
positions):
TermPositions are ordered by term (the term is implicit, from the .tis file).
Positions entries are ordered by increasing document number (the document
number is implicit from the .frq file).
The idea is to change this order such that positions are ordered first by
document and then by term.
> Transpose positions in index
> ----------------------------
>
> Key: LUCENE-3325
> URL: https://issues.apache.org/jira/browse/LUCENE-3325
> Project: Lucene - Java
> Issue Type: Wish
> Components: core/index
> Reporter: Paul Elschot
> Priority: Minor
>
> When positions are used in queries with many terms, each term in each
> document causes a seek in the positions, and in large indexes these seeks can
> be far apart even when the terms are in the same document.
> The number of (disk) cache misses of such position seeks might be reduced by
> putting the positions for all terms in the same document directly behind each
> other. This should have a noticable effect when terms are alphabetically
> close, for example for truncations, and it should also help when the
> documents have few enough positions to fill a cache entry (disk page, cache
> line).
> This might also help the performance of highlighting based on indexed
> positions.
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