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Posted to dev@lucene.apache.org by "Robert Muir (JIRA)" <ji...@apache.org> on 2011/01/26 13:29:44 UTC
[jira] Commented: (LUCENE-502) TermScorer caches values
unnecessarily
[ https://issues.apache.org/jira/browse/LUCENE-502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986981#action_12986981 ]
Robert Muir commented on LUCENE-502:
------------------------------------
Can we close this one?
It seems it was geared towards multitermqueries, but these are using different codepaths these days (e.g. Filter rewrite).
I think as this issue stands though, I would be against changing the defaults...
(separately: in LUCENE-2392, you can control this in your Similarity yourself)
> TermScorer caches values unnecessarily
> --------------------------------------
>
> Key: LUCENE-502
> URL: https://issues.apache.org/jira/browse/LUCENE-502
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Affects Versions: 1.9
> Reporter: Steven Tamm
> Priority: Minor
> Attachments: LUCENE-502.patch, TermScorer.patch
>
>
> TermScorer aggressively caches the doc and freq of 32 documents at a time for each term scored. When querying for a lot of terms, this causes a lot of garbage to be created that's unnecessary. The SegmentTermDocs from which it retrieves its information doesn't have any optimizations for bulk loading, and it's unnecessary.
> In addition, it has a SCORE_CACHE, that's of limited benefit. It's caching the result of a sqrt that should be placed in DefaultSimilarity, and if you're only scoring a few documents that contain those terms, there's no need to precalculate the SQRT, especially on modern VMs.
> Enclosed is a patch that replaces TermScorer with a version that does not cache the docs or feqs. In the case of a lot of queries, that saves 196 bytes/term, the unnecessary disk IO, and extra SQRTs which adds up.
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