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From "Paul Elschot (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1427) QueryWrapperFilter should not do scoring
Date Tue, 28 Oct 2008 21:00:46 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12643337#action_12643337
] 

Paul Elschot commented on LUCENE-1427:
--------------------------------------

bq. ... are there other places where not having to provide a repeatable iterator buys us some
compelling freedom?

One might want to cache the Filter based on the version (last mod time) of the index, and
not based on the actual index reader. In that case the original reader could not be available
when the Filter is used.

I don't know whether that is compelling given the current cost of (re)opening an index.

> QueryWrapperFilter should not do scoring
> ----------------------------------------
>
>                 Key: LUCENE-1427
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1427
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.9
>
>
> The purpose of QueryWrapperFilter is to simply filter to include the docIDs that match
the query.
> Its implementation is wasteful now because it computes scores for those matching docs
even though the score is unused.  We could fix this by getting a Scorer and iterating through
the docs without asking for the score:
> {code}
> Index: src/java/org/apache/lucene/search/QueryWrapperFilter.java
> ===================================================================
> --- src/java/org/apache/lucene/search/QueryWrapperFilter.java	(revision 707060)
> +++ src/java/org/apache/lucene/search/QueryWrapperFilter.java	(working copy)
> @@ -62,11 +62,9 @@
>    public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
>      final OpenBitSet bits = new OpenBitSet(reader.maxDoc());
>  
> -    new IndexSearcher(reader).search(query, new HitCollector() {
> -      public final void collect(int doc, float score) {
> -        bits.set(doc);  // set bit for hit
> -      }
> -    });
> +    final Scorer scorer = query.weight(new IndexSearcher(reader)).scorer(reader);
> +    while(scorer.next())
> +      bits.set(scorer.doc());
>      return bits;
>    }
> {code}
> Maybe I'm missing something, but this seams like a simple win?

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