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https://issues.apache.org/jira/browse/LUCENE-4198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16335533#comment-16335533
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Jim Ferenczi commented on LUCENE-4198:
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The patch looks great. The new API seems contained and easy to use. I like the
simplicity of the implementation of max score for the term scorer.
I have some questions though, the SlowImpactEnum returns NO_MORE_DOCS when
advanceShallow is used, is it allowed (the contract is that this API should
always return a docId greater than the current doc ?) ? The name is also a bit
misleading since it seems that it is only for postings that don't index impacts
or that contain a single document.Why do you need to compute the impact lazily
? Is it for queries that don't use score for sorting ? You said it helps with
conjunctions but the bmw patch uses the impacts for conjunctions as well so I
guess it's for all other queries that don't require this information ?
> Allow codecs to index term impacts
> ----------------------------------
>
> Key: LUCENE-4198
> URL: https://issues.apache.org/jira/browse/LUCENE-4198
> Project: Lucene - Core
> Issue Type: Sub-task
> Components: core/index
> Reporter: Robert Muir
> Priority: Major
> Attachments: LUCENE-4198-BMW.patch, LUCENE-4198.patch,
> LUCENE-4198.patch, LUCENE-4198.patch, LUCENE-4198.patch, LUCENE-4198.patch,
> LUCENE-4198_flush.patch
>
>
> Subtask of LUCENE-4100.
> Thats an example of something similar to impact indexing (though, his
> implementation currently stores a max for the entire term, the problem is the
> same).
> We can imagine other similar algorithms too: I think the codec API should be
> able to support these.
> Currently it really doesnt: Stefan worked around the problem by providing a
> tool to 'rewrite' your index, he passes the IndexReader and Similarity to it.
> But it would be better if we fixed the codec API.
> One problem is that the Postings writer needs to have access to the
> Similarity. Another problem is that it needs access to the term and
> collection statistics up front, rather than after the fact.
> This might have some cost (hopefully minimal), so I'm thinking to experiment
> in a branch with these changes and see if we can make it work well.
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