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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2392) Enable flexible scoring
Date Mon, 12 Apr 2010 01:13:42 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12855802#action_12855802
] 

Robert Muir commented on LUCENE-2392:
-------------------------------------

Mike, I don't think overlapTermCount should really exist in the Stats.
Trying to implement some concrete FieldSimProviders, it starts getting messy.
When using term unique pivoted length norm, i don't want to count these positionIncrement=0
terms either...
so do we need a uniqueOverlapTermCount?
Even when using non-unique (BM25) pivoted length norm, we don't want to count these when summing
to calculate 
averages either.

So i know you probably see this as 'baking something into the index' but I think positionIncrement=0
means 
"doesn't contribute to the document length" by definition, and the discountOverlaps=false
(no longer the default)
should be considered deprecated compatibility behavior :)

> Enable flexible scoring
> -----------------------
>
>                 Key: LUCENE-2392
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2392
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>             Fix For: 3.1
>
>         Attachments: LUCENE-2392.patch
>
>
> This is a first step (nowhere near committable!), implementing the
> design iterated to in the recent "Baby steps towards making Lucene's
> scoring more flexible" java-dev thread.
> The idea is (if you turn it on for your Field; it's off by default) to
> store full stats in the index, into a new _X.sts file, per doc (X
> field) in the index.
> And then have FieldSimilarityProvider impls that compute doc's boost
> bytes (norms) from these stats.
> The patch is able to index the stats, merge them when segments are
> merged, and provides an iterator-only API.  It also has starting point
> for per-field Sims that use the stats iterator API to compute boost
> bytes.  But it's not at all tied into actual searching!  There's still
> tons left to do, eg, how does one configure via Field/FieldType which
> stats one wants indexed.
> All tests pass, and I added one new TestStats unit test.
> The stats I record now are:
>   - field's boost
>   - field's unique term count (a b c a a b --> 3)
>   - field's total term count (a b c a a b --> 6)
>   - total term count per-term (sum of total term count for all docs
>     that have this term)
> Still need at least the total term count for each field.

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