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From "Chris Male (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2395) Add a scoring DistanceQuery that does not need caches and separate filters
Date Thu, 15 Apr 2010 11:14:49 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12857278#action_12857278
] 

Chris Male commented on LUCENE-2395:
------------------------------------

+1

This will replace the work I was doing on improving the DistanceFilter and the DistanceSortSource.
 Instead we will have a proper DistanceQuery where the sorting is done through the existing
sorting by score functionality in Lucene.  The CartesianShapeFilter will then be able to be
used as a Filter with the new Query.

This also addresses the current problems with caching calculated distances and means that
Spatial will work with per segment.

> Add a scoring DistanceQuery that does not need caches and separate filters
> --------------------------------------------------------------------------
>
>                 Key: LUCENE-2395
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2395
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: contrib/spatial
>            Reporter: Uwe Schindler
>             Fix For: 3.1
>
>
> In a chat with Chris Male and my own ideas when implemnting for PANGAEA, I thought about
the broken distance query in contrib. It lacks the folloing features:
> - It needs a query for the encldoing bbox (which is constant score)
> - It needs a separate filter for filtering out distances
> - It has no scoring, so if somebody wants to sort by distance, he needs to use the custom
sort. For that to work, spatial caches distance calculation (which is borken for multi-segment
search)
> The idea is now to combine all three things into one query, but customizeable:
> We first thought about extending CustomScoreQuery and calculate the distance from FieldCache
in the customScore method and return a score of 1 for distance=0, score=0 on the max distance
and score<0 for farer hits, that are in the bounding box but not in the distance circle.
To filter out such negative scores, we would need to override the scorer in CustomScoreQuery
which is priate.
> My proposal is now to use a very stripped down CustomScoreQuery (but not extend it) that
does call a method getDistance(docId) in its scorer's advance and nextDoc that calculates
the distance for the current doc. It stores this distance also in the scorer. If the distance
> maxDistance it throws away the hit and calls nextDoc() again. The score() method will
reurn per default weight.value*(maxDistance - distance)/maxDistance and uses the precalculated
distance. So the distance is only calculated one time in nextDoc()/advance().
> To be able to plug in custom scoring, the following methods in the query can be overridden:
> - float getDistanceScore(double distance) - returns per default: (maxDistance - distance)/maxDistance;
allows score customization
> - DocIdSet getBoundingBoxDocIdSet(Reader, LatLng sw, LatLng ne) - returns an DocIdSet
for the bounding box. Per default it returns e.g. the docIdSet of a NRF or a cartesian tier
filter. You can even plug in any other DocIdSet, e.g. wrap a Query with QueryWrapperFilter
> - support a setter for the GeoDistanceCalculator that is used by the scorer to get the
distance.
> This query is almost finished in my head, it just needs coding :-)

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