[LUCENE-2395] Add a scoring DistanceQuery that does not need caches and separate filters

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Component/s: modules/spatial
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Uwe Schindler
• Created: 15/Apr/10 11:08
• Updated: 28/Aug/22 12:24
• Resolved: 02/Dec/13 06:15

Description

In a chat with Chris Male and my own ideas when implementing for PANGAEA, I thought about the broken distance query in contrib. It lacks the following features:

• It needs a query/filter for the enclosing bbox (which is constant score)
• It needs a separate filter for filtering out hits to far away (inside bbox but outside distance limit)
• 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 broken 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.
• a LatLng provider (similar to CustomScoreProvider/ValueSource) that returns for a given doc id the lat/lng. This method is called per IndexReader one time in scorer creation and will retrieve the coordinates. By that we support FieldCache or whatever.

This query is almost finished in my head, it just needs coding

Issue Links

• depends upon: LUCENE-2148 Improve Spatial Point2D and Rectangle Classes
• depends upon: LUCENE-2151 Abstract the distance calculation process in the Spatial contrib
• depends upon: LUCENE-2152 Abstract Spatial distance filtering process and supported field formats