Solr 4.2.1 sorting by distance to polygon centre.

[Guido Medina]

Hi,

I got everything in place, my polygons are indexing properly, I played a 
bit with LSP which helped me a lot, now, I have JTS 1.13 inside 
solr.war; here is my challenge:

I have big polygon (A) which contains smaller polygons (B and C), B and 
C have some intersection, so if I search for a coordinate inside the 3, 
I would like to sort by the distance to the centre of the polygons that 
match the criteria.

As example, let's say dot B is on the centre of B, dot C is at the 
centre of C and dot A is at the intersection of B and C which happens to 
be the centre of A, so for dot A should be polygon A first and so on. I 
could compute with the distances using the result but since Solr is 
doing a heavy load already, why not just include the sort in it.

Here is my field type definition:

        <!-- Spatial field type -->
        <fieldType name="location_rpt" 
class="solr.SpatialRecursivePrefixTreeFieldType"
spatialContextFactory="com.spatial4j.core.context.jts.JtsSpatialContextFactory"
                   units="degrees"/>


Field definition:

        <!-- JTS spatial polygon field -->
        <field name="geopolygon" type="location_rpt" indexed="true" 
stored="false" required="false" multiValued="true"/>


I'm using the Solr admin UI first to shape my query and then moving to 
our web app which uses solrj, here is the XML form of my result which 
includes the query I'm making, which scores all distances to 1.0 (Not 
what I want):

|<?xml version="1.0" encoding="UTF-8"?>
<response>

<lst  name="responseHeader">
  <int  name="status">0</int>
  <int  name="QTime">9</int>
  <lst  name="params">
    <str  name="fl">id,score</str>
    <str  name="sort">score asc</str>
    <str  name="indent">true</str>
    <str  name="q">*:*</str>
    <str  name="_">1366111120720</str>
    <str  name="wt">xml</str>
    <str  name="fq">{!score=distance}geopolygon:"Intersects(-6.271906 
53.379284)"</str>
  </lst>
</lst>
<result  name="response"  numFound="3"  start="0"  maxScore="1.0">
  <doc>
    <str  name="id">uid13972</str>
    <float  name="score">1.0</float></doc>
  <doc>
    <str  name="id">uid13979</str>
    <float  name="score">1.0</float></doc>
  <doc>
    <str  name="id">uid13974</str>
    <float  name="score">1.0</float></doc>
</result>
</response>|


Thanks for all responses,

Guido.