Question

I have a Solr schema in which a field is declared as TrieFloatField:

    <fieldType name="tfloat" class="solr.TrieFloatField" precisionStep="8" omitNorms="true" positionIncrementGap="0"/>

(...)

    <field
                name="someField"
                type="tfloat"
                indexed="true"
                stored="false"
                multiValued="false" />

If I use it to sort the results like so:

solrQuery.addSortField("someField", ORDER.asc);
solrQuery.addSortField("score", ORDER.desc);

The float numbers are not returned in correct numerical order, i.e.: I’d get results such as :

0.31 0.67 0.80 15.13 0.09 15.13 0.04

What’s even stranger is that when I use this field to sort my results, some sorting DOES happen (they’re in a different order that if, let’s say, I don’t use any sort field at all). Also, even if I change the sort order from asc to desc, the results are in the same order.

I thought that the TrieFloat type would work well for this. However I now see in the docs that they only mention that it’s “Floating point field accessible Lucene TrieRange processing”:

http://lucene.apache.org/solr/api-4_0_0-ALPHA/org/apache/solr/schema/TrieFloatField.html

and I honestly don’t really know what that means. I also see that there’s a SortableFloatField:

http://www.jarvana.com/jarvana/view/org/apache/solr/solr-core/3.5.0/solr-core-3.5.0-javadoc.jar!/org/apache/solr/schema/SortableFloatField.html

but the docs don’t really say anything about how it behaves when being used as a sort criteria.

My question simply is: which one of those two types (or what other type) is good for storing float numbers such that they can be used for proper (natural) ascending and descending sorting in a Solr query

Answer 1

Both classes should work, but TrieFloatField will require much less memory than SortableDoubleField (given that the former uses a float field cache while the latter uses a String field cache). Note that if you don’t need to perform range queries, you should set precisionStep=0.

However the bug you hit is very strange…