Disable IDF scoring on certain fields

[Brian Lamb]

Hi all,

I have a field defined in my schema.xml file as

<fieldType name="edgengram" class="solr.TextField"
positionIncrementGap="1000">
   <analyzer>
     <tokenizer class="solr.LowerCaseTokenizerFactory" />
     <filter class="solr.EdgeNGramFilterFactory" minGramSize="1"
maxGramSize="25" side="front" />
   </analyzer>
</fieldType>
<field name="myfield" multiValued="true" type="edgengram" indexed="true"
stored="true" required="false" omitNorms="true" />

I would like do disable IDF scoring on this field. I am not interested in
how rare the term is, I only care if the term is present or not. The idea is
that if a user does a search for "myfield:dog OR myfield:pony", that any
document containing dog or pony would be scored identically. In the case
that both showed up, that record would be moved to the top but all the
records where they both showed up would have the same score.

So long story short, how can I disable the idf score for this particular
field?

Thanks,

Brian Lamb