I've got a query in Sitecore the boosts on template type, but this is skewed by the IDF (inverse document frequency). Is it possible to set sitecore/Lucene to ignore the IDF?
Or if anyone has any other ideas on how to boost the results of certain template types
On Lucene, you will need to implement a customScorer as far as I can see. I would not go in that direction.
If you move to Solr (recommended approach anyway) you can use function queries (in a boostFunction parameter) to boost with a precise value or use the ^= constant score facility in a boost query
in Solr it would look like:
https://<solrhost>/solr/<collectionname>/<handlername - query>?q=searh+for&bq=_template:<id>"^=10
you will just add a number of bq parameters for multiple template ids.
I don't know possible way disable idf. But you can try negative boosting by fields. Usual the most search pages use Title and Body for search by documents, so boost this fields on 0 or 0.25, try any value that less then 1 and find yours.
