title: Searchkick multi-model search relevancy issues
body: <p>We've been in the process of rebuilding our old "quick navigation"/search from Tire into Searchkick because the results with the standard analyzers and tokenizers seemed fine for our needs. However, we need to search across several models and this is causing us some issues.</p>
  
  <p>The domain is webhosting. Consider objects representing a Server containing Accounts, containing Databases and Applications. The Applications have many Domains, which in turn has an SslCertificate.</p>
  
  <p>That means when we search for "something", if we have a database "something", an account "something", and a domain "something.com" we want the Account on top, followed by the database and the domain. The problem is that because we're searching across different indexes these scores are not reliable.</p>
  
  <p>The settings use number_of_shards 1 for all models. I believe the problem originates in the fact that, if I understood correctly, "uniqueness" is rewarded. That is to say, if there is 1 database match out of 5000 objects, and  1 account match out of 100, the database match is more unique and will score higher.</p>
  
  <p>How do we go about tweaking this? As far as I understood it there is no way to boost scores for fields in certain models.</p>