title: Why RavenDB reads all documents in indexing process and not only collections used by index?
body: <p>I have quite large database with ~2.6 million documents where I have two collections each 1.2 million and rest are small collections (&lt;1000 documents). When I create new index for small collection, it takes lot of time indexing to complete (so temp indexes are useless). It seems that RavenDB indexing process reads each document in DB and checks if it should be added to index. I think it would perform better to index only collections used by index.</p>
  
  <p>Also when using Smuggler to export data and I want to export only one small collection, it reads all documents and exporting might take quite a lot of time. Same time custom app which uses RavenDB Linq API and indexes can export data in seconds.</p>
  
  <p>Why RavenDB behaves like this? And maybe there is some configuration setting which might change this behavior?</p>