title: alternative to bitmap index in postgresql
body: <p>I have a table with hundreds of millions rows with schema like below. </p>
  
  <pre><code>tabe AA {
   id integer primay key,
   prop0 boolean not null,
   prop1 boolean not null,
   prop2 smallint not null,
   ...
  }
  </code></pre>
  
  <p>The each "property" field (prop0, prop1, ...) has a small number of distinct values. And I usually query to find "id" from the given conditions of properties fields. I think Bitmap index is best for this query. But postgresql seems not support bitmap index.</p>
  
  <p>I tried b-tree index on each field but these indexes are not used according to the query explain.</p>
  
  <p>Is there a good alternative way to do this?</p>
  
  <p>(i'm using postgresql 9)</p>