title: Sphinx: Filtering MVA on multiple fields
body: <p>I would like to be able to filter my orders on an amount range AND a specific user_id
  The expected result would be to get only the orders where the specified user did a bid on in a certain amount range. </p>
  
  <p>For example there is an order with id 1. User 5 bid on it for an amount of 200.
  Now if I want to filter I set the user_id filter to 5 and set a range filter on amount for 150-250.</p>
  
  <p>How do I configure sphinx to be able to filter in that way? </p>
  
  <p>I have the following tables:</p>
  
  <p>Order:</p>
  
  <pre><code>+-------------+-----------------------+
  | Field       | Type                  |
  +-------------+-----------------------+
  | id          | mediumint(8) unsigned |
  | title       | varchar(100)          |
  | description | text                  |
  +-------------+-----------------------+
  </code></pre>
  
  <p>Bid:</p>
  
  <pre><code>+--------------+-----------------------+
  | Field        | Type                  |
  +--------------+-----------------------+
  | id           | mediumint(8) unsigned |
  | order_id     | mediumint(8) unsigned |
  | user_id      | mediumint(8) unsigned |
  | amount       | mediumint(9)          |
  +--------------+-----------------------+
  </code></pre>
  
  <p>I've tried the following in the sphinx configuration. But I cannot set the user_id as leading. The result is that I get all the orders where there are bids on in that amount range (from all the users), and I get all the orders where the user did a bid on.</p>
  
  <pre><code>sql_attr_multi  = uint amount from query; SELECT order_id as id, amount FROM bids
  sql_attr_multi  = uint user_id from query; SELECT order_id as id, user_id FROM bids
  </code></pre>
  
  <p>Thanks</p>