title: 10000 rows - selecting according to where clause - performance
body: <p>I have a database table with 10000 rows in it and I'd like to select a few thousand items using something like the following:</p>
  
  <p><code>SELECT id FROM models WHERE category_id = 2</code></p>
  
  <p>EDIT: The <code>id</code> column is the primary index of the table. Also, the table has another index on <code>category_id</code>.</p>
  
  <p>My question is what would be the impact on performance? Would the query run slow? Should I consider splitting my <code>models</code> table into separate tables (one table for each category)?</p>