title: mysql: very simple SELECT id ORDER BY LIMIT will not use INDEX as expected (?!)
body: <p>I have a simple table with about 3 million records. I made the neccessary indexes, i also force the index PRIMARY but still doesnt work. <strong>It searches for nearly all 3 million rows instead of using the index</strong> to execute this one (record_id is INT auto-increment):</p>
  
  <pre><code>EXPLAIN SELECT record_id
  FROM myrecords
  FORCE INDEX (
  PRIMARY )
  ORDER BY record_id ASC
  LIMIT 2955900 , 300
  
  id  select_type     table     type  possible_keys   key     key_len     ref     rows    Extra
  1   SIMPLE          myrecords index NULL            PRIMARY 4           NULL    2956200 Using index
  </code></pre>
  
  <p>The index is</p>
  
  <pre><code>Keyname Type    Unique  Packed  Column      Cardinality Collation   Null
  PRIMARY BTREE   Yes     No      record_id   2956742     A           No  
  </code></pre>
  
  <p>I would like to know why this FORCED index is not being used the right way.</p>
  
  <p>Without forcing index 'primary' both ASC and DESC tried, result is the same. Table has been repaired-optimized-analyzed. No luck.</p>
  
  <p>query needs over a minute to execute!</p>
  
  <p>WHAT I EXPECTED: query should proccess only 300 rows since that column is indexed. not nearly all 3 million of them as you can see in the first code-formatted block (scroll a little to the right)</p>