title: I/O bound by reads? Ways to optimize?
body: <p>In SQLite, I am reading data from one database using <code>SELECT</code>, perform some modifications and write it to another database.</p>
  
  <p>Looking at the output of <code>iotop</code>, the process performance (using one core only) is I/O bound (IO>80%, CPU&lt;20%). Most of the action that I can see in <code>iotop</code> is going on under 'DISK READ', and only every now and then there is something shown under 'DISK WRITE'.</p>
  
  <p>Is it likely that the process performance is bound by the <code>SELECT</code>/read transactions? Basically all performance related information for SQLite that I see on the web is about <code>INSERT</code>/write. Is there anything to know and optimize about reading data?</p>
  
  <p>Could an inefficient query, i.e. by SELECT on a field with missing index have a stronger impact on IO than on CPU?</p>