 at any time.
  </P
><P
>   Once an index is created, no further intervention is required: the
   system will update the index when the table is modified, and it will
   use the index in queries when it thinks doing so would be more efficient
   than a sequential table scan.  But you might have to run the
   <TT
CLASS="COMMAND"
>ANALYZE</TT
> command regularly to update
   statistics to allow the query planner to make educated decisions.
   See <A
HREF="performance-tips.html"
>Chapter 14</A
> for informatio