n about
   how to find out whether an index is used and when and why the
   planner might choose <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>not</I
></SPAN
> to use an index.
  </P
><P
>   Indexes can also benefit <TT
CLASS="COMMAND"
>UPDATE</TT
> and
   <TT
CLASS="COMMAND"
>DELETE</TT
> commands with search conditions.
   Indexes can moreover be used in join searches.  Thus,
   an index defined on a column that is part of a join condition can
   also significantly speed up queries with joins.
  </P
><P
> 