ppose we have a table similar to this:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE TABLE test1 (
    id integer,
    content varchar
);</PRE
><P>
   and the application issues many queries of the form:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT content FROM test1 WHERE id = <TT
CLASS="REPLACEABLE"
><I
>constant</I
></TT
>;</PRE
><P>
   With no advance preparation, the system would have to scan the entire
   <TT
CLASS="STRUCTNAME"
>test1</TT
> table, row by row, to find all
   matching entries.  If there are many r