<DD
><P
>        Sets the planner's assumption about the effective size of the
        disk cache that is available to a single query.  This is
        factored into estimates of the cost of using an index; a
        higher value makes it more likely index scans will be used, a
        lower value makes it more likely sequential scans will be
        used. When setting this parameter you should consider both
        <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>'s shared buffers and the
        portion of th