</para>

<para>

This is often called "index-only scans" or "covering indexes".

This is possible for heap pages with exclusively all-visible

tuples, as reported by the visibility map.

</para>

<listitem>

<para>

Reduce overhead of creating virtual transaction id locks ((Robert

Reduce overhead of creating virtual transaction id locks (Robert

Haas, Jeff Davis)

</para>

</listitem>