t scan the partition will
    generally scan a large part of the partition or just a small part.
    An index will be helpful in the latter case but not the former.
   </p><p>
    Partition pruning can be performed not only during the planning of a
    given query, but also during its execution.  This is useful as it can
    allow more partitions to be pruned when clauses contain expressions
    whose values are not known at query planning time, for example,
    parameters defined in a <code class="command"