<listitem>

<para>

Constraint exclusion only works when the query's <literal>WHERE</>

clause contains constants. A parameterized query will not be

parameter value might select at run time. Forthe same reason,

<quote>stable</> functions such as <function>CURRENT_DATE</function>

must be avoided.

clause contains constants (or externally supplied parameters).

<function>CURRENT_TIMESTAMP</function> cannot be optimized, sincethe

planner cannot know which partition thefunction value might fall

into at run time.

</para>

</listitem>