+ -->
+ <warning>
+ <para>
+ Experimental. Do not use in production code.
+ </para>
+ </warning>
+
+ </section>
+
+
+
+ <section id="querymodel-zebra-local-attr-limit">
+ <title>Local Approximative Limit Attribute (type 11)</title>
+ <para>
+ &zebra; computes - unless otherwise configured -
+ the exact hit count for every &apt;
+ (leaf) in the query tree. These hit counts are returned as part of
+ the searchResult-1 facility in the binary encoded &z3950; search
+ response packages.
+ </para>
+ <para>
+ By setting an estimation limit size of the resultset of the &apt;
+ leaves, &zebra; stoppes processing the result set when the limit
+ length is reached.
+ Hit counts under this limit are still precise, but hit counts over it
+ are estimated using the statistics gathered from the chopped
+ result set.
+ </para>
+ <para>
+ Specifying a limit of <literal>0</literal> resuts in exact hit counts.
+ </para>
+ <para>
+ For example, we might be interested in exact hit count for a, but
+ for b we allow hit count estimates for 1000 and higher.
+ <screen>
+ Z> find @and a @attr 11=1000 b
+ </screen>
+ </para>
+ <note>
+ <para>
+ The estimated hit count facility makes searches faster, as one
+ only needs to process large hit lists partially.
+ It is mostly used in huge databases, where you you want trade
+ exactness of hit counts against speed of execution.
+ </para>
+ </note>
+ <warning>
+ <para>
+ Do not use approximative hit count limits
+ in conjunction with relevance ranking, as re-sorting of the
+ result set only works when the entire result set has
+ been processed.
+ </para>
+ </warning>
+ </section>