- <sect3 id="querymodel-zebra-attr-limit">
- <title>Zebra Extension Approximative Limit Attribute (type 9)</title>
- </sect3>
- <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 Z39.50 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>
- 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 9=1000 b
- </screen>
- </para>
- <note>
- 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.
- </note>
- <warning>
- Do not use approximative hit count limits
- in conjunction with relevance ranking, as re-sorting of the
- result set obviosly only works when the entire result set has
- been processed.
- </warning>
- <warning>
- This facility clashes with rank weight, because there all
- documents in the hit lists need to be examined for scoring and
- re-sorting.
- It is an experimental
- extension. Do not use in production code.
- </warning>
+ <section id="querymodel-zebra-attr-termref">
+ <title>&zebra; Extension Term Reference Attribute (type 10)</title>
+ <para>
+ &zebra; supports the searchResult-1 facility.
+ If the Term Reference Attribute (type 10) is
+ given, that specifies a subqueryId value returned as part of the
+ search result. It is a way for a client to name an &acro.apt; part of a
+ query.
+ </para>