Oracle Text 查询重写模板不起作用

Question

为什么 Oracle 文档示例中的最后两个重写规则不起作用？

来源 http://docs.oracle.com/cd/B28359_01/text.111/b28303/query.htm#i1007557

Query applications sometimes parse end user queries, interpreting a query string in one or more ways using different operator combinations. For example, if a user enters a query of kukui nut, your application might enter the queries {kukui nut} and {kukui or nut} to increase recall.

The query rewrite feature enables you to submit a single query that expands the original query into the rewritten versions. The results are returned with no duplication.

You specify your rewrite sequences with the query template feature. The rewritten versions of the query are executed efficiently with a single call to CONTAINS or CATSEARCH.

The following template defines a query rewrite sequence. The query of {kukui nut} is rewritten as follows:

{kukui} {nut}

{kukui} ; {nut}

{kukui} AND {nut}

{kukui} ACCUM {nut}

The query rewrite template for these transformations is as follows:

select id from docs where CONTAINS (text,
 '<query>
   <textquery lang="ENGLISH" grammar="CONTEXT"> kukui nut
     <progression>
       <seq><rewrite>transform((TOKENS, "{", "}", " "))</rewrite></seq>
       <seq><rewrite>transform((TOKENS, "{", "}", " ; "))</rewrite></seq>
       <seq><rewrite>transform((TOKENS, "{", "}", "AND"))</rewrite></seq>
       <seq><rewrite>transform((TOKENS, "{", "}", "ACCUM"))</rewrite></seq>
     </progression>
   </textquery>
  <score datatype="INTEGER" algorithm="COUNT"/>
</query>')>0;

Answer 1

Oracle 提供的示例中存在错误。查询运算符必须用空格分隔:

<seq><rewrite>transform((TOKENS, "{", "}", " AND "))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "{", "}", " ACCUM "))</rewrite></seq>

所以“AND”和“ACCUM”而不是文档中的“AND”和“ACCUM”。