带有布尔运算符的奇怪 Solr/Lucene 行为 [英] Weird Solr/Lucene behaviors with boolean operators

问题描述

我在使用 Solr/Lucene 查询语法中的 - 运算符时遇到了奇怪的行为.如果我执行查询

I'm crashing into a weird behavior with - operators in Solr/Lucene query syntax. If I execute the query

-text AND -text 

我得到了所有预期的结果(很多)，但是如果我加上一些括号，比如

I get all expected results (lot), but if I put some parenthesis like

-text AND (-text) 

或

(-text) AND (-text) 

然后我根本没有得到任何结果.我不明白为什么.你对这种行为有什么解释吗?

then I get no results at all. I can't understand why. Do you have an explanation for this behavior?

提前致谢.

推荐答案

这个问题已经在Solr 邮件列表.他们还在官方常见问题解答中添加了一个条目，内容为:

The question have been answered very well in Solr mailing list. They have also added an entry in the offical FAQ, that says:

布尔查询必须至少有一个正"查询.表达式(即；必须或应该)以匹配.Solr 试图对此提供帮助，如果要求执行仅包含否定子句在最顶层的 BooleanQuery，它会添加一个匹配所有文档的查询(即:*:*)

Boolean queries must have at least one "positive" expression (ie; MUST or SHOULD) in order to match. Solr tries to help with this, and if asked to execute a BooleanQuery that does contains only negatived clauses at the topmost level, it adds a match all docs query (ie: *:*)

如果顶级 BoolenQuery 在其内部某处包含一个仅包含否定子句的嵌套 BooleanQuery，则不会修改该嵌套查询，并且它(根据定义)不匹配任何文档——如果需要，意味着外部查询将不匹配.

If the top level BoolenQuery contains somewhere inside of it a nested BooleanQuery which contains only negated clauses, that nested query will not be modified, and it (by definition) an't match any documents -- if it is required, that means the outer query will not match.

只有否定"的表达式值总是返回 0 结果，除了在最顶层，解析器在查询的开头默默地添加一个 *:*.

So expressions with only "negative" values return always 0 results, except at the topmost level, where the parser silently add a *:* at the beginning of the query.

因此 -text AND -text 被转换为 *:* -text AND -text 所以它有结果，而(-text) 不会转换为 (*:* -text)，因为它不在最顶层，所以 (-text) 没有给出任何结果.

Therefore -text AND -text is transformed to *:* -text AND -text and so it has results, while (-text) isn't transformed to (*:* -text), because it is not at the topmost level, and so (-text) gives no results.

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