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Clarify docs about boolean operator precedence. (#30808) 

Unfortunately, the classic queryparser does not honor the usual precedence
rules of boolean operators. See
https://issues.apache.org/jira/browse/LUCENE-3674.
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Adrien Grand 2018-06-05 08:59:17 +02:00 committed by GitHub
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24
docs/reference/query-dsl/query-string-syntax.asciidoc
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@ -233,26 +233,10 @@ states that:
* `news` must not be present
* `quick` and `brown` are optional -- their presence increases the relevance
The familiar operators `AND`, `OR` and `NOT` (also written `&&`, `||` and `!`)
are also supported. However, the effects of these operators can be more
complicated than is obvious at first glance. `NOT` takes precedence over
`AND`, which takes precedence over `OR`. While the `+` and `-` only affect
the term to the right of the operator, `AND` and `OR` can affect the terms to
the left and right.
****
Rewriting the above query using `AND`, `OR` and `NOT` demonstrates the
complexity:
`quick OR brown AND fox AND NOT news`::
This is incorrect, because `brown` is now a required term.
`(quick OR brown) AND fox AND NOT news`::
This is incorrect because at least one of `quick` or `brown` is now required
and the search for those terms would be scored differently from the original
query.
The familiar boolean operators `AND`, `OR` and `NOT` (also written `&&`, `||`
and `!`) are also supported but beware that they do not honor the usual
precedence rules, so parentheses should be used whenever multiple operators are
used together. For instance the previous query could be rewritten as:
`((quick AND fox) OR (brown AND fox) OR fox) AND NOT news`::