Here is a follow-up to a previous message I posted, dealing with converting
user-entered boolean logic into a Query. Why does the QueryParser construct
the same query for the following two strings?
It has no precedence rules. AND and OR appear to be to connect two terms in some kind of relationship, but BooleanQuery clauses don't work that way - each clause has a required/prohibited flags. A parser would need to be more clever to do what you expect here...
"apple AND orange OR pear AND grape"
(apple AND orange) OR (pear AND grape) does what you expect.
I think a user's expectation would be that the first query matches things
containing apple and orange, or containing pear and grape. And that the
second query would only match things containing all four items. However, the
same query is constructed both times (the constructed query requires all
four).
I think we are running in circles with QueryParser more often than not. What we really need to admit is that no single expression syntax is going to make everyone happy and that each application really deserves its own custom one. Many thanks to the creator and maintainers of QueryParser, though, it is pretty decent for general purpose use.
If it's any consolation, though, I do agree with your issue here and think that the precedence rules should work like mathematics naturally does with AND and OR operators. Changing it presents a backwards compatibility issue, though (which is of no concern to me personally).
Erik
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