: The following query does not work as expected for me:
: "alwaysTrueField:true (-name:john)"
: neither does this:
: "alwaysTrueField:true +(-name:john)"
: Does lucene run a sub-query for each part of the query inside
: parentheses, which is why the NOT query that is alone doesn't work? I am
Basically yes, the parens force the creation of a BooleanQuery, which is
invalid since it only contains prohited clauses.
: Any suggestions on how to work around this (buggy?) behaviour?
I use the following (1.4.3) method to deal with situations like this...
/**
* tests a BooleanQuery to see if it is directly usable, meaning it
* has at least one clause that is not prohibited.
*
* @param bq a BooleanQuery to test
* @returns false if bq null or contains all prohibited items, else true
*/
public static boolean usableBooleanQuery(BooleanQuery bq) {
if (null == bq) {
return false;
}
/* if we find *1* clause that's not prohibited, return true */
BooleanClause[] clauses = bq.getClauses();
for (int c = 0; clauses != null && c < clauses.length; c++) {
if (! clauses[c].prohibited) {
return true;
}
}
return false;
}
It can be used something like this...
Query at = new TermQuery(new Term("alwaysTrueField","true));
Query user = queryParser.parse(userInput);
if (user instanceof BooleanQuery) {
BooleanQuery bq = (BooleanQuery)user;
if (! usableBooleanQuery(bq)) {
bq.add(at, true, false); /* add 'always true' clause directly */
return bq;
}
}
/* if we made it here, wrape both clauses.
BooleanQuery q = new BooleanQuery();
q.add(at, true, false);
q.add(user, true, false);
return q;
(i think that's right, the specific cases where i use it are more
complicated so i can't cut/paste ... but i'm pretty sure the logic is
correct in that example, you should write some unit tests to be sure
before you do something like this.)
-Hoss
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