How to change default conjunction with Lucene MultiFieldQueryParser

Question

I have some code using Lucene that leaves the default conjunction operator as OR, and I want to change it to AND. Some of the code just uses a plain QueryParser, and that's fine - I can just call setDefaultOperator on those instances.

Unfortunately, in one place the code uses a MultiFieldQueryParser, and calls the static "parse" method (taking String, String[], BooleanClause.Occur[], Analyzer), so it seems that setDefaultOperator can't help, because it's an instance method.

Is there a way to keep using the same parser but have the default conjunction changed?

Answer 1

The MultiFieldQueryParser class extends the QueryParser class. Perhaps you could simply configure an instance of this class rather than relying on its static methods? If you really need to configure the BooleanClause.Occur values, you could do it afterward.

String queryString = ...;
String[] fields = ...;
Analyzer analyzer = ...;

MultiFieldQueryParser queryParser = new MultiFieldQueryParser(fields, analyzer);
queryParser.setDefaultOperator(QueryParser.Operator.AND);

Query query = queryParser.parse(queryString);

// If you're not happy with MultiFieldQueryParser's default Occur (SHOULD), you can re-configure it afterward:
if (query instanceof BooleanQuery) {
    BooleanClause.Occur[] flags = ...;
    BooleanQuery booleanQuery = (BooleanQuery) query;
    BooleanClause[] clauses = booleanQuery.getClauses();
    for (int i = 0; i < clauses.length; i++) {
        clauses[i].setOccur(flags[i]);
    }
}