/**
* Expert: called when re-writing queries under MultiSearcher.
*
* <p>Create a single query suitable for use by all subsearchers (in 1-1 correspondence with
* queries). This is an optimization of the OR of all queries. We handle the common optimization
* cases of equal queries and overlapping clauses of boolean OR queries (as generated by
* MultiTermQuery.rewrite()). Be careful overriding this method as queries[0] determines which
* method will be called and is not necessarily of the same type as the other queries.
*/
public Query combine(Query[] queries) {
HashSet<Query> uniques = new HashSet<Query>();
for (int i = 0; i < queries.length; i++) {
Query query = queries[i];
BooleanClause[] clauses = null;
// check if we can split the query into clauses
boolean splittable = (query instanceof BooleanQuery);
if (splittable) {
BooleanQuery bq = (BooleanQuery) query;
splittable = bq.isCoordDisabled();
clauses = bq.getClauses();
for (int j = 0; splittable && j < clauses.length; j++) {
splittable = (clauses[j].getOccur() == BooleanClause.Occur.SHOULD);
}
}
if (splittable) {
for (int j = 0; j < clauses.length; j++) {
uniques.add(clauses[j].getQuery());
}
} else {
uniques.add(query);
}
}
// optimization: if we have just one query, just return it
if (uniques.size() == 1) {
return uniques.iterator().next();
}
BooleanQuery result = new BooleanQuery(true);
for (final Query query : uniques) result.add(query, BooleanClause.Occur.SHOULD);
return result;
}
