org.apache.lucene.search.grouping.GroupSelector Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.search.grouping;
import java.io.IOException;
import java.util.Collection;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Scorable;
/**
* Defines a group, for use by grouping collectors
*
* A GroupSelector acts as an iterator over documents. For each segment, clients
* should call {@link #setNextReader(LeafReaderContext)}, and then {@link #advanceTo(int)}
* for each matching document.
*
* @param the type of the group value
*/
public abstract class GroupSelector {
/**
* What to do with the current value
*/
public enum State { SKIP, ACCEPT }
/**
* Set the LeafReaderContext
*/
public abstract void setNextReader(LeafReaderContext readerContext) throws IOException;
/**
* Set the current Scorer
*/
public abstract void setScorer(Scorable scorer) throws IOException;
/**
* Advance the GroupSelector's iterator to the given document
*/
public abstract State advanceTo(int doc) throws IOException;
/**
* Get the group value of the current document
*
* N.B. this object may be reused, for a persistent version use {@link #copyValue()}
*/
public abstract T currentValue() throws IOException;
/**
* @return a copy of the group value of the current document
*/
public abstract T copyValue() throws IOException;
/**
* Set a restriction on the group values returned by this selector
*
* If the selector is positioned on a document whose group value is not contained
* within this set, then {@link #advanceTo(int)} will return {@link State#SKIP}
*
* @param groups a set of {@link SearchGroup} objects to limit selections to
*/
public abstract void setGroups(Collection> groups);
}