org.apache.jackrabbit.oak.plugins.index.cursor.ConcatCursor 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.jackrabbit.oak.plugins.index.cursor;
import java.util.HashSet;
import java.util.List;
import org.apache.jackrabbit.oak.api.Result.SizePrecision;
import org.apache.jackrabbit.oak.query.FilterIterators;
import org.apache.jackrabbit.oak.query.QueryImpl;
import org.apache.jackrabbit.oak.spi.query.Cursor;
import org.apache.jackrabbit.oak.spi.query.IndexRow;
import org.apache.jackrabbit.oak.spi.query.QueryLimits;
/**
* A cursor that combines multiple cursors into a single cursor.
*/
class ConcatCursor extends AbstractCursor {
private final HashSet seen = new HashSet();
private final List cursors;
private final QueryLimits settings;
private boolean init;
private boolean closed;
private Cursor currentCursor;
private int cursorListIndex;
private IndexRow current;
ConcatCursor(List cursors, QueryLimits settings) {
this.cursors = cursors;
this.settings = settings;
nextCursor();
}
private void nextCursor() {
if (cursorListIndex >= cursors.size()) {
init = true;
closed = true;
} else {
currentCursor = cursors.get(cursorListIndex++);
}
}
@Override
public IndexRow next() {
if (closed) {
throw new IllegalStateException("This cursor is closed");
}
if (!init) {
fetchNext();
init = true;
}
IndexRow result = current;
init = false;
return result;
}
@Override
public boolean hasNext() {
if (!closed && !init) {
fetchNext();
init = true;
}
return !closed;
}
private void fetchNext() {
while (true) {
while (!currentCursor.hasNext()) {
nextCursor();
if (closed) {
return;
}
}
IndexRow c = currentCursor.next();
String p = c.getPath();
if (seen.contains(p)) {
continue;
}
current = c;
markSeen(p);
return;
}
}
private void markSeen(String path) {
seen.add(path);
FilterIterators.checkMemoryLimit(seen.size(), settings);
}
@Override
public long getSize(SizePrecision precision, long max) {
// this is the worst case (duplicate entries are counted twice)
long total = 0;
for (Cursor c : cursors) {
long t = c.getSize(precision, max);
if (t < 0) {
return -1;
}
total = QueryImpl.saturatedAdd(total, t);
}
return total;
}
}