| /* |
| * 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.iotdb.db.queryengine.execution.operator.process; |
| |
| import org.apache.iotdb.db.queryengine.execution.operator.Operator; |
| import org.apache.iotdb.db.queryengine.execution.operator.OperatorContext; |
| |
| import com.google.common.util.concurrent.ListenableFuture; |
| import org.apache.tsfile.read.common.block.TsBlock; |
| |
| import static com.google.common.base.Preconditions.checkArgument; |
| import static java.util.Objects.requireNonNull; |
| |
| public class LimitOperator implements ProcessOperator { |
| |
| private final OperatorContext operatorContext; |
| private long remainingLimit; |
| private final Operator child; |
| |
| public LimitOperator(OperatorContext operatorContext, long limit, Operator child) { |
| this.operatorContext = requireNonNull(operatorContext, "operatorContext is null"); |
| checkArgument(limit >= 0, "limit must be at least zero"); |
| this.remainingLimit = limit; |
| this.child = requireNonNull(child, "child operator is null"); |
| } |
| |
| @Override |
| public OperatorContext getOperatorContext() { |
| return operatorContext; |
| } |
| |
| @Override |
| public ListenableFuture<?> isBlocked() { |
| return child.isBlocked(); |
| } |
| |
| @Override |
| public TsBlock next() throws Exception { |
| TsBlock block = child.nextWithTimer(); |
| if (block == null) { |
| return null; |
| } |
| TsBlock res = block; |
| if (block.getPositionCount() <= remainingLimit) { |
| remainingLimit -= block.getPositionCount(); |
| } else { |
| res = block.getRegion(0, (int) remainingLimit); |
| remainingLimit = 0; |
| } |
| return res; |
| } |
| |
| @Override |
| public boolean hasNext() throws Exception { |
| return remainingLimit > 0 && child.hasNextWithTimer(); |
| } |
| |
| @Override |
| public void close() throws Exception { |
| child.close(); |
| } |
| |
| @Override |
| public boolean isFinished() throws Exception { |
| return remainingLimit == 0 || child.isFinished(); |
| } |
| |
| @Override |
| public long calculateMaxPeekMemory() { |
| return child.calculateMaxPeekMemoryWithCounter(); |
| } |
| |
| @Override |
| public long calculateMaxReturnSize() { |
| return child.calculateMaxReturnSize(); |
| } |
| |
| @Override |
| public long calculateRetainedSizeAfterCallingNext() { |
| return child.calculateRetainedSizeAfterCallingNext(); |
| } |
| } |