zhztheplayer commented on a change in pull request #7030: URL: https://github.com/apache/arrow/pull/7030#discussion_r440098238
########## File path: java/dataset/src/main/java/org/apache/arrow/dataset/jni/NativeScanner.java ########## @@ -0,0 +1,143 @@ +/* + * 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.arrow.dataset.jni; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.Collections; +import java.util.NoSuchElementException; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.stream.Collectors; + +import org.apache.arrow.dataset.scanner.ScanTask; +import org.apache.arrow.dataset.scanner.Scanner; +import org.apache.arrow.memory.ArrowBuf; +import org.apache.arrow.memory.BufferAllocator; +import org.apache.arrow.memory.BufferLedger; +import org.apache.arrow.memory.NativeUnderlingMemory; +import org.apache.arrow.memory.Ownerships; +import org.apache.arrow.vector.ipc.message.ArrowFieldNode; +import org.apache.arrow.vector.ipc.message.ArrowRecordBatch; +import org.apache.arrow.vector.types.pojo.Schema; +import org.apache.arrow.vector.util.SchemaUtility; + +/** + * Native implementation of {@link Scanner}. Note that it currently emits only a single scan task of type + * {@link NativeScanTask}, which is internally a combination of all scan task instances returned by the + * native scanner. + */ +public class NativeScanner implements Scanner { + + private final AtomicBoolean closed = new AtomicBoolean(false); + private final AtomicBoolean executed = new AtomicBoolean(false); + private final NativeContext context; + private final long scannerId; + + public NativeScanner(NativeContext context, long scannerId) { + this.context = context; + this.scannerId = scannerId; + } + + ScanTask.BatchIterator execute() { + if (closed.get()) { + throw new NativeInstanceClosedException(); + } + if (!executed.compareAndSet(false, true)) { + throw new UnsupportedOperationException("NativeScanner cannot be executed more than once. Consider creating " + + "new scanner instead"); + } + return new ScanTask.BatchIterator() { + private ArrowRecordBatch peek = null; + + @Override + public void close() { + NativeScanner.this.close(); + } + + @Override + public boolean hasNext() { + if (closed.get()) { Review comment: Thanks for catching! I've pushed a mutex solution. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
