spark VectorizedDeltaLengthByteArrayReader 源码

spark VectorizedDeltaLengthByteArrayReader 代码

文件路径：/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedDeltaLengthByteArrayReader.java

/*
 * 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.spark.sql.execution.datasources.parquet;

import static org.apache.spark.sql.types.DataTypes.IntegerType;

import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteBuffer;
import org.apache.parquet.bytes.ByteBufferInputStream;
import org.apache.parquet.io.ParquetDecodingException;
import org.apache.spark.sql.execution.vectorized.OnHeapColumnVector;
import org.apache.spark.sql.execution.vectorized.WritableColumnVector;

/**
 * An implementation of the Parquet DELTA_LENGTH_BYTE_ARRAY decoder that supports the vectorized
 * interface.
 */
public class VectorizedDeltaLengthByteArrayReader extends VectorizedReaderBase implements
    VectorizedValuesReader {

  private final VectorizedDeltaBinaryPackedReader lengthReader;
  private ByteBufferInputStream in;
  private WritableColumnVector lengthsVector;
  private int currentRow = 0;

  VectorizedDeltaLengthByteArrayReader() {
    lengthReader = new VectorizedDeltaBinaryPackedReader();
  }

  @Override
  public void initFromPage(int valueCount, ByteBufferInputStream in) throws IOException {
    lengthsVector = new OnHeapColumnVector(valueCount, IntegerType);
    lengthReader.initFromPage(valueCount, in);
    lengthReader.readIntegers(lengthReader.getTotalValueCount(), lengthsVector, 0);
    this.in = in.remainingStream();
  }

  @Override
  public void readBinary(int total, WritableColumnVector c, int rowId) {
    ByteBuffer buffer;
    ByteBufferOutputWriter outputWriter = ByteBufferOutputWriter::writeArrayByteBuffer;
    int length;
    for (int i = 0; i < total; i++) {
      length = lengthsVector.getInt(rowId + i);
      try {
        buffer = in.slice(length);
      } catch (EOFException e) {
        throw new ParquetDecodingException("Failed to read " + length + " bytes");
      }
      outputWriter.write(c, rowId + i, buffer, length);
    }
    currentRow += total;
  }

  public ByteBuffer getBytes(int rowId) {
    int length = lengthsVector.getInt(rowId);
    try {
      return in.slice(length);
    } catch (EOFException e) {
      throw new ParquetDecodingException("Failed to read " + length + " bytes");
    }
  }

  @Override
  public void skipBinary(int total) {
    for (int i = 0; i < total; i++) {
      int remaining = lengthsVector.getInt(currentRow + i);
      while (remaining > 0) {
        remaining -= in.skip(remaining);
      }
    }
    currentRow += total;
  }
}

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