ArrowTest.java

import org.apache.arrow.memory.RootAllocator;
import org.apache.arrow.vector.IntVector;
import org.apache.arrow.vector.VectorSchemaRoot;
import org.apache.arrow.vector.ipc.ArrowFileReader;
import org.apache.arrow.vector.ipc.SeekableReadChannel;
import org.apache.arrow.vector.ipc.message.ArrowBlock;
import org.apache.arrow.vector.types.pojo.Schema;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

public class ArrowTest {
  public static void main(String[] args) throws IOException {
    File arrowFile = new File("/home/chathura/Downloads/test.arrow");
    FileInputStream fileInputStream = new FileInputStream(arrowFile);
    SeekableReadChannel seekableReadChannel = new SeekableReadChannel(fileInputStream.getChannel());
    ArrowFileReader arrowFileReader = new ArrowFileReader(seekableReadChannel,
        new RootAllocator(Integer.MAX_VALUE));

    VectorSchemaRoot root = arrowFileReader.getVectorSchemaRoot(); // get root
    Schema schema = root.getSchema(); // get schema

    List<ArrowBlock> arrowBlocks = arrowFileReader.getRecordBlocks();

    System.out.println(root.getFieldVectors().size());


    Iterator<Integer> x = new Iterator<Integer>() {
      int currentBlock = 0;
      int currentCell = 0;

      IntVector intVector;

      private void loadNextBlock() {
        try {
          if (currentBlock + 1 < arrowBlocks.size()) {
            arrowFileReader.loadRecordBatch(arrowBlocks.get(currentBlock++));
            intVector = (IntVector) root.getFieldVectors().get(0);
          } else {
            intVector = null;
          }
          currentCell = 0;
        } catch (IOException e) {
          e.printStackTrace();
        }
      }

      {
        // load the block intially
        loadNextBlock();
      }

      @Override
      public boolean hasNext() {
        return intVector != null && currentCell < intVector.getValueCount();
      }

      @Override
      public Integer next() {
        int value = intVector.get(currentCell++);

        // progress to next block
        if (!hasNext()) {
          loadNextBlock();
        }

        return value;
      }
    };


    int count = 0;
    while (x.hasNext()) {
      count++;
      System.out.println(x.next());
    }
    System.out.println("Read : " + count);
  }
}