Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/831#discussion_r118617482
  
    --- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/pcap/PcapRecordReader.java
 ---
    @@ -0,0 +1,295 @@
    +/*
    + * 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
    + * <p>
    + * http://www.apache.org/licenses/LICENSE-2.0
    + * <p>
    + * 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.drill.exec.store.pcap;
    +
    +import com.google.common.collect.ImmutableList;
    +import com.google.common.collect.ImmutableMap;
    +import org.apache.drill.common.exceptions.ExecutionSetupException;
    +import org.apache.drill.common.expression.SchemaPath;
    +import org.apache.drill.common.types.TypeProtos;
    +import org.apache.drill.common.types.TypeProtos.MajorType;
    +import org.apache.drill.common.types.TypeProtos.MinorType;
    +import org.apache.drill.common.types.Types;
    +import org.apache.drill.exec.exception.SchemaChangeException;
    +import org.apache.drill.exec.expr.TypeHelper;
    +import org.apache.drill.exec.ops.OperatorContext;
    +import org.apache.drill.exec.physical.impl.OutputMutator;
    +import org.apache.drill.exec.record.MaterializedField;
    +import org.apache.drill.exec.store.AbstractRecordReader;
    +import org.apache.drill.exec.store.pcap.decoder.Packet;
    +import org.apache.drill.exec.store.pcap.decoder.PacketDecoder;
    +import org.apache.drill.exec.store.pcap.dto.ColumnDto;
    +import org.apache.drill.exec.store.pcap.schema.PcapTypes;
    +import org.apache.drill.exec.store.pcap.schema.Schema;
    +import org.apache.drill.exec.vector.NullableBigIntVector;
    +import org.apache.drill.exec.vector.NullableIntVector;
    +import org.apache.drill.exec.vector.NullableTimeStampVector;
    +import org.apache.drill.exec.vector.NullableVarCharVector;
    +import org.apache.drill.exec.vector.ValueVector;
    +
    +import java.io.FileInputStream;
    +import java.io.IOException;
    +import java.io.InputStream;
    +import java.nio.ByteBuffer;
    +import java.util.List;
    +import java.util.Map;
    +
    +import static java.nio.charset.StandardCharsets.UTF_8;
    +import static org.apache.drill.exec.store.pcap.Utils.parseBytesToASCII;
    +
    +public class PcapRecordReader extends AbstractRecordReader {
    +
    +  private OutputMutator output;
    +
    +  private final PacketDecoder decoder;
    +  private ImmutableList<ProjectedColumnInfo> projectedCols;
    +
    +  private byte[] buffer = new byte[100000];
    +  private int offset = 0;
    +  private InputStream in;
    +  private int validBytes;
    +
    +  private static final Map<PcapTypes, MinorType> TYPES;
    +
    +  private static class ProjectedColumnInfo {
    +    ValueVector vv;
    +    ColumnDto pcapColumn;
    +  }
    +
    +  static {
    +    TYPES = ImmutableMap.<PcapTypes, TypeProtos.MinorType>builder()
    +        .put(PcapTypes.STRING, MinorType.VARCHAR)
    +        .put(PcapTypes.INTEGER, MinorType.INT)
    +        .put(PcapTypes.LONG, MinorType.BIGINT)
    +        .put(PcapTypes.TIMESTAMP, MinorType.TIMESTAMP)
    +        .build();
    +  }
    +
    +  public PcapRecordReader(final String inputPath,
    +                          final List<SchemaPath> projectedColumns) {
    +    try {
    +      this.in = new FileInputStream(inputPath);
    +      this.decoder = getPacketDecoder();
    +      validBytes = in.read(buffer);
    +    } catch (IOException e) {
    +      throw new RuntimeException("File " + inputPath + " not Found");
    +    }
    +    setColumns(projectedColumns);
    +  }
    +
    +  @Override
    +  public void setup(final OperatorContext context, final OutputMutator 
output) throws ExecutionSetupException {
    +    this.output = output;
    +  }
    +
    +  @Override
    +  public int next() {
    +    projectedCols = getProjectedColsIfItNull();
    +    try {
    +      return parsePcapFilesAndPutItToTable();
    --- End diff --
    
    Drill has certain protocols that are not entirely obvious, but that are 
needed here. Each call to `next()` produces a batch of rows. Drill requires 
that the batch contain no more than 64K rows. (Bad things happen if the batch 
has more.) So, the trick for a record reader is to read up to some maximum 
number of records into each batch, return, and wait to be called again for the 
next batch.
    
    Depending on the size of the data, 64K may be to large and 8K or some other 
number may be better. Try to avoid causing any vector to be larger than 16 MB. 
(We're working on a project to enforce this, and the result will make it much 
easier to write a record reader. Too bad your project is just a bit too early 
to benefit.)
    
    If I read this code correctly, each call to `next()` returns just one 
record, until EOF at which time it returns 0.
    
    You'll find that the rest of Drill will be *very* slow with a batch size of 
1 record. So, perhaps put this into a loop to read 8K or so rows into a single 
batch, then return the total record count. You should see a nice execution 
speed-up.


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