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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill pull request #1027: DRILL-4779 : Kafka storage plugin
Date Thu, 09 Nov 2017 21:14:38 GMT
Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/1027#discussion_r150087815
  
    --- Diff: contrib/storage-kafka/src/main/java/org/apache/drill/exec/store/kafka/KafkaScanBatchCreator.java
---
    @@ -0,0 +1,61 @@
    +/**
    + * 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.drill.exec.store.kafka;
    +
    +import java.util.List;
    +
    +import org.apache.drill.common.exceptions.ExecutionSetupException;
    +import org.apache.drill.common.expression.SchemaPath;
    +import org.apache.drill.exec.ops.FragmentContext;
    +import org.apache.drill.exec.physical.base.GroupScan;
    +import org.apache.drill.exec.physical.impl.BatchCreator;
    +import org.apache.drill.exec.physical.impl.ScanBatch;
    +import org.apache.drill.exec.record.CloseableRecordBatch;
    +import org.apache.drill.exec.record.RecordBatch;
    +import org.apache.drill.exec.store.RecordReader;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import com.google.common.base.Preconditions;
    +import com.google.common.collect.Lists;
    +
    +public class KafkaScanBatchCreator implements BatchCreator<KafkaSubScan> {
    +  static final Logger logger = LoggerFactory.getLogger(KafkaScanBatchCreator.class);
    +
    +  @Override
    +  public CloseableRecordBatch getBatch(FragmentContext context, KafkaSubScan subScan,
List<RecordBatch> children)
    +      throws ExecutionSetupException {
    +    Preconditions.checkArgument(children.isEmpty());
    +    List<RecordReader> readers = Lists.newArrayList();
    +    List<SchemaPath> columns = null;
    +    for (KafkaSubScan.KafkaSubScanSpec scanSpec : subScan.getPartitionSubScanSpecList())
{
    +      try {
    +        if ((columns = subScan.getCoulmns()) == null) {
    +          columns = GroupScan.ALL_COLUMNS;
    +        }
    --- End diff --
    
    When will the columns be null? Not sure this is a valid state. However, as noted above,
an empty list is a valid state (used for `COUNT(*)` queries.)


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