[GitHub] drill pull request #1223: DRILL-6324: Unnest initial implementation

[amansinha100 <gi...@git.apache.org>]

Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/1223#discussion_r182904205
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/unnest/UnnestImpl.java ---
    @@ -0,0 +1,137 @@
    +/*
    + * 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.physical.impl.unnest;
    +
    +import com.google.common.collect.ImmutableList;
    +import org.apache.drill.exec.exception.SchemaChangeException;
    +import org.apache.drill.exec.ops.FragmentContext;
    +import org.apache.drill.exec.physical.base.LateralContract;
    +import org.apache.drill.exec.record.BatchSchema.SelectionVectorMode;
    +import org.apache.drill.exec.record.RecordBatch;
    +import org.apache.drill.exec.record.TransferPair;
    +import org.apache.drill.exec.vector.ValueVector;
    +import org.apache.drill.exec.vector.complex.RepeatedValueVector;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import java.util.List;
    +
    +/**
    + * Contains the actual unnest operation. Unnest is a simple transfer operation in this impelementation.
    + * For use as a table function, we will need to change the logic of the unnest method to operate on
    + * more than one row at a time and remove any dependence on Lateral
    + * {@link org.apache.drill.exec.physical.impl.flatten.FlattenTemplate}.
    + * This class follows the pattern of other operators that generate code at runtime. Normally this class
    + * would be abstract and have placeholders for doSetup and doEval. Unnest however, doesn't require code
    + * generation so we can simply implement the code in a simple class that looks similar to the code gen
    + * templates used by other operators but does not implement the doSetup and doEval methods.
    + */
    +public class UnnestImpl implements Unnest {
    +  private static final Logger logger = LoggerFactory.getLogger(UnnestImpl.class);
    +
    +  private static final int OUTPUT_ROW_COUNT = ValueVector.MAX_ROW_COUNT;
    +
    +  private ImmutableList<TransferPair> transfers;
    +  private LateralContract lateral; // corresponding lateral Join (or other operator implementing the Lateral Contract)
    +  private SelectionVectorMode svMode;
    +  private RepeatedValueVector fieldToUnnest;
    +  private RepeatedValueVector.RepeatedAccessor accessor;
    +
    +  /**
    +   * The output batch limit starts at OUTPUT_ROW_COUNT, but may be decreased
    +   * if records are found to be large.
    +   */
    +  private int outputLimit = OUTPUT_ROW_COUNT;
    +
    +
    +  // The index in the unnest column that is being processed.We start at zero and continue until
    +  // InnerValueCount is reached or  if the batch limit is reached
    +  // this allows for groups to be written between batches if we run out of space, for cases where we have finished
    +  // a batch on the boundary it will be set to 0
    +  private int innerValueIndex = 0;
    +
    +  @Override
    +  public void setUnnestField(RepeatedValueVector unnestField) {
    +    this.fieldToUnnest = unnestField;
    +    this.accessor = RepeatedValueVector.RepeatedAccessor.class.cast(unnestField.getAccessor());
    +  }
    +
    +  @Override
    +  public RepeatedValueVector getUnnestField() {
    +    return fieldToUnnest;
    +  }
    +
    +  @Override
    +  public void setOutputCount(int outputCount) {
    +    outputLimit = outputCount;
    +  }
    +
    +  @Override
    +  public final int unnestRecords(final int recordCount) {
    +    switch (svMode) {
    --- End diff --
    
    Is this additional check needed since setup() would have already checked svMode ?


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