processing/src/main/java/org/apache/druid/query/groupby/epinephelinae/column/NullableNumericGroupByColumnSelectorStrategy.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.druid.query.groupby.epinephelinae.column;

import org.apache.druid.common.config.NullHandling;
import org.apache.druid.query.groupby.ResultRow;
import org.apache.druid.query.groupby.epinephelinae.Grouper;
import org.apache.druid.query.groupby.epinephelinae.GrouperBufferComparatorUtils;
import org.apache.druid.query.ordering.StringComparator;
import org.apache.druid.segment.ColumnValueSelector;

import javax.annotation.Nullable;
import java.nio.ByteBuffer;

/**
 * A wrapper around a numeric {@link GroupByColumnSelectorStrategy} that makes it null-aware. Should only be used
 * for numeric strategies, not for string strategies.
 *
 * @see org.apache.druid.segment.BaseNullableColumnValueSelector#isNull() for why this only works in the numeric case
 */
public class NullableNumericGroupByColumnSelectorStrategy implements GroupByColumnSelectorStrategy
{
  private final GroupByColumnSelectorStrategy delegate;
  private final byte[] nullKeyBytes;

  public NullableNumericGroupByColumnSelectorStrategy(GroupByColumnSelectorStrategy delegate)
  {
    this.delegate = delegate;
    this.nullKeyBytes = new byte[delegate.getGroupingKeySize() + 1];
    this.nullKeyBytes[0] = NullHandling.IS_NULL_BYTE;
  }

  @Override
  public int getGroupingKeySize()
  {
    return delegate.getGroupingKeySize() + Byte.BYTES;
  }

  @Override
  public void processValueFromGroupingKey(
      GroupByColumnSelectorPlus selectorPlus,
      ByteBuffer key,
      ResultRow resultRow,
      int keyBufferPosition
  )
  {
    if (key.get(keyBufferPosition) == NullHandling.IS_NULL_BYTE) {
      resultRow.set(selectorPlus.getResultRowPosition(), null);
    } else {
      delegate.processValueFromGroupingKey(selectorPlus, key, resultRow, keyBufferPosition + Byte.BYTES);
    }
  }

  @Override
  public int initColumnValues(ColumnValueSelector selector, int columnIndex, Object[] values)
  {
    if (selector.isNull()) {
      values[columnIndex] = null;
      return 0;
    } else {
      return delegate.initColumnValues(selector, columnIndex, values);
    }
  }

  @Override
  public int writeToKeyBuffer(int keyBufferPosition, ColumnValueSelector selector, ByteBuffer keyBuffer)
  {
    if (selector.isNull()) {
      keyBuffer.position(keyBufferPosition);
      keyBuffer.put(nullKeyBytes);
      return 0;
    } else {
      keyBuffer.put(keyBufferPosition, NullHandling.IS_NOT_NULL_BYTE);
      return delegate.writeToKeyBuffer(keyBufferPosition + Byte.BYTES, selector, keyBuffer);
    }
  }

  @Override
  public Grouper.BufferComparator bufferComparator(
      int keyBufferPosition,
      @Nullable StringComparator stringComparator
  )
  {
    return GrouperBufferComparatorUtils.makeNullHandlingBufferComparatorForNumericData(
        keyBufferPosition,
        delegate.bufferComparator(keyBufferPosition + Byte.BYTES, stringComparator)
    );
  }

  @Override
  public void initGroupingKeyColumnValue(
      int keyBufferPosition,
      int dimensionIndex,
      Object rowObj,
      ByteBuffer keyBuffer,
      int[] stack
  )
  {
    if (rowObj == null) {
      keyBuffer.position(keyBufferPosition);
      keyBuffer.put(nullKeyBytes);
    } else {
      keyBuffer.put(keyBufferPosition, NullHandling.IS_NOT_NULL_BYTE);

      // No need to update stack ourselves; we expect the delegate to do this.
      delegate.initGroupingKeyColumnValue(
          keyBufferPosition + Byte.BYTES,
          dimensionIndex,
          rowObj,
          keyBuffer,
          stack
      );
    }
  }

  @Override
  public boolean checkRowIndexAndAddValueToGroupingKey(
      int keyBufferPosition,
      Object rowObj,
      int rowValIdx,
      ByteBuffer keyBuffer
  )
  {
    // rows from a nullable column always have a single value, multi-value is not currently supported
    // this method handles row values after the first in a multivalued row, so just return false
    return false;
  }

  @Override
  public void reset()
  {
    delegate.reset();
  }
}