library/src/main/java/com/datatorrent/lib/streamquery/index/NegateExpression.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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 com.datatorrent.lib.streamquery.index;

import java.util.Map;

import javax.validation.constraints.Null;


/**
 * An implementation of Unary Expression that implements filter method using negate metric sql semantic on column value.
 * <p>
 * @displayName: Negate Expression
 * @category: streamquery/index
 * @tag: expression, alias
 * @since 0.3.4
 */
public class NegateExpression extends UnaryExpression
{

  /**
   * @param column   Name of column value to be negated.
   */
  public NegateExpression(@Null String column, String alias)
  {
    super(column, alias);
    if (this.alias == null)  this.alias = "NEGATE(" + column + ")";
  }

  /* (non-Javadoc)
   * @see com.datatorrent.lib.streamquery.index.Index#filter(java.util.Map, java.util.Map)
   */
  @Override
  public void filter(Map<String, Object> row, Map<String, Object> collect)
  {
    if (!row.containsKey(column)) return;
    collect.put(alias, -((Number)row.get(column)).doubleValue());
  }
}