library/src/main/java/com/datatorrent/lib/streamquery/SelectOperator.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;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import com.datatorrent.api.BaseOperator;
import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.lib.streamquery.condition.Condition;
import com.datatorrent.lib.streamquery.index.Index;

/**
 * An implementation of that provides sql select query semantics on live data stream. <br>
 * <p>
 * Stream rows passing condition are emitted on output port stream. <br>
 * <br>
 * <b>StateFull : NO,</b> all row data is processed in current time window. <br>
 * <b>Partitions : Yes, </b> No Input dependency among input rows. <br>
 * <br>
 * <b>Ports</b>:<br>
 * <b> inport : </b> Input hash map(row) port, expects
 * HashMap&lt;String,Object&gt;<<br>
 * <b> outport : </b> Output hash map(row) port, emits
 * HashMap&lt;String,Object&gt;<br>
 * <br>
 * <b> Properties : <b> <br>
 * <b> condition : </b> Select condition for selecting rows. <br>
 * <b> columns : </b> Column names/aggregate functions for select. <br>
 * <br>
 * @displayName: Select
 * @category: streamquery
 * @tag: sql select operator, index, sql condition
 * @since 0.3.3
 */
public class SelectOperator extends BaseOperator
{

  /**
   * select columns/expression;
   */
  private ArrayList<Index> indexes = new ArrayList<Index>();

  /**
   * condition.
   */
  private Condition condition = null;

  /**
   * add index.
   */
  public void addIndex(Index index)
  {
    indexes.add(index);
  }

  /**
   * set condition.
   */
  public void setCondition(Condition condition)
  {
    this.condition = condition;
  }

  /**
   * Input port that takes a map of &lt;string,object&gt;.
   */
  public final transient DefaultInputPort<Map<String, Object>> inport = new DefaultInputPort<Map<String, Object>>()
  {

    @Override
    public void process(Map<String, Object> tuple)
    {
      if ((condition != null) && (!condition.isValidRow(tuple)))
        return;
      if (indexes.size() == 0) {
        outport.emit(tuple);
        return;
      }
      Map<String, Object> result = new HashMap<String, Object>();
      for (int i = 0; i < indexes.size(); i++) {
        indexes.get(i).filter(tuple, result);
      }
      outport.emit(result);
    }
  };

  /**
   * Output port that emits a map of &lt;string,object&gt;.
   */
  public final transient DefaultOutputPort<Map<String, Object>> outport = new DefaultOutputPort<Map<String, Object>>();
}