com.datatorrent.lib.streamquery.function.MaxMinFunction Maven / Gradle / Ivy
/**
* 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 com.datatorrent.lib.streamquery.function;
import java.util.ArrayList;
import java.util.Map;
import javax.validation.constraints.NotNull;
import org.apache.commons.lang.StringUtils;
/**
* An implementation of function index that implements sql max and sql min function semantic.
*
* e.g : sql => SELECT MAX/MIN(column_name) FROM table_name.
*
* Properties :
* column : column name for values max/min computation.
* alias : Alias name for output value.
* isMax : Flag to indicate max/min compute value.
* @displayName Max Min Function
* @category Stream Manipulators
* @tags sql max, sql min
* @since 0.3.4
*/
public class MaxMinFunction extends FunctionIndex
{
/**
* Flag to indicate max/min compute value, compute max if true.
*/
private boolean isMax = true;
/**
* @param column column name for values max/min computation.
* @param alias Alias name for output.
* @param isMax Flag to indicate max/min compute value.
*/
public MaxMinFunction(@NotNull String column, String alias, boolean isMin)
{
super(column, alias);
isMax = !isMin;
}
/**
* Compute max/min for given column.
* @return max/min value.
*/
@Override
public Object compute(ArrayList> rows) throws Exception
{
double minMax = 0.0;
for (Map row : rows) {
double value = ((Number)row.get(column)).doubleValue();
if ((isMax && (minMax < value)) || (!isMax && (minMax > value))) {
minMax = value;
}
}
return minMax;
}
/**
* Aggregate output name.
* @return name string.
*/
@Override
protected String aggregateName()
{
if (!StringUtils.isEmpty(alias)) {
return alias;
}
if (isMax) {
return "MAX(" + column + ")";
}
return "MIN(" + column + ")";
}
public boolean isMax()
{
return isMax;
}
public void setMax(boolean isMax)
{
this.isMax = isMax;
}
}