/// <summary>Combines values for a given key.</summary>
/// <param name="key">
/// the key is expected to be a Text object, whose prefix indicates
/// the type of aggregation to aggregate the values.
/// </param>
/// <param name="values">the values to combine</param>
/// <param name="context">to collect combined values</param>
/// <exception cref="System.IO.IOException"/>
/// <exception cref="System.Exception"/>
protected internal override void Reduce(Text key, IEnumerable <Text> values, Reducer.Context
context)
{
string keyStr = key.ToString();
int pos = keyStr.IndexOf(ValueAggregatorDescriptor.TypeSeparator);
string type = Sharpen.Runtime.Substring(keyStr, 0, pos);
long uniqCount = context.GetConfiguration().GetLong(UniqValueCount.MaxNumUniqueValues
, long.MaxValue);
ValueAggregator aggregator = ValueAggregatorBaseDescriptor.GenerateValueAggregator
(type, uniqCount);
foreach (Text val in values)
{
aggregator.AddNextValue(val);
}
IEnumerator <object> outputs = aggregator.GetCombinerOutput().GetEnumerator();
while (outputs.HasNext())
{
object v = outputs.Next();
if (v is Text)
{
context.Write(key, (Text)v);
}
else
{
context.Write(key, new Text(v.ToString()));
}
}
}
/// <param name="key">
/// the key is expected to be a Text object, whose prefix indicates
/// the type of aggregation to aggregate the values. In effect, data
/// driven computing is achieved. It is assumed that each aggregator's
/// getReport method emits appropriate output for the aggregator. This
/// may be further customized.
/// </param>
/// <param name="values">the values to be aggregated</param>
/// <param name="context"></param>
/// <exception cref="System.IO.IOException"/>
/// <exception cref="System.Exception"/>
protected internal override void Reduce(Text key, IEnumerable <Text> values, Reducer.Context
context)
{
string keyStr = key.ToString();
int pos = keyStr.IndexOf(ValueAggregatorDescriptor.TypeSeparator);
string type = Sharpen.Runtime.Substring(keyStr, 0, pos);
keyStr = Sharpen.Runtime.Substring(keyStr, pos + ValueAggregatorDescriptor.TypeSeparator
.Length);
long uniqCount = context.GetConfiguration().GetLong(UniqValueCount.MaxNumUniqueValues
, long.MaxValue);
ValueAggregator aggregator = ValueAggregatorBaseDescriptor.GenerateValueAggregator
(type, uniqCount);
foreach (Text value in values)
{
aggregator.AddNextValue(value);
}
string val = aggregator.GetReport();
key = new Text(keyStr);
context.Write(key, new Text(val));
}
