/// <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="output">to collect combined values</param>
/// <exception cref="System.IO.IOException"/>
public override void Reduce(Text key, IEnumerator <Text> values, OutputCollector <Text
, Text> output, Reporter reporter)
{
string keyStr = key.ToString();
int pos = keyStr.IndexOf(ValueAggregatorDescriptor.TypeSeparator);
string type = Sharpen.Runtime.Substring(keyStr, 0, pos);
ValueAggregator aggregator = ValueAggregatorBaseDescriptor.GenerateValueAggregator
(type);
while (values.HasNext())
{
aggregator.AddNextValue(values.Next());
}
IEnumerator outputs = aggregator.GetCombinerOutput().GetEnumerator();
while (outputs.HasNext())
{
object v = outputs.Next();
if (v is Text)
{
output.Collect(key, (Text)v);
}
else
{
output.Collect(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 customiized.
/// </param>
/// <param name="values">the values to be aggregated</param>
/// <exception cref="System.IO.IOException"/>
public override void Reduce(Text key, IEnumerator <Text> values, OutputCollector <Text
, Text> output, Reporter reporter)
{
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);
ValueAggregator aggregator = ValueAggregatorBaseDescriptor.GenerateValueAggregator
(type);
while (values.HasNext())
{
aggregator.AddNextValue(values.Next());
}
string val = aggregator.GetReport();
key = new Text(keyStr);
output.Collect(key, new Text(val));
}
/// <param name="type">the aggregation type</param>
/// <param name="id">the aggregation id</param>
/// <param name="val">the val associated with the id to be aggregated</param>
/// <returns>
/// an Entry whose key is the aggregation id prefixed with
/// the aggregation type.
/// </returns>
public static KeyValuePair <Text, Text> GenerateEntry(string type, string id, Text
val)
{
return(ValueAggregatorBaseDescriptor.GenerateEntry(type, id, val));
}