org.apache.pig.piggybank.evaluation.util.apachelogparser

Class HostExtractor

java.lang.Object

org.apache.pig.EvalFunc<java.lang.String>

org.apache.pig.piggybank.evaluation.util.apachelogparser.HostExtractor

public class HostExtractor
extends EvalFunc<java.lang.String>

HostExtractor takes a url and returns the host. For example, http://sports.espn.go.com/mlb/recap?gameId=281009122 leads to sports.espn.go.com Pig latin usage looks like host = FOREACH row GENERATE org.apache.pig.piggybank.evaluation.util.apachelogparser.HostExtractor(referer);

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.pig.EvalFunc

EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
HostExtractor()

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.String	exec(Tuple input) This callback method must be implemented by all subclasses.
java.util.List<FuncSpec>	getArgToFuncMapping() Allow a UDF to specify type specific implementations of itself.

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, outputSchema, progress, setInputSchema, setPigLogger, setReporter, setUDFContextSignature, warn

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HostExtractor

public HostExtractor()

Method Detail

exec

public java.lang.String exec(Tuple input)
                      throws java.io.IOException

Description copied from class: EvalFunc

This callback method must be implemented by all subclasses. This is the method that will be invoked on every Tuple of a given dataset. Since the dataset may be divided up in a variety of ways the programmer should not make assumptions about state that is maintained between invocations of this method.

Specified by:

exec in class EvalFunc<java.lang.String>

Parameters:

input - the Tuple to be processed.

Returns:

result, of type T.

Throws:

java.io.IOException

getArgToFuncMapping

public java.util.List<FuncSpec> getArgToFuncMapping()
                                             throws FrontendException

Description copied from class: EvalFunc

Allow a UDF to specify type specific implementations of itself. For example, an implementation of arithmetic sum might have int and float implementations, since integer arithmetic performs much better than floating point arithmetic. Pig's typechecker will call this method and using the returned list plus the schema of the function's input data, decide which implementation of the UDF to use.

Overrides:

getArgToFuncMapping in class EvalFunc<java.lang.String>

Returns:

A List containing FuncSpec objects representing the EvalFunc class which can handle the inputs corresponding to the schema in the objects. Each FuncSpec should be constructed with a schema that describes the input for that implementation. For example, the sum function above would return two elements in its list:

1. FuncSpec(this.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.DOUBLE)))
2. FuncSpec(IntSum.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.INTEGER)))

This would indicate that the main implementation is used for doubles, and the special implementation IntSum is used for ints.

Throws:

FrontendException