org.apache.pig
Class TypedOutputEvalFunc<OUT>

java.lang.Object
  org.apache.pig.EvalFunc<OUT>
      org.apache.pig.TypedOutputEvalFunc<OUT>

Direct Known Subclasses:

PrimitiveEvalFunc

public abstract class TypedOutputEvalFunc<OUT>
extends EvalFunc<OUT>

Base class for Pig UDFs that are functions from Tuples to generic type OUT. Handles marshalling objects, basic error checking, etc. Also infers outputSchema and provides a function to verify the input Tuple.

Extend this class and implement the

OUT exec(Tuple input)

method when writting a UDF that operates on multiple inputs from the Tuple.

Nested Class Summary

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

EvalFunc.SchemaType

Field Summary

protected Class<OUT>

outTypeClass

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

TypedOutputEvalFunc()

Method Summary

protected String	getCounterGroup() Incremented counters will use this as the counter group.
Class<OUT>	getOutputTypeClass()
protected static <T> List<Class<?>>	getTypeArguments(Class<T> baseClass, Class<? extends T> childClass) Get the actual type arguments a child class has used to extend a generic base class.
protected static void	safeIncrCounter(String group, String name, Long increment)
protected void	verifyInput(Tuple input, int minimumSize)
protected static void	verifyUdfInput(String klass, Tuple input, int minimumSize) Increment Hadoop counters for bad inputs which are either null or too small.

Methods inherited from class org.apache.pig.EvalFunc

exec, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, 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

Field Detail

outTypeClass

protected Class<OUT> outTypeClass

Constructor Detail

TypedOutputEvalFunc

public TypedOutputEvalFunc()

Method Detail

getOutputTypeClass

public Class<OUT> getOutputTypeClass()

verifyInput

protected void verifyInput(Tuple input,
                           int minimumSize)
                    throws IOException

Throws:

IOException

getCounterGroup

protected String getCounterGroup()

Incremented counters will use this as the counter group. Typically this works fine, since the subclass name is enough to identify the UDF. In some cases though (i.e. a UDF wrapper that is a facade to a number of different transformation functions), a more specific group name is needed.

getTypeArguments

protected static <T> List<Class<?>> getTypeArguments(Class<T> baseClass,
                                                     Class<? extends T> childClass)

Get the actual type arguments a child class has used to extend a generic base class.

Parameters:

baseClass - the base class

childClass - the child class

Returns:

a list of the raw classes for the actual type arguments.

verifyUdfInput

protected static void verifyUdfInput(String klass,
                                     Tuple input,
                                     int minimumSize)
                              throws IOException

Increment Hadoop counters for bad inputs which are either null or too small.

Parameters:

klass - the name of the calling class, for recording purposes

input - the tuple passed to the UDF.

minimumSize - the minimum size required of the tuple.

Throws:

IOException

safeIncrCounter

protected static void safeIncrCounter(String group,
                                      String name,
                                      Long increment)