org.apache.pig.builtin

Class LOWER

java.lang.Object

org.apache.pig.EvalFunc<String>

org.apache.pig.builtin.LOWER

Direct Known Subclasses:

LOWER

public class LOWER
extends EvalFunc<String>

LOWER implements eval function to convert a string to lower case Example: A = load 'mydata' as (name); B = foreach A generate LOWER(name);

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
LOWER()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	allowCompileTimeCalculation() Whether the UDF should be evaluated at compile time if all inputs are constant.
String	exec(Tuple input) Method invoked on every tuple during foreach evaluation
List<FuncSpec>	getArgToFuncMapping() Allow a UDF to specify type specific implementations of itself.
Schema	outputSchema(Schema input) This method gives a name to the column.

Methods inherited from class org.apache.pig.EvalFunc

finish, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, needEndOfAllInputProcessing, progress, setEndOfAllInput, 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

LOWER

public LOWER()

Method Detail

exec

public String exec(Tuple input)
            throws IOException

Method invoked on every tuple during foreach evaluation

Specified by:

exec in class EvalFunc<String>

Parameters:

input - tuple; first column is assumed to have the column to convert

Returns:

result, of type T.

Throws:

IOException

outputSchema

public Schema outputSchema(Schema input)

This method gives a name to the column.

Overrides:

outputSchema in class EvalFunc<String>

Parameters:

input - - schema of the input data

Returns:

schema of the input data

getArgToFuncMapping

public 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<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

allowCompileTimeCalculation

public boolean allowCompileTimeCalculation()

Description copied from class: EvalFunc

Whether the UDF should be evaluated at compile time if all inputs are constant. This is applicable for most UDF, however, if a UDF will access hdfs file which is not available at compile time, it has to be false

Overrides:

allowCompileTimeCalculation in class EvalFunc<String>

Returns:

Whether or not compile time calculation is allowed, default to false to ensure legacy UDF will get the right behavior