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

Class DateExtractor

java.lang.Object

org.apache.pig.EvalFunc<String>

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

public class DateExtractor
extends EvalFunc<String>

DateExtractor has four different constructors which each allow for different functionality. The incomingDateFormat ("dd/MMM/yyyy:HH:mm:ss Z" by default) is used to match the date string that gets passed in from the log. The outgoingDateFormat ("yyyy-MM-dd" by default) is used to format the returned string. Different constructors exist for each combination; please use the appropriate respective constructor. Note that any data that exists in the SimpleDateFormat schema can be supported. For example, if you were starting with the default incoming format and wanted to extract just the year, you would use the single string constructor DateExtractor("yyyy"). From pig latin you will need to use aliases to use a non-default format, like define MyDateExtractor org.apache.pig.piggybank.evaluation.util.apachelogparser.DateExtractor("yyyy-MM"); A = FOREACH row GENERATE DateExtractor(dayTime); If a string cannot be parsed, null will be returned and an error message printed to stderr. By default, the DateExtractor uses the GMT timezone. You can use the three-parameter constructor to override the timezone.

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
DateExtractor() forms the formats based on default incomingDateFormat and default outgoingDateFormat
DateExtractor(String outgoingDateString) forms the formats based on passed outgoingDateString and the default incomingDateFormat
DateExtractor(String incomingDateString, String outgoingDateString) forms the formats based on passed incomingDateString and outgoingDateString
DateExtractor(String incomingDateString, String outgoingDateString, String timeZoneID) forms the formats based on passed incomingDateString and outgoingDateString

Method Summary

Methods

Modifier and Type	Method and Description
String	exec(Tuple input) This callback method must be implemented by all subclasses.
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, needEndOfAllInputProcessing, outputSchema, 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

DateExtractor

public DateExtractor()

forms the formats based on default incomingDateFormat and default outgoingDateFormat

Parameters:

outgoingDateString - outgoingDateFormat is based on outgoingDateString

DateExtractor

public DateExtractor(String outgoingDateString)

forms the formats based on passed outgoingDateString and the default incomingDateFormat

Parameters:

outgoingDateString - outgoingDateFormat is based on outgoingDateString

DateExtractor

public DateExtractor(String incomingDateString,
             String outgoingDateString)

forms the formats based on passed incomingDateString and outgoingDateString

Parameters:

incomingDateString - incomingDateFormat is based on incomingDateString

outgoingDateString - outgoingDateFormat is based on outgoingDateString

DateExtractor

public DateExtractor(String incomingDateString,
             String outgoingDateString,
             String timeZoneID)

forms the formats based on passed incomingDateString and outgoingDateString

Parameters:

incomingDateString - incomingDateFormat is based on incomingDateString

outgoingDateString - outgoingDateFormat is based on outgoingDateString

timeZoneID - time zone id in which dates should be expressed.

Method Detail

exec

public String exec(Tuple input)
            throws 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<String>

Parameters:

input - the Tuple to be processed.

Returns:

result, of type T.

Throws:

IOException

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