org.apache.hadoop.hive.ql.exec

Class UDF

java.lang.Object

org.apache.hadoop.hive.ql.exec.UDF

Direct Known Subclasses:

UDFAscii, UDFBase64, UDFBaseBitOP, UDFBin, UDFConv, UDFDayOfMonth, UDFE, UDFExampleAdd, UDFExampleArraySum, UDFExampleFormat, UDFExampleMapConcat, UDFExampleStructPrint, UDFFindInSet, UDFFromUnixTime, UDFHex, UDFHour, UDFJson, UDFLength, UDFLike, UDFMath, UDFMinute, UDFMonth, UDFOPLongDivide, UDFParseUrl, UDFPI, UDFRand, UDFRegExp, UDFRegExpExtract, UDFRegExpReplace, UDFRepeat, UDFReverse, UDFRowSequence, UDFSecond, UDFSign, UDFSpace, UDFSubstr, UDFToBoolean, UDFToByte, UDFToDouble, UDFToFloat, UDFToInteger, UDFToLong, UDFToShort, UDFToString, UDFUnbase64, UDFUnhex, UDFWeekOfYear, UDFXPathBoolean, UDFXPathDouble, UDFXPathFloat, UDFXPathInteger, UDFXPathLong, UDFXPathShort, UDFXPathString, UDFYear

public class UDF
extends Object

A User-defined function (UDF) for use with Hive.

New UDF classes need to inherit from this UDF class (or from GenericUDF which provides more flexibility at the cost of more complexity).

Requirements for all classes extending this UDF are:

• Implement one or more methods named evaluate which will be called by Hive (the exact way in which Hive resolves the method to call can be configured by setting a custom UDFMethodResolver). The following are some examples:
  • public int evaluate();
  • public int evaluate(int a);
  • public double evaluate(int a, double b);
  • public String evaluate(String a, int b, Text c);
  • public Text evaluate(String a);
  • public String evaluate(List<Integer> a); (Note that Hive Arrays are represented as Lists in Hive. So an ARRAY<int> column would be passed in as a List<Integer>.)
• evaluate should never be a void method. However it can return null if needed.
• Return types as well as method arguments can be either Java primitives or the corresponding Writable class.

One instance of this class will be instantiated per JVM and it will not be called concurrently.

See Also:

Description, UDFType

Constructor Summary

Constructors

Modifier	Constructor and Description
	UDF() The constructor.
protected	UDF(UDFMethodResolver rslv) The constructor with user-provided UDFMethodResolver.

Method Summary

Methods

Modifier and Type	Method and Description
String[]	getRequiredFiles() This can be overridden to include files required by this UDF.
String[]	getRequiredJars() This can be overridden to include JARs required by this UDF.
UDFMethodResolver	getResolver() Get the method resolver.
void	setResolver(UDFMethodResolver rslv) Sets the resolver.

Methods inherited from class java.lang.Object

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

Constructor Detail

UDF

public UDF()

The constructor.

UDF

protected UDF(UDFMethodResolver rslv)

The constructor with user-provided UDFMethodResolver.

Method Detail

setResolver

public void setResolver(UDFMethodResolver rslv)

Sets the resolver.

Parameters:

rslv - The method resolver to use for method resolution.

getResolver

public UDFMethodResolver getResolver()

Get the method resolver.

getRequiredJars

public String[] getRequiredJars()

This can be overridden to include JARs required by this UDF.

Returns:

an array of paths to files to include, null by default.

See Also:

GenericUDF.getRequiredJars()

getRequiredFiles

public String[] getRequiredFiles()

This can be overridden to include files required by this UDF.

Returns:

an array of paths to files to include, null by default.

See Also:

GenericUDF.getRequiredFiles()