Shulou(Shulou.com)05/31 Report--

In this issue, the editor will bring you the implementation method of hive extension function development. The article is rich in content and analyzes and describes for you from a professional point of view. I hope you can get something after reading this article.

Provides the following two implementations: an inherits the org.apache.hadoop.hive.ql.exec.UDF class

The code package is packageorg.apache.hadoop.hive.ql.udf

The evaluate method is implemented, and the system automatically converts to the matching method implementation according to the input parameters and return parameter types.

For example:

UDFTestLength.java:

Importorg.apache.hadoop.io.IntWritable

Importorg.apache.hadoop.io.Text

Public classUDFTestLength extends UDF {

IntWritable result = new IntWritable ()

Public IntWritable evaluate (Text s) {

If (slots = null) {

Return null

}

Result.set (countUDF8Characters (s)

Return result

}

}

B inherits the org.apache.hadoop.hive.ql.udf.generic.GenericUDF class

The code package is packageorg.apache.hadoop.hive.ql.udf. Generic

Implement initialize, evaluate, getDisplayString methods

For example:

@ Description (name = "url_to_map", value = "_ FUNC_ (text,delimiter1, delimiter2) -"

Public class GenericUDFUrlToMap extends GenericUDF {

HashMap ret = new HashMap ()

@ Override

Public ObjectInspector initialize (ObjectInspector [] arguments)

ThrowsUDFArgumentException {

... ...

ReturnObjectInspectorFactory.getStandardMapObjectInspector (

PrimitiveObjectInspectorFactory.javaStringObjectInspector

PrimitiveObjectInspectorFactory.javaStringObjectInspector)

}

@ Override

Public Object evaluate (DeferredObject [] arguments) throws HiveException {

Ret.clear ()

... ...

Return ret

}

@ Override

Public String getDisplayString (String [] children) {

StringBuildersb = new StringBuilder ()

Sb.append ("url_to_map ("))

Assert (children.length

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