com.pervasive.datarush.analytics.text

Class TextStemmer

java.lang.Object

com.pervasive.datarush.operators.AbstractLogicalOperator

com.pervasive.datarush.operators.StreamingOperator

com.pervasive.datarush.operators.ExecutableOperator

com.pervasive.datarush.analytics.text.TextStemmer

All Implemented Interfaces:

LogicalOperator, PipelineOperator<RecordPort>, RecordPipelineOperator

public class TextStemmer
extends ExecutableOperator
implements RecordPipelineOperator

Stems a TokenizedText field. This operator can be used to stem a tokenized text field. Stemming is the process for removing the commoner morphological and inflexional endings from words. The TextStemmer has three properties: input field, output field, and the stemmer that should be used. The input field must be a tokenized text object. The tokenized text object will have all of it's tokens stemmed using the specified stemmer algorithm. This will produce a new tokenized text object that will be encoded into the output field. This object can then be used for further text processing tasks.

Constructor Summary

Constructors

Constructor and Description
TextStemmer() Default constructor.
TextStemmer(String textField) Constructor specifying the tokenized text field to stem.
TextStemmer(String textField, StemmerType type) Constructor specifying the tokenized text field to stem and the stemmer to utilize.

Method Summary

Modifier and Type	Method and Description
protected void	computeMetadata(StreamingMetadataContext ctx) Implementations must adhere to the following contracts
protected void	execute(ExecutionContext ctx) Executes the operator.
RecordPort	getInput() Get the input port of this operator.
String	getInputField() Get the tokenized text field to stem.
RecordPort	getOutput() Get the output port of this operator.
String	getOutputField() Get the stemmed output field.
StemmerType	getStemmerType() Get the stemmer that will be used.
void	setInputField(String textField) Set the field to stem.
void	setOutputField(String tokenField) Set the stemmed output field.
void	setStemmerType(StemmerType type) Set the stemmer the operator should use.

Methods inherited from class com.pervasive.datarush.operators.ExecutableOperator

cloneForExecution, getNumInputCopies, getPortSettings, handleInactiveOutput

Methods inherited from class com.pervasive.datarush.operators.AbstractLogicalOperator

disableParallelism, getInputPorts, getOutputPorts, newInput, newInput, newOutput, newRecordInput, newRecordInput, newRecordOutput, notifyError

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.pervasive.datarush.operators.LogicalOperator

disableParallelism, getInputPorts, getOutputPorts

Constructor Detail

TextStemmer

public TextStemmer()

Default constructor. Use setInputField(String) and setOutputField(String) to set the name of the text field to stem and its output field.

TextStemmer

public TextStemmer(String textField)

Constructor specifying the tokenized text field to stem.

Parameters:

textField - name of the field to stem

TextStemmer

public TextStemmer(String textField,
                   StemmerType type)

Constructor specifying the tokenized text field to stem and the stemmer to utilize.

Parameters:

textField - name of the field to stem

type - stemmer algorithm to use

Method Detail

setInputField

public void setInputField(String textField)

Set the field to stem.

If this field does not exist in the input, or is not of type TokenizedText, an exception will be thrown at composition time.

Parameters:

textField - the name of the field to stem

getInputField

public String getInputField()

Get the tokenized text field to stem.

Returns:

The name of the field to stem

setOutputField

public void setOutputField(String tokenField)

Set the stemmed output field. If unspecified will overwrite the original input field.

Parameters:

tokenField - name of the token output field

getOutputField

public String getOutputField()

Get the stemmed output field. If unspecified will overwrite the original input field.

Returns:

The name of the stemmed output field

setStemmerType

public void setStemmerType(StemmerType type)

Set the stemmer the operator should use.

Parameters:

type - the stemmer algorithm to use

getStemmerType

public StemmerType getStemmerType()

Get the stemmer that will be used.

Returns:

the stemmer to use

getInput

public RecordPort getInput()

Get the input port of this operator.

Specified by:

getInput in interface PipelineOperator<RecordPort>

Returns:

input port

getOutput

public RecordPort getOutput()

Get the output port of this operator.

Specified by:

getOutput in interface PipelineOperator<RecordPort>

Returns:

output port

computeMetadata

protected void computeMetadata(StreamingMetadataContext ctx)

Description copied from class: StreamingOperator

Implementations must adhere to the following contracts

General

Regardless of input ports/output port types, all implementations must do the following:

1. Validation. Validation of configuration should always be performed first.
2. Declare parallelizability.. Implementations must declare parallelizability by calling StreamingMetadataContext.parallelize(ParallelismStrategy).

Input record ports

Implementations with input record ports must declare the following:

1. Required data ordering:
Implementations that have data ordering requirements must declare them by calling RecordPort#setRequiredDataOrdering, otherwise data may arrive in any order.
2. Required data distribution (only applies to parallelizable operators):
Implementations that have data distribution requirements must declare them by calling RecordPort#setRequiredDataDistribution, otherwise data will arrive in an unspecified partial distribution.

Note that if the upstream operator's output distribution/ordering is compatible with those required, we avoid a re-sort/re-distribution which is generally a very large savings from a performance standpoint. In addition, some operators may chose to query the upstream output distribution/ordering by calling RecordPort#getSourceDataDistribution and RecordPort#getSourceDataOrdering. These should be viewed as a hints to help chose a more efficient algorithm. In such cases, though, operators must still declare data ordering and data distribution requirements; otherwise there is no guarantee that data will arrive sorted/distributed as required.

Output record ports

Implementations with output record ports must declare the following:

1. Type: Implementations must declare their output type by calling RecordPort#setType.

Implementations with output record ports may declare the following:

1. Output data ordering: Implementations that can make guarantees as to their output ordering may do so by calling RecordPort#setOutputDataOrdering
2. Output data distribution (only applies to parallelizable operators): Implementations that can make guarantees as to their output distribution may do so by calling RecordPort#setOutputDataDistribution

Note that both of these properties are optional; if unspecified, performance may suffer since the framework may unnecessarily re-sort/re-distributed the data.

Input model ports

In general, there is nothing special to declare for input model ports. Models are implicitly duplicated to all partitions when going from non-parallel to parallel operators. The case of a model going from a parallel to a non-parallel node is a special case of a "model reducer" operator. In the case of a model reducer, the downstream operator, must declare the following:

1. Merge handler: Model reducers must declare a merge handler by calling AbstractModelPort#setMergeHandler.

Note that MergeModel is a convenient, re-usable model reducer, parameterized with a merge-handler.

Output model ports

SimpleModelPort's have no associated metadata and therefore there is never any output metadata to declare. PMMLPort's, on the other hand, do have associated metadata. For all PMMLPorts, implementations must declare the following:

1. pmmlModelSpec: Implementations must declare the PMML model spec by calling PMMLPort.setPMMLModelSpec.

Specified by:

computeMetadata in class StreamingOperator

Parameters:

ctx - the context

execute

protected void execute(ExecutionContext ctx)

Description copied from class: ExecutableOperator

Executes the operator. Implementations should adhere to the following contracts:

1. Following execution, all input ports must be at end-of-data.
2. Following execution, all output ports must be at end-of-data.

Specified by:

execute in class ExecutableOperator

Parameters:

ctx - context in which to lookup physical ports bound to logical ports