Module datarush.library
Package com.pervasive.datarush.operators.source

Class GenerateConstant

java.lang.Object
com.pervasive.datarush.operators.AbstractLogicalOperator
com.pervasive.datarush.operators.StreamingOperator
com.pervasive.datarush.operators.ExecutableOperator
com.pervasive.datarush.operators.source.GenerateConstant
All Implemented Interfaces:
LogicalOperator, RecordSourceOperator, SourceOperator<RecordPort>
public final class GenerateConstant extends ExecutableOperator implements RecordSourceOperator
Generates copies of a constant value.

  • Constructor Details

    • GenerateConstant

      public GenerateConstant()
      The default constructor. Prior to graph compilation the following properties should be specified

    • GenerateConstant

      public GenerateConstant(RecordToken constant, long rowCount)
      Creates a new instance of GenerateConstant, specifying the minimal set of required parameters.
      Parameters:
      constant - the constant to generate
      rowCount - the number of rows

  • Method Details

    • getOutput

      public RecordPort getOutput()
      Description copied from interface: RecordSourceOperator
      Gets the record port providing the output data from the source.
      Specified by:
      getOutput in interface RecordSourceOperator
      Specified by:
      getOutput in interface SourceOperator<RecordPort>
      Returns:
      the output port for the source

    • getConstant

      public RecordToken getConstant()
      Returns the value to generate
      Returns:
      the value to generate

    • setConstant

      public void setConstant(RecordToken constant)
      Sets the value to generate
      Parameters:
      constant - the value to generate

    • getRowCount

      public long getRowCount()
      Returns the number of values to generate
      Returns:
      the number of values to generate

    • setRowCount

      public void setRowCount(long rowCount)
      Sets the number of values to generate
      Parameters:
      rowCount - the number of values to generate

    • 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:
        2. 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):
        3. 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