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

Class FilterRows

  • All Implemented Interfaces:
    LogicalOperator, PipelineOperator<RecordPort>, RecordPipelineOperator
    public class FilterRows
extends AbstractExecutableRecordPipeline
    Filters records based on a specified predicate.

    Row selection is controlled by evaluation of the predicate against the input record. Records for which the predicate evaluates to true are emitted on the output flow. A secondary flow consisting of any records for which the predicate is false or null is also produced.

    • Constructor Detail

      • FilterRows

        public FilterRows()
        Defines a filter which accepts all records by default.

      • FilterRows

        public FilterRows​(ScalarValuedFunction p)
        Defines a filter using the specified predicate.
        Parameters:
        p - the predicate to use for filtering. The function provided must evaluate to a boolean value.

    • Method Detail

      • getRejects

        public RecordPort getRejects()
        Gets the port providing records which failed the predicate test.
        Returns:
        all records for which the predicate evaluated to false or null

      • getPredicate

        public ScalarValuedFunction getPredicate()
        Gets the predicate used by the filter operation.
        Returns:
        the predicate being used for filtering

      • setPredicate

        public void setPredicate​(ScalarValuedFunction p)
        Sets the predicate for the filter operation.
        Parameters:
        p - the predicate to use for filtering. The function provided must evaluate to a boolean value.

      • setPredicate

        public void setPredicate​(String predicateExpression)
        Sets the predicate(s) to use for filtering based on an expression similar to a where clause of a SQL query.
        Parameters:
        predicateExpression - predicate expression to apply

      • 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

      • handleInactiveOutput

        protected boolean handleInactiveOutput​(LogicalPort output)
        Description copied from class: ExecutableOperator
        Called when one of our outputs is no longer being read, to perform any cleanup necessary. The default implementation is a no-op; subclasses may wish to override it.
        Overrides:
        handleInactiveOutput in class ExecutableOperator
        Parameters:
        output - the output that has just gone inactive
        Returns:
        false if the operator should terminate when there are no more outputs.

      • 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

      • cloneForExecution

        protected ExecutableOperator cloneForExecution()
        Description copied from class: ExecutableOperator
        Performs a deep copy of the operator for execution. The default implementation is implemented in terms of JSON serialization: we perform a JSON serialization followed by a JSON deserialization. As a best-practice, operator implementations should not override this method. If they must override, though, then they must guarantee that cloneForExecution copies any instance variables that are modified by execute.
        Overrides:
        cloneForExecution in class ExecutableOperator
        Returns:
        a deep copy of this operator