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

Class MergeFields

  • All Implemented Interfaces:
    LogicalOperator, RecordSourceOperator, SourceOperator<RecordPort>
    public class MergeFields
extends ExecutableOperator
implements RecordSourceOperator
    Merges two streams of data with an equivalent number of rows into one. The output type contains all the fields from the "left" input followed by those from the "right" input. If any names exist in both the left and right input, the collision is resolved by renaming the fields from the right. Refer to TypeUtil.merge(RecordTokenType...) for more details on the resolution mechanism.

    This operator is non-parallel, as the equivalence of input sizes cannot be guaranteed in a parallel context; using this operator will force a gather of the input to a single machine. Even then, care must be taken to ensure the ordering of input records is consistent with the desired result. Generally, this operator only makes sense when used inside a DeferredCompositeOperator where these guarantees can be made.

    • Constructor Detail

      • MergeFields

        public MergeFields()

    • Method Detail

      • getLeftInput

        public RecordPort getLeftInput()
        Gets the record port providing the "left" input for the merge. This is the input merged into the output first. Names from this port will be taken intact.
        Returns:
        the "left" input port of the merge

      • getRightInput

        public RecordPort getRightInput()
        Gets the record port providing the "right" input for the merge. The right input is merged into the output after the left. This may cause name collisions; collisions will be resolved by renaming the offending fields from the right. Non-colliding names are taken intact.
        Returns:
        the "right" input port of the merge

      • 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