com.pervasive.datarush.functions

Class EvaluationContext

java.lang.Object

com.pervasive.datarush.functions.EvaluationContext

public class EvaluationContext
extends Object

An object describing the context in which a subexpression of a larger expression is being evaluated. The context captures global information pertaining to the top-level expression containing the subexpression.

Constructor Summary

Constructors

Constructor and Description
EvaluationContext(RecordValued input)

Method Summary

Methods

Modifier and Type	Method and Description
FunctionEvaluator	constructEvaluator(EvaluatorFactory factory, List<Object> arguments, ScalarSettable result) Creates an evaluator for a top-level expression, binding its output to the provided result buffer.
ScalarValued	constructSubexpressionEvaluation(EvaluatorFactory factory, List<Object> arguments, ScalarTokenType resultType) Creates an evaluation of a subexpression which can be used as input to the evaluator of the expression containing it.
FunctionEvaluator	createMemoizingEvaluator(FunctionEvaluator f) Creates an evaluator for the top-level expression which memoizes subexpression values.
RecordValued	getInput() Gets the input record used for the top-level expression.

Methods inherited from class java.lang.Object

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

Constructor Detail

EvaluationContext

public EvaluationContext(RecordValued input)

Method Detail

getInput

public RecordValued getInput()

Gets the input record used for the top-level expression.

Returns:

createMemoizingEvaluator

public FunctionEvaluator createMemoizingEvaluator(FunctionEvaluator f)

Creates an evaluator for the top-level expression which memoizes subexpression values.

Parameters:

f - the top-level evaluator

Returns:

an evaluator caching intermediate results

constructEvaluator

public FunctionEvaluator constructEvaluator(EvaluatorFactory factory,
                                   List<Object> arguments,
                                   ScalarSettable result)

Creates an evaluator for a top-level expression, binding its output to the provided result buffer.

Parameters:

factory - a factory for constructing the top-level function

arguments - the arguments to pass to the function evaluator

result - the buffer into which evaluation results are to be written

Returns:

a new evaluator

constructSubexpressionEvaluation

public ScalarValued constructSubexpressionEvaluation(EvaluatorFactory factory,
                                            List<Object> arguments,
                                            ScalarTokenType resultType)

Creates an evaluation of a subexpression which can be used as input to the evaluator of the expression containing it.

Parameters:

factory - a factory for constructing the subexpression function

arguments - the arguments to pass to the function evaluator

Returns:

an object containing the current value of the subexpression