Module datarush.library
Package com.pervasive.datarush.functions

Class ConstantReference

java.lang.Object
com.pervasive.datarush.functions.ConstantReference
All Implemented Interfaces:
ScalarValuedFunction
public final class ConstantReference extends Object implements ScalarValuedFunction
A reference to a known value. The defined function returns the value. These can be used to combine constant values with other functions. Note however, that many of the built-in functions provide convenience signatures which do not require direct use of this class.

  • Constructor Details

    • ConstantReference

      public ConstantReference(ScalarValued v)
      Defines a function evaluating to the specified value
      Parameters:
      v - the value to return from the function

  • Method Details

    • getUpperBound

      public ScalarTokenType getUpperBound()
      Description copied from interface: ScalarValuedFunction
      Gets the upper bound on the output type of the function. This need not be the exact type of the output, but is expected to be a type to which the actual output type is assignable, as according to TokenType#isAssignableFrom(TokenType).

      This value is used to detect type consistency issues as early as possible. It is always valid to return TokenTypeConstant#SCALAR, in which case no type consistency issues can be caught early.

      Specified by:
      getUpperBound in interface ScalarValuedFunction
      Returns:
      the most specific type to which any possible return type is assignable.

    • validateInputType

      public ScalarTokenType validateInputType(RecordTokenType inputType)
      Description copied from interface: ScalarValuedFunction
      Calculates the actual output type of the function given the specified input type.

      The type returned must be assignable to the type returned by ScalarValuedFunction.getUpperBound(). If this is not the case, runtime type errors may arise.

      Specified by:
      validateInputType in interface ScalarValuedFunction
      Parameters:
      inputType - the type of the record used as input to the function
      Returns:
      the return type of the function for the given input record schema

    • getEvaluator

      public FunctionEvaluator getEvaluator(RecordValued input, ScalarSettable output)
      Description copied from interface: ScalarValuedFunction
      Constructs an instance of an evaluator for the function. The evaluator returns the result of the the function applied to the specified input into the given output target.

      Implementations may assume that the input and output are known to be compatible with the function. Normally, this method is only invoked by the DataRush framework, which guarantees this is the case. In general, to satisfy this requirement, callers are expected to:

      • verify that validateInputType(input.getType()) does not throw an exception
      • verify the output type returned is assignable to result.getType()
      Failure to meet this contract may result in runtime exceptions.
      Specified by:
      getEvaluator in interface ScalarValuedFunction
      Parameters:
      input - the record source to use as context for evaluating the function
      output - the buffer into which evaluation results are to be stored
      Returns:
      an evaluator bound to the provided input and output

    • getSubexpressionEvaluation

      public ScalarValued getSubexpressionEvaluation(EvaluationContext ctx)
      Description copied from interface: ScalarValuedFunction
      Constructs an instance of an evaluation of the function in the context of a larger expression.
      Specified by:
      getSubexpressionEvaluation in interface ScalarValuedFunction
      Parameters:
      ctx - the expression context in which the function is being evaluated as a subexpression
      Returns:
      an object representing the subexpression's current value

    • hashCode

      public int hashCode()
      Description copied from interface: ScalarValuedFunction

      ScalarValuedFunctions should override this method in a manner consistent with ScalarValuedFunction.equals(Object).

      Specified by:
      hashCode in interface ScalarValuedFunction
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object obj)
      Description copied from interface: ScalarValuedFunction

      ScalarValuedFunctions should override this method to indicate whether they are equal to another ScalarValuedFunction.

      Specified by:
      equals in interface ScalarValuedFunction
      Overrides:
      equals in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • constant

      public static ScalarValuedFunction constant(byte[] value)
      Creates a function evaluating to the specified binary constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(boolean value)
      Creates a function evaluating to the specified boolean constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(char value)
      Creates a function evaluating to the specified char constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(int value)
      Creates a function evaluating to the specified int constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(long value)
      Creates a function evaluating to the specified long constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(float value)
      Creates a function evaluating to the specified float constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(double value)
      Creates a function evaluating to the specified double constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(BigDecimal value)
      Creates a function evaluating to the specified numeric constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(String value)
      Creates a function evaluating to the specified string constant.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static <O> ScalarValuedFunction constant(O value)
      Creates a function evaluating to the specified object constant.
      Type Parameters:
      O - the type of the object
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • constant

      public static ScalarValuedFunction constant(ScalarToken value)
      Creates a function evaluating to the specified value.
      Parameters:
      value - the constant value to return
      Returns:
      the constant function

    • nullValue

      @Deprecated public static ScalarValuedFunction nullValue(String fieldName)
      Deprecated.
      Untyped null tokens are now supported. Use nullValue() to generate a null token without an input type.
      Creates a function, of the same type as the specified field, evaluating to null.
      Parameters:
      fieldName - an input field, the type of which will be used as the result type
      Returns:
      the null function

    • nullValue

      @Deprecated public static ScalarValuedFunction nullValue(ScalarValuedFunction expr)
      Deprecated.
      Untyped null tokens are now supported. Use nullValue() to generate a null token without an input type.
      Creates a function, of the same type as the specified expression, evaluating to null.
      Parameters:
      fieldName - an expression, the type of which will be used as the result type
      Returns:
      the null function

    • nullValue

      public static ScalarValuedFunction nullValue()
      Creates a function evaluating to null.
      Returns:
      the null function

    • getRequiredFields

      public Collection<String> getRequiredFields()
      Description copied from interface: ScalarValuedFunction
      Get the input fields required in the function input. An empty collection implies no specific fields are required.
      Specified by:
      getRequiredFields in interface ScalarValuedFunction
      Returns:
      the names of fields which must be present in the record input schema

    • remapFieldReferences

      public ScalarValuedFunction remapFieldReferences(Map<String,String> oldToNewMapping)
      Description copied from interface: ScalarValuedFunction
      Creates a new function, equivalent to the given function, but with all field references renamed according to the given mapping.
      Specified by:
      remapFieldReferences in interface ScalarValuedFunction
      Parameters:
      oldToNewMapping - a mapping from old names to new names. If a name is not present in the given mapping, it will remain as-is.
      Returns:
      a new function with all field reference renamed appropriately

    • mapFieldsToFunctions

      public ScalarValuedFunction mapFieldsToFunctions(Map<String,ScalarValuedFunction> mapping)
      Description copied from interface: ScalarValuedFunction
      Creates a new function, equivalent to the given function, but with specified field references mapped to functions.
      Specified by:
      mapFieldsToFunctions in interface ScalarValuedFunction
      Parameters:
      mapping - a mapping from field names to functions. If a name is not present in the given mapping, it will remain as-is.
      Returns:
      a new function with all field reference mapped appropriately