org.apache.cassandra.cql3.functions

Interface ScalarFunction

All Superinterfaces:

AssignmentTestable, Function

All Known Subinterfaces:

PartialScalarFunction

All Known Implementing Classes:

FromJsonFct, JavaBasedUDFunction, NativeScalarFunction, TimeFcts.FloorDateFunction, TimeFcts.FloorTimestampFunction, TimeFcts.FloorTimeUuidFunction, ToJsonFct, TokenFct, UDFunction

public interface ScalarFunction
extends Function

Determines a single output value based on any number of input values.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.cassandra.cql3.AssignmentTestable

AssignmentTestable.TestResult

Field Summary

Fields inherited from interface org.apache.cassandra.cql3.functions.Function

UNRESOLVED

Method Summary

Modifier and Type	Method and Description
java.nio.ByteBuffer	execute(ProtocolVersion protocolVersion, java.util.List<java.nio.ByteBuffer> parameters) Applies this function to the specified parameter.
boolean	isCalledOnNullInput()
default boolean	isMonotonic() Checks if the function is monotonic.
default ScalarFunction	partialApplication(ProtocolVersion protocolVersion, java.util.List<java.nio.ByteBuffer> partialParameters) Does a partial application of the function.

Methods inherited from interface org.apache.cassandra.cql3.functions.Function

addFunctionsTo, argTypes, columnName, compare, isAggregate, isNative, isPure, name, referencesUserType, returnType

Methods inherited from interface org.apache.cassandra.cql3.AssignmentTestable

testAssignment

Method Detail

isCalledOnNullInput

boolean isCalledOnNullInput()

isMonotonic

default boolean isMonotonic()

Checks if the function is monotonic.

A function is monotonic if it is either entirely nonincreasing or nondecreasing given an ordered set of inputs.

Returns:

true if the function is monotonic false otherwise.

execute

java.nio.ByteBuffer execute(ProtocolVersion protocolVersion,
                            java.util.List<java.nio.ByteBuffer> parameters)
                     throws InvalidRequestException

Applies this function to the specified parameter.

Parameters:

protocolVersion - protocol version used for parameters and return value

parameters - the input parameters

Returns:

the result of applying this function to the parameter

Throws:

InvalidRequestException - if this function cannot not be applied to the parameter

partialApplication

default ScalarFunction partialApplication(ProtocolVersion protocolVersion,
                                          java.util.List<java.nio.ByteBuffer> partialParameters)

Does a partial application of the function. That is, given only some of the parameters of the function provided, return a new function that only expect the parameters not provided.

To take an example, if you consider the function

     text foo(int a, text b, text c, int d)
 

then foo.partialApplication([3, <ommitted>, 'bar', <omitted>]) will return a function bar of signature:

     text bar(text b, int d)
 

and such that for any value of b and d, bar(b, d) == foo(3, b, 'bar', d).

Parameters:

protocolVersion - protocol version used for parameters

partialParameters - a list of input parameters for the function where some parameters can be Function.UNRESOLVED. The input must be of size this.argsType().size(). For convenience, it is allowed both to pass a list with all parameters being Function.UNRESOLVED (the function is then returned directly) and with none of them unresolved (in which case, if the function is pure, it is computed and a dummy no-arg function returning the result is returned).

Returns:

a function corresponding to the partial application of this function to the parameters of partialParameters that are not Function.UNRESOLVED.