All Known Subinterfaces:

ChangelogFunction, SpecializedFunction

All Known Implementing Classes:

AggregateFunction, AggregateFunctionDefinition, AsyncLookupFunction, AsyncPredictFunction, AsyncScalarFunction, AsyncTableFunction, BuiltInFunctionDefinition, ImperativeAggregateFunction, LookupFunction, PredictFunction, ProcedureDefinition, ProcessTableFunction, PythonAggregateFunction, PythonScalarFunction, PythonTableAggregateFunction, PythonTableFunction, ScalarFunction, ScalarFunctionDefinition, TableAggregateFunction, TableAggregateFunctionDefinition, TableFunction, TableFunctionDefinition, TemporalTableFunction, UserDefinedFunction
```
@PublicEvolving
public interface FunctionDefinition
```
Definition of a function. Instances of this class provide all details necessary to validate a function call and perform planning.
A pure function definition doesn't have to contain a runtime implementation. This can be provided by the planner at later stages. A UserDefinedFunction is a function definition that includes a runtime implementation already.

See Also:

UserDefinedFunction

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`FunctionKind`	`getKind()`	Returns the kind of function this definition describes.
`default Set<FunctionRequirement>`	`getRequirements()`	Returns the set of requirements this definition demands.
`TypeInference`	`getTypeInference(DataTypeFactory typeFactory)`	Returns the logic for performing type inference of a call to this function definition.
`default boolean`	`isDeterministic()`	Returns information about the determinism of the function's results.
`default boolean`	`supportsConstantFolding()`	If the constant-folding should be run during planning time on calls to this function.

- Method Detail
  - getKind
```
FunctionKind getKind()
```
    Returns the kind of function this definition describes.
  - getTypeInference
```
TypeInference getTypeInference(DataTypeFactory typeFactory)
```
    Returns the logic for performing type inference of a call to this function definition.
    The type inference process is responsible for inferring unknown types of input arguments, validating input arguments, and producing result types. The type inference process happens independent of a function body. The output of the type inference is used to search for a corresponding runtime implementation.
    Instances of type inference can be created by using TypeInference.newBuilder().
    See BuiltInFunctionDefinitions for concrete usage examples.
  - getRequirements
```
default Set<FunctionRequirement> getRequirements()
```
    Returns the set of requirements this definition demands.
  - isDeterministic
```
default boolean isDeterministic()
```
    Returns information about the determinism of the function's results.
    It returns true if and only if a call to this function is guaranteed to always return the same result given the same parameters. true is assumed by default. If the function is not purely functional like random(), date(), now(), ... this method must return false.
    Furthermore, return false if the planner should always execute this function on the cluster side. In other words: the planner should not perform constant expression reduction during planning for constant calls to this function.
  - supportsConstantFolding
```
default boolean supportsConstantFolding()
```
    If the constant-folding should be run during planning time on calls to this function. If not, the expression will be left as-is and the call will be made during runtime.

Interface FunctionDefinition

Method Summary

Method Detail

getKind

getTypeInference

getRequirements

isDeterministic

supportsConstantFolding