Timo Walther created FLINK-12711:
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Summary: Separate function implementation and definition
Key: FLINK-12711
URL: https://issues.apache.org/jira/browse/FLINK-12711
Project: Flink
Issue Type: Sub-task
Components: Table SQL / API
Reporter: Timo Walther
Assignee: Timo Walther
This issue continues the work that was started in FLINK-11449. It distinguishes
between function with implementation (UDFs) and function with no implementation.
The rough design looks as follows:
{noformat}
1. `interface FunctionDefinition`
--> general interface for describing a function
--> goal: separation of runtime and planning/optimization
--> long-term methods: `getKind()` (aggregate, scalar, table),
`getTypeInference()`
2. `interface UserDefinedFunctionDefinition extends FunctionDefinition`
--> interface for describing a function with implementation
--> methods: `createImplementation(): UserDefinedFunction`
--> default: getTypeInference() = Util.DEFAULT_INFERENCE // future work
3. `class BuiltInFunctionDefinition implements FunctionDefinition`
--> class for describing a function where the planner provides an
implementation
--> methods: `getName(): String`
4. Add `getKind` to `AggregateFunction`, `ScalarFunction`, `TableFunction`
{noformat}
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