dawidwys commented on a change in pull request #8661: [FLINK-12711][table]
Separate function implementation and definition
URL: https://github.com/apache/flink/pull/8661#discussion_r294262182
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File path:
flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/UserDefinedFunction.java
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@@ -24,11 +24,18 @@
import java.io.Serializable;
/**
- * Base class for all user-defined functions such as scalar functions, table
functions,
- * or aggregation functions.
+ * Base class for all user-defined functions.
+ *
+ * <p>User-defined functions combine the logical definition of a function for
validation and planning
+ * (see {@link UserDefinedFunctionDefinition}) and contain a corresponding
runtime implementation.
+ *
+ * @see ScalarFunction
+ * @see TableFunction
+ * @see AggregateFunction
+ * @see TableAggregateFunction
*/
@PublicEvolving
-public abstract class UserDefinedFunction implements Serializable {
+public abstract class UserDefinedFunction implements
UserDefinedFunctionDefinition, Serializable {
Review comment:
Why the `UserDefinedFunction` extends from the
`UserDefinedFunctionDefinition`? Isn't it an implementation? I think it is the
`ScalarFunctionDefinition`, `TableFunctionDefinition` etc. that should
extend from the `UserDefinedFunctionDefinition`.
As it is implemented now, the method `createImplementation` is never used. I
think it should replace the calls to
`AggregateFunctionDefinition#getAggregateFunction`,
`ScalarFunctionDefinition#getScalarFunction` etc.
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