dawidwys commented on a change in pull request #11280: [FLINK-16377][table]
Support inline user defined functions in expression dsl
URL: https://github.com/apache/flink/pull/11280#discussion_r397676230
##########
File path:
flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/expressions/ApiExpressionUtils.java
##########
@@ -198,4 +204,48 @@ public static boolean isFunction(Expression expression,
BuiltInFunctionDefinitio
}
return false;
}
+
+ /**
+ * Extracts a {@link FunctionIdentifier} for the given {@link
CallExpression}. If the call is an inline funcion
+ * ({@link CallExpression#getFunctionIdentifier()} returns empty)
+ * <ul>
+ * <li>it uses {@link BuiltInFunctionDefinition#getName()} ()} for
built in functions</li>
+ * <li>it uses {@link UserDefinedFunction#functionIdentifier()} for
user defined functions</li>
+ * <li>it uses {@link FunctionDefinition#toString()} ()} for any
other functions</li>
+ * </ul>
+ */
+ public static FunctionIdentifier getFunctionIdentifier(CallExpression
callExpression) {
+ if (callExpression.getFunctionIdentifier().isPresent()) {
+ return callExpression.getFunctionIdentifier().get();
+ } else {
+ return getInlineFunctionIdentifier(callExpression);
+ }
+ }
+
+ private static FunctionIdentifier
getInlineFunctionIdentifier(CallExpression callExpression) {
+ FunctionDefinition functionDefinition =
callExpression.getFunctionDefinition();
+ if (functionDefinition instanceof BuiltInFunctionDefinition) {
+ return
FunctionIdentifier.of(((BuiltInFunctionDefinition)
functionDefinition).getName());
Review comment:
Not sure, theoretically `BuiltInFunctionDefinition` can also be registered
in an arbitrary path. Then having a `FunctionIdentifier` in the function
definition would be wrong. `FunctionDefinition` is not aware of the path it
comes from. It can even be registered at multiple locations.
As far as I understand the difference between built-in and user defined
functions is where the implementation comes from. For user defined functions
the implementation comes from the definition whereas for bult-in it is looked
up in the planner.
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