[GitHub] [flink] leonardBang commented on a change in pull request #16020: [FLINK-21911][table-api] Add built-in greatest/least functions support #15821

[GitBox <gi...@apache.org>]

leonardBang commented on a change in pull request #16020:
URL: https://github.com/apache/flink/pull/16020#discussion_r671707964



##########
File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java
##########
@@ -283,6 +283,26 @@
                     .outputTypeStrategy(nullable(explicit(DataTypes.BOOLEAN())))
                     .build();
 
+    public static final BuiltInFunctionDefinition GREATEST =
+            BuiltInFunctionDefinition.newBuilder()
+                    .name("greatest")
+                    .kind(SCALAR)
+                    .inputTypeStrategy(
+                            comparable(ConstantArgumentCount.from(1), StructuredComparision.FULL))
+                    .outputTypeStrategy(nullable(TypeStrategies.COMMON))

Review comment:
       IIUC, ` nullable(TypeStrategy initialStrategy)` has done for this? 
   ```
     /**
        * A type strategy that can be used to make a result type nullable if any of the input arguments
        * is nullable. Otherwise the type will be not null.
        */
       public static TypeStrategy nullable(TypeStrategy initialStrategy) {
           return nullable(ConstantArgumentCount.any(), initialStrategy);
       }
   ```




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