[GitHub] [flink] twalthr commented on a diff in pull request #19637: [FLINK-25567][table] Add support casting of multisets to multisets

["twalthr (via GitHub)" <gi...@apache.org>]

twalthr commented on code in PR #19637:
URL: https://github.com/apache/flink/pull/19637#discussion_r1144847060


##########
flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/operations/utils/ValuesOperationFactory.java:
##########
@@ -197,10 +199,18 @@ private Optional<ResolvedExpression> convertToExpectedType(
                     && targetLogicalType.is(ARRAY)) {
                 return convertArrayToExpectedType(
                         sourceExpression, (CollectionDataType) targetDataType, postResolverFactory);
-            } else if (functionDefinition == BuiltInFunctionDefinitions.MAP
-                    && targetLogicalType.is(MAP)) {
-                return convertMapToExpectedType(
-                        sourceExpression, (KeyValueDataType) targetDataType, postResolverFactory);
+            } else if (functionDefinition == BuiltInFunctionDefinitions.MAP) {
+                if (targetLogicalType.is(MAP)) {

Review Comment:
   This piece of code confuses me. Why is the function `MAP` but the target type MULTISET? On an API level those two data types should be treated completely different.



##########
flink-table/flink-table-common/src/main/java/org/apache/flink/table/functions/BuiltInFunctionDefinitions.java:
##########
@@ -1693,6 +1693,14 @@ ANY, and(logical(LogicalTypeRoot.BOOLEAN), LITERAL)
                     .outputTypeStrategy(SpecificTypeStrategies.MAP)
                     .build();
 
+    public static final BuiltInFunctionDefinition MULTISET =
+            BuiltInFunctionDefinition.newBuilder()
+                    .name("multiset")

Review Comment:
   nit: let's use upper case for all new functions



##########
flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/codegen/calls/ScalarOperatorGens.scala:
##########
@@ -1433,7 +1435,10 @@ object ScalarOperatorGens {
       .map(_._2.last)
       .values
       .toSeq
-    val valueType = mapType.getValueType
+    val valueType = resultType match {
+      case mapType1: MapType => mapType1.getValueType
+      case _ => DataTypes.INT().getLogicalType

Review Comment:
   nit: it's better to call `new IntType()` at code gen level, I guess it should be not null?



##########
flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/codegen/ExprCodeGenerator.scala:
##########
@@ -715,9 +715,9 @@ class ExprCodeGenerator(ctx: CodeGeneratorContext, nullableInput: Boolean)
       case ARRAY_VALUE_CONSTRUCTOR =>
         generateArray(ctx, resultType, operands)
 
-      // maps
-      case MAP_VALUE_CONSTRUCTOR =>
-        generateMap(ctx, resultType, operands)
+      // maps and multisets
+      case MAP_VALUE_CONSTRUCTOR | MULTISET_VALUE =>

Review Comment:
   Let's also call it `MULTISET_VALUE_CONSTRUCTOR` to be in sync with map and array



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