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[FLINK-39253][table] Preserve field names in ROW function from AS aliases #27775

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[FLINK-39253][table] Preserve field names in ROW function from AS aliases #27775

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17 changes: 17 additions & 0 deletions ...in/java/org/apache/flink/table/expressions/resolver/rules/ResolveCallByArgumentsRule.java
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Original file line number Diff line number Diff line change
Expand Up @@ -681,6 +681,23 @@ public List<DataType> getArgumentDataTypes() {
.collect(Collectors.toList());
}

@Override
public Optional<String> getArgumentName(int pos) {
final ResolvedExpression arg = getArgument(pos);

if (arg instanceof CallExpression) {
final CallExpression call = (CallExpression) arg;
if (call.getFunctionDefinition() == BuiltInFunctionDefinitions.AS) {
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@davidradl davidradl Mar 17, 2026

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I notice here there is a way of aliasing using = as well as AS. Does Flink support this? If so can we add a unit test to ensure this works in the same way as AS.

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@autophagy autophagy Mar 17, 2026

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I don't believe Flink does support it, but I'll verify

final List<ResolvedExpression> children = call.getResolvedChildren();
if (children.size() >= 2 && children.get(1) instanceof ValueLiteralExpression) {
return ((ValueLiteralExpression) children.get(1)).getValueAs(String.class);
}
}
}

return Optional.empty();
}

@Override
public Optional<DataType> getOutputDataType() {
return Optional.empty();
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5 changes: 5 additions & 0 deletions .../flink-table-common/src/main/java/org/apache/flink/table/types/inference/CallContext.java
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Expand Up @@ -113,6 +113,11 @@ default Optional<ChangelogMode> getOutputChangelogMode() {
*/
List<DataType> getArgumentDataTypes();

/** Returns the name/alias of the argument at the given position if one is available. */
default Optional<String> getArgumentName(int pos) {
return Optional.empty();
}

/**
* Returns the inferred output data type of the function call.
*
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7 changes: 6 additions & 1 deletion ...mmon/src/main/java/org/apache/flink/table/types/inference/strategies/RowTypeStrategy.java
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Expand Up @@ -37,7 +37,12 @@ public Optional<DataType> inferType(CallContext callContext) {
List<DataType> argumentDataTypes = callContext.getArgumentDataTypes();
DataTypes.Field[] fields =
IntStream.range(0, argumentDataTypes.size())
.mapToObj(idx -> DataTypes.FIELD("f" + idx, argumentDataTypes.get(idx)))
.mapToObj(
idx -> {
String fieldName =
callContext.getArgumentName(idx).orElse("f" + idx);
return DataTypes.FIELD(fieldName, argumentDataTypes.get(idx));
})
.toArray(DataTypes.Field[]::new);

return Optional.of(DataTypes.ROW(fields).notNull());
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6 changes: 6 additions & 0 deletions ...le-common/src/main/java/org/apache/flink/table/types/inference/utils/CastCallContext.java
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Expand Up @@ -115,6 +115,12 @@ public List<DataType> getArgumentDataTypes() {
return expectedArguments;
}

@Override
public Optional<String> getArgumentName(int pos) {
// argument names remain regardless of casting
return originalContext.getArgumentName(pos);
}

@Override
public Optional<DataType> getOutputDataType() {
return Optional.ofNullable(outputDataType);
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18 changes: 17 additions & 1 deletion ...ble-planner/src/test/java/org/apache/flink/table/planner/functions/RowFunctionITCase.java
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Expand Up @@ -115,7 +115,23 @@ Stream<TestSetSpec> getTestSetSpecs() {
DataTypes.FIELD("b", DataTypes.TINYINT()),
DataTypes.FIELD("c", DataTypes.BIGINT()),
DataTypes.FIELD("d", DataTypes.BOOLEAN()))
.notNull()));
.notNull()),
TestSetSpec.forFunction(
BuiltInFunctionDefinitions.ROW, "with aliased fields using .as()")
.onFieldsWithData(100, "abc", 75.50)
.andDataTypes(DataTypes.INT(), DataTypes.STRING(), DataTypes.DOUBLE())
.testTableApiResult(
row($("f0").as("a"), $("f1").as("b"), $("f2").as("c")),
Row.of(100, "abc", 75.50),
DataTypes.ROW(
DataTypes.FIELD("a", DataTypes.INT()),
DataTypes.FIELD("b", DataTypes.STRING()),
DataTypes.FIELD("c", DataTypes.DOUBLE()))
.notNull())
.testTableApiResult(
row($("f0").as("a"), $("f1").as("b"), $("f2").as("c")).get("a"),
100,
DataTypes.INT()));
}

// --------------------------------------------------------------------------------------------
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