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[FLINK-39677][table] Fix ARRAY_SORT comparator contract violation #28155

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[FLINK-39677][table] Fix ARRAY_SORT comparator contract violation #28155

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41 changes: 41 additions & 0 deletions ...ner/src/test/java/org/apache/flink/table/planner/functions/CollectionFunctionsITCase.java
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,10 @@
import org.apache.flink.types.Row;
import org.apache.flink.util.CollectionUtil;

import org.apache.commons.lang3.ArrayUtils;

import java.time.LocalDate;
import java.util.Arrays;
import java.util.Map;
import java.util.stream.Stream;

Expand Down Expand Up @@ -56,6 +59,7 @@ Stream<TestSetSpec> getTestSetSpecs() {
arraySliceTestCases(),
arrayMinTestCases(),
arraySortTestCases(),
arraySortBigIntDuplicatesTestCases(),
arrayExceptTestCases(),
arrayIntersectTestCases(),
splitTestCases(),
Expand Down Expand Up @@ -1602,6 +1606,43 @@ private Stream<TestSetSpec> arraySortTestCases() {
DataTypes.ARRAY(DataTypes.DATE())));
}

private Stream<TestSetSpec> arraySortBigIntDuplicatesTestCases() {
final int size = 64;
Long[] allEqual = new Long[size];
Arrays.fill(allEqual, 42L);

Long[] manyDuplicates = new Long[size];
for (int i = 0; i < size; i++) {
manyDuplicates[i] = (long) (i % 4);
}
Long[] manyDuplicatesSortedAsc = manyDuplicates.clone();
Arrays.sort(manyDuplicatesSortedAsc);
Long[] manyDuplicatesSortedDesc = manyDuplicatesSortedAsc.clone();
ArrayUtils.reverse(manyDuplicatesSortedDesc);

return Stream.of(
TestSetSpec.forFunction(BuiltInFunctionDefinitions.ARRAY_SORT)
.onFieldsWithData(allEqual, manyDuplicates)
.andDataTypes(
DataTypes.ARRAY(DataTypes.BIGINT()),
DataTypes.ARRAY(DataTypes.BIGINT()))
.testResult(
call("ARRAY_SORT", $("f0")),
"ARRAY_SORT(f0)",
allEqual,
DataTypes.ARRAY(DataTypes.BIGINT()))
.testResult(
call("ARRAY_SORT", $("f1")),
"ARRAY_SORT(f1)",
manyDuplicatesSortedAsc,
DataTypes.ARRAY(DataTypes.BIGINT()))
.testResult(
call("ARRAY_SORT", $("f1"), false),
"ARRAY_SORT(f1, false)",
manyDuplicatesSortedDesc,
DataTypes.ARRAY(DataTypes.BIGINT())));
}

private Stream<TestSetSpec> arrayExceptTestCases() {
return Stream.of(
TestSetSpec.forFunction(BuiltInFunctionDefinitions.ARRAY_EXCEPT)
Expand Down
10 changes: 8 additions & 2 deletions ...time/src/main/java/org/apache/flink/table/runtime/functions/scalar/ArraySortFunction.java
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Original file line number Diff line number Diff line change
Expand Up @@ -109,8 +109,14 @@ public ArraySortComparator(boolean isAscending) {
@Override
public int compare(Object o1, Object o2) {
try {
boolean isGreater = (boolean) greaterHandle.invoke(o1, o2);
return isAscending ? (isGreater ? 1 : -1) : (isGreater ? -1 : 1);
// Two probes so equal elements return 0 (Comparator contract).
if ((boolean) greaterHandle.invoke(o1, o2)) {
return isAscending ? 1 : -1;
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@raminqaf raminqaf May 15, 2026

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Nit one:
maybe we can extract this into a variable and re-use it

int sign = isAscending ? 1 : -1;

if ((boolean) greaterHandle.invoke(o1, o2)) return sign;

if ((boolean) greaterHandle.invoke(o2, o1)) return -sign;

return 0;

}
if ((boolean) greaterHandle.invoke(o2, o1)) {
return isAscending ? -1 : 1;
}
Comment on lines +113 to +118
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@snuyanzin snuyanzin May 13, 2026

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instead of having 2 invocations we could have 2 evaluators

  1. for isGreaterOrEqueal
  2. for isLessOrEqual

WDYT?

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@jnh5y jnh5y May 13, 2026

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What would this get us?

It seems like it would only add more MethodHandles in this class?

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@jnh5y jnh5y May 13, 2026

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I mean, I could see adding a builtin COMPARE(a, b) → -1/0/+1 function in BuiltInFunctionDefinitions. Would that be better?

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@snuyanzin snuyanzin May 13, 2026

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we don't have such function right?
adding a new function ideally requires research what other vendors provide to follow the most common syntax.

From existing we could use CASE ...WHEN which is lazy

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@jnh5y jnh5y May 13, 2026

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I thinking of an internal-only function like $HASH_CODE$1 as an option.

How would CASE ...WHEN work here?

Are either of these ideas worth it? Or should we just go with the current approach?

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@dylanhz dylanhz May 15, 2026

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I think the CASE WHEN approach might fit this PR better.

An internal compare function/expression could be a good long-term direction for unifying ordering semantics, but it probably needs broader discussion.

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@jnh5y jnh5y May 15, 2026

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I opened an alternative version of this change over here: #28159.

Notably, there is already code generation for "compare" since it is needed for various operators. We just need an internal function to reference.

return 0;
} catch (Throwable e) {
throw new RuntimeException(e);
}
Expand Down