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Fix SmartHLL ClassCastException in GROUP BY ORDER BY #18841

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Fix SmartHLL ClassCastException in GROUP BY ORDER BY #18841

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bc04586
Fix SmartHLL ClassCastException in GROUP BY ORDER BY
ilamhs Jun 23, 2026
c3447bd
Drop redundant threshold check in extractGroupByResult
ilamhs Jun 25, 2026
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8 changes: 4 additions & 4 deletions ...inot/core/query/aggregation/function/BaseDistinctCountSmartSketchAggregationFunction.java
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Original file line number Diff line number Diff line change
Expand Up @@ -508,16 +508,16 @@ public final Object extractAggregationResult(AggregationResultHolder aggregation
}

@Override
public final Set extractGroupByResult(GroupByResultHolder groupByResultHolder, int groupKey) {
public final Object extractGroupByResult(GroupByResultHolder groupByResultHolder, int groupKey) {
Object result = groupByResultHolder.getResult(groupKey);
if (result == null) {
return EMPTY_PLACEHOLDER;
}

if (result instanceof DictIdsWrapper) {
return convertToValueSet((DictIdsWrapper) result);
if (result instanceof DictIdsWrapper dictIdsWrapper) {
return convertToValueSet(dictIdsWrapper);
} else {
return (Set) result;
return result;
}
}

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26 changes: 26 additions & 0 deletions ...e/pinot/core/query/aggregation/function/DistinctCountSmartHLLAggregationFunctionTest.java
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Expand Up @@ -20,12 +20,15 @@

import com.clearspring.analytics.stream.cardinality.HyperLogLog;
import java.util.List;
import java.util.Set;
import org.apache.pinot.common.request.context.ExpressionContext;
import org.apache.pinot.common.utils.DataSchema;
import org.apache.pinot.core.query.aggregation.groupby.ObjectGroupByResultHolder;
import org.apache.pinot.spi.data.FieldSpec;
import org.testng.annotations.Test;

import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertFalse;
import static org.testng.Assert.assertNotNull;
import static org.testng.Assert.assertTrue;

Expand Down Expand Up @@ -151,6 +154,29 @@ public void testHLLOperations() {
assertTrue(mergedCardinality >= 700 && mergedCardinality <= 800, "Merged cardinality: " + mergedCardinality);
}

@Test
public void itExtractsHLLFromGroupByResultHolderWhenSketchConverted() {
DistinctCountSmartHLLAggregationFunction function = new DistinctCountSmartHLLAggregationFunction(
List.of(ExpressionContext.forIdentifier("col"),
ExpressionContext.forLiteral(FieldSpec.DataType.STRING, "threshold=5;dictThreshold=5")));

ObjectGroupByResultHolder holder = new ObjectGroupByResultHolder(10, 10);

HyperLogLog hll = new HyperLogLog(12);
for (int i = 0; i < 100; i++) {
hll.offer(i);
}
holder.setValueForKey(0, hll);

Object extracted = function.extractGroupByResult(holder, 0);
assertTrue(extracted instanceof HyperLogLog,
"Expected HyperLogLog but got: " + (extracted == null ? "null" : extracted.getClass().getName()));
assertFalse(extracted instanceof Set, "HyperLogLog must not be cast to Set");

int cardinality = function.extractFinalResult(extracted);
assertTrue(cardinality >= 90 && cardinality <= 110, "Cardinality out of range: " + cardinality);
}

@Test
public void testAdaptiveConversion() {
// Test adaptive conversion enabled by default (100K threshold)
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