apache/druid · error · java.lang.UnsupportedOperationException

HyperUniquesAggregator does not support getLong()

Error message

HyperUniquesAggregator does not support getLong()

What it means

HyperUniquesAggregator cannot return a long: the aggregator's product is an HLL sketch whose cardinality estimate is a double obtained through the sketch, not a long primitive. getLong() throws UnsupportedOperationException to prevent silent precision/type errors.

Solutions

Read the sketch via get()/getHyperLogLogCollector() and use its estimate (cast to long if integral output is desired)
Keep using the native query uniques result/post-aggregator path (e.g. cardinality post-agg) instead of direct getLong
Check the factory type name before calling getLong
In SQL, use APPROX_COUNT_DISTINCT_DS_HLL which yields a BIGINT-typed result

Example fix

// before
long l = agg.getLong(); // throws
// after
HyperLogLogCollector hll = ((HyperUniquesAggregator) agg).getHyperLogLogCollector();
long l2 = hll == null ? 0L : (long) hll.estimateCardinality();

Defensive patterns

Strategy: try-catch

Validate before calling

if (!"hyperUnique".equals(factory.getTypeName())) { l = agg.getLong(); }

Type guard

static Long safeLong(Aggregator a) { try { return a.getLong(); } catch (UnsupportedOperationException e) { return null; } }

Try / catch

try { l = agg.getLong(); } catch (UnsupportedOperationException e) { l = (long) sketchEstimate(agg); }

Prevention

Derive cardinality estimates from the HLL sketch, then cast to long if needed
Check getTypeName() before integer access
Update integrations when swapping count metrics for hyperUnique

When it happens

Trigger: Calling getLong() on a HyperUniquesAggregator when result extraction assumes integer metrics.

Common situations: Custom result serialization treating every aggregator as long; plugins replacing a count aggregator with hyperUnique without changing downstream accessors.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/38d38b59f0eb7d5e. Report an issue: GitHub.

Appendix: source

Thrown at processing/src/main/java/org/apache/druid/query/aggregation/hyperloglog/HyperUniquesAggregator.java:75

  {
    if (collector == null) {
      return null;
    }
    // Must make a new collector duplicating the underlying buffer to ensure the object from "get" is usable
    // in a thread-safe manner.
    return HyperLogLogCollector.makeCollectorSharingStorage(collector);
  }

  @Override
  public float getFloat()
  {
    throw new UnsupportedOperationException("HyperUniquesAggregator does not support getFloat()");
  }

  @Override
  public long getLong()
  {
    throw new UnsupportedOperationException("HyperUniquesAggregator does not support getLong()");
  }

  @Override
  public double getDouble()
  {
    throw new UnsupportedOperationException("HyperUniquesAggregator does not support getDouble()");
  }

  @Override
  public void close()
  {
    // no resources to cleanup
  }
}

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