apache/druid · error · IllegalStateException

Cannot return long for Null Value

Error message

Cannot return long for Null Value

What it means

Same contract as getFloat(): NullableNumericAggregator tracks a null result state and refuses to return a primitive long when the aggregated value is null. Returning 0L would mask the null, so an IllegalStateException is thrown from getLong().

Source

Thrown at processing/src/main/java/org/apache/druid/query/aggregation/NullableNumericAggregator.java:92

      return null;
    }
    return delegate.get();
  }

  @Override
  public float getFloat()
  {
    if (isNullResult) {
      throw new IllegalStateException("Cannot return float for Null Value");
    }
    return delegate.getFloat();
  }

  @Override
  public long getLong()
  {
    if (isNullResult) {
      throw new IllegalStateException("Cannot return long for Null Value");
    }
    return delegate.getLong();
  }

  @Override
  public double getDouble()
  {
    if (isNullResult) {
      throw new IllegalStateException("Cannot return double for Null Value");
    }
    return delegate.getDouble();
  }

  @Override
  public boolean isNull()
  {
    return isNullResult || delegate.isNull();
  }

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Check agg.isNull() before calling getLong() and handle the null branch (e.g., return null or a default)
2. Verify the input column actually contains non-null long values in the queried segments
3. Ensure aggregator init/reset is called correctly so isNullResult reflects only the current aggregation
4. If the null is unexpected, inspect the selector/factory wiring to confirm the base aggregator is reading the intended column

Example fix

// before
long v = agg.getLong();
// after
Long v = agg.isNull() ? null : agg.getLong();

if (agg.isNull()) {
  return null;
}

Long value = agg.isNull() ? null : agg.getLong();

try {
  return agg.getLong();
} catch (IllegalStateException e) {
  if (e.getMessage().contains("Cannot return long for Null Value")) {
    return null;
  }
  throw e;
}

When it happens

Trigger: Calling getLong() while isNullResult is true — i.e., the wrapped aggregator aggregated only null values and no valid long result exists.

Common situations: Long-typed aggregations (sum, longMin/longMax, longFirst/longLast) over columns that are entirely null or missing; result-extraction code that ignores isNull(); mixed-schema segments where a column is absent in some segments.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Cannot return float for Null Value
• Cannot return double for Null Value
• Cannot return float for Null Value
• Cannot return long for Null Value
• Cannot return double for Null Value

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/04fe7380ed91d226. Report an issue: GitHub.