apache/druid · error · IllegalArgumentException

A-Not-B requires at least 1 sketch

Error message

A-Not-B requires at least 1 sketch

What it means

The NOT (A-Not-B) set operation of ArrayOfDoublesSketchOperations requires at least one input sketch to compute a difference. The apply() method validates this and throws IllegalArgumentException when sketches.length < 1, since A-Not-B cannot be evaluated with no sketches.

Source

Thrown at extensions-core/datasketches/src/main/java/org/apache/druid/query/aggregation/datasketches/tuple/ArrayOfDoublesSketchOperations.java:71

    },
    INTERSECT {
      @Override
      public ArrayOfDoublesSketch apply(final int nominalEntries, final int numberOfValues, final ArrayOfDoublesSketch[] sketches)
      {
        final ArrayOfDoublesIntersection intersection = new ArrayOfDoublesSetOperationBuilder()
            .setNominalEntries(nominalEntries).setNumberOfValues(numberOfValues).buildIntersection();
        for (final ArrayOfDoublesSketch sketch : sketches) {
          intersection.intersect(sketch, COMBINER);
        }
        return intersection.getResult();
      }
    },
    NOT {
      @Override
      public ArrayOfDoublesSketch apply(final int nominalEntries, final int numberOfValues, final ArrayOfDoublesSketch[] sketches)
      {
        if (sketches.length < 1) {
          throw new IAE("A-Not-B requires at least 1 sketch");
        }

        if (sketches.length == 1) {
          return sketches[0];
        }

        ArrayOfDoublesSketch result = sketches[0];
        for (int i = 1; i < sketches.length; i++) {
          final ArrayOfDoublesAnotB aNotB = new ArrayOfDoublesSetOperationBuilder().setNumberOfValues(numberOfValues)
              .buildAnotB();
          aNotB.update(result, sketches[i]);
          result = aNotB.getResult();
        }
        return result;
      }
    };

    public abstract ArrayOfDoublesSketch apply(int nominalEntries, int numberOfValues, ArrayOfDoublesSketch[] sketches);

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Ensure the post-aggregator fields actually produce sketches for the queried data
2. Check query filters/intervals are not excluding all rows feeding the aggregation
3. Guard the operation site with a length check before calling apply

Example fix

// before
ArrayOfDoublesSketch result = Operation.NOT.apply(nominalEntries, numValues, sketches);
// after
if (sketches.length == 0) {
  return null; // or an empty sketch
}
ArrayOfDoublesSketch result = Operation.NOT.apply(nominalEntries, numValues, sketches);

if (sketches == null || sketches.length < 1) {
  throw new IllegalArgumentException("NOT operation requires at least 1 sketch");
}

boolean hasSketches = sketches != null && sketches.length >= 1;

try {
  result = Operation.NOT.apply(nominalEntries, numValues, sketches);
} catch (IllegalArgumentException e) {
  if (e.getMessage().contains("requires at least 1 sketch")) {
    result = null; // or empty sketch
  } else {
    throw e;
  }
}

When it happens

Trigger: Invoking ArrayOfDoublesSketchOperations.Operation.NOT.apply() with an empty sketches array, typically from ArrayOfDoublesSketchSetOpPostAggregator when its input fields produce no sketches.

Common situations: A post-aggregator whose field expression filters out all rows and yields no sketches; misconfigured query with an empty or all-null field list that survives the fields>1 constructor check but produces nothing at runtime.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Illegal number of fields[%d], must be > 1
• AggregatorFactoryNotMergeableException(this, other)
• Object is not of a type that can be deserialized to a quanti
• Comparing histograms is not supported
• Cannot accept both 'splitPoints' and 'numBins'

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/5706b23f3d8c1a38. Report an issue: GitHub.