redis/jedis · error · UnsupportedAggregationException

AGG_MIN policy requires Comparable types or KeyValue, but…

Error message

AGG_MIN policy requires Comparable types or KeyValue, but got: ${min.getClass().getName()} and ${input.getClass().getName()}

What it means

MinAggregator.add throws UnsupportedAggregationException when the current min value is neither Comparable nor a KeyValue, so AGG_MIN cannot order the elements. Same contract as MaxAggregator but for the minimum.

Solutions

Ensure all values passed to add() are Comparable and mutually comparable, or KeyValue instances
Normalize types before aggregation (e.g. parse all to Long/Double)
Handle non-comparable data outside the aggregator

Example fix

// before
minAgg.add(obj);
// after
if (obj instanceof Comparable) { minAgg.add(obj); } else { minAgg.add(Long.valueOf(obj.hashCode())); }

Defensive patterns

Strategy: type-guard

Validate before calling

if (!(value instanceof Comparable) && !(value instanceof KeyValue)) { throw new IllegalArgumentException("AGG_MIN needs Comparable or KeyValue"); }

Type guard

boolean isMinCompatible(Object o) { return o instanceof Comparable || o instanceof KeyValue; }

Try / catch

try { minAgg.add(value); } catch (UnsupportedAggregationException e) { log.error("Non-comparable value: {}", value.getClass()); throw e; }

Prevention

Only aggregate Comparable or KeyValue results
Normalize to one Comparable type before aggregation
Avoid mixing String and numeric types across add() calls

When it happens

Trigger: Calling add() with an operand that is not Comparable and not KeyValue, or whose compareTo is incompatible with the accumulated min.

Common situations: Aggregating raw byte arrays or custom objects returned by module commands; mixing types (String then Long) across add() calls.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of redis/jedis@6dac31d4c2 (2026-09-08). Data as JSON: /api/errors/1a24445891a2727d. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/redis/clients/jedis/executors/aggregators/MinAggregator.java:40

      return;
    }

    // Handle KeyValue types
    if (min instanceof KeyValue && input instanceof KeyValue) {
      min = (T) aggregateKeyValueMin((KeyValue<?, ?>) min, (KeyValue<?, ?>) input);
      return;
    }

    // Handle Comparable types
    if (min instanceof Comparable && input instanceof Comparable) {
      Comparable<Object> minComp = (Comparable<Object>) min;
      if (minComp.compareTo(input) > 0) {
        min = input;
      }
      return;
    }

    throw new UnsupportedAggregationException(
        "AGG_MIN policy requires Comparable types or KeyValue, but got: " + min.getClass().getName()
            + " and " + input.getClass().getName());
  }

  @Override
  public T getResult() {
    return min;
  }

  @SuppressWarnings("unchecked")
  private KeyValue<?, ?> aggregateKeyValueMin(KeyValue<?, ?> kv1, KeyValue<?, ?> kv2) {
    Object minKey = ((Comparable<Object>) kv1.getKey()).compareTo(kv2.getKey()) <= 0 ? kv1.getKey()
        : kv2.getKey();
    Object minValue = ((Comparable<Object>) kv1.getValue()).compareTo(kv2.getValue()) <= 0
        ? kv1.getValue()
        : kv2.getValue();
    return new KeyValue<>(minKey, minValue);
  }

View on GitHub (pinned to 6dac31d4c2)