apache/druid · error · ISE

Unsupported expression type[%s]

Error message

Unsupported expression type[%s]

What it means

getTypeStrategy() switches on the ExpressionType's kind (LONG, DOUBLE, STRING, ARRAY, COMPLEX). Any other ExprType value has no TypeStrategy and triggers ISE 'Unsupported expression type[x]'. This is an internal invariant check — valid ExpressionTypes are always one of the handled kinds, so this indicates a malformed or future-version ExpressionType reached the factory.

Source

Thrown at processing/src/main/java/org/apache/druid/math/expr/ExpressionTypeFactory.java:121

        break;
      case DOUBLE:
        strategy = TypeStrategies.DOUBLE;
        break;
      case STRING:
        strategy = TypeStrategies.STRING;
        break;
      case ARRAY:
        strategy = new TypeStrategies.ArrayTypeStrategy(expressionType);
        break;
      case COMPLEX:
        TypeStrategy<?> complexStrategy = TypeStrategies.getComplex(expressionType.getComplexTypeName());
        if (complexStrategy == null) {
          throw new IAE("Cannot find strategy for type [%s]", expressionType.asTypeString());
        }
        strategy = complexStrategy;
        break;
      default:
        throw new ISE("Unsupported expression type[%s]", expressionType.getType());
    }
    return strategy;
  }
}

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Only pass ExpressionTypes produced by ExpressionTypeFactory/ExpressionType constants into getTypeStrategy().
2. Align all Druid module versions so ExprType enums are consistent.
3. If a new ExprType was added by an extension, register a corresponding TypeStrategy and extend the switch upstream.
4. Catch ISE, log expressionType.getType(), and trace where the malformed type was constructed.

ExprType kind = exprType.getType();
if (kind != ExprType.LONG && kind != ExprType.DOUBLE && kind != ExprType.STRING
    && kind != ExprType.ARRAY && kind != ExprType.COMPLEX) {
  throw new IllegalStateException("No TypeStrategy for ExprType " + kind);
}

boolean hasTypeStrategy(ExpressionType t) {
  switch (t.getType()) {
    case LONG: case DOUBLE: case STRING: case ARRAY: case COMPLEX: return true;
    default: return false;
  }
}

try {
  TypeStrategy<?> s = ExpressionTypeFactory.getInstance().getTypeStrategy(exprType);
} catch (IllegalStateException e) {
  log.error("Unsupported ExprType %s", exprType.getType()); throw e;
}

When it happens

Trigger: Calling ExpressionTypeFactory.getInstance().getTypeStrategy(exprType) with an ExpressionType whose getType() is not LONG/DOUBLE/STRING/ARRAY/COMPLEX (hand-constructed, corrupted, or from an incompatible Druid version).

Common situations: Custom expression extensions introducing new ExprType values without registering a strategy; deserializing expression types across mismatched Druid versions; test code constructing ExpressionType directly.

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

• Unsupported value type[%s]
• Unsupported expression type[%s]
• FLOAT types are not supported natively by Druid expressions
• Unsupported unknown value type
• Cannot implicitly cast [%s] to [%s]

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/1f07a87405c99fe6. Report an issue: GitHub.