apache/druid · error · Types.InvalidCastException

Cannot cast [%s] to [%s] (Types.InvalidCastException from in

Error message

Cannot cast [%s] to [%s] (Types.InvalidCastException from invalidCast)

What it means

A typed ExprEval subclass (ExprEval.java:888, castTo) throws invalidCast when asked to cast its value to an ExpressionType combination it does not support. The message 'Cannot cast [from] to [to]' surfaces Druid's Types.InvalidCastException; it indicates an unsupported expression-level type coercion in a query.

Source

Thrown at processing/src/main/java/org/apache/druid/math/expr/ExprEval.java:888

          return ExprEval.ofString(asString());
        case ARRAY:
          switch (castTo.getElementType().getType()) {
            case DOUBLE:
              return ExprEval.ofDoubleArray(asArray());
            case LONG:
              return ExprEval.ofLongArray(value == null ? null : new Object[]{value.longValue()});
            case STRING:
              return ExprEval.ofStringArray(value == null ? null : new Object[]{value.toString()});
            default:
              ExpressionType elementType = (ExpressionType) castTo.getElementType();
              return new ArrayExprEval(castTo, new Object[]{castTo(elementType).value()});
          }
        case COMPLEX:
          if (ExpressionType.NESTED_DATA.equals(castTo)) {
            return new NestedDataExprEval(value);
          }
      }
      throw invalidCast(type(), castTo);
    }

    @Override
    public Expr toExpr()
    {
      if (value == null) {
        return new NullDoubleExpr();
      }
      return new DoubleExpr(value.doubleValue());
    }
  }

  private static class LongExprEval extends NumericExprEval
  {
    private static final LongExprEval TRUE = new LongExprEval(Evals.asLong(true));
    private static final LongExprEval FALSE = new LongExprEval(Evals.asLong(false));
    private static final LongExprEval OF_NULL = new LongExprEval(null);

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Remove the cast or cast to a supported target type for that source type.
2. Extract a scalar member from complex/nested data before casting (e.g. json_value / nested field access).
3. Use TRY_CAST to get NULL instead of the exception where supported.
4. Check EXPLAIN output for implicit casts the planner inserted.

Example fix

// before
SELECT CAST(complex_col AS BIGINT) FROM t
// after
SELECT CAST(json_value(complex_col, '$.x') AS BIGINT) FROM t

When it happens

Trigger: Invoking cast() / CAST() on an expression whose runtime ExprEval type has no conversion to the requested target type (e.g. casting an unsupported complex value type to a numeric type, or incompatible nested-data casts).

Common situations: CAST(... AS BIGINT) on complex/nested columns without extracting a scalar first; queries mixing complex types across engine versions; nested GROUP BY or functions that implicitly coerce complex values.

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

• Cannot implicitly cast [%s] to [%s]
• second argument must be a base64 encoded STRING value but go
• Invalid type [%s]
• second argument should be STRING but got %s instead
• second argument must be a a scalar type but got %s instead

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/b68b6a95e091d1b0. Report an issue: GitHub.