pentaho/pentaho-kettle · critical · RuntimeException

: There was a data type error: the data type of " +…

Error message

 : There was a data type error: the data type of " + object.getClass().getName() + " object [" + object + "] does not correspond to value meta [" + toStringMeta() + "]

What it means

A RuntimeException thrown by ValueMetaTimestamp.writeData when a ClassCastException (or KettleValueException) occurs while writing — i.e. the runtime object is not the type the value metadata declares (e.g. a String where a Timestamp is expected).

Solutions

Align the row metadata with actual object types (use RowMetaUtil / verify with a 'Verify rows' pattern)
Convert the value before writing: valueMeta.convertData(sourceMeta, data)
Inspect object.getClass() at the write site and fix the producing transform

Example fix

// before
row[0] = "2024-01-05 10:00:00"; // meta says Timestamp
// after
row[0] = tsMeta.convertData(stringMeta, row[0]); // now a Timestamp

Defensive patterns

Strategy: type-guard

Validate before calling

if (object != null && !(object instanceof java.sql.Timestamp)
 && valueMeta.getStorageType() == ValueMetaInterface.STORAGE_TYPE_NORMAL) {
  object = valueMeta.convertData(dateMeta, object);
}

Type guard

boolean isTimestampData(ValueMetaInterface vm, Object o) {
  if (o == null) return true;
  switch (vm.getStorageType()) {
    case ValueMetaInterface.STORAGE_TYPE_NORMAL: return o instanceof java.sql.Timestamp;
    case ValueMetaInterface.STORAGE_TYPE_INDEXED: return o instanceof Integer;
    case ValueMetaInterface.STORAGE_TYPE_BINARY_STRING: return o instanceof byte[];
    default: return false;
  }
}

Try / catch

try {
  meta.writeData(out, object);
} catch (RuntimeException e) {
  if (e.getMessage().contains("data type error")) {
    object = meta.convertData(sourceMeta, object);
    meta.writeData(out, object);
  } else throw e;
}

Prevention

Keep row metadata and actual object types in sync through the whole pipeline
Convert at transform boundaries, never assume the previous step's types
Run pipelines in development with data-type verification enabled

When it happens

Trigger: Writing a row whose field holds a String/Date/byte[] while the meta says Timestamp with a storage type that triggers a cast, e.g. STORAGE_TYPE_INDEXED with a non-Integer object, or normal storage with a non-Timestamp object.

Common situations: Row layout drift between transforms (field type changed upstream), heterogeneous input files, incorrectly typed data injected via custom code.

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 pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/523c36e7a56e327d. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/pentaho/di/core/row/value/ValueMetaTimestamp.java:610

            // Handle binary string content -- only when not NULL
            // In this case, we opt not to convert anything at all for speed.
            // That way, we can save on CPU power.
            // Since the streams can be compressed, volume shouldn't be an issue
            // at all.
            //
            writeBinaryString( outputStream, (byte[]) object );
            break;

          case STORAGE_TYPE_INDEXED:
            writeInteger( outputStream, (Integer) object ); // just an index
            break;

          default:
            throw new KettleFileException( toString() + " : Unknown storage type " + getStorageType() );
        }
      }
    } catch ( ClassCastException e ) {
      throw new RuntimeException( toString() + " : There was a data type error: the data type of "
        + object.getClass().getName() + " object [" + object + "] does not correspond to value meta ["
        + toStringMeta() + "]" );
    } catch ( IOException e ) {
      throw new KettleFileException( toString() + " : Unable to write value timestamp data to output stream", e );
    } catch ( KettleValueException e ) {
      throw new RuntimeException( toString() + " : There was a data type error: the data type of "
        + object.getClass().getName() + " object [" + object + "] does not correspond to value meta ["
        + toStringMeta() + "]" );
    }
  }

  @Override
  public Object readData( DataInputStream inputStream ) throws KettleFileException, KettleEOFException,
    SocketTimeoutException {
    try {
      // Is the value NULL?
      if ( inputStream.readBoolean() ) {
        return null; // done

View on GitHub (pinned to f3058517a1)