What causes " : Unable to serialize indexe storage type for data type " in pentaho/pentaho-kettle?

Ensure every element in the index array is of a type supported by writeData (String, Long/Integer, Double, Date, Boolean, byte[], BigDecimal, InetAddress)

pentaho/pentaho-kettle · error · KettleFileException

: Unable to serialize indexe storage type for data type

Error message

 : Unable to serialize indexe storage type for data type

What it means

KettleFileException thrown by ValueMetaBase.writeData for STORAGE_TYPE_INDEXED values when an individual index entry's type is not serializable by the writer's inner switch (unsupported for String, Number, Integer, Date, Boolean, Binary, BigNumber, etc.). It indicates an index table containing values of a data type the binary writer cannot serialize.

Solutions

Ensure every element in the index array is of a type supported by writeData (String, Long/Integer, Double, Date, Boolean, byte[], BigDecimal, InetAddress)
Convert unsupported index entries to supported types when building the indexed value meta
Fall back to STORAGE_TYPE_NORMAL for values whose types the indexed writer cannot handle

Example fix

// before
index[i] = new Timestamp(...); // not matched by writer switch
// after
if (index[i] instanceof Timestamp) {
  index[i] = new Date(((Timestamp) index[i]).getTime());
}

Defensive patterns

Strategy: validation

Validate before calling

// Validate every index entry before assigning an indexed storage type:
static void validateIndexedEntries(ValueMetaInterface vmi, Object[] index) throws KettleFileException {
  for (int i = 0; i < index.length; i++) {
    Object o = index[i];
    if (o == null) continue;
    Class<?> expected = expectedClassFor(vmi.getType());
    if (!expected.isInstance(o)) {
      throw new KettleFileException("Index entry " + i + " expects " + expected.getName()
          + " but is " + o.getClass().getName());
    }
  }
}

Try / catch

try {
  valueMeta.writeData(out, object);
} catch (KettleFileException e) {
  if (String.valueOf(e.getMessage()).contains("Unable to serialize indexe")) {
    LOG.error("Indexed field " + valueMeta.getName() + " has an unsupported entry type");
    // convert entries to supported classes or switch storage type and retry
  } else { throw e; }
}

Prevention

Build index arrays only with the exact classes the value meta's type maps to
Convert Timestamp to Date, Integer to Long, etc., when populating lookup tables
Prefer STORAGE_TYPE_NORMAL unless the indexed-encoding performance benefit is measured and needed
Unit-test writeData/readData round-trips for indexed value metas

When it happens

Trigger: writeData() on an indexed ValueMeta whose index array holds, e.g., java.util.Date subclasses, BigDecimal beyond supported cases, or arbitrary objects; the inner default branch throws for that element's type.

Common situations: Building indexed storage types from lookup tables containing unsupported classes; metadata generated by custom code or plugins with mixed-type index arrays.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/6abe96d9ee54f27d. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/pentaho/di/core/row/value/ValueMetaBase.java:3013

                    writeNumber( outputStream, (Double) index[i] );
                    break;
                  case TYPE_INTEGER:
                    writeInteger( outputStream, (Long) index[i] );
                    break;
                  case TYPE_DATE:
                    writeDate( outputStream, (Date) index[i] );
                    break;
                  case TYPE_BIGNUMBER:
                    writeBigNumber( outputStream, (BigDecimal) index[i] );
                    break;
                  case TYPE_BOOLEAN:
                    writeBoolean( outputStream, (Boolean) index[i] );
                    break;
                  case TYPE_BINARY:
                    writeBinary( outputStream, (byte[]) index[i] );
                    break;
                  default:
                    throw new KettleFileException( toString()
                        + " : Unable to serialize indexe storage type for data type " + getType() );
                }
              } catch ( ClassCastException e ) {
                throw new RuntimeException( toString() + " : There was a data type error: the data type of "
                    + index[i].getClass().getName() + " object [" + index[i] + "] does not correspond to value meta ["
                    + toStringMeta() + "]" );
              }
            }
          }
          break;

        case STORAGE_TYPE_BINARY_STRING:
          // Save the storage meta data...
          //
          outputStream.writeBoolean( storageMetadata != null );

          if ( storageMetadata != null ) {
            storageMetadata.writeMeta( outputStream );

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