pentaho/pentaho-kettle · error · KettleXMLException

MergeRowsMeta.Exception.UnableToLoadStepInfo

MergeRowsMeta.Exception.UnableToLoadStepInfo

Error message

MergeRowsMeta.Exception.UnableToLoadStepInfo

What it means

Thrown by MergeRowsMeta.readData (called from loadXML) when parsing the Merge Rows step's XML node fails. It reads the 'reference' and 'compare' stream subjects from the stepnode and wraps any Exception in a KettleXMLException.

Solutions

  1. Inspect KettleXMLException.getCause() for the precise parsing failure.
  2. Open the .ktr in Spoon and re-save the Merge Rows step to regenerate clean XML.
  3. Verify the step node contains well-formed <reference> and <compare> elements.
  4. Restore the file from version control or backup if corrupted.

Example fix

// before (missing closing tag)
<reference>Ref step
// after
<reference>Ref step</reference>
Defensive patterns

Strategy: try-catch

Validate before calling

// Validate the transformation XML is well-formed before loading
Document doc = XMLHandler.loadXMLFile(ktrFile);
if (doc == null) throw new IllegalArgumentException("Unreadable transformation XML");

Try / catch

try {
  TransMeta tm = new TransMeta(ktrFile);
} catch (KettleXMLException e) {
  log.error("Merge rows step XML load failed: " + e.getCause(), e);
}

Prevention

When it happens

Trigger: loadXML on a .ktr whose <merge_rows> node is malformed or triggers an exception while reading tags or resolving info streams — corrupted XML, hand-edited files, or incompatible-version step XML.

Common situations: Hand-edited or merge-conflicted .ktr breaking <reference>/<compare> tags; opening a transformation saved by a newer Kettle version; truncated file transfer.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/2f1d31dcab807ded. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/trans/steps/mergerows/MergeRowsMeta.java:198

        Node keynode = XMLHandler.getSubNodeByNr( keysnode, "key", i );
        keyFields[i] = XMLHandler.getNodeValue( keynode );
      }

      for ( int i = 0; i < nrValues; i++ ) {
        Node valuenode = XMLHandler.getSubNodeByNr( valuesnode, "value", i );
        valueFields[i] = XMLHandler.getNodeValue( valuenode );
      }

      flagField = XMLHandler.getTagValue( stepnode, "flag_field" );

      List<StreamInterface> infoStreams = getStepIOMeta().getInfoStreams();
      StreamInterface referenceStream = infoStreams.get( 0 );
      StreamInterface compareStream = infoStreams.get( 1 );

      compareStream.setSubject( XMLHandler.getTagValue( stepnode, "compare" ) );
      referenceStream.setSubject( XMLHandler.getTagValue( stepnode, "reference" ) );
    } catch ( Exception e ) {
      throw new KettleXMLException(
        BaseMessages.getString( PKG, "MergeRowsMeta.Exception.UnableToLoadStepInfo" ), e );
    }
  }

  @Override
  public void setDefault() {
    flagField = "flagfield";
    allocate( 0, 0 );
  }

  @Override
  public void readRep( Repository rep, IMetaStore metaStore, ObjectId id_step, List<DatabaseMeta> databases ) throws KettleException {
    try {
      int nrKeys = rep.countNrStepAttributes( id_step, "key_field" );
      int nrValues = rep.countNrStepAttributes( id_step, "value_field" );

      allocate( nrKeys, nrValues );

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