pentaho/pentaho-kettle · error · KettleException

Unable to find field name for formula [

Error message

Unable to find field name for formula [

What it means

KettleException thrown in Formula.calcFields() when a FormulaMetaFunction has an empty fieldName, i.e. the formula result has neither a new field name nor (checked earlier) a replace field. Every formula must produce output into a named field, so the step refuses to compute it.

Solutions

1. Open the Formula step dialog and set the 'New field' name (or a 'Replace value' field) for every formula row.
2. Remove any leftover blank formula rows.
3. Validate the transformation (Ctrl+T) which surfaces empty formula field names at design time.

Example fix

// before
new FormulaMetaFunction(fn, null, "NVL(x,0)", ...); // no field name
// after
new FormulaMetaFunction(fn, "defaulted_x", "NVL(x,0)", ...);

if (Utils.isEmpty(fn.getFieldName()) && Utils.isEmpty(fn.getReplaceField())) {
  throw new KettleException("Formula row needs a field name or replace field: " + fn.getFormula());
}

When it happens

Trigger: A formula row exists in the step meta whose 'New field' name is blank and 'Replace value' is also blank; this passes dialog edits but fails when the first row is processed.

Common situations: User added a formula row in the dialog but never filled in the field name; a transformation was hand-edited in XML and the field_name attribute was dropped; import from another environment lost attributes.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• No name was specified for result value #
• Unknown field specified to replace with a formula result: [
• A connection of type PALO is expected
• A server socket allocation always has to accompanied by…
• AccessInput.Exception.CouldnotFindField

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/760a6f5e35c5b2e8. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/trans/steps/formula/Formula.java:128

    try {
      Object[] outputRowData = RowDataUtil.createResizedCopy( r, data.outputRowMeta.size() );
      int tempIndex = rowMeta.size();

      // Assign this tempRowData to the formula context
      //
      data.context.setRowData( outputRowData );

      // Initialize parsers etc. Only do it once.
      //
      if ( data.formulas == null ) {
        // Create a set of LValues to put the parsed results in...
        data.formulas = new org.pentaho.reporting.libraries.formula.Formula[meta.getFormula().length];
        for ( int i = 0; i < meta.getFormula().length; i++ ) {
          FormulaMetaFunction fn = meta.getFormula()[i];
          if ( !Utils.isEmpty( fn.getFieldName() ) ) {
            data.formulas[i] = data.createFormula( meta.getFormula()[i].getFormula() );
          } else {
            throw new KettleException( "Unable to find field name for formula ["
              + Const.NVL( fn.getFormula(), "" ) + "]" );
          }
        }
      }

      for ( int i = 0; i < meta.getFormula().length; i++ ) {
        FormulaMetaFunction fn = meta.getFormula()[i];
        if ( !Utils.isEmpty( fn.getFieldName() ) ) {
          if ( data.formulas[i] == null ) {
            data.formulas[i] = data.createFormula( meta.getFormula()[i].getFormula() );
          }

          // this is main part of all this step: calculate formula
          Object formulaResult = data.formulas[i].evaluate();
          if ( formulaResult instanceof LibFormulaErrorValue ) {
            // inspect why it is happens to get clear error message.
            throw new KettleException( "Error calculate formula. Formula "
                + fn.getFormula() + " output field: " + fn.getFieldName() + ", error is: " + formulaResult.toString() );

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