pentaho/pentaho-kettle · error · KettleException

AvroInput.Error.UnableToParseArrayIndex

AvroInput.Error.UnableToParseArrayIndex

Error message

AvroInput.Error.UnableToParseArrayIndex

What it means

Inside the array selector '[...]', the text between the brackets must parse as an integer element index. Integer.parseInt failed on the extracted index, so convertToKettleValue throws this KettleException including the bad index string.

Solutions

  1. Replace the bracket content with a plain non-negative integer: '$.tags[2]'.
  2. Use '[*]' if you want all elements expanded rather than a specific index.
  3. Trim the path of stray spaces/characters inside brackets and re-save the step.

Example fix

// before
$.tags[abc]
// after
$.tags[0]
Defensive patterns

Strategy: validation

Validate before calling

// Validate bracket content parses as an integer before configuring
java.util.regex.Matcher m = java.util.regex.Pattern.compile("\\[(.*?)\\]").matcher(path);
while (m.find()) {
  String idx = m.group(1).trim();
  if (!idx.equals("*") && !idx.matches("\\d+")) {
    throw new IllegalArgumentException("Bad array index: [" + idx + "]");
  }
}

Type guard

boolean isIntegerIndex(String segment) {
  if (segment == null || !segment.startsWith("[")) return false;
  String idx = segment.substring(1, segment.indexOf(']')).trim();
  return idx.matches("\\d+");
}

Try / catch

try {
  Object v = reader.convertToKettleValue(...);
} catch (KettleException e) {
  if (e.getMessage().contains("UnableToParseArrayIndex")) {
    // correct the index literal in the path and re-run
  } else throw e;
}

Prevention

When it happens

Trigger: Writing a non-numeric index such as '$.tags[*' handled elsewhere, '$.tags[abc]', '$.tags[ ]', or '$.tags[01x]' in a field path where a numeric index is required.

Common situations: Typos in hand-written paths; pasting a map key where an array index is expected; whitespace/hidden characters inside the brackets.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/757c06facc47edd1. Report an issue: GitHub.

Appendix: source

Thrown at plugins/avro-format/core/src/main/java/org/pentaho/di/trans/steps/avro/input/AvroNestedReader.java:547

    if ( array == null ) {
      return null;
    }

    if ( avroInputField.getTempParts().size() == 0 ) {
      throw new KettleException( BaseMessages.getString( PKG, "AvroInput.Error.MalformedPathArray" ) );
    }

    String part = avroInputField.getTempParts().remove( 0 );
    if ( !( part.charAt( 0 ) == '[' ) ) {
      throw new KettleException( BaseMessages.getString( PKG, "AvroInput.Error.MalformedPathArray2", part ) );
    }

    String index = part.substring( 1, part.indexOf( ']' ) );
    int arrayI = 0;
    try {
      arrayI = Integer.parseInt( index.trim() );
    } catch ( NumberFormatException e ) {
      throw new KettleException( BaseMessages.getString( PKG, "AvroInput.Error.UnableToParseArrayIndex", index ) );
    }

    if ( part.indexOf( ']' ) < part.length() - 1 ) {
      // more dimensions to the array
      part = part.substring( part.indexOf( ']' ) + 1, part.length() );
      avroInputField.getTempParts().add( 0, part );
    }

    if ( arrayI >= array.size() || arrayI < 0 ) {
      return null;
    }

    Object element = array.get( arrayI );
    Schema elementType = s.getElementType();

    if ( element == null ) {
      return null;
    }

View on GitHub (pinned to f3058517a1)