apache/iceberg · warning

Failed to scan delegate parser in {}:

Error message

Failed to scan delegate parser in {}: 

What it means

ExtendedParser scans a Spark parser object reflectively to locate a delegate ParserInterface (e.g. when wrapping Spark's parser for extensions). If reflection fails for any reason, the exception is swallowed and only a warning with the parser class name is logged, and the method returns null. Callers must handle the null delegate.

Source

Thrown at spark/v4.1/spark/src/main/java/org/apache/iceberg/spark/ExtendedParser.java:99

    return null;
  }

  private static ParserInterface getNextDelegateParser(ParserInterface parser) {
    try {
      Class<?> clazz = parser.getClass();
      while (clazz != null) {
        for (Field field : clazz.getDeclaredFields()) {
          field.setAccessible(true);
          Object value = field.get(parser);
          if (value instanceof ParserInterface && value != parser) {
            return (ParserInterface) value;
          }
        }
        clazz = clazz.getSuperclass();
      }
    } catch (Exception e) {
      log().warn("Failed to scan delegate parser in {}: ", parser.getClass().getName(), e);
    }

    return null;
  }

  private static Logger log() {
    return LoggerFactory.getLogger(ExtendedParser.class);
  }

  List<RawOrderField> parseSortOrder(String orderString) throws AnalysisException;
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Verify the Spark/Iceberg versions are compatible (the extended parser matches the Spark internals version)
2. Check JDK module/access errors in the chained exception; add --add-opens for the relevant packages if encapsulation blocks reflection
3. If the warning is benign (parser has no delegate), rely on the null-return handling in the calling code

Example fix

// before
java --add-opens=java.base/java.lang=ALL-UNNAMED
// after
java --add-opens=java.base/java.lang=ALL-UNNAMED \
     --add-opens=org.apache.spark.sql.catalyst/org.apache.spark.sql.catalyst.parser=ALL-UNNAMED

// verify parser extension is present and Spark version matches the Iceberg connector
System.out.println(spark.version());

if (delegate == null) { /* fall back to the original parser instead of using the wrapper */ }

When it happens

Trigger: findParser calls getNextDelegateParser against a parser whose class hierarchy/fields do not expose a ParserInterface in an expected way, or field access is blocked (module access restrictions, changed Spark internals).

Common situations: Spark version upgrades changing internal parser structure; JDK strong encapsulation blocking setAccessible on Spark internals; custom parser extensions that do not follow the standard delegate pattern.

Understand the failure class

Background: "is deprecated and will be removed" — deprecation warnings for old API names, keywords, and options, and how to migrate before the removal release — this error's family across 29 libraries.

Related errors

• Failed to scan delegate parser in {}:
• Unable to parse sortOrder: %s
• e.message (wrapped as IcebergParseException with command con
• msg (dynamic parse error message)
• Invalid transform argument

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/bc8e999304e2ebdc. Report an issue: GitHub.