apache/iceberg · error · IllegalArgumentException

Unknown file format %s

Error message

Unknown file format %s

What it means

SinkUtil.writeProperties builds per-format compression write properties for AVRO, PARQUET, and ORC; any other FileFormat hits the default branch and throws IllegalArgumentException. It guards against FileFormat values unknown to this Flink connector version.

Source

Thrown at flink/v2.3/flink/src/main/java/org/apache/iceberg/flink/sink/SinkUtil.java:151

        writeProperties.put(PARQUET_SHRED_VARIANTS, String.valueOf(conf.parquetShredVariants()));
        writeProperties.put(
            PARQUET_VARIANT_BUFFER_SIZE, String.valueOf(conf.parquetVariantInferenceBufferSize()));

        break;
      case AVRO:
        writeProperties.put(AVRO_COMPRESSION, conf.avroCompressionCodec());
        String avroCompressionLevel = conf.avroCompressionLevel();
        if (avroCompressionLevel != null) {
          writeProperties.put(AVRO_COMPRESSION_LEVEL, conf.avroCompressionLevel());
        }

        break;
      case ORC:
        writeProperties.put(ORC_COMPRESSION, conf.orcCompressionCodec());
        writeProperties.put(ORC_COMPRESSION_STRATEGY, conf.orcCompressionStrategy());
        break;
      default:
        throw new IllegalArgumentException(String.format("Unknown file format %s", format));
    }

    return writeProperties;
  }
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Set the table's format property to avro, parquet, or orc
2. Upgrade the Iceberg Flink connector to a version that supports the requested format
3. Only call SinkUtil.writeProperties with FileFormat values intended for data files

Example fix

// before
tableBuilder.format("avif")
// after
tableBuilder.format("parquet")

FileFormat fmt = FileFormat.fromString(table.properties().getOrDefault(TableProperties.DEFAULT_FILE_FORMAT, "parquet"));
if (fmt != FileFormat.AVRO && fmt != FileFormat.PARQUET && fmt != FileFormat.ORC) {
  throw new IllegalArgumentException("Flink sink supports only avro|parquet|orc, got: " + fmt);
}

When it happens

Trigger: Calling SinkUtil.writeProperties with a format like AVIF or PUFFIN/other non-data formats, or a FileFormat added in a newer Iceberg spec while running an older connector.

Common situations: Programmatic table creation setting an exotic file format; copying format strings from another tool; version skew between table metadata and connector jars.

Related errors

• Unrecognized WRITE_DISTRIBUTION_MODE:
• Unrecognized WRITE_DISTRIBUTION_MODE:
• Unknown catalog-type: %s (Must be 'hive', 'hadoop' or 'rest'
• Class %s does not implement DynamicRecordGeneratorSQL
• Failed to instantiate DynamicRecordGeneratorSQL %s

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/f3ef90a532c198d0. Report an issue: GitHub.