apache/iceberg · error · UnsupportedOperationException

Cannot modify ManifestFileWrapper wrapper via set

Error message

Cannot modify ManifestFileWrapper wrapper via set

What it means

ManifestFileWrapper is a read-only StructLike view over a ManifestFile in V1Metadata. Its set(pos, value) is intentionally unimplemented because manifests are immutable metadata; mutating a wrapped manifest file would corrupt table metadata. The library throws UnsupportedOperationException to enforce read-only access.

Solutions

1. Do not call set on the wrapper; construct a new ManifestFile/Record instead of mutating the wrapped one
2. If you need a mutable record, copy fields via get(pos) into your own Record and modify that
3. Check that custom writers use ManifestFile itself, not the read-only wrapper, when serializing

Example fix

// before
structLike.set(0, newPath);
// after
Record copy = GenericRecord.create(MANIFEST_LIST_SCHEMA.asStruct()).copy(structLike);
copy.set(0, newPath);

if (wrapper instanceof V1Metadata.ManifestFileWrapper) { throw new IllegalStateException("read-only wrapper; copy fields instead of set()"); }

boolean isReadOnlyWrapper(Object s) { return s instanceof V1Metadata.ManifestFileWrapper || s instanceof V1Metadata.ManifestEntryWrapper || s instanceof V1Metadata.DataFileWrapper; }

try { structLike.set(pos, value); } catch (UnsupportedOperationException e) { Record copy = GenericRecord.create(schema.asStruct()).copy(structLike); copy.set(pos, value); }

When it happens

Trigger: Calling set(pos, value) on a ManifestFileWrapper obtained via V1Metadata.ManifestFileWrapper.wrap(manifestFile), e.g. when writing manifests via a GenericDataWriter or when code treats the StructLike as mutable.

Common situations: Custom catalog or writer code that reuses a mutable StructLike buffer across records and calls set() on manifest-file structs; reflection-based frameworks (Avro/GenericData) attempting in-place mutation of manifest list records.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Cannot modify DataFileWrapper wrapper via set
• Cannot modify ManifestEntryWrapper wrapper via set
• Cannot modify ManifestEntryWrapper wrapper via set
• Cannot modify ManifestFileWrapper wrapper via set
• Backup table name cannot be specified

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/bcd54ccbaffcb31e. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/V1Metadata.java:68

   * <p>This is used to maintain compatibility with v1 by writing manifest list files with the old
   * schema, instead of writing a sequence number into metadata files in v1 tables.
   */
  static class ManifestFileWrapper implements ManifestFile, StructLike {
    private ManifestFile wrapped = null;

    public ManifestFile wrap(ManifestFile file) {
      this.wrapped = file;
      return this;
    }

    @Override
    public int size() {
      return MANIFEST_LIST_SCHEMA.columns().size();
    }

    @Override
    public <T> void set(int pos, T value) {
      throw new UnsupportedOperationException("Cannot modify ManifestFileWrapper wrapper via set");
    }

    @Override
    public <T> T get(int pos, Class<T> javaClass) {
      return javaClass.cast(get(pos));
    }

    private Object get(int pos) {
      switch (pos) {
        case 0:
          return path();
        case 1:
          return length();
        case 2:
          return partitionSpecId();
        case 3:
          return snapshotId();
        case 4:

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