apache/iceberg · error · UnsupportedOperationException

Cannot modify ManifestFileWrapper wrapper via set

Error message

Cannot modify ManifestFileWrapper wrapper via set

What it means

V2Metadata.ManifestFileWrapper is a read-only StructLike view over a V2 ManifestFile. Manifest files are immutable metadata; set(pos, value) deliberately throws UnsupportedOperationException so wrapped manifest-list records cannot be altered in place.

Solutions

1. Construct a new ManifestFile/Record instead of mutating the wrapper
2. Copy fields out with get(pos) into your own record and modify the copy
3. Ensure custom writers serialize the ManifestFile itself, not the read-only wrapper

Example fix

// before
wrapper.set(12, partitionsField);
// after
Record copy = GenericRecord.create(MANIFEST_LIST_SCHEMA.asStruct()).copy(wrapper);
copy.set(12, partitionsField);

if (wrapper instanceof V2Metadata.ManifestFileWrapper) { throw new IllegalStateException("read-only wrapper; copy before modifying"); }

boolean isReadOnlyManifest(Object s) { return s instanceof V2Metadata.ManifestFileWrapper; }

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

When it happens

Trigger: Calling set(pos, value) on V2Metadata.ManifestFileWrapper.wrap(manifestFile), e.g. from generic writers or mutation-style StructLike code.

Common situations: Custom catalog/writer code reusing mutable records across manifest files; frameworks that assume all StructLike views are writable.

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/0e14798ee6deba66. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/V2Metadata.java:79

    ManifestFileWrapper(long commitSnapshotId, long sequenceNumber) {
      this.commitSnapshotId = commitSnapshotId;
      this.sequenceNumber = sequenceNumber;
    }

    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 wrapped.path();
        case 1:
          return wrapped.length();
        case 2:
          return wrapped.partitionSpecId();
        case 3:
          checkContentType(wrapped.content());
          return wrapped.content().id();

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