What causes "Does not support setValue." in apache/iceberg?

Replace entry.setValue(v) with map.put(entry.getKey(), v)

apache/iceberg · error · UnsupportedOperationException

Does not support setValue.

Error message

Does not support setValue.

What it means

StructLikeMap exposes its entries as Map.Entry views backed by the key's StructLike wrapper. The entry's setValue is intentionally unsupported because values are stored in an internal wrapper map; mutating through the entry view would bypass the map's invariants, so it always throws UnsupportedOperationException.

Solutions

Replace entry.setValue(v) with map.put(entry.getKey(), v)
Use StructLikeMap.transformValues(func) for bulk value transformation
Rebuild the map into a plain Map if entry mutation semantics are required

Example fix

// before
for (Map.Entry<Record, String> e : map.entrySet()) {
  e.setValue(e.getValue().toUpperCase(Locale.ROOT));
}
// after
StructLikeMap<String> updated = map.transformValues(v -> v.toUpperCase(Locale.ROOT));

Defensive patterns

Strategy: fallback

Prevention

Never call setValue on entries from StructLikeMap.entrySet()
Use map.put(key, value) for updates
Use transformValues for bulk value changes
Remember StructLikeMap entries are read-only views

When it happens

Trigger: Iterating a StructLikeMap's entrySet() and calling entry.setValue(newValue) to update a mapping in place.

Common situations: Refactoring code from HashMap to StructLikeMap where an in-place entry mutation loop existed; bulk value updates during iteration.

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

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/e3a1f333d9be70ef. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/util/StructLikeMap.java:190

    public int hashCode() {
      return inner.hashCode();
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      } else if (o == null || getClass() != o.getClass()) {
        return false;
      }

      StructLikeEntry<?> that = (StructLikeEntry<?>) o;
      return inner.equals(that.inner);
    }

    @Override
    public R setValue(R value) {
      throw new UnsupportedOperationException("Does not support setValue.");
    }
  }

  public <U> StructLikeMap<U> transformValues(Function<T, U> func) {
    StructLikeMap<U> result = create(type);
    wrapperMap.forEach((key, value) -> result.put(key.get(), func.apply(value)));
    return result;
  }
}

View on GitHub (pinned to 86d9c8fc54)