apache/iceberg · error · IndexOutOfBoundsException

Child columns is null hence cannot find index:

Error message

Child columns is null hence cannot find index: 

What it means

childColumn(pos) indexes into the accessor's child column vectors (the element vectors of a list or fields of a struct). It throws IndexOutOfBoundsException when childColumns is null, meaning this accessor was created without nested child vectors — the column is not nested, so there is no child vector to look up.

Solutions

1. Check childColumn availability (non-null childColumns / list-typed column) before calling
2. Verify the vectorized reader was built with nested-type support so child columns are populated
3. Fall back to the non-vectorized read path for nested columns when children are absent

Example fix

// before
ChildVectorT child = accessor.childColumn(0); // throws if childColumns == null
// after
if (accessor.getChildColumns() != null && accessor.getChildColumns().length > 0) {
  ChildVectorT child = accessor.childColumn(0);
}

if (accessor.getChildColumns() == null) { throw new IllegalStateException("accessor has no child columns"); }

try { return accessor.childColumn(pos); } catch (IndexOutOfBoundsException e) { /* recreate accessor with nested support or fall back */ }

When it happens

Trigger: Calling childColumn(pos) on an accessor constructed without child columns (non-list/non-struct column), or after a factory path that returns null children for unsupported nested types.

Common situations: Assuming list support in vectorized reads and calling childColumn on primitive accessors; vectorized readers built with childColumns omitted (e.g. nested types disabled) while downstream code still requests children.

Related errors

• Struct type is not supported
• Unsupported type: array
• Cannot convert dict encoded field
• Cannot convert nested accessor to position
• Cannot read files that require applying delete files

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/0b32700f8676f62b. Report an issue: GitHub.

Appendix: source

Thrown at arrow/src/main/java/org/apache/iceberg/arrow/vectorized/ArrowVectorAccessor.java:92

  }

  public DecimalT getDecimal(int rowId, int precision, int scale) {
    throw new UnsupportedOperationException("Unsupported type: decimal");
  }

  public Utf8StringT getUTF8String(int rowId) {
    throw new UnsupportedOperationException("Unsupported type: UTF8String");
  }

  public ArrayT getArray(int rowId) {
    throw new UnsupportedOperationException("Unsupported type: array");
  }

  public ChildVectorT childColumn(int pos) {
    if (childColumns != null) {
      return childColumns[pos];
    } else {
      throw new IndexOutOfBoundsException("Child columns is null hence cannot find index: " + pos);
    }
  }

  public final ValueVector getVector() {
    return vector;
  }
}

View on GitHub (pinned to 86d9c8fc54)