apache/iceberg · error · UnsupportedOperationException

Cannot evaluate

Error message

Cannot evaluate 

What it means

BoundExtract represents an extract expression (pulling a value from a variant/object by path). Its eval(StructLike) has no general implementation, so calling it throws UnsupportedOperationException. Extract expressions must be resolved/lowered by the engine before evaluation.

Source

Thrown at api/src/main/java/org/apache/iceberg/expressions/BoundExtract.java:61

  @Override
  public Type type() {
    return type;
  }

  @Override
  public boolean isEquivalentTo(BoundTerm<?> other) {
    if (other instanceof BoundExtract) {
      BoundExtract<?> that = (BoundExtract<?>) other;
      return ref.isEquivalentTo(that.ref) && path.equals(that.path) && type.equals(that.type);
    }

    return false;
  }

  @Override
  public T eval(StructLike struct) {
    throw new UnsupportedOperationException("Cannot evaluate " + this);
  }

  @Override
  public String toString() {
    return "extract(" + ref + ", path=" + path + ", type=" + type + ")";
  }
}

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Lower extract expressions into engine-native evaluation before binding/evaluating
2. Filter out extract expressions from pure Iceberg row evaluation paths
3. Use ExpressionVisitors to detect BoundExtract and handle it specially
4. Upgrade Iceberg to a version with engine support for the extract operation

Example fix

// before
Object v = boundExtract.eval(rowStruct); // throws
// after
if (boundExtract instanceof BoundExtract) {
  // handle via engine-specific variant accessor, not generic eval
  return;
}
Object v = expr.eval(rowStruct);

if (expr instanceof BoundExtract) { /* route to variant-capable evaluator */ }

boolean isExtract = expr instanceof BoundExtract;

try { v = expr.eval(struct); } catch (UnsupportedOperationException e) { if (e.getMessage().contains("Cannot evaluate")) { /* lower to engine-native evaluation */ } else { throw e; } }

When it happens

Trigger: Calling eval(StructLike) directly on a BoundExtract expression instead of letting the scan/residual machinery handle it; binding an extract expression and trying row evaluation.

Common situations: Variant-type filter pushdown where the engine must interpret the extract path; custom evaluators encountering extract expressions they cannot lower.

Related errors

• Invalid aggregate:
• does not implement eval(StructLike)
• does not implement eval(DataFile)
• does not implement hasValue(DataFile)
• does not implement newAggregator()

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/27fa62d8eaeaf242. Report an issue: GitHub.