apache/iceberg · error · UnsupportedOperationException

Transform is not supported:

Error message

Transform is not supported: 

What it means

Thrown when converting a Spark sort expression's transform to an Iceberg term and the transform is not one of the supported set (identity, year/month/day/hour, bucket, truncate, zorder, etc.). The default branch rejects unknown Transform values.

Source

Thrown at spark/v4.0/spark/src/main/java/org/apache/iceberg/spark/Spark3Util.java:408

          return org.apache.iceberg.expressions.Expressions.month(colName);
        case "date":
        case "day":
        case "days":
          return org.apache.iceberg.expressions.Expressions.day(colName);
        case "date_hour":
        case "hour":
        case "hours":
          return org.apache.iceberg.expressions.Expressions.hour(colName);
        case "truncate":
          return org.apache.iceberg.expressions.Expressions.truncate(colName, findWidth(transform));
        case "zorder":
          return new Zorder(
              Stream.of(transform.references())
                  .map(ref -> DOT.join(ref.fieldNames()))
                  .map(org.apache.iceberg.expressions.Expressions::ref)
                  .collect(Collectors.toList()));
        default:
          throw new UnsupportedOperationException("Transform is not supported: " + transform);
      }

    } else if (expr instanceof NamedReference) {
      NamedReference ref = (NamedReference) expr;
      return org.apache.iceberg.expressions.Expressions.ref(DOT.join(ref.fieldNames()));

    } else {
      throw new UnsupportedOperationException("Cannot convert unknown expression: " + expr);
    }
  }

  /**
   * Converts Spark transforms into a {@link PartitionSpec}.
   *
   * @param schema the table schema
   * @param partitioning Spark Transforms
   * @return a PartitionSpec
   */

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Use a supported transform: identity, year, month, day, hour, bucket, truncate, or zorder
2. Check the exact transform named in the message and map it to a supported equivalent
3. Upgrade Iceberg if the transform is newly standardized in Spark

Example fix

-- before
CREATE TABLE t (id bigint) USING iceberg SORTED BY (date_trunc('week', ts));
-- after
CREATE TABLE t (id bigint) USING iceberg SORTED BY (day(ts));

Transform t = ...; Set<String> supported = Set.of("identity","year","month","day","hour","bucket","truncate","zorder"); if (!supported.contains(t.name().toLowerCase(Locale.ROOT))) { throw new IllegalArgumentException("Transform not supported: " + t.name()); }

boolean isSupportedTransform(Transform<?> t) { return List.of("identity","year","month","day","hour","bucket","truncate","zorder").contains(t.name().toLowerCase(Locale.ROOT)); }

try { SortOrder order = Spark3Util.toIcebergTerm(transform, ...); } catch (UnsupportedOperationException e) { LOG.error("Map this transform manually: {}", e.getMessage()); throw e; }

When it happens

Trigger: Using a Spark transform (e.g. unsupported function-based transform) in sort columns or bucketing DDL that Spark3Util.toIcebergTerm translates, with the transform falling into the default case.

Common situations: Custom Spark transforms in CREATE TABLE ... CLUSTERED BY / SORTED BY; Spark upgrades adding new standard transforms; typos in transform functions.

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

• Transform is not supported: ${transform}
• Unable to parse sortOrder: %s
• Cannot find width for transform: %s
• Cannot specify the 'sort-order' because it's a reserved tabl
• Cannot mix identity sort columns and a Zorder sort expressio

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/9259b1d145c75ee8. Report an issue: GitHub.