apache/iceberg · error · UnsupportedOperationException

Unknown position: (expected 0- )

Error message

Unknown position: ${pos} (expected 0-${BASE_TYPE.fields().size() - 1})

What it means

BasePartitionStatistics.internalGet(int pos) maps positional field indexes (0..BASE_TYPE.fields().size()-1) to partition-statistics field values. An out-of-range or unrecognized position falls through the switch and throws UnsupportedOperationException via unknownPosition(pos). This is an internal invariant violation, not a user-facing validation.

Solutions

1. Use the position constants defined by the class (e.g. PARTITION_POSITION, SNAPSHOT_ID_POSITION) instead of hardcoding indexes
2. Align the reader's schema with the table's partition-statistics schema (refresh to the same Iceberg version)
3. Wrap access in a check: if (pos < BASE_TYPE.fields().size()) before calling

Example fix

// before
row.get(7, Object.class); // beyond known fields -> Unknown position: 7
// after
Types.StructType type = PartitionStatistics.TYPE;
if (7 < type.fields().size()) {
  row.get(7, Object.class);
}

if (pos < 0 || pos >= PartitionStatistics.TYPE.fields().size()) throw new IllegalArgumentException("bad pos");

boolean isValidPos(int pos) { return pos >= 0 && pos < PartitionStatistics.TYPE.fields().size(); }

try { return internalGet(pos); } catch (UnsupportedOperationException e) { if (e.getMessage().startsWith("Unknown position")) { return null; } throw e; }

When it happens

Trigger: Calling internalGet with a position >= number of schema fields in PartitionStatistics, e.g. from a StructLike accessor using a stale or foreign schema; a code path assuming extra fields that this class does not define.

Common situations: Reading partition statistics with code compiled against a different Iceberg spec version whose field layout differs; custom StructLike wrappers reusing wrong position constants.

Related errors

• Can't modify an empty struct
• Can't retrieve values from an empty struct
• Cannot set fields in a TypeProjection
• Cannot update InternalRecordWrapper
• Cannot update partition statistics of a

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/bbf0b67aebadb5df. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/BasePartitionStatistics.java:176

        return totalDataFileSizeInBytes;
      case POSITION_DELETE_RECORD_COUNT_POSITION:
        return positionDeleteRecordCount;
      case POSITION_DELETE_FILE_COUNT_POSITION:
        return positionDeleteFileCount;
      case EQUALITY_DELETE_RECORD_COUNT_POSITION:
        return equalityDeleteRecordCount;
      case EQUALITY_DELETE_FILE_COUNT_POSITION:
        return equalityDeleteFileCount;
      case TOTAL_RECORD_COUNT_POSITION:
        return totalRecordCount;
      case LAST_UPDATED_AT_POSITION:
        return lastUpdatedAt;
      case LAST_UPDATED_SNAPSHOT_ID_POSITION:
        return lastUpdatedSnapshotId;
      case DV_COUNT_POSITION:
        return dvCount;
      default:
        throw unknownPosition(pos);
    }
  }

  @Override
  protected <T> void internalSet(int pos, T value) {
    if (value == null) {
      return;
    }

    switch (pos) {
      case PARTITION_POSITION:
        this.partition = (StructLike) value;
        break;
      case SPEC_ID_POSITION:
        this.specId = (int) value;
        break;
      case DATA_RECORD_COUNT_POSITION:
        this.dataRecordCount = (long) value;

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