apache/iceberg · error · ValidationException

Cannot apply non-unique WAP ID. Found multiple snapshots wit

Error message

Cannot apply non-unique WAP ID. Found multiple snapshots with WAP ID '%s'

What it means

PublishChangesProcedure promotes a staged (WAP) snapshot written with a spark.wap.id to the table's current state via cherry-pick. WAP IDs must uniquely identify one staged snapshot; if two snapshots carry the same staged WAP ID, publishing is ambiguous and this ValidationException is thrown.

Source

Thrown at spark/v4.2/spark/src/main/java/org/apache/iceberg/spark/procedures/PublishChangesProcedure.java:102

  public ProcedureParameter[] parameters() {
    return PARAMETERS;
  }

  @Override
  public Iterator<Scan> call(InternalRow args) {
    ProcedureInput input = new ProcedureInput(spark(), tableCatalog(), PARAMETERS, args);

    Identifier tableIdent = input.ident(TABLE_PARAM);
    String wapId = input.asString(WAP_ID_PARAM);

    return modifyIcebergTable(
        tableIdent,
        table -> {
          Snapshot matchingSnap = null;
          for (Snapshot snap : table.snapshots()) {
            if (wapId.equals(WapUtil.stagedWapId(snap))) {
              if (matchingSnap != null) {
                throw new ValidationException(
                    "Cannot apply non-unique WAP ID. Found multiple snapshots with WAP ID '%s'",
                    wapId);
              } else {
                matchingSnap = snap;
              }
            }
          }

          if (matchingSnap == null) {
            throw new ValidationException("Cannot apply unknown WAP ID '%s'", wapId);
          }

          long wapSnapshotId = matchingSnap.snapshotId();
          table.manageSnapshots().cherrypick(wapSnapshotId).commit();
          Snapshot currentSnapshot = table.currentSnapshot();
          InternalRow outputRow = newInternalRow(wapSnapshotId, currentSnapshot.snapshotId());
          return asScanIterator(OUTPUT_TYPE, outputRow);
        });

View on GitHub (pinned to 86d9c8fc54)

Solutions

1. Ensure each write uses a unique spark.wap.id (generate a UUID per write job).
2. Expire or delete the duplicate staged snapshots so only one has the target WAP ID, then retry publish_changes.
3. List snapshots to find duplicates (SELECT * FROM table.snapshots) and publish the correct one after cleanup.

Example fix

// before
spark.conf.set("spark.wap.id", "wap-123") // reused in two jobs
// after
spark.conf.set("spark.wap.id", java.util.UUID.randomUUID().toString())

val dupes = spark.table(s"$t.snapshots")
  .filter(col("summary.wap.id") === wapId).count()
require(dupes <= 1, s"$wapId used by $dupes staged snapshots")

When it happens

Trigger: Calling call publish_changes(table => ..., wap_id => 'X') when table.snapshots() contains more than one snapshot whose staged WAP ID equals 'X'.

Common situations: Reusing the same spark.wap.id across multiple writes without publishing in between; a retry job that re-wrote data with the same hard-coded WAP ID.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• Cannot apply non-unique WAP ID. Found multiple snapshots wit
• Cannot apply unknown WAP ID '${wapId}'
• Cannot apply unknown WAP ID '%s'
• Cannot process unknown snapshot operation: ${op.toLowerCase(
• Cannot apply non-unique WAP ID. Found multiple snapshots wit

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/cf31ebcde261cfed. Report an issue: GitHub.