apache/beam · error · java.lang.IllegalArgumentException

is missing expected tag

Error message

%s %s is missing expected tag: %s

What it means

SingleStoreSchemaTransformWriteProvider expects exactly one input PCollectionRow under INPUT_TAG. expand() throws IllegalArgumentException when the input tuple does not contain that tag, so rows to write cannot be located.

Solutions

1. Wrap the input PCollection<Row> with the exact tag: PCollectionRowTuple.of(SingleStoreSchemaTransformWriteProvider.INPUT_TAG, rows).
2. Import/reference the provider's INPUT_TAG constant instead of a hardcoded string.
3. Verify the transform receives a single PCollectionRow, not multiple tags.

Example fix

// before
PCollectionRowTuple.of("rows", rowPc).apply(writeTransform)

// after
PCollectionRowTuple.of(SingleStoreSchemaTransformWriteProvider.INPUT_TAG, rowPc).apply(writeTransform)

if (!inputTuple.has(SingleStoreSchemaTransformWriteProvider.INPUT_TAG)) {
  throw new IllegalStateException("Writer input must use INPUT_TAG");
}

When it happens

Trigger: Calling expand with a PCollectionRowTuple built with a different tag name (e.g. PCollectionRowTuple.of("rows", pc)) or with an empty tuple.

Common situations: Hand-built composition using the wrong tag constant; YAML/Beam pipelines wiring the writer input under an ad-hoc name; refactors renaming the local tag but not the wiring.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• input is expected to be empty
• configuration with is not compatible with a format
• Converting to Beam schema type is not supported
• Failed to get number of partitions in the database
• Failed to validate

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/ec0718090a6b3610. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/io/singlestore/src/main/java/org/apache/beam/sdk/io/singlestore/schematransform/SingleStoreSchemaTransformWriteProvider.java:96

  public List<String> outputCollectionNames() {
    return Collections.singletonList(OUTPUT_TAG);
  }

  /**
   * An implementation of {@link SchemaTransform} for SingleStoreDB write jobs configured using
   * {@link SingleStoreSchemaTransformWriteConfiguration}.
   */
  private static class SingleStoreWriteSchemaTransform extends SchemaTransform {
    private final SingleStoreSchemaTransformWriteConfiguration configuration;

    SingleStoreWriteSchemaTransform(SingleStoreSchemaTransformWriteConfiguration configuration) {
      this.configuration = configuration;
    }

    @Override
    public PCollectionRowTuple expand(PCollectionRowTuple input) {
      if (!input.has(INPUT_TAG)) {
        throw new IllegalArgumentException(
            String.format(
                "%s %s is missing expected tag: %s",
                getClass().getSimpleName(), input.getClass().getSimpleName(), INPUT_TAG));
      }
      SingleStoreIO.DataSourceConfiguration dataSourceConfiguration =
          configuration.getDataSourceConfiguration();
      String table = configuration.getTable();
      Integer batchSize = configuration.getBatchSize();

      SingleStoreIO.Write<Row> write = SingleStoreIO.writeRows();

      if (dataSourceConfiguration != null) {
        write = write.withDataSourceConfiguration(dataSourceConfiguration);
      }

      if (table != null && !table.isEmpty()) {
        write = write.withTable(table);
      }

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