Wrong JDBC type. Expected '{}' but got '{}'. Overriding with

Error message

Wrong JDBC type. Expected '{}' but got '{}'. Overriding with '{}'.

What it means

In ReadFromMySqlSchemaTransformProvider.from, the JDBC type supplied in the configuration does not match the provider's own dialect (mysql). The provider logs a warning and silently overrides the configured jdbcType with its own value instead of failing.

Source

Thrown at sdks/java/io/jdbc/src/main/java/org/apache/beam/sdk/io/jdbc/providers/ReadFromMySqlSchemaTransformProvider.java:60

    return getUrn(ExternalTransforms.ManagedTransforms.Urns.MYSQL_READ);
  }

  @Override
  public String description() {
    return inheritedDescription("MySQL", "ReadFromMySql", "mysql", 3306);
  }

  @Override
  protected String jdbcType() {
    return MYSQL;
  }

  @Override
  public @UnknownKeyFor @NonNull @Initialized SchemaTransform from(
      JdbcReadSchemaTransformConfiguration configuration) {
    String jdbcType = configuration.getJdbcType();
    if (jdbcType != null && !jdbcType.isEmpty() && !jdbcType.equals(jdbcType())) {
      LOG.warn(
          "Wrong JDBC type. Expected '{}' but got '{}'. Overriding with '{}'.",
          jdbcType(),
          jdbcType,
          jdbcType());
      configuration = configuration.toBuilder().setJdbcType(jdbcType()).build();
    }

    Integer fetchSize = configuration.getFetchSize();
    if (fetchSize != null
        && fetchSize > 0
        && configuration.getJdbcUrl() != null
        && !configuration.getJdbcUrl().contains("useCursorFetch=true")) {
      throw new IllegalArgumentException(
          "It is required to set useCursorFetch=true"
              + " in the JDBC URL when using fetchSize for MySQL");
    }
    return new MySqlReadSchemaTransform(configuration);
  }

View on GitHub (pinned to 12126d8942)

Solutions

Remove the jdbcType field from the configuration and let the provider set its own dialect
Set jdbcType to 'mysql' when using the MySQL provider (use ReadFromPostgresSchemaTransformProvider for Postgres)
Route the configuration to the correct provider matching the configured jdbcType

Example fix

// before
configuration = JdbcReadSchemaTransformConfiguration.builder()
  .setJdbcType("postgres")
  .setUrl(url).build();
// after
configuration = JdbcReadSchemaTransformConfiguration.builder()
  .setJdbcType("mysql") // or omit; provider overrides anyway
  .setUrl(url).build();

Defensive patterns

Strategy: validation

Validate before calling

// before building the configuration
if (jdbcType != null && !jdbcType.isEmpty() && !"mysql".equals(jdbcType)) {
  throw new IllegalArgumentException("ReadFromMySql requires jdbcType=mysql, got: " + jdbcType);
}

Prevention

Match jdbcType to the provider (mysql -> ReadFromMySql, postgresql -> ReadFromPostgres)
Omit jdbcType and let the provider set its own dialect
Parameterize pipeline YAML per database rather than sharing a jdbcType field across providers

When it happens

Trigger: Constructing a JdbcReadSchemaTransformConfiguration with a non-empty jdbcType that is not 'mysql' (e.g., 'postgresql') and passing it to the MySQL schema transform provider.

Common situations: Users building pipeline YAML/config that sets jdbcType once and reuses it across database providers, or typo'd jdbcType values; common when switching a pipeline between MySQL and Postgres providers.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/b9cd4f9a7c52ea43. Report an issue: GitHub.