SonarSource/sonarqube · error · java.lang.IllegalStateException

Unsupported dialect for drop of index:

Error message

Unsupported dialect for drop of index: 

What it means

DropIndexChange.createDropIndexSqlStatement builds DROP INDEX SQL per dialect; MsSql requires "ON <table>", Oracle plain DROP INDEX, H2/PostgreSQL support IF EXISTS. An unknown dialect id throws IllegalStateException "Unsupported dialect for drop of index: <dialect>".

Source

Thrown at server/sonar-db-migration/src/main/java/org/sonar/server/platform/db/migration/step/DropIndexChange.java:64

  @Override
  public void execute(Context context) throws SQLException {
    findExistingIndexName()
      .map(index -> createDropIndexSqlStatement(getDialect(), index))
      .ifPresent(context::execute);
  }

  private Optional<String> findExistingIndexName() throws SQLException {
    try (Connection connection = getDatabase().getDataSource().getConnection()) {
      return DatabaseUtils.findExistingIndex(connection, tableName, indexName);
    }
  }

  private String createDropIndexSqlStatement(Dialect dialect, String actualIndexName) {
    return switch (dialect.getId()) {
      case MsSql.ID -> "DROP INDEX " + actualIndexName + " ON " + tableName;
      case Oracle.ID -> "DROP INDEX " + actualIndexName;
      case H2.ID, PostgreSql.ID -> "DROP INDEX IF EXISTS " + actualIndexName;
      default -> throw new IllegalStateException("Unsupported dialect for drop of index: " + dialect);
    };
  }
}

View on GitHub (pinned to 184c821202)

Solutions

1. Confirm the configured dialect is one of the four supported engines.
2. If a new dialect is required, add a case to createDropIndexSqlStatement with correct DROP INDEX syntax.
3. Grep for switch (dialect.getId()) across sonar-db-migration to find all builders needing the new case.

Example fix

// before
default -> throw new IllegalStateException("Unsupported dialect for drop of index: " + dialect);
// after
case MySql.ID -> "DROP INDEX " + actualIndexName;
default -> throw new IllegalStateException("Unsupported dialect for drop of index: " + dialect);

if (!List.of(MsSql.ID, Oracle.ID, H2.ID, PostgreSql.ID).contains(dialect.getId())) {
  throw new IllegalArgumentException("DROP INDEX unsupported for " + dialect.getId());
}

boolean supportsDropIndex(Dialect d) { return Set.of(MsSql.ID, Oracle.ID, H2.ID, PostgreSql.ID).contains(d.getId()); }

try {
  new DropIndexChange(dialect, tableName, indexName).execute(context);
} catch (IllegalStateException e) {
  LOG.error("Index drop unsupported: {}", e.getMessage());
}

When it happens

Trigger: A DropIndexChange step executing DROP INDEX on a Dialect whose id is not mssql, oracle, h2, or postgresql.

Common situations: Unsupported database engines; new dialect integrated without updating DropIndexChange; corrupted/incorrect sonar.jdbc.dialect configuration.

Related errors

• Unsupported dialect for drop of constraint:
• Unsupported database '%s'
• Unsupported DB:
• Unsupported dialect id
• Unsupported dialect id

AI-assisted analysis of SonarSource/sonarqube@184c821202 (2026-09-09). Data as JSON: /api/errors/9be47bad256c16c0. Report an issue: GitHub.