Added INDEX to speed up block orphaning.

NOTE: first startup after this commit can take a while due to building index!

SQL statement "DELETE FROM HistoricAccountBalances WHERE height >= ?" required
a full table scan and so was very slow on VMs/routers. This statement used by
HSQLDBAccountRepository.deleteBalancesFromHeight(), itself called during
Block.orphan().

Symptoms particularly evident during shutdown where above statement could take
upwards of 15 minutes on single-CPU, small-memory VMs!

Statement wasn't noticed before as slow-query checking wasn't involved.
Slow-query checking now applies to HSQLDBRepository.delete() and
HSQLDBRepository.exists() calls.

Added test for correct HSQLDB interrupt handling.

Fixed some typos.

src/main/java/org/qortal/repository/hsqldb/HSQLDBDatabaseUpdates.java

@@ -923,6 +923,11 @@ public class HSQLDBDatabaseUpdates {
 					stmt.execute("ALTER TABLE Accounts DROP initial_level");
 					break;
 
+				case 65:
+					// Add INDEX to speed up very slow "DELETE FROM HistoricAccountBalances WHERE height >= ?"
+					stmt.execute("CREATE INDEX IF NOT EXISTS HistoricAccountBalancesHeightIndex ON HistoricAccountBalances (height)");
+					break;
+
 				default:
 					// nothing to do
 					return false;

src/main/java/org/qortal/repository/hsqldb/HSQLDBRepository.java

@@ -500,9 +500,18 @@ public class HSQLDBRepository implements Repository {
 		try (PreparedStatement preparedStatement = this.prepareStatement(sql)) {
 			prepareExecute(preparedStatement, objects);
 
+			long beforeQuery = System.currentTimeMillis();
+
 			if (preparedStatement.execute())
 				throw new SQLException("Database produced results, not row count");
 
+			long queryTime = System.currentTimeMillis() - beforeQuery;
+			if (this.slowQueryThreshold != null && queryTime > this.slowQueryThreshold) {
+				LOGGER.info(String.format("HSQLDB query took %d ms: %s", queryTime, sql), new SQLException("slow query"));
+
+				logStatements();
+			}
+
 			int rowCount = preparedStatement.getUpdateCount();
 			if (rowCount == -1)
 				throw new SQLException("Database returned invalid row count");
@@ -516,7 +525,7 @@ public class HSQLDBRepository implements Repository {
 	 * <p>
 	 * Performs "CALL IDENTITY()" SQL statement to retrieve last value used when INSERTing into a table that has an IDENTITY column.
 	 * <p>
-	 * Typically used after INSERTing NULL as the IDENTIY column's value to fetch what value was actually stored by HSQLDB.
+	 * Typically used after INSERTing NULL as the IDENTITY column's value to fetch what value was actually stored by HSQLDB.
 	 * 
 	 * @return Long
 	 * @throws SQLException
@@ -557,12 +566,9 @@ public class HSQLDBRepository implements Repository {
 		sql.append(whereClause);
 		sql.append(" LIMIT 1");
 
-		try (PreparedStatement preparedStatement = this.prepareStatement(sql.toString());
-				ResultSet resultSet = this.checkedExecuteResultSet(preparedStatement, objects)) {
-			if (resultSet == null)
-				return false;
-
-			return true;
+		try (ResultSet resultSet = this.checkedExecute(sql.toString(), objects)) {
+			// If matching row is found then resultSet will not be null
+			return resultSet != null;
 		}
 	}
 

src/main/java/org/qortal/repository/hsqldb/HSQLDBRepositoryFactory.java

@@ -31,7 +31,7 @@ public class HSQLDBRepositoryFactory implements RepositoryFactory {
 	 * 
 	 * @param connectionUrl
 	 * @throws DataException <i>without throwable</i> if repository in use by another process.
-	 * @throws DataException <i>with throwable</i> if repository cannot be opened for someother reason.
+	 * @throws DataException <i>with throwable</i> if repository cannot be opened for some other reason.
 	 */
 	public HSQLDBRepositoryFactory(String connectionUrl) throws DataException {
 		// one-time initialization goes in here
@@ -47,10 +47,10 @@ public class HSQLDBRepositoryFactory implements RepositoryFactory {
 
 			HsqlException he = (HsqlException) cause;
 			if (he.getErrorCode() == -ErrorCode.LOCK_FILE_ACQUISITION_FAILURE)
-				throw new DataException("Unable to open repository: " + e.getMessage());
+				throw new DataException("Unable to lock repository: " + e.getMessage());
 
 			if (he.getErrorCode() != -ErrorCode.ERROR_IN_LOG_FILE && he.getErrorCode() != -ErrorCode.M_DatabaseScriptReader_read)
-				throw new DataException("Unable to open repository: " + e.getMessage(), e);
+				throw new DataException("Unable to read repository: " + e.getMessage(), e);
 
 			// Attempt recovery?
 			HSQLDBRepository.attemptRecovery(connectionUrl);