In previous version of jaybird (2.2) I was able to execute Services API to Firebird server to get active transaction markers: OIT, OAT, Next, etc.
In version 3.0, I can't find out how to do it properly. There are only ISC-constants (like isc_info_oldest_snapshot) but no methods.
So, I see one way to do that: Get query of database header by StatisticsManager. But it is not so easy, because it will return text that needs to be parsed:
StatisticsManager SM = new FBStatisticsManager(); //"PURE_JAVA", "NATIVE", "EMBEDDED"
SM.setHost("localhost");
SM.setUser("sysdba");
SM.setPort(3053);
SM.setPassword("masterkey");
SM.setDatabase("c:\\Firebird\\3.0.2\\examples\\empbuild\\EMPLOYEE.FDB");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
SM.setLogger(baos);
SM.getHeaderPage();
String outputstr2 = new String( baos.toByteArray(), java.nio.charset.StandardCharsets.UTF_8 );
and now I need to parse the text:
Database "C:\FIREBIRD\3.0.2\EXAMPLES\EMPBUILD\EMPLOYEE.FDB"
Database header page information:
Flags 0
Generation 806
System Change Number 12
Page size 8192
ODS version 12.0
Oldest transaction 520
Oldest active 521
Oldest snapshot 521
Next transaction 521
Sequence number 0
Next attachment ID 857
Implementation HW=AMD/Intel/x64 little-endian OS=Windows CC=MSVC
Shadow count 0
Page buffers 0
Next header page 0
Database dialect 3
Creation date Apr 15, 2016 17:38:34
Attributes
Variable header data:
Database backup GUID: {6F41E937-76D5-4C67-6CAE-F8556AD27BEE}
Database GUID: {EE5B2713-7B17-43B0-0CB3-0616B4B8A63D}
*END*
May be it is possible to get direct values?
upd: Old version of code was:
/** [ActiveCount, OAT, OST, OIT, Next] */
public static int[] getTxInfo( final GDS gds,
final String host,
final int port,
final String databasePath,
final String user,
final String password ) throws Exception {
final byte[] queryItems = {
ISCConstants.isc_info_oldest_transaction,
ISCConstants.isc_info_oldest_active,
ISCConstants.isc_info_oldest_snapshot,
ISCConstants.isc_info_next_transaction,
ISCConstants.isc_info_active_transactions,
ISCConstants.isc_info_end
};
byte[] response = queryDB(
gds, host, port, databasePath, user, password,
queryItems, DEFAULT_BUFFER_SIZE
);
int i = 0;
final int[] result = new int[5];
while ( response[i] != ISCConstants.isc_info_end ) {
final byte code = response[i++];
switch ( code ) {
case ISCConstants.isc_info_active_transactions: {
//здесь идет столько блоков isc_info_active_transactions, сколько
//реально активных транзакций в данный момент
final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
i += LENGTH_LEN;
//final int res = gds.iscVaxInteger( response, i, valueLen );
i += valueLen;
result[0]++;
break;
}
case ISCConstants.isc_info_oldest_active: {
final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
i += LENGTH_LEN;
final int res = gds.iscVaxInteger( response, i, valueLen );
i += valueLen;
result[1] = res;
break;
}
case ISCConstants.isc_info_oldest_snapshot: {
final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
i += LENGTH_LEN;
final int res = gds.iscVaxInteger( response, i, valueLen );
i += valueLen;
result[2] = res;
break;
}
case ISCConstants.isc_info_oldest_transaction: {
final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
i += LENGTH_LEN;
final int res = gds.iscVaxInteger( response, i, valueLen );
i += valueLen;
result[3] = res;
break;
}
case ISCConstants.isc_info_next_transaction: {
final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
i += LENGTH_LEN;
final int res = gds.iscVaxInteger( response, i, valueLen );
i += valueLen;
result[4] = res;
break;
}
case ISCConstants.isc_info_truncated: {
//этот код означает "буфер слишком маленький, дайте больше"
//обычно это бывает когда слишком много активных транзакций
//сначала пробуем увеличить буфер
if ( response.length == DEFAULT_BUFFER_SIZE ) {
response = queryDB(
gds, host, port, databasePath, user, password,
queryItems, 32 * DEFAULT_BUFFER_SIZE
);
result[0] = 0;//на всякий случай
//начинаем разбор заново
i = 0;
} else {
//32Кб буфера оказалось тоже недостаточно -- пичалька. Но
//делать нечего -- просто обойдемся без числа активных транзакций
response = queryDB(
gds, host, port, databasePath, user, password,
new byte[]{
ISCConstants.isc_info_oldest_transaction,
ISCConstants.isc_info_oldest_active,
ISCConstants.isc_info_oldest_snapshot,
ISCConstants.isc_info_next_transaction,
ISCConstants.isc_info_end
}, DEFAULT_BUFFER_SIZE
);
result[0] = -1;
//начинаем разбор заново
i = 0;
}
break;
}
default:
throw new FBSQLException( "Unrecognized response code: " + code + " (response=" + Arrays.toString( result ) + ")" );
}
}
return result;
}
where
public static byte[] queryDB( final GDS gds,
final String host,
final int port,
final String databasePath,
final String user,
final String password,
final byte[] queryItems,
final int bufferLength ) throws Exception {
return doWithDB(
gds, host, port, databasePath, user, password,
new DBOperation<byte[]>() {
public byte[] doWithDB( final GDS gds,
final IscDbHandle db ) throws GDSException {
return gds.iscDatabaseInfo(
db,
queryItems,
bufferLength
);
}
}
);
}
Is it enough?
I have added the functionality to Jaybird 3.0.0, see this commit.
I have added two ways to get this information:
Using StatisticsManager:
StatisticsManager statsMan = new FBStatisticsManager();
statsMan.setHost("localhost");
statsMan.setDatabase("/path/to/your.fdb");
statsMan.setUser("youruser");
statsMan.setPassword("yourpassword");
DatabaseTransactionInfo info = statsMan.getDatabaseTransactionInfo();
A convenience method to use an existing Connection to get this information:
try (Connection connection = dataSource.getConnection()) {
DatabaseTransactionInfo info = FBStatisticsManager
.getDatabaseTransactionInfo(connection);
}
The only requirement is that the connection instance unwraps to the FirebirdConnection interface.
For a future version I will consider if I can expose the database information query facility in a more general way so it is not necessary to use the internal FbDatabase interface.