A join cursor is returned when calling {@link Database#join Database.join}.
To open a join cursor using two secondary cursors:
Transaction txn = ...
Database primaryDb = ...
SecondaryDatabase secondaryDb1 = ...
SecondaryDatabase secondaryDb2 = ...
SecondaryCursor cursor1 = null;
SecondaryCursor cursor2 = null;
JoinCursor joinCursor = null;
try {
DatabaseEntry key = new DatabaseEntry();
DatabaseEntry data = new DatabaseEntry();
cursor1 = secondaryDb1.openSecondaryCursor(txn, null);
cursor2 = secondaryDb2.openSecondaryCursor(txn, null);
key.setData(...); // initialize key for secondary index 1
OperationStatus status1 =
cursor1.getSearchKey(key, data, LockMode.DEFAULT);
key.setData(...); // initialize key for secondary index 2
OperationStatus status2 =
cursor2.getSearchKey(key, data, LockMode.DEFAULT);
if (status1 == OperationStatus.SUCCESS &&
status2 == OperationStatus.SUCCESS) {
SecondaryCursor[] cursors = {cursor1, cursor2};
joinCursor = primaryDb.join(cursors, null);
while (true) {
OperationStatus joinStatus = joinCursor.getNext(key, data,
LockMode.DEFAULT);
if (joinStatus == OperationStatus.SUCCESS) {
// Do something with the key and data.
} else {
break;
}
}
}
} finally {
if (cursor1 != null) {
cursor1.close();
}
if (cursor2 != null) {
cursor2.close();
}
if (joinCursor != null) {
joinCursor.close();
}
}
*/
public class JoinCursor {
private Database database;
private Dbc dbc;
private JoinConfig config;
JoinCursor(final Database database,
final Dbc dbc,
final JoinConfig config) {
this.database = database;
this.dbc = dbc;
this.config = config;
}
/**
Closes the cursors that have been opened by this join cursor.
The cursors passed to {@link Database#join Database.join} are not closed by this method, and should be closed by the caller.
@throws DatabaseException if a failure occurs. */ public void close() throws DatabaseException { dbc.close(); } /** Returns the primary database handle associated with this cursor.
@return the primary database handle associated with this cursor. */ public Database getDatabase() { return database; } /** Returns this object's configuration.
@return this object's configuration. */ public JoinConfig getConfig() { return config; } /** Returns the next primary key resulting from the join operation.
An entry is returned by the join cursor for each primary key/data pair having all secondary key values that were specified using the array of secondary cursors passed to {@link Database#join Database.join}.
@param key the primary key returned as output. Its byte array does not need to be initialized by the caller.
@return {@link com.sleepycat.db.OperationStatus#NOTFOUND OperationStatus.NOTFOUND} if no matching key/data pair is found; {@link com.sleepycat.db.OperationStatus#KEYEMPTY OperationStatus.KEYEMPTY} if the database is a Queue or Recno database and the specified key exists, but was never explicitly created by the application or was later deleted; otherwise, {@link com.sleepycat.db.OperationStatus#SUCCESS OperationStatus.SUCCESS}.
@param lockMode the locking attributes; if null, default attributes are used.
@throws NullPointerException if a DatabaseEntry parameter is null or does not contain a required non-null byte array.
@throws DeadlockException if the operation was selected to resolve a deadlock.
@throws IllegalArgumentException if an invalid parameter was specified.
@throws DatabaseException if a failure occurs. */ public OperationStatus getNext(final DatabaseEntry key, LockMode lockMode) throws DatabaseException { return OperationStatus.fromInt( dbc.get(key, DatabaseEntry.IGNORE, DbConstants.DB_JOIN_ITEM | LockMode.getFlag(lockMode))); } /** Returns the next primary key and data resulting from the join operation.
An entry is returned by the join cursor for each primary key/data pair having all secondary key values that were specified using the array of secondary cursors passed to {@link Database#join Database.join}.
@param key the primary key returned as output. Its byte array does not need to be initialized by the caller.
@param data the primary data returned as output. Its byte array does not need to be initialized by the caller.
@return {@link com.sleepycat.db.OperationStatus#NOTFOUND OperationStatus.NOTFOUND} if no matching key/data pair is found; {@link com.sleepycat.db.OperationStatus#KEYEMPTY OperationStatus.KEYEMPTY} if the database is a Queue or Recno database and the specified key exists, but was never explicitly created by the application or was later deleted; otherwise, {@link com.sleepycat.db.OperationStatus#SUCCESS OperationStatus.SUCCESS}.
@param lockMode the locking attributes; if null, default attributes are used.
@throws NullPointerException if a DatabaseEntry parameter is null or does not contain a required non-null byte array.
@throws DeadlockException if the operation was selected to resolve a deadlock.
@throws IllegalArgumentException if an invalid parameter was specified.
@throws DatabaseException if a failure occurs. */ public OperationStatus getNext(final DatabaseEntry key, final DatabaseEntry data, LockMode lockMode) throws DatabaseException { return OperationStatus.fromInt( dbc.get(key, data, LockMode.getFlag(lockMode) | ((data == null) ? 0 : data.getMultiFlag()))); } }