/**
* Inserts an entity and returns null, or updates it if the primary key already exists and returns
* the existing entity.
*
* <p>If a {@link PrimaryKey#sequence} is used and the primary key field of the given entity is
* null or zero, this method will assign the next value from the sequence to the primary key field
* of the given entity.
*
* @param txn the transaction used to protect this operation, null to use auto-commit, or null if
* the store is non-transactional.
* @param entity the entity to be inserted or updated.
* @return the existing entity that was updated, or null if the entity was inserted.
* @throws DatabaseException the base class for all BDB exceptions.
*/
public E put(Transaction txn, E entity) throws DatabaseException {
DatabaseEntry keyEntry = new DatabaseEntry();
DatabaseEntry dataEntry = new DatabaseEntry();
assignKey(entity, keyEntry);
boolean autoCommit = false;
Environment env = db.getEnvironment();
if (transactional && txn == null && DbCompat.getThreadTransaction(env) == null) {
txn = env.beginTransaction(null, getAutoCommitTransactionConfig());
autoCommit = true;
}
CursorConfig cursorConfig = null;
if (concurrentDB) {
cursorConfig = new CursorConfig();
DbCompat.setWriteCursor(cursorConfig, true);
}
boolean failed = true;
Cursor cursor = db.openCursor(txn, cursorConfig);
LockMode lockMode = locking ? LockMode.RMW : null;
try {
while (true) {
OperationStatus status = cursor.getSearchKey(keyEntry, dataEntry, lockMode);
if (status == OperationStatus.SUCCESS) {
E existing = entityBinding.entryToObject(keyEntry, dataEntry);
entityBinding.objectToData(entity, dataEntry);
cursor.put(keyEntry, dataEntry);
failed = false;
return existing;
} else {
entityBinding.objectToData(entity, dataEntry);
status = cursor.putNoOverwrite(keyEntry, dataEntry);
if (status != OperationStatus.KEYEXIST) {
failed = false;
return null;
}
}
}
} finally {
cursor.close();
if (autoCommit) {
if (failed) {
txn.abort();
} else {
txn.commit();
}
}
}
}
public static Database buildtertiary(Database std) {
try {
// configure new database instance
io.deleteFile("tertiarydb");
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setType(DatabaseType.HASH);
dbConfig.setAllowCreate(true);
dbConfig.setUnsortedDuplicates(true);
Database tdb = new Database("tertiarydb", null, dbConfig);
// configure cursors and entries
Cursor stdCurs = std.openCursor(null, null);
Cursor tCurs = tdb.openCursor(null, null);
DatabaseEntry stdKey = new DatabaseEntry();
DatabaseEntry stdData = new DatabaseEntry();
DatabaseEntry tKey = new DatabaseEntry();
DatabaseEntry tData = new DatabaseEntry();
// extract from linearly constructed database to populate <song>,<users> table, making
// use of songs grouped by id
String currUsers = "";
String prevID = "default";
boolean firstIter = true;
while (stdCurs.getNext(stdKey, stdData, LockMode.DEFAULT) == OperationStatus.SUCCESS) {
// get rating data from current row
String[] currIDUser = (new String(stdKey.getData())).split(",");
String currID = currIDUser[0].trim();
String currUser = currIDUser[1].trim();
String currRating = (new String(stdData.getData()));
stdKey.setData(null);
stdData.setData(null);
if (currID.equals(prevID) || firstIter) {
// concatenate new username with current string
currUsers += "(" + currUser + "," + currRating + ")";
} else if (!firstIter) {
// insert completed <usernames> into table under key <song id>
tKey.setData(prevID.getBytes());
tData.setData(currUsers.substring(0, currUsers.length()).getBytes());
tCurs.put(tKey, tData);
tKey.setData(null);
tData.setData(null);
// DEBUG:
// System.out.println(prevID+","+currUsers.substring(0, currUsers.length()-1));
// start the new <usernames> for the next song (in currID)
currUsers = "(" + currUser + "," + currRating + ")";
}
prevID = currID;
firstIter = false;
}
// repeat iteration for last song
tKey.setData(prevID.getBytes());
tData.setData(currUsers.substring(0, currUsers.length()).getBytes());
tCurs.put(tKey, tData);
tKey.setData(null);
tData.setData(null);
// DEBUG:
// io.debugread(tdb);
tCurs.close();
return tdb;
} catch (Exception e) {
System.out.println(" error creating <song>,<users> tertiary table\n");
System.out.println(e.getMessage());
}
return null; // should never happen
}