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package org.hsqldb;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.hsqldb.error.Error;
import org.hsqldb.error.ErrorCode;
import org.hsqldb.lib.DoubleIntIndex;
import org.hsqldb.lib.HashSet;
import org.hsqldb.lib.HsqlDeque;
import org.hsqldb.lib.IntKeyHashMapConcurrent;
import org.hsqldb.lib.LongDeque;
import org.hsqldb.persist.CachedObject;
/**
* Manages rows involved in transactions
*
* @author Fred Toussi (fredt@users dot sourceforge.net)
* @version 2.0.0
* @since 2.0.0
*/
public class TransactionManagerMVCC extends TransactionManagerCommon
implements TransactionManager {
// functional unit - merged committed transactions
HsqlDeque committedTransactions = new HsqlDeque();
LongDeque committedTransactionTimestamps = new LongDeque();
// locks
boolean isLockedMode;
Session catalogWriteSession;
//
int redoCount = 0;
//
public TransactionManagerMVCC(Database db) {
database = db;
hasPersistence = database.logger.isLogged();
lobSession = database.sessionManager.getSysLobSession();
rowActionMap = new IntKeyHashMapConcurrent(10000);
txModel = MVCC;
}
public long getGlobalChangeTimestamp() {
return globalChangeTimestamp.get();
}
public boolean isMVRows() {
return true;
}
public int getTransactionControl() {
return MVCC;
}
public void setTransactionControl(Session session, int mode) {
writeLock.lock();
try {
// statement runs as transaction
if (liveTransactionTimestamps.size() == 1) {
switch (mode) {
case MVCC :
break;
case MVLOCKS : {
TransactionManagerMV2PL manager =
new TransactionManagerMV2PL(database);
manager.globalChangeTimestamp.set(
globalChangeTimestamp.get());
manager.liveTransactionTimestamps.addLast(
session.transactionTimestamp);
database.txManager = manager;
break;
}
case LOCKS : {
TransactionManager2PL manager =
new TransactionManager2PL(database);
manager.globalChangeTimestamp.set(
globalChangeTimestamp.get());
database.txManager = manager;
break;
}
}
return;
}
} finally {
writeLock.unlock();
}
throw Error.error(ErrorCode.X_25001);
}
public void completeActions(Session session) {}
public boolean prepareCommitActions(Session session) {
Object[] list = session.rowActionList.getArray();
int limit = session.rowActionList.size();
if (session.abortTransaction) {
// System.out.println("cascade fail " + session + " " + session.actionTimestamp);
return false;
}
writeLock.lock();
try {
for (int i = 0; i < limit; i++) {
RowAction rowact = (RowAction) list[i];
if (!rowact.canCommit(session, session.tempSet)) {
// System.out.println("commit conflicts " + session + " " + session.actionTimestamp);
return false;
}
}
session.actionTimestamp = nextChangeTimestamp();
for (int i = 0; i < limit; i++) {
RowAction action = (RowAction) list[i];
action.prepareCommit(session);
}
for (int i = 0; i < session.tempSet.size(); i++) {
Session current = (Session) session.tempSet.get(i);
current.abortTransaction = true;
}
return true;
} finally {
writeLock.unlock();
session.tempSet.clear();
}
}
public boolean commitTransaction(Session session) {
if (session.abortTransaction) {
return false;
}
int limit = session.rowActionList.size();
Object[] list = session.rowActionList.getArray();
writeLock.lock();
try {
for (int i = 0; i < limit; i++) {
RowAction rowact = (RowAction) list[i];
if (!rowact.canCommit(session, session.tempSet)) {
// System.out.println("commit conflicts " + session + " " + session.actionTimestamp);
return false;
}
}
endTransaction(session);
// new actionTimestamp used for commitTimestamp
session.actionTimestamp = nextChangeTimestamp();
for (int i = 0; i < limit; i++) {
RowAction action = (RowAction) list[i];
action.commit(session);
}
for (int i = 0; i < session.tempSet.size(); i++) {
Session current = (Session) session.tempSet.get(i);
current.abortTransaction = true;
}
persistCommit(session, list, limit);
// session.actionTimestamp is the committed tx timestamp
if (getFirstLiveTransactionTimestamp() > session.actionTimestamp) {
mergeTransaction(session, list, 0, limit,
session.actionTimestamp);
finaliseRows(session, list, 0, limit, true);
} else {
list = session.rowActionList.toArray();
addToCommittedQueue(session, list);
}
endTransactionTPL(session);
//
countDownLatches(session);
} finally {
writeLock.unlock();
}
session.tempSet.clear();
if (session != lobSession && lobSession.rowActionList.size() > 0) {
lobSession.isTransaction = true;
lobSession.actionIndex = lobSession.rowActionList.size();
lobSession.commit(false);
}
return true;
}
public void rollback(Session session) {
writeLock.lock();
try {
session.abortTransaction = false;
session.actionTimestamp = nextChangeTimestamp();
rollbackPartial(session, 0, session.transactionTimestamp);
endTransaction(session);
endTransactionTPL(session);
countDownLatches(session);
} finally {
writeLock.unlock();
}
}
public void rollbackSavepoint(Session session, int index) {
long timestamp = session.sessionContext.savepointTimestamps.get(index);
Integer oi = (Integer) session.sessionContext.savepoints.get(index);
int start = oi.intValue();
while (session.sessionContext.savepoints.size() > index + 1) {
session.sessionContext.savepoints.remove(
session.sessionContext.savepoints.size() - 1);
session.sessionContext.savepointTimestamps.removeLast();
}
rollbackPartial(session, start, timestamp);
}
public void rollbackAction(Session session) {
rollbackPartial(session, session.actionIndex, session.actionTimestamp);
}
/**
* rollback the row actions from start index in list and
* the given timestamp
*/
void rollbackPartial(Session session, int start, long timestamp) {
Object[] list = session.rowActionList.getArray();
int limit = session.rowActionList.size();
if (start == limit) {
return;
}
for (int i = start; i < limit; i++) {
RowAction action = (RowAction) list[i];
if (action != null) {
action.rollback(session, timestamp);
} else {
System.out.println("null action in rollback " + start);
}
}
// rolled back transactions can always be merged as they have never been
// seen by other sessions
writeLock.lock();
try {
mergeRolledBackTransaction(session, timestamp, list, start, limit);
finaliseRows(session, list, start, limit, false);
} finally {
writeLock.unlock();
}
session.rowActionList.setSize(start);
}
public RowAction addDeleteAction(Session session, Table table, Row row,
int[] colMap) {
RowAction action = addDeleteActionToRow(session, table, row, colMap);
if (action == null) {
writeLock.lock();
try {
rollbackAction(session);
if (session.isolationLevel == SessionInterface
.TX_REPEATABLE_READ || session
.isolationLevel == SessionInterface.TX_SERIALIZABLE) {
session.tempSet.clear();
session.abortTransaction = true;
throw Error.error(ErrorCode.X_40501);
}
// can redo when conflicting action is already committed
if (row.rowAction != null && row.rowAction.isDeleted()) {
session.tempSet.clear();
session.redoAction = true;
redoCount++;
throw Error.error(ErrorCode.X_40501);
}
boolean canWait = checkDeadlock(session, session.tempSet);
if (canWait) {
Session current = (Session) session.tempSet.get(0);
session.redoAction = true;
current.waitingSessions.add(session);
session.waitedSessions.add(current);
session.latch.countUp();
} else {
session.redoAction = false;
session.abortTransaction = true;
}
session.tempSet.clear();
redoCount++;
throw Error.error(ErrorCode.X_40501);
} finally {
writeLock.unlock();
}
}
session.rowActionList.add(action);
return action;
}
public void addInsertAction(Session session, Table table, Row row) {
RowAction action = row.rowAction;
if (action == null) {
System.out.println("null insert action " + session + " "
+ session.actionTimestamp);
}
session.rowActionList.add(action);
if (!row.isMemory()) {
rowActionMap.put(action.getPos(), action);
}
}
// functional unit - accessibility of rows
public boolean canRead(Session session, Row row, int mode, int[] colMap) {
RowAction action = row.rowAction;
if (mode == TransactionManager.ACTION_READ) {
if (action == null) {
return true;
}
return action.canRead(session, TransactionManager.ACTION_READ);
}
if (mode == ACTION_REF) {
boolean result;
if (action == null) {
result = true;
} else {
result = action.canRead(session,
TransactionManager.ACTION_READ);
}
return result;
/*
if (result) {
synchronized (row) {
if (row.isMemory()) {
result = RowAction.addRefAction(session, row, colMap);
} else {
ReentrantReadWriteLock.WriteLock mapLock =
rowActionMap.getWriteLock();
mapLock.lock();
try {
action = row.rowAction;
if (action == null) {
action =
(RowAction) rowActionMap.get(row.getPos());
row.rowAction = action;
}
result = RowAction.addRefAction(session, row,
colMap);
if (result && action == null) {
rowActionMap.put(row.getPos(), action);
}
} finally {
mapLock.unlock();
}
}
}
if (result) {
session.rowActionList.add(row.rowAction);
} else {
if (!session.tempSet.isEmpty()) {
Session current = (Session) session.tempSet.get(0);
session.redoAction = true;
session.latch.countUp();
current.waitingSessions.add(session);
session.waitedSessions.add(current);
session.tempSet.clear();
throw Error.error(ErrorCode.X_40501);
}
}
return true;
}
return false;
*/
}
if (action == null) {
return true;
}
return action.canRead(session, mode);
}
public boolean canRead(Session session, int id, int mode) {
RowAction action = (RowAction) rowActionMap.get(id);
if (action == null) {
return true;
}
return action.canRead(session, mode);
}
/**
* add transaction info to a row just loaded from the cache. called only
* for CACHED tables
*/
public void setTransactionInfo(CachedObject object) {
Row row = (Row) object;
RowAction rowact = (RowAction) rowActionMap.get(row.position);
row.rowAction = rowact;
}
/**
* remove the transaction info
*/
public void removeTransactionInfo(CachedObject object) {
rowActionMap.remove(object.getPos());
}
/**
* add a list of actions to the end of queue
*/
void addToCommittedQueue(Session session, Object[] list) {
synchronized (committedTransactionTimestamps) {
// add the txList according to commit timestamp
committedTransactions.addLast(list);
// get session commit timestamp
committedTransactionTimestamps.addLast(session.actionTimestamp);
/* debug 190
if (committedTransactions.size() > 64) {
System.out.println("******* excessive transaction queue");
}
// debug 190 */
}
}
/**
* expire all committed transactions that are no longer in scope
*/
void mergeExpiredTransactions(Session session) {
long timestamp = getFirstLiveTransactionTimestamp();
while (true) {
long commitTimestamp;
Object[] actions;
synchronized (committedTransactionTimestamps) {
if (committedTransactionTimestamps.isEmpty()) {
break;
}
commitTimestamp = committedTransactionTimestamps.getFirst();
if (commitTimestamp < timestamp) {
committedTransactionTimestamps.removeFirst();
actions = (Object[]) committedTransactions.removeFirst();
} else {
break;
}
}
mergeTransaction(session, actions, 0, actions.length,
commitTimestamp);
finaliseRows(session, actions, 0, actions.length, true);
}
}
public void beginTransaction(Session session) {
writeLock.lock();
try {
session.actionTimestamp = nextChangeTimestamp();
session.transactionTimestamp = session.actionTimestamp;
session.isTransaction = true;
liveTransactionTimestamps.addLast(session.transactionTimestamp);
transactionCount++;
} finally {
writeLock.unlock();
}
}
/**
* add session to the end of queue when a transaction starts
* (depending on isolation mode)
*/
public void beginAction(Session session, Statement cs) {
if (session.isTransaction) {
return;
}
if (cs == null) {
return;
}
writeLock.lock();
try {
session.isPreTransaction = true;
if (!isLockedMode && !cs.isCatalogChange()) {
return;
}
beingActionTPL(session, cs);
} finally {
writeLock.unlock();
}
}
/**
* add session to the end of queue when a transaction starts
* (depending on isolation mode)
*/
public void beginActionResume(Session session) {
writeLock.lock();
try {
session.actionTimestamp = nextChangeTimestamp();
if (!session.isTransaction) {
session.transactionTimestamp = session.actionTimestamp;
session.isTransaction = true;
liveTransactionTimestamps.addLast(session.actionTimestamp);
transactionCount++;
}
session.isPreTransaction = false;
} finally {
writeLock.unlock();
}
}
RowAction addDeleteActionToRow(Session session, Table table, Row row,
int[] colMap) {
RowAction action = null;
synchronized (row) {
if (row.isMemory()) {
action = RowAction.addDeleteAction(session, table, row,
colMap);
} else {
ReentrantReadWriteLock.WriteLock mapLock =
rowActionMap.getWriteLock();
mapLock.lock();
try {
/* using rowActionMap as source */
action = (RowAction) rowActionMap.get(row.getPos());
if (action == null) {
if (row.rowAction != null) {
// test code
action = row.rowAction;
}
action = RowAction.addDeleteAction(session, table,
row, colMap);
if (action != null) {
rowActionMap.put(row.getPos(), action);
}
} else {
if (row.rowAction != action) {
// test code
action = row.rowAction;
}
row.rowAction = action;
action = RowAction.addDeleteAction(session, table,
row, colMap);
}
/*
action = row.rowAction;
if (action == null) {
action = (RowAction) rowActionMap.get(row.getPos());
}
if (action == null) {
action = RowAction.addDeleteAction(session, table,
row, colMap);
if (action != null) {
rowActionMap.put(row.getPos(), action);
row.rowAction = action;
}
} else {
// possibly from rowActionMap
row.rowAction = action;
action = action.addDeleteAction(session, colMap);
}
*/
} finally {
mapLock.unlock();
}
}
}
return action;
}
/**
* remove session from queue when a transaction ends
* and expire any committed transactions
* that are no longer required. remove transactions ended before the first
* timestamp in liveTransactionsSession queue
*/
void endTransaction(Session session) {
long timestamp = session.transactionTimestamp;
session.isTransaction = false;
int index = liveTransactionTimestamps.indexOf(timestamp);
if (index >= 0) {
transactionCount--;
liveTransactionTimestamps.remove(index);
mergeExpiredTransactions(session);
}
}
// functional unit - list actions and translate id's
/**
* Return a lookup of all row ids for cached tables in transactions.
* For auto-defrag, as currently there will be no RowAction entries
* at the time of defrag.
*/
public DoubleIntIndex getTransactionIDList() {
return super.getTransactionIDList();
}
/**
* Convert row ID's for cached table rows in transactions
*/
public void convertTransactionIDs(DoubleIntIndex lookup) {
super.convertTransactionIDs(lookup);
}
private void countDownLatches(Session session) {
for (int i = 0; i < session.waitingSessions.size(); i++) {
Session current = (Session) session.waitingSessions.get(i);
current.waitedSessions.remove(session);
current.latch.countDown();
}
session.waitingSessions.clear();
}
void getTransactionSessions(HashSet set) {
Session[] sessions = database.sessionManager.getAllSessions();
for (int i = 0; i < sessions.length; i++) {
long timestamp = sessions[i].getTransactionTimestamp();
if (liveTransactionTimestamps.contains(timestamp)) {
set.add(sessions[i]);
} else if (sessions[i].isPreTransaction) {
set.add(sessions[i]);
}
}
}
void endTransactionTPL(Session session) {
if (catalogWriteSession != session) {
return;
}
catalogWriteSession = null;
isLockedMode = false;
}
boolean beingActionTPL(Session session, Statement cs) {
if (cs == null) {
return true;
}
if (session.abortTransaction) {
return false;
}
session.tempSet.clear();
if (cs.isCatalogChange()) {
if (catalogWriteSession == null) {
getTransactionSessions(session.tempSet);
session.tempSet.remove(session);
if (session.tempSet.isEmpty()) {
catalogWriteSession = session;
isLockedMode = true;
} else {
catalogWriteSession = session;
isLockedMode = true;
setWaitingSessionTPL(session);
}
return true;
} else {
catalogWriteSession.waitingSessions.add(session);
session.latch.countUp();
return true;
}
}
if (!isLockedMode) {
return true;
}
boolean needsLock = cs.getTableNamesForRead().length > 0
|| cs.getTableNamesForWrite().length > 0;
if (!needsLock) {
return true;
}
if (cs.getTableNamesForWrite().length > 0) {
if (cs.getTableNamesForWrite()[0].schema
== SqlInvariants.LOBS_SCHEMA_HSQLNAME) {
return true;
}
} else if (cs.getTableNamesForRead().length > 0) {
if (cs.getTableNamesForRead()[0].schema
== SqlInvariants.LOBS_SCHEMA_HSQLNAME) {
return true;
}
}
catalogWriteSession.waitingSessions.add(session);
session.latch.countUp();
return true;
}
}