Use a single read-write lock for the DB - don't optimise prematurely.

briar-core/src/org/briarproject/db/Database.java

@@ -38,29 +38,22 @@ import org.briarproject.api.transport.TemporarySecret;
  * terminated by calling either {@link #abortTransaction(T)} or
  * {@link #commitTransaction(T)}, even if an exception is thrown.
  * <p>
- * Locking is provided by the DatabaseComponent implementation. To prevent
+ * Read-write locking is provided by the DatabaseComponent implementation.
- * deadlock, locks must be acquired in the following (alphabetical) order:
- * <ul>
- * <li> contact
- * <li> identity
- * <li> message
- * <li> retention
- * <li> setting
- * <li> subscription
- * <li> transport
- * <li> window
- * </ul>
- * If table A has a foreign key pointing to table B, we get a read lock on A to
- * read A, a write lock on A to write A, and write locks on A and B to write B.
  */
 interface Database<T> {
 
-	/** Opens the database and returns true if the database already existed. */
+	/**
+	 * Opens the database and returns true if the database already existed.
+	 * <p>
+	 * Locking: write.
+	 */
 	boolean open() throws DbException, IOException;
 
 	/**
 	 * Prevents new transactions from starting, waits for all current
 	 * transactions to finish, and closes the database.
+	 * <p>
+	 * Locking: write.
 	 */
 	void close() throws DbException, IOException;
 
@@ -92,8 +85,7 @@ interface Database<T> {
 	 * Stores a contact associated with the given local and remote pseudonyms,
 	 * and returns an ID for the contact.
 	 * <p>
-	 * Locking: contact write, message write, retention write,
+	 * Locking: write.
-	 * subscription write, transport write, window write.
 	 */
 	ContactId addContact(T txn, Author remote, AuthorId local)
 			throws DbException;
@@ -101,7 +93,7 @@ interface Database<T> {
 	/**
 	 * Stores an endpoint.
 	 * <p>
-	 * Locking: window write.
+	 * Locking: write.
 	 */
 	void addEndpoint(T txn, Endpoint ep) throws DbException;
 
@@ -109,29 +101,28 @@ interface Database<T> {
 	 * Subscribes to a group, or returns false if the user already has the
 	 * maximum number of subscriptions.
 	 * <p>
-	 * Locking: message write, subscription write.
+	 * Locking: write.
 	 */
 	boolean addGroup(T txn, Group g) throws DbException;
 
 	/**
 	 * Stores a local pseudonym.
 	 * <p>
-	 * Locking: contact write, identity write, message write, retention write,
+	 * Locking: write.
-	 * subscription write, transport write, window write.
 	 */
 	void addLocalAuthor(T txn, LocalAuthor a) throws DbException;
 
 	/**
 	 * Stores a message.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void addMessage(T txn, Message m, boolean local) throws DbException;
 
 	/**
 	 * Records that a message has been offered by the given contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void addOfferedMessage(T txn, ContactId c, MessageId m) throws DbException;
 
@@ -139,7 +130,7 @@ interface Database<T> {
 	 * Stores the given temporary secrets and deletes any secrets that have
 	 * been made obsolete.
 	 * <p>
-	 * Locking: window write.
+	 * Locking: write.
 	 */
 	void addSecrets(T txn, Collection<TemporarySecret> secrets)
 			throws DbException;
@@ -147,10 +138,10 @@ interface Database<T> {
 	/**
 	 * Initialises the status of the given message with respect to the given
 	 * contact.
+	 * <p>
+	 * Locking: write.
 	 * @param ack whether the message needs to be acknowledged.
 	 * @param seen whether the contact has seen the message.
-	 * <p>
-	 * Locking: message write.
 	 */
 	void addStatus(T txn, ContactId c, MessageId m, boolean ack, boolean seen)
 			throws DbException;
@@ -159,7 +150,7 @@ interface Database<T> {
 	 * Stores a transport and returns true if the transport was not previously
 	 * in the database.
 	 * <p>
-	 * Locking: transport write, window write.
+	 * Locking: write.
 	 */
 	boolean addTransport(T txn, TransportId t, long maxLatency)
 			throws DbException;
@@ -167,49 +158,49 @@ interface Database<T> {
 	/**
 	 * Makes a group visible to the given contact.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	void addVisibility(T txn, ContactId c, GroupId g) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact.
 	 * <p>
-	 * Locking: contact read.
+	 * Locking: read.
 	 */
 	boolean containsContact(T txn, AuthorId a) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact.
 	 * <p>
-	 * Locking: contact read.
+	 * Locking: read.
 	 */
 	boolean containsContact(T txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns true if the user subscribes to the given group.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	boolean containsGroup(T txn, GroupId g) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given local pseudonym.
 	 * <p>
-	 * Locking: identity read.
+	 * Locking: read.
 	 */
 	boolean containsLocalAuthor(T txn, AuthorId a) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given message.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	boolean containsMessage(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given transport.
 	 * <p>
-	 * Locking: transport read.
+	 * Locking: read.
 	 */
 	boolean containsTransport(T txn, TransportId t) throws DbException;
 
@@ -217,7 +208,7 @@ interface Database<T> {
 	 * Returns true if the user subscribes to the given group and the group is
 	 * visible to the given contact.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	boolean containsVisibleGroup(T txn, ContactId c, GroupId g)
 			throws DbException;
@@ -226,7 +217,7 @@ interface Database<T> {
 	 * Returns true if the database contains the given message and the message
 	 * is visible to the given contact.
 	 * <p>
-	 * Locking: message read, subscription read.
+	 * Locking: read.
 	 */
 	boolean containsVisibleMessage(T txn, ContactId c, MessageId m)
 			throws DbException;
@@ -234,7 +225,7 @@ interface Database<T> {
 	/**
 	 * Returns the number of messages offered by the given contact.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	int countOfferedMessages(T txn, ContactId c) throws DbException;
 
@@ -242,49 +233,49 @@ interface Database<T> {
 	 * Returns the status of all groups to which the user subscribes or can
 	 * subscribe, excluding inbox groups.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	Collection<GroupStatus> getAvailableGroups(T txn) throws DbException;
 
 	/**
 	 * Returns the configuration for the given transport.
 	 * <p>
-	 * Locking: transport read.
+	 * Locking: read.
 	 */
 	TransportConfig getConfig(T txn, TransportId t) throws DbException;
 
 	/**
 	 * Returns the contact with the given ID.
 	 * <p>
-	 * Locking: contact read.
+	 * Locking: read.
 	 */
 	Contact getContact(T txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns the IDs of all contacts.
 	 * <p>
-	 * Locking: contact read.
+	 * Locking: read.
 	 */
 	Collection<ContactId> getContactIds(T txn) throws DbException;
 
 	/**
 	 * Returns all contacts.
 	 * <p>
-	 * Locking: contact read, window read.
+	 * Locking: read.
 	 */
 	Collection<Contact> getContacts(T txn) throws DbException;
 
 	/**
 	 * Returns all contacts associated with the given local pseudonym.
 	 * <p>
-	 * Locking: contact read.
+	 * Locking: read.
 	 */
 	Collection<ContactId> getContacts(T txn, AuthorId a) throws DbException;
 
 	/**
 	 * Returns all endpoints.
 	 * <p>
-	 * Locking: window read.
+	 * Locking: read.
 	 */
 	Collection<Endpoint> getEndpoints(T txn) throws DbException;
 
@@ -298,14 +289,14 @@ interface Database<T> {
 	/**
 	 * Returns the group with the given ID, if the user subscribes to it.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	Group getGroup(T txn, GroupId g) throws DbException;
 
 	/**
 	 * Returns all groups to which the user subscribes.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	Collection<Group> getGroups(T txn) throws DbException;
 
@@ -313,7 +304,7 @@ interface Database<T> {
 	 * Returns the ID of the inbox group for the given contact, or null if no
 	 * inbox group has been set.
 	 * <p>
-	 * Locking: contact read, subscription read.
+	 * Locking: read.
 	 */
 	GroupId getInboxGroupId(T txn, ContactId c) throws DbException;
 
@@ -321,7 +312,7 @@ interface Database<T> {
 	 * Returns the headers of all messages in the inbox group for the given
 	 * contact, or null if no inbox group has been set.
 	 * <p>
-	 * Locking: contact read, identity read, message read, subscription read.
+	 * Locking: read.
 	 */
 	Collection<MessageHeader> getInboxMessageHeaders(T txn, ContactId c)
 			throws DbException;
@@ -329,21 +320,21 @@ interface Database<T> {
 	/**
 	 * Returns the local pseudonym with the given ID.
 	 * <p>
-	 * Locking: identity read.
+	 * Locking: read.
 	 */
 	LocalAuthor getLocalAuthor(T txn, AuthorId a) throws DbException;
 
 	/**
 	 * Returns all local pseudonyms.
 	 * <p>
-	 * Locking: identity read.
+	 * Locking: read.
 	 */
 	Collection<LocalAuthor> getLocalAuthors(T txn) throws DbException;
 
 	/**
 	 * Returns the local transport properties for all transports.
 	 * <p>
-	 * Locking: transport read.
+	 * Locking: read.
 	 */
 	Map<TransportId, TransportProperties> getLocalProperties(T txn)
 			throws DbException;
@@ -351,7 +342,7 @@ interface Database<T> {
 	/**
 	 * Returns the local transport properties for the given transport.
 	 * <p>
-	 * Locking: transport read.
+	 * Locking: read.
 	 */
 	TransportProperties getLocalProperties(T txn, TransportId t)
 			throws DbException;
@@ -359,14 +350,14 @@ interface Database<T> {
 	/**
 	 * Returns the body of the message identified by the given ID.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	byte[] getMessageBody(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns the headers of all messages in the given group.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	Collection<MessageHeader> getMessageHeaders(T txn, GroupId g)
 			throws DbException;
@@ -375,7 +366,7 @@ interface Database<T> {
 	 * Returns the IDs of some messages received from the given contact that
 	 * need to be acknowledged, up to the given number of messages.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	Collection<MessageId> getMessagesToAck(T txn, ContactId c, int maxMessages)
 			throws DbException;
@@ -384,7 +375,7 @@ interface Database<T> {
 	 * Returns the IDs of some messages that are eligible to be offered to the
 	 * given contact, up to the given number of messages.
 	 * <p>
-	 * Locking: message read, subscription read.
+	 * Locking: read.
 	 */
 	Collection<MessageId> getMessagesToOffer(T txn, ContactId c,
 			int maxMessages) throws DbException;
@@ -393,7 +384,7 @@ interface Database<T> {
 	 * Returns the IDs of some messages that are eligible to be sent to the
 	 * given contact, up to the given total length.
 	 * <p>
-	 * Locking: message read, subscription read.
+	 * Locking: read.
 	 */
 	Collection<MessageId> getMessagesToSend(T txn, ContactId c, int maxLength)
 			throws DbException;
@@ -402,7 +393,7 @@ interface Database<T> {
 	 * Returns the IDs of some messages that are eligible to be requested from
 	 * the given contact, up to the given number of messages.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	Collection<MessageId> getMessagesToRequest(T txn, ContactId c,
 			int maxMessages) throws DbException;
@@ -411,7 +402,7 @@ interface Database<T> {
 	 * Returns the IDs of the oldest messages in the database, with a total
 	 * size less than or equal to the given size.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	Collection<MessageId> getOldMessages(T txn, int size) throws DbException;
 
@@ -420,28 +411,28 @@ interface Database<T> {
 	 * has no parent, or the parent is absent from the database, or the parent
 	 * belongs to a different group.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	MessageId getParent(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns the message identified by the given ID, in serialised form.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	byte[] getRawMessage(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns true if the given message is marked as read.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	boolean getReadFlag(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns all remote properties for the given transport.
 	 * <p>
-	 * Locking: transport read.
+	 * Locking: read.
 	 */
 	Map<ContactId, TransportProperties> getRemoteProperties(T txn,
 			TransportId t) throws DbException;
@@ -451,7 +442,7 @@ interface Database<T> {
 	 * given contact and have been requested by the contact, up to the given
 	 * total length.
 	 * <p>
-	 * Locking: message read, subscription read.
+	 * Locking: read.
 	 */
 	Collection<MessageId> getRequestedMessagesToSend(T txn, ContactId c,
 			int maxLength) throws DbException;
@@ -459,7 +450,7 @@ interface Database<T> {
 	/**
 	 * Returns a retention ack for the given contact, or null if no ack is due.
 	 * <p>
-	 * Locking: retention write.
+	 * Locking: write.
 	 */
 	RetentionAck getRetentionAck(T txn, ContactId c) throws DbException;
 
@@ -467,7 +458,7 @@ interface Database<T> {
 	 * Returns a retention update for the given contact and updates its expiry
 	 * time using the given latency, or returns null if no update is due.
 	 * <p>
-	 * Locking: message read, retention write.
+	 * Locking: write.
 	 */
 	RetentionUpdate getRetentionUpdate(T txn, ContactId c, long maxLatency)
 			throws DbException;
@@ -475,21 +466,21 @@ interface Database<T> {
 	/**
 	 * Returns all temporary secrets.
 	 * <p>
-	 * Locking: window read.
+	 * Locking: read.
 	 */
 	Collection<TemporarySecret> getSecrets(T txn) throws DbException;
 
 	/**
 	 * Returns all settings.
 	 * <p>
-	 * Locking: setting read.
+	 * Locking: read.
 	 */
 	Settings getSettings(T txn) throws DbException;
 
 	/**
 	 * Returns all contacts who subscribe to the given group.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	Collection<Contact> getSubscribers(T txn, GroupId g) throws DbException;
 
@@ -497,7 +488,7 @@ interface Database<T> {
 	 * Returns a subscription ack for the given contact, or null if no ack is
 	 * due.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	SubscriptionAck getSubscriptionAck(T txn, ContactId c) throws DbException;
 
@@ -505,7 +496,7 @@ interface Database<T> {
 	 * Returns a subscription update for the given contact and updates its
 	 * expiry time using the given latency, or returns null if no update is due.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	SubscriptionUpdate getSubscriptionUpdate(T txn, ContactId c,
 			long maxLatency) throws DbException;
@@ -514,7 +505,7 @@ interface Database<T> {
 	 * Returns a collection of transport acks for the given contact, or null if
 	 * no acks are due.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	Collection<TransportAck> getTransportAcks(T txn, ContactId c)
 			throws DbException;
@@ -522,7 +513,7 @@ interface Database<T> {
 	/**
 	 * Returns the maximum latencies of all local transports.
 	 * <p>
-	 * Locking: transport read.
+	 * Locking: read.
 	 */
 	Map<TransportId, Long> getTransportLatencies(T txn) throws DbException;
 
@@ -531,7 +522,7 @@ interface Database<T> {
 	 * updates their expiry times using the given latency, or returns null if
 	 * no updates are due.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	Collection<TransportUpdate> getTransportUpdates(T txn, ContactId c,
 			long maxLatency) throws DbException;
@@ -539,14 +530,14 @@ interface Database<T> {
 	/**
 	 * Returns the number of unread messages in each subscribed group.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: read.
 	 */
 	Map<GroupId, Integer> getUnreadMessageCounts(T txn) throws DbException;
 
 	/**
 	 * Returns the IDs of all contacts to which the given group is visible.
 	 * <p>
-	 * Locking: subscription read.
+	 * Locking: read.
 	 */
 	Collection<ContactId> getVisibility(T txn, GroupId g) throws DbException;
 
@@ -555,7 +546,7 @@ interface Database<T> {
 	 * in the given rotation period and returns the old value, or -1 if the
 	 * counter does not exist.
 	 * <p>
-	 * Locking: window write.
+	 * Locking: write.
 	 */
 	long incrementConnectionCounter(T txn, ContactId c, TransportId t,
 			long period) throws DbException;
@@ -564,7 +555,7 @@ interface Database<T> {
 	 * Increments the retention time versions for all contacts to indicate that
 	 * the database's retention time has changed and updates should be sent.
 	 * <p>
-	 * Locking: retention write.
+	 * Locking: write.
 	 */
 	void incrementRetentionVersions(T txn) throws DbException;
 
@@ -572,7 +563,7 @@ interface Database<T> {
 	 * Marks the given messages as not needing to be acknowledged to the
 	 * given contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void lowerAckFlag(T txn, ContactId c, Collection<MessageId> acked)
 			throws DbException;
@@ -581,7 +572,7 @@ interface Database<T> {
 	 * Marks the given messages as not having been requested by the given
 	 * contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void lowerRequestedFlag(T txn, ContactId c, Collection<MessageId> requested)
 			throws DbException;
@@ -590,7 +581,7 @@ interface Database<T> {
 	 * Merges the given configuration with the existing configuration for the
 	 * given transport.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	void mergeConfig(T txn, TransportId t, TransportConfig config)
 			throws DbException;
@@ -599,7 +590,7 @@ interface Database<T> {
 	 * Merges the given properties with the existing local properties for the
 	 * given transport.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	void mergeLocalProperties(T txn, TransportId t, TransportProperties p)
 			throws DbException;
@@ -607,36 +598,35 @@ interface Database<T> {
 	/**
 	 * Merges the given settings with the existing settings.
 	 * <p>
-	 * Locking: setting write.
+	 * Locking: write.
 	 */
 	void mergeSettings(T txn, Settings s) throws DbException;
 
 	/**
 	 * Marks a message as needing to be acknowledged to the given contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void raiseAckFlag(T txn, ContactId c, MessageId m) throws DbException;
 
 	/**
 	 * Marks a message as having been requested by the given contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void raiseRequestedFlag(T txn, ContactId c, MessageId m) throws DbException;
 
 	/**
 	 * Marks a message as having been seen by the given contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void raiseSeenFlag(T txn, ContactId c, MessageId m) throws DbException;
 
 	/**
 	 * Removes a contact from the database.
 	 * <p>
-	 * Locking: contact write, message write, retention write,
+	 * Locking: write.
-	 * subscription write, transport write, window write.
 	 */
 	void removeContact(T txn, ContactId c) throws DbException;
 
@@ -644,7 +634,7 @@ interface Database<T> {
 	 * Unsubscribes from a group. Any messages belonging to the group are
 	 * deleted from the database.
 	 * <p>
-	 * Locking: message write, subscription write.
+	 * Locking: write.
 	 */
 	void removeGroup(T txn, GroupId g) throws DbException;
 
@@ -652,15 +642,14 @@ interface Database<T> {
 	 * Removes a local pseudonym (and all associated contacts) from the
 	 * database.
 	 * <p>
-	 * Locking: contact write, identity write, message write, retention write,
+	 * Locking: write.
-	 * subscription write, transport write, window write.
 	 */
 	void removeLocalAuthor(T txn, AuthorId a) throws DbException;
 
 	/**
 	 * Removes a message (and all associated state) from the database.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void removeMessage(T txn, MessageId m) throws DbException;
 
@@ -668,7 +657,7 @@ interface Database<T> {
 	 * Removes an offered message that was offered by the given contact, or
 	 * returns false if there is no such message.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	boolean removeOfferedMessage(T txn, ContactId c, MessageId m)
 			throws DbException;
@@ -677,7 +666,7 @@ interface Database<T> {
 	 * Removes the given offered messages that were offered by the given
 	 * contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void removeOfferedMessages(T txn, ContactId c,
 			Collection<MessageId> requested) throws DbException;
@@ -685,14 +674,14 @@ interface Database<T> {
 	/**
 	 * Removes a transport (and all associated state) from the database.
 	 * <p>
-	 * Locking: transport write, window write.
+	 * Locking: write.
 	 */
 	void removeTransport(T txn, TransportId t) throws DbException;
 
 	/**
 	 * Makes a group invisible to the given contact.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	void removeVisibility(T txn, ContactId c, GroupId g) throws DbException;
 
@@ -700,7 +689,7 @@ interface Database<T> {
 	 * Resets the transmission count and expiry time of the given message with
 	 * respect to the given contact.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void resetExpiryTime(T txn, ContactId c, MessageId m) throws DbException;
 
@@ -708,7 +697,7 @@ interface Database<T> {
 	 * Sets the connection reordering window for the given endpoint in the
 	 * given rotation period.
 	 * <p>
-	 * Locking: window write.
+	 * Locking: write.
 	 */
 	void setConnectionWindow(T txn, ContactId c, TransportId t, long period,
 			long centre, byte[] bitmap) throws DbException;
@@ -718,7 +707,7 @@ interface Database<T> {
 	 * true, unless an update with an equal or higher version number has
 	 * already been received from the contact.
 	 * <p>
-	 * Locking: message write, subscription write.
+	 * Locking: write.
 	 */
 	boolean setGroups(T txn, ContactId c, Collection<Group> groups,
 			long version) throws DbException;
@@ -727,14 +716,14 @@ interface Database<T> {
 	 * Makes a group visible to the given contact, adds it to the contact's
 	 * subscriptions, and sets it as the inbox group for the contact.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	public void setInboxGroup(T txn, ContactId c, Group g) throws DbException;
 
 	/**
 	 * Marks a message as read or unread.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void setReadFlag(T txn, MessageId m, boolean read) throws DbException;
 
@@ -742,7 +731,7 @@ interface Database<T> {
 	 * Sets the remote transport properties for the given contact, replacing
 	 * any existing properties.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	void setRemoteProperties(T txn, ContactId c,
 			Map<TransportId, TransportProperties> p) throws DbException;
@@ -753,7 +742,7 @@ interface Database<T> {
 	 * unless an update with an equal or higher version number has already been
 	 * received from the contact.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	boolean setRemoteProperties(T txn, ContactId c, TransportId t,
 			TransportProperties p, long version) throws DbException;
@@ -763,7 +752,7 @@ interface Database<T> {
 	 * true, unless an update with an equal or higher version number has
 	 * already been received from the contact.
 	 * <p>
-	 * Locking: retention write.
+	 * Locking: write.
 	 */
 	boolean setRetentionTime(T txn, ContactId c, long retention, long version)
 			throws DbException;
@@ -772,7 +761,7 @@ interface Database<T> {
 	 * Records a retention ack from the given contact for the given version,
 	 * unless the contact has already acked an equal or higher version.
 	 * <p>
-	 * Locking: retention write.
+	 * Locking: write.
 	 */
 	void setRetentionUpdateAcked(T txn, ContactId c, long version)
 			throws DbException;
@@ -781,7 +770,7 @@ interface Database<T> {
 	 * Records a subscription ack from the given contact for the given version,
 	 * unless the contact has already acked an equal or higher version.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	void setSubscriptionUpdateAcked(T txn, ContactId c, long version)
 			throws DbException;
@@ -790,7 +779,7 @@ interface Database<T> {
 	 * Records a transport ack from the give contact for the given version,
 	 * unless the contact has already acked an equal or higher version.
 	 * <p>
-	 * Locking: transport write.
+	 * Locking: write.
 	 */
 	void setTransportUpdateAcked(T txn, ContactId c, TransportId t,
 			long version) throws DbException;
@@ -798,7 +787,7 @@ interface Database<T> {
 	/**
 	 * Makes a group visible or invisible to future contacts by default.
 	 * <p>
-	 * Locking: subscription write.
+	 * Locking: write.
 	 */
 	void setVisibleToAll(T txn, GroupId g, boolean all) throws DbException;
 
@@ -807,7 +796,7 @@ interface Database<T> {
 	 * with respect to the given contact, using the latency of the transport
 	 * over which it was sent.
 	 * <p>
-	 * Locking: message write.
+	 * Locking: write.
 	 */
 	void updateExpiryTime(T txn, ContactId c, MessageId m, long maxLatency)
 			throws DbException;

briar-core/src/org/briarproject/db/JdbcDatabase.java

@@ -71,8 +71,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " value VARCHAR NOT NULL,"
 					+ " PRIMARY KEY (key))";
 
-	// Locking: identity
-	// Dependents: contact, message, retention, subscription, transport, window
 	private static final String CREATE_LOCAL_AUTHORS =
 			"CREATE TABLE localAuthors"
 					+ " (authorId HASH NOT NULL,"
@@ -82,8 +80,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " created BIGINT NOT NULL,"
 					+ " PRIMARY KEY (authorId))";
 
-	// Locking: contact
-	// Dependents: message, retention, subscription, transport, window
 	private static final String CREATE_CONTACTS =
 			"CREATE TABLE contacts"
 					+ " (contactId COUNTER,"
@@ -97,8 +93,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES localAuthors (authorId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: subscription
-	// Dependents: message
 	private static final String CREATE_GROUPS =
 			"CREATE TABLE groups"
 					+ " (groupId HASH NOT NULL,"
@@ -107,7 +101,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " visibleToAll BOOLEAN NOT NULL,"
 					+ " PRIMARY KEY (groupId))";
 
-	// Locking: subscription
 	private static final String CREATE_GROUP_VISIBILITIES =
 			"CREATE TABLE groupVisibilities"
 					+ " (contactId INT NOT NULL,"
@@ -121,7 +114,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES groups (groupId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: subscription
 	private static final String CREATE_CONTACT_GROUPS =
 			"CREATE TABLE contactGroups"
 					+ " (contactId INT NOT NULL,"
@@ -133,7 +125,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: subscription
 	private static final String CREATE_GROUP_VERSIONS =
 			"CREATE TABLE groupVersions"
 					+ " (contactId INT NOT NULL,"
@@ -148,7 +139,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: message
 	private static final String CREATE_MESSAGES =
 			"CREATE TABLE messages"
 					+ " (messageId HASH NOT NULL,"
@@ -182,7 +172,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: message
 	private static final String CREATE_STATUSES =
 			"CREATE TABLE statuses"
 					+ " (messageId HASH NOT NULL,"
@@ -206,7 +195,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private static final String INDEX_STATUSES_BY_CONTACT =
 			"CREATE INDEX statusesByContact ON statuses (contactId)";
 
-	// Locking: retention
 	private static final String CREATE_RETENTION_VERSIONS =
 			"CREATE TABLE retentionVersions"
 					+ " (contactId INT NOT NULL,"
@@ -222,15 +210,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: transport
-	// Dependents: window
 	private static final String CREATE_TRANSPORTS =
 			"CREATE TABLE transports"
 					+ " (transportId VARCHAR NOT NULL,"
 					+ " maxLatency BIGINT NOT NULL,"
 					+ " PRIMARY KEY (transportId))";
 
-	// Locking: transport
 	private static final String CREATE_TRANSPORT_CONFIGS =
 			"CREATE TABLE transportConfigs"
 					+ " (transportId VARCHAR NOT NULL,"
@@ -241,7 +226,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: transport
 	private static final String CREATE_TRANSPORT_PROPS =
 			"CREATE TABLE transportProperties"
 					+ " (transportId VARCHAR NOT NULL,"
@@ -252,7 +236,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: transport
 	private static final String CREATE_TRANSPORT_VERSIONS =
 			"CREATE TABLE transportVersions"
 					+ " (contactId INT NOT NULL,"
@@ -269,7 +252,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: transport
 	private static final String CREATE_CONTACT_TRANSPORT_PROPS =
 			"CREATE TABLE contactTransportProperties"
 					+ " (contactId INT NOT NULL,"
@@ -281,7 +263,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: transport
 	private static final String CREATE_CONTACT_TRANSPORT_VERSIONS =
 			"CREATE TABLE contactTransportVersions"
 					+ " (contactId INT NOT NULL,"
@@ -293,7 +274,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: window
 	private static final String CREATE_ENDPOINTS =
 			"CREATE TABLE endpoints"
 					+ " (contactId INT NOT NULL,"
@@ -308,7 +288,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE)";
 
-	// Locking: window
 	private static final String CREATE_SECRETS =
 			"CREATE TABLE secrets"
 					+ " (contactId INT NOT NULL,"