YapDatabaseConnectionPool

@interface YapDatabaseConnectionPool : NSObject

The connection pool class was designed to help you optimize background read-only transactions. As a reminder:

This leaves only non-main-thread read-only transactions. What’s the recommendation for them? You could create a single read-only connection that will be shared by all background tasks. However, since all transactions are serialized via the shared connection, this implies that background taskA may have to wait for background taskB to finish its read-only transaction before background taskA can execute its transaction. And for background tasks, this is NOT the preferred scenario.

The connection pool was designed to increase the performance in these scenarios. It will create connections on demand, up to (but not over) the connectionLimit. And it will vend connections using a simple load balancer that’s based on the number of pending transactions that each connection has. (So you’ll be handed the connection with the smallest queue of pending work.)

This allows for increased parallelization amongst your background tasks.

  • Initializes a new connction pool with default configuration values. All database connections are created on demand, so you can configure the pool after initialization.

    Declaration

    Objective-C

    - (nonnull instancetype)initWithDatabase:(nonnull YapDatabase *)database;

    Swift

    init(database: YapDatabase)

  • Specifies the maximum number of connections the pool is allowed to create. Connections are created on demand, so the limit may never be reached.

    You can update this property at anytime.

    The default value is 3. Zero is not a valid number, and will be treated as the default value.

    Declaration

    Objective-C

    @property (assign, readwrite, atomic) NSUInteger connectionLimit;

    Swift

    var connectionLimit: UInt { get set }

  • By default, new database connections inherit their default configuration settings via YapDatabase.connectionDefaults, the same way that all connections do when one invokes [database newConnection]. You may optionally configure an alternative set of defaults specifically for connections created via this pool.

    The default value for this property is nil, which means new database connections will inherit their configuration from YapDatabase.connectionDefaults.

    Declaration

    Objective-C

    @property (readwrite, strong, atomic)
    YapDatabaseConnectionConfig *_Nonnull connectionDefaults;

    Swift

    var connectionDefaults: YapDatabaseConnectionConfig { get set }

  • Allows you to perform additional configuration on a newly created connection. This block is invoked BEFORE the connection is returned to the caller.

    Declaration

    Objective-C

    @property (readwrite, copy, atomic) void (^_Nonnull)
    (YapDatabaseConnection *_Nonnull) didCreateNewConnectionBlock;

    Swift

    var didCreateNewConnectionBlock: (YapDatabaseConnection) -> Void { get set }

  • Returns an existing connection from the pool, or creates a new connection, depending upon the pool’s configuration, and the number of pending/active transactions for existing connections.

    • If there’s an existing connection in the pool that doesn’t have pending/active transactions, then that connection is returned.
    • Otherwise, if the connection count is below connectionCount, a new connection is created & returned.
    • Otherwise, an existing connection will be automatically chosen based on the number of pending/active transactions.

    Declaration

    Objective-C

    - (nonnull YapDatabaseConnection *)connection;

    Swift

    func connection() -> YapDatabaseConnection