3.41.0.txt

doc/release_notes/3.41.0.txt
Last Update: 2012-11-01 08:50:01 -0700

New Features

  • A connection_validator extension has been added, which automatically determines if connections checked out from the pool are still valid. If they are not valid, the connection is disconnected and another connection is used automatically, transparent to user code.

    Checking if connections are valid requires a query, so this extension causes a performance hit. For that reason, connections are only checked by default if they have been inactive for more than a configured amount of time (1 hour by default). You can choose to validate connections on every checkout via:

    DB.pool.connection_validation_timeout = -1

    However, this can cause a substantial performance hit unless you are purposely using coarse connection checkouts via manual calls to Database#synchronize (for example, in a Rack middleware). Using coarse checkouts can greatly reduce the amount of concurrency that Sequel supports (for example, limiting the number of concurrent requests to the number of database connections), so this method is not without its tradeoffs.

  • Sequel.delay has been added for a generic form of delayed evaluation. This method takes a block and delays evaluating it until query literalization. By default, Sequel evaluates most arguments immediately:

    foo = 1
    ds = DB[:bar].where(:baz=>foo)
    # SELECT * FROM bar WHERE (baz = 1)
    foo = 2
    ds
    # SELECT * FROM bar WHERE (baz = 1)

    Using Sequel.delay, you can delay the evaluation:

    foo = 1
    ds = DB[:bar].where(:baz=>Sequel.delay{foo})
    # SELECT * FROM bar WHERE (baz = 1)
    foo = 2
    ds
    # SELECT * FROM bar WHERE (baz = 2)
  • Sequel now supports the :unlogged option when creating tables on PostgreSQL, to create an UNLOGGED table.

  • On SQLite, Database#transaction now supports a :mode option for setting up IMMEDIATE/EXCLUSIVE SQLite transactions. Sequel also supports a Database#transaction_mode accessor for setting the default transaction mode on SQLite.

  • Most pg_* extension objects (e.g. PGArray) now support the as method for creating an SQL::AliasedExpression object.

  • The single_table_inheritance plugin now supports non-bijective mappings. In lay terms, this means that a one-to-one mapping of column values to classes is no longer required. You can now have multiple column values that map to a single class in the :model_map option, and specify a :key_chooser option to choose which column value to use for the given model class.

  • The touch plugin now handles the touching of many_to_many associations, and other associations that use joined datasets.

  • ConnectionPool#pool_type has been added. It returns a symbol representing the type of connection pool in use (similar to Database#database_type).

  • Database#valid_connection? has been added for checking if a given connection is still valid.

  • Database#disconnect_connection is now part of the public API, and can be used to disconnect a given connection.

Other Improvements

  • Uniqueness validation now correctly handles nil values. Previously, it checked the underlying table for other rows where the column IS NULL, but that is incorrect behavior. Sequel's new (correct) behavior is to skip the uniqueness check if the column is nil.

  • Foreign key parsing is now supported on Microsoft SQL Server.

  • Dataset#reverse and reverse_order now accept virtual row blocks.

  • Changing the name of the primary key column, and possibly other schema changes on the primary key column, are now supported on MySQL.

  • Primary key columns are now specifically marked as NOT NULL on SQLite, as non-integer primary keys on SQLite are not considered NOT NULL by default.

  • Failure to create a native prepared statement is now handled better in the postgres, mysql, and mysql2 adapters.

  • Firebird now emulates selecting data without an underlying table (e.g. DB.get(1)).

  • Finding the name of the constraint that sets column defaults on Microsoft SQL Server now works correctly on JRuby 1.7.

  • An additional type of disconnect error is now recognized in the jdbc/sqlserver adapter.

  • Many adapters have been fixed so that they don't raise an exception if trying to disconnect an already disconnected connection.

  • Many adapters have been fixed so that Database#log_connection_execute logs and executes the given SQL on the connection.

  • Many adapters have been fixed so that Database#database_error_classes returns an array of database exception classes for that adapter.

  • Database#log_exception now handles a nil exception message.

  • Dataset#limit(nil, nil) now resets offset in addition to limit, but you should still use Dataset#unlimited instead.

  • A bin/sequel usage quide has been added to the documentation.

Backwards Compatibility

  • Sequel now treats clob columns as strings instead of blobs (except on DB2 when use_clob_as_blob = true). This can make it so the values are returned as strings instead of SQL::Blob values. Since SQL::Blob is a String subclass, this generally will not affect user code unless you are passing the values as input to a separate blob column.

  • The Database <-> ConnectionPool interface was completely changed. Sequel no longer supports custom connection procs or disconnection procs in the connection pools. The :disconnection_proc Database option is no longer respected, and blocks passed to Database.new are now ignored.

    This change should not be user-visible, but if you had any code that was monkeying with the connection pool internals, you may need to modify it.

  • Code that was using the uniqueness check to also check for presence should add a separate check for presence. Such code was broken, as it only worked if there was already a NULL column value in the table. If you were relying on this broken behavior, you should clean up the NULL data in the column and then mark the database column as NOT NULL.

  • If you have code that specifically abuses the fact that non-integer primary keys on SQLite allow NULL values by default, it will no longer work.