[Hiki] create - tut-libgda-transactions (ruby-gnome2-doc-cvs) - Ruby-GNOME2

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        URL = http://ruby-gnome2.sourceforge.jp/?tut-libgda-transactions
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= Managing transactions

The special methods we need to do this are defined in Gda::Transaction, Gda::Connection and Gda::Command classes, and they are:

 * Gda::Transaction.new;
 * Gda::Connection#begin_transaction;
 * Gda::Connection#commit_transaction;
 * Gda::Connection#rollback_transaction;
 * Gda::Command#set_transaction or Gda::Command#transaction=.

Things you have to do to manage transactions are:

(1) Create transaction
(2) Change, if needed, the isolation level
(3) Link transaction to a connection
(4) For each command you want to execute:
    (1) Create command
    (2) Link transaction to command
    (3) Execute command
(5) Commit or rollback transaction

Here you can see an example: 

  def process_accounts(conn)
      # Creates first transaction.
      transaction_one = Gda::Transaction.new("accounts1")
      # Changes the isolation level.
      transaction_one.isolation_level = Gda::Transaction::ISOLATION_SERIALIZABLE
      # Links it to connection.
      conn.begin_transaction(transaction_one)

      command = Gda::Command.new("UPDATE accounts SET balance=balance+50 WHERE account_code=456",
                                 Gda::Command::TYPE_SQL,
                                 Gda::Command::OPTION_STOP_ON_ERRORS)
      # Links command to transaction.
      command.transaction = transaction_one
      conn.execute_non_query(command)

      command = Gda::Command.new("UPDATE accounts SET balance=balance-50 WHERE account_code=12",
                                 Gda::Command::TYPE_SQL,
                                 Gda::Command::OPTION_STOP_ON_ERRORS)
      command.transaction = transaction_one
      conn.execute_non_query(command)

      # Makes commit on transaction.
      conn.commit_transaction(transaction_one)

      transaction_two = Gda::Transaction.new("accounts2")
      transaction_two.isolation_level = Gda::Transaction::ISOLATION_SERIALIZABLE
      conn.begin_transaction(transaction_two)

      command = Gda::Command.new("UPDATE accounts SET balance=balance+400 WHERE account_code=456",
                                 Gda::Command::TYPE_SQL,
                                 Gda::Command::OPTION_STOP_ON_ERRORS)
      command.transaction = transaction_two
      conn.execute_non_query(command)

      command = Gda::Command.new("UPDATE accounts SET balance=balance-400 WHERE account_code=12",
                                 Gda::Command::TYPE_SQL,
                                 Gda::Command::OPTION_STOP_ON_ERRORS)
      command.transaction = transaction_two
      conn.execute_non_query(command)

      # Makes rollback on second transaction.
      conn.rollback_transaction(transaction_two)

      execute_sql_command(conn, "SELECT * FROM accounts")
  end

Ruby-GNOME2

[ruby-gnome2-doc-cvs] [Hiki] create - tut-libgda-transactions