ruby-****@sourc*****
ruby-****@sourc*****
2003年 9月 29日 (月) 19:21:40 JST
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REMOTE_ADDR = 217.117.55.140
REMOTE_HOST =
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",
+
+ command = Gda::Command.new("UPDATE accounts SET balance=balance+50 WHERE ref_customer=1",
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",
+
+ command = Gda::Command.new("UPDATE accounts SET balance=balance-50 WHERE ref_customer=2",
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",
+
+ command = Gda::Command.new("UPDATE accounts SET balance=balance+400 WHERE ref_customer=1",
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",
+
+ command = Gda::Command.new("UPDATE accounts SET balance=balance-400 WHERE ref_customer=2",
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