diff options
Diffstat (limited to 'activerecord/lib/active_record')
6 files changed, 215 insertions, 51 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb index 189c6c7b5a..cecbc6b3ac 100644 --- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb @@ -53,36 +53,119 @@ module ActiveRecord def delete(sql, name = nil) delete_sql(sql, name) end + + # Checks whether there is currently no transaction active. This is done + # by querying the database driver, and does not use the transaction + # house-keeping information recorded by #increment_open_transactions and + # friends. + # + # Returns true if there is no transaction active, false if there is a + # transaction active, and nil if this information is unknown. + # + # Not all adapters supports transaction state introspection. Currently, + # only the PostgreSQL adapter supports this. + def outside_transaction? + nil + end - # Wrap a block in a transaction. Returns result of block. - def transaction(start_db_transaction = true) + # Runs the given block in a database transaction, and returns the result + # of the block. + # + # == Nested transactions support + # + # Most databases don't support true nested transactions. At the time of + # writing, the only database that supports true nested transactions that + # we're aware of, is MS-SQL. + # + # In order to get around this problem, #transaction will emulate the effect + # of nested transactions, by using savepoints: + # http://dev.mysql.com/doc/refman/5.0/en/savepoints.html + # Savepoints are supported by MySQL and PostgreSQL, but not SQLite3. + # + # It is safe to call this method if a database transaction is already open, + # i.e. if #transaction is called within another #transaction block. In case + # of a nested call, #transaction will behave as follows: + # + # - The block will be run without doing anything. All database statements + # that happen within the block are effectively appended to the already + # open database transaction. + # - However, if +start_db_transaction+ is set to true, then the block will + # be run inside a new database savepoint, effectively making the block + # a sub-transaction. + # - If the #transactional_fixtures attribute is set to true, then the first + # nested call to #transaction will create a new savepoint instead of + # doing nothing. This makes it possible for toplevel transactions in unit + # tests to behave like real transactions, even though a database + # transaction has already been opened. + # + # === Caveats + # + # MySQL doesn't support DDL transactions. If you perform a DDL operation, + # then any created savepoints will be automatically released. For example, + # if you've created a savepoint, then you execute a CREATE TABLE statement, + # then the savepoint that was created will be automatically released. + # + # This means that, on MySQL, you shouldn't execute DDL operations inside + # a #transaction call that you know might create a savepoint. Otherwise, + # #transaction will raise exceptions when it tries to release the + # already-automatically-released savepoints: + # + # Model.connection.transaction do # BEGIN + # Model.connection.transaction(true) do # CREATE SAVEPOINT rails_savepoint_1 + # Model.connection.create_table(...) + # # rails_savepoint_1 now automatically released + # end # RELEASE savepoint rails_savepoint_1 <--- BOOM! database error! + # end + def transaction(start_db_transaction = false) + start_db_transaction ||= open_transactions == 0 || (open_transactions == 1 && transactional_fixtures) transaction_open = false begin if block_given? if start_db_transaction - begin_db_transaction + if open_transactions == 0 + begin_db_transaction + else + create_savepoint + end + increment_open_transactions transaction_open = true end yield end rescue Exception => database_transaction_rollback - if transaction_open + if transaction_open && !outside_transaction? transaction_open = false - rollback_db_transaction + decrement_open_transactions + if open_transactions == 0 + rollback_db_transaction + else + rollback_to_savepoint + end end raise unless database_transaction_rollback.is_a? ActiveRecord::Rollback end ensure - if transaction_open + if outside_transaction? + @open_transactions = 0 + elsif transaction_open + decrement_open_transactions begin - commit_db_transaction + if open_transactions == 0 + commit_db_transaction + else + release_savepoint + end rescue Exception => database_transaction_rollback - rollback_db_transaction + if open_transactions == 0 + rollback_db_transaction + else + rollback_to_savepoint + end raise end end end - + # Begins the transaction (and turns off auto-committing). def begin_db_transaction() end diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb index bfafcfb3ab..5137b0f78c 100755 --- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb @@ -66,6 +66,12 @@ module ActiveRecord def supports_ddl_transactions? false end + + # Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite + # does not. + def supports_savepoints? + false + end # Should primary key values be selected from their corresponding # sequence before the insert statement? If true, next_sequence_value @@ -159,6 +165,24 @@ module ActiveRecord def decrement_open_transactions @open_transactions -= 1 end + + def create_savepoint + end + + def rollback_to_savepoint + end + + def release_savepoint + end + + def current_savepoint_name + "rails_savepoint_#{open_transactions}" + end + + # Whether this AbstractAdapter is currently being used inside a unit test + # with transactional fixtures turned on. See DatabaseStatements#transaction + # for more information about the effect of this option. + attr_accessor :transactional_fixtures def log_info(sql, name, ms) if @logger && @logger.debug? diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb index 60729c63db..b2345fd571 100644 --- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb +++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb @@ -210,6 +210,10 @@ module ActiveRecord def supports_migrations? #:nodoc: true end + + def supports_savepoints? #:nodoc: + true + end def native_database_types #:nodoc: NATIVE_DATABASE_TYPES @@ -349,6 +353,17 @@ module ActiveRecord # Transactions aren't supported end + def create_savepoint + execute("SAVEPOINT #{current_savepoint_name}") + end + + def rollback_to_savepoint + execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}") + end + + def release_savepoint + execute("RELEASE SAVEPOINT #{current_savepoint_name}") + end def add_limit_offset!(sql, options) #:nodoc: if limit = options[:limit] diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb index 6685cb8663..5a8d99924d 100644 --- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb +++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb @@ -272,6 +272,10 @@ module ActiveRecord def supports_ddl_transactions? true end + + def supports_savepoints? + true + end # Returns the configured supported identifier length supported by PostgreSQL, # or report the default of 63 on PostgreSQL 7.x. @@ -528,45 +532,28 @@ module ActiveRecord def rollback_db_transaction execute "ROLLBACK" end + + if PGconn.public_method_defined?(:transaction_status) + # ruby-pg defines Ruby constants for transaction status, + # ruby-postgres does not. + PQTRANS_IDLE = defined?(PGconn::PQTRANS_IDLE) ? PGconn::PQTRANS_IDLE : 0 + + def outside_transaction? + @connection.transaction_status == PQTRANS_IDLE + end + end - # ruby-pg defines Ruby constants for transaction status, - # ruby-postgres does not. - PQTRANS_IDLE = defined?(PGconn::PQTRANS_IDLE) ? PGconn::PQTRANS_IDLE : 0 - - # Check whether a transaction is active. - def transaction_active? - @connection.transaction_status != PQTRANS_IDLE + def create_savepoint + execute("SAVEPOINT #{current_savepoint_name}") end - # Wrap a block in a transaction. Returns result of block. - def transaction(start_db_transaction = true) - transaction_open = false - begin - if block_given? - if start_db_transaction - begin_db_transaction - transaction_open = true - end - yield - end - rescue Exception => database_transaction_rollback - if transaction_open && transaction_active? - transaction_open = false - rollback_db_transaction - end - raise unless database_transaction_rollback.is_a? ActiveRecord::Rollback - end - ensure - if transaction_open && transaction_active? - begin - commit_db_transaction - rescue Exception => database_transaction_rollback - rollback_db_transaction - raise - end - end + def rollback_to_savepoint + execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}") end + def release_savepoint + execute("RELEASE SAVEPOINT #{current_savepoint_name}") + end # SCHEMA STATEMENTS ======================================== diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb index 129306d335..039d5a4e8e 100644 --- a/activerecord/lib/active_record/fixtures.rb +++ b/activerecord/lib/active_record/fixtures.rb @@ -938,6 +938,7 @@ module ActiveRecord end ActiveRecord::Base.connection.increment_open_transactions ActiveRecord::Base.connection.begin_db_transaction + ActiveRecord::Base.connection.transactional_fixtures = true # Load fixtures for every test. else Fixtures.reset_cache @@ -960,6 +961,7 @@ module ActiveRecord if run_in_transaction? && ActiveRecord::Base.connection.open_transactions != 0 ActiveRecord::Base.connection.rollback_db_transaction ActiveRecord::Base.connection.decrement_open_transactions + ActiveRecord::Base.connection.transactional_fixtures = false end ActiveRecord::Base.clear_active_connections! end diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb index 0a27ea980e..aaa298dc49 100644 --- a/activerecord/lib/active_record/transactions.rb +++ b/activerecord/lib/active_record/transactions.rb @@ -120,16 +120,69 @@ module ActiveRecord # end # # One should restart the entire transaction if a StatementError occurred. + # + # == Nested transactions + # + # #transaction calls can be nested. By default, this makes all database + # statements in the nested transaction block become part of the parent + # transaction. For example: + # + # User.transaction do + # User.create(:username => 'Kotori') + # User.transaction do + # User.create(:username => 'Nemu') + # raise ActiveRecord::Rollback + # end + # end + # + # User.find(:all) # => empty + # + # It is also possible to treat a certain #transaction call as its own + # sub-transaction, by passing <tt>:nest => true</tt> to #transaction. If + # anything goes wrong inside that transaction block, then the parent + # transaction will remain unaffected. For example: + # + # User.transaction do + # User.create(:username => 'Kotori') + # User.transaction(:nest => true) do + # User.create(:username => 'Nemu') + # raise ActiveRecord::Rollback + # end + # end + # + # User.find(:all) # => Returns only Kotori + # + # Most databases don't support true nested transactions. At the time of + # writing, the only database that we're aware of that supports true nested + # transactions, is MS-SQL. Because of this, Active Record emulates nested + # transactions by using savepoints. See + # http://dev.mysql.com/doc/refman/5.0/en/savepoints.html + # for more information about savepoints. + # + # === Caveats + # + # If you're on MySQL, then do not use DDL operations in nested transactions + # blocks that are emulated with savepoints. That is, do not execute statements + # like 'CREATE TABLE' inside such blocks. This is because MySQL automatically + # releases all savepoints upon executing a DDL operation. When #transaction + # is finished and tries to release the savepoint it created earlier, a + # database error will occur because the savepoint has already been + # automatically released. The following example demonstrates the problem: + # + # Model.connection.transaction do # BEGIN + # Model.connection.transaction(true) do # CREATE SAVEPOINT rails_savepoint_1 + # Model.connection.create_table(...) # rails_savepoint_1 now automatically released + # end # RELEASE savepoint rails_savepoint_1 + # # ^^^^ BOOM! database error! + # end module ClassMethods # See ActiveRecord::Transactions::ClassMethods for detailed documentation. - def transaction(&block) - connection.increment_open_transactions - - begin - connection.transaction(connection.open_transactions == 1, &block) - ensure - connection.decrement_open_transactions - end + def transaction(options = {}, &block) + options.assert_valid_keys :nest + + # See the API documentation for ConnectionAdapters::DatabaseStatements#transaction + # for useful information. + connection.transaction(options[:nest], &block) end end |