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author | Eugene Kenny <elkenny@gmail.com> | 2018-08-13 16:51:54 +0100 |
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committer | Eugene Kenny <elkenny@gmail.com> | 2018-08-13 16:51:54 +0100 |
commit | 0ac81ee6ff3d1625fdbcc40b12c00cbff2208077 (patch) | |
tree | 525e64b50d3eaa9e0d545f170510ae1b9ffd67b1 /activerecord/lib/active_record/connection_adapters/abstract/transaction.rb | |
parent | f2970a08b57ebcdb9cbf8eec5d10a7f04eb7b9d3 (diff) | |
download | rails-0ac81ee6ff3d1625fdbcc40b12c00cbff2208077.tar.gz rails-0ac81ee6ff3d1625fdbcc40b12c00cbff2208077.tar.bz2 rails-0ac81ee6ff3d1625fdbcc40b12c00cbff2208077.zip |
Omit BEGIN/COMMIT statements for empty transactions
If a transaction is opened and closed without any queries being run, we
can safely omit the `BEGIN` and `COMMIT` statements, as they only exist
to modify the connection's behaviour inside the transaction. This
removes the overhead of those statements when saving a record with no
changes, which makes workarounds like `save if changed?` unnecessary.
This implementation buffers transactions inside the transaction manager
and materializes them the next time the connection is used. For this to
work, the adapter needs to guard all connection use with a call to
`materialize_transactions`. Because of this, adapters must opt in to get
this new behaviour by implementing `supports_lazy_transactions?`.
If `raw_connection` is used to get a reference to the underlying
database connection, the behaviour is disabled and transactions are
opened eagerly, as we can't know how the connection will be used.
However when the connection is checked back into the pool, we can assume
that the application won't use the reference again and reenable lazy
transactions. This prevents a single `raw_connection` call from
disabling lazy transactions for the lifetime of the connection.
Diffstat (limited to 'activerecord/lib/active_record/connection_adapters/abstract/transaction.rb')
-rw-r--r-- | activerecord/lib/active_record/connection_adapters/abstract/transaction.rb | 76 |
1 files changed, 63 insertions, 13 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb index b59df2fff7..564b226b39 100644 --- a/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb @@ -91,12 +91,14 @@ module ActiveRecord end class Transaction #:nodoc: - attr_reader :connection, :state, :records, :savepoint_name + attr_reader :connection, :state, :records, :savepoint_name, :isolation_level def initialize(connection, options, run_commit_callbacks: false) @connection = connection @state = TransactionState.new @records = [] + @isolation_level = options[:isolation] + @materialized = false @joinable = options.fetch(:joinable, true) @run_commit_callbacks = run_commit_callbacks end @@ -105,6 +107,14 @@ module ActiveRecord records << record end + def materialize! + @materialized = true + end + + def materialized? + @materialized + end + def rollback_records ite = records.uniq while record = ite.shift @@ -141,24 +151,30 @@ module ActiveRecord end class SavepointTransaction < Transaction - def initialize(connection, savepoint_name, parent_transaction, options, *args) - super(connection, options, *args) + def initialize(connection, savepoint_name, parent_transaction, *args) + super(connection, *args) parent_transaction.state.add_child(@state) - if options[:isolation] + if isolation_level raise ActiveRecord::TransactionIsolationError, "cannot set transaction isolation in a nested transaction" end - connection.create_savepoint(@savepoint_name = savepoint_name) + + @savepoint_name = savepoint_name + end + + def materialize! + connection.create_savepoint(savepoint_name) + super end def rollback - connection.rollback_to_savepoint(savepoint_name) + connection.rollback_to_savepoint(savepoint_name) if materialized? @state.rollback! end def commit - connection.release_savepoint(savepoint_name) + connection.release_savepoint(savepoint_name) if materialized? @state.commit! end @@ -166,22 +182,23 @@ module ActiveRecord end class RealTransaction < Transaction - def initialize(connection, options, *args) - super - if options[:isolation] - connection.begin_isolated_db_transaction(options[:isolation]) + def materialize! + if isolation_level + connection.begin_isolated_db_transaction(isolation_level) else connection.begin_db_transaction end + + super end def rollback - connection.rollback_db_transaction + connection.rollback_db_transaction if materialized? @state.full_rollback! end def commit - connection.commit_db_transaction + connection.commit_db_transaction if materialized? @state.full_commit! end end @@ -190,6 +207,9 @@ module ActiveRecord def initialize(connection) @stack = [] @connection = connection + @has_unmaterialized_transactions = false + @materializing_transactions = false + @lazy_transactions_enabled = true end def begin_transaction(options = {}) @@ -203,11 +223,41 @@ module ActiveRecord run_commit_callbacks: run_commit_callbacks) end + transaction.materialize! unless @connection.supports_lazy_transactions? && lazy_transactions_enabled? @stack.push(transaction) + @has_unmaterialized_transactions = true if @connection.supports_lazy_transactions? transaction end end + def disable_lazy_transactions! + materialize_transactions + @lazy_transactions_enabled = false + end + + def enable_lazy_transactions! + @lazy_transactions_enabled = true + end + + def lazy_transactions_enabled? + @lazy_transactions_enabled + end + + def materialize_transactions + return if @materializing_transactions + return unless @has_unmaterialized_transactions + + @connection.lock.synchronize do + begin + @materializing_transactions = true + @stack.each { |t| t.materialize! unless t.materialized? } + ensure + @materializing_transactions = false + end + @has_unmaterialized_transactions = false + end + end + def commit_transaction @connection.lock.synchronize do transaction = @stack.last |