diff options
Diffstat (limited to 'activerecord')
| -rw-r--r-- | activerecord/lib/active_record/transactions.rb | 20 |
1 files changed, 11 insertions, 9 deletions
diff --git a/activerecord/lib/active_record/transactions.rb b/activerecord/lib/active_record/transactions.rb index f8c6c7b53e..443f318067 100644 --- a/activerecord/lib/active_record/transactions.rb +++ b/activerecord/lib/active_record/transactions.rb @@ -131,7 +131,7 @@ module ActiveRecord # # +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: + # transaction. For example, the following behavior may be surprising: # # User.transaction do # User.create(:username => 'Kotori') @@ -141,13 +141,15 @@ module ActiveRecord # end # end # - # User.find(:all) # => Returns Kotori and Nemu, because - # AcriveRecord::Rollback do not re-raise + # creates both "Kotori" and "Nemu". Reason is the <tt>ActiveRecord::Rollback</tt> + # exception in the nested block does not issue a ROLLBACK. Since these exceptions + # are captured in transaction blocks, the parent block does not see it and the + # real transaction is committed. # - # It is also possible to requires a sub-transaction by passing - # <tt>:requires_new => true</tt>. If anything goes wrong, the - # database rolls back to the beginning of the sub-transaction - # without rolling back the parent transaction. For example: + # In order to get a ROLLBACK for the nested transaction you may ask for a real + # sub-transaction by passing <tt>:requires_new => true</tt>. If anything goes wrong, + # the database rolls back to the beginning of the sub-transaction without rolling + # back the parent transaction. If we add it to the previous example: # # User.transaction do # User.create(:username => 'Kotori') @@ -157,12 +159,12 @@ module ActiveRecord # end # end # - # User.find(:all) # => Returns only Kotori + # only "Kotori" is created. (This works on MySQL and PostgreSQL, but not on SQLite3.) # # 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 + # transactions by using savepoints on MySQL and PostgreSQL. See # http://dev.mysql.com/doc/refman/5.0/en/savepoints.html # for more information about savepoints. # |