diff --git a/README.textile b/README.textile index f7c1e20..39c0772 100644 --- a/README.textile +++ b/README.textile @@ -21,16 +21,31 @@ Here is an overview of the strategies supported for each library: (Default strategy for each library is denoted in bold) -The ActiveRecord @:deletion@ strategy is useful for when the @:truncation@ strategy causes -locks (as reported by some Oracle DB users). The @:deletion@ option has been reported to -be faster than @:truncation@ in some cases as well. In general, the best approach is to use -@:transaction@ since it is the fastest. - Database Cleaner also includes a @null@ strategy (that does no cleaning at all) which can be used with any ORM library. You can also explicitly use it by setting your strategy to @nil@. For support or to discuss development please use the "Google Group":http://groups.google.com/group/database_cleaner. +h2(fastest). What strategy is fastest? + +For the SQL libraries the fastest option will be to use @:transaction@ as transactions are +simply rolled back. If you can use this strategy you should. However, if you wind up needing +to use multiple database connections in your tests (i.e. your tests run in a different proceess +than your application) then using this strategy becomes a bit more difficult. You can get around the +problem a number of ways. One common approach is to force all processes to use the same database +connection ("common ActiveRecord hack":http://blog.plataformatec.com.br/2011/12/three-tips-to-improve-the-performance-of-your-test-suite/) however this approach has been reported to result in +non-deterministic failures. Another approach is to have the transactions rolled back in the +application's process and relax the isolation level of the database (so the tests can read the +uncommited transactions). An easier, but slower, solution is to use the @:truncation@ or +@:deletion@ strategy. + +So what is fastest out of @:deletion@ and @:truncation@? Well, it depends on your table structure +and what percentage of tables you populate in an average test. The reasoning is out the the +scope of this README but here is a "good SO answer on this topic for Postgres":http://stackoverflow.com/questions/11419536/postgresql-truncation-speed/11423886#11423886. Some people report +much faster speeds with @:deletion@ while others say @:truncation@ is faster for them. The best approach therefore +is it try all options on your test suite and see what is faster. If you are using ActiveRecord then take a look +at the "additional options":#ar_truncation available for @:truncation@. + h2. Dependencies Because database_cleaner supports multiple ORMs, it doesn't make sense to include all the dependencies @@ -82,21 +97,18 @@ strategy the remaining time. To accomplish this you can say: # then make the DatabaseCleaner.start and DatabaseCleaner.clean calls appropriately -h3. Minitest Example +h3(#ar_truncation). Additional ActiveRecord options for Truncation -
-DatabaseCleaner.strategy = :transaction
+The following options are available for ActiveRecord's @:truncation@ strategy _only_ for 
+MySQL and Postgres.
 
-class MiniTest::Spec
-  before :each do
-    DatabaseCleaner.start
-  end
+* @:pre_count@ - When set to @true@ this will check each table for existing rows before 
+truncating it.  This can speed up test suites when many of the tables to be truncated 
+are never populated. Defaults to @:false@. (Also, see the section on "What strategy is fastest?":#fastest)
+* @:reset_ids@ - This only matters when @:pre_count@ is used, and it will make sure that a 
+tables auto-incrementing id is reset even if there are no rows in the table (e.g. records 
+were created in the test but also removed before DatabaseCleaner gets to it). Defaults to @true@.
 
-  after :each do
-    DatabaseCleaner.clean
-  end
-end
-
h3. RSpec Example @@ -119,6 +131,22 @@ RSpec.configure do |config| end +h3. Minitest Example + +
+DatabaseCleaner.strategy = :transaction
+
+class MiniTest::Spec
+  before :each do
+    DatabaseCleaner.start
+  end
+
+  after :each do
+    DatabaseCleaner.clean
+  end
+end
+
+ h3. Cucumber Example Add this to your features/support/env.rb file: @@ -178,39 +206,9 @@ Configuration options h2. Why? -One of my motivations for writing this library was to have an easy way to -turn on what Rails calls "transactional_fixtures" in my non-rails -ActiveRecord projects. For example, Cucumber ships with a Rails world that -will wrap each scenario in a transaction. This is great, but what if you are -using ActiveRecord in a non-rails project? You used to have to copy-and-paste -the needed code, but with DatabaseCleaner you can now say: - -
-  #env.rb
-  require 'database_cleaner'
-  require 'database_cleaner/cucumber'
-  DatabaseCleaner.strategy = :transaction
-
- -Now lets say you are running your features and it requires that another process be -involved (i.e. Selenium running against your app's server.) You can simply change -your strategy type: - -
-  #env.rb
-  require 'database_cleaner'
-  require 'database_cleaner/cucumber'
-  DatabaseCleaner.strategy = :truncation
-
- -You can have the best of both worlds and use the best one for the job: -
-  #env.rb
-  require 'database_cleaner'
-  require 'database_cleaner/cucumber'
-  DatabaseCleaner.strategy = (ENV['SELENIUM'] == 'true') ? :truncation : :transaction
-
- +One of my motivations for writing this library was to have an easy way to turn on what Rails calls "transactional_fixtures" +in my non-rails ActiveRecord projects. After copying and pasting code to do this several times I decided to package it up +as a gem and same everyone a bit of time. h2. Common Errors