Guo Xiang Tan 40fa96777d FEATURE: Post deployment migrations. (#6406) ... This moves us away from the delayed drops pattern which was problematic on two counts. First, it uses a hardcoded "delay for" duration which may be too short for certain deployment strategies. Second, delayed drop doesn't ensure that it only runs after the latest application code has been deployed. If the migration runs and the application code fails to deploy, running the migration after "delay for" has been met will cause the application to blow up. The new strategy allows post deployment migrations to be skipped if the env `SKIP_POST_DEPLOYMENT_MIGRATIONS` is provided. ``` SKIP_POST_DEPLOYMENT_MIGRATIONS=1 rake db:migrate -> deploy app servers SKIP_POST_DEPLOYMENT_MIGRATIONS=0 rake db:migrate ``` To aid with the generation of a post deployment migration, a generator has been added. Simply run `rails generate post_migration`.		2018-10-08 15:47:38 +08:00
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drop_table
remove_column
rename_column
rename_table