Db: test: clone、 db: test: clone_struct、 db: test: load 和 db: test: ready 之间的区别是什么？

你必须承认，对于一个刚接触 Rails 和数据库的新手来说，rubyonRails.org 上的官方解释让这四个任务听起来完全一样。语录:

rake db:test:clone  Recreate the test database from
the current environment’s database schema


rake db:test:clone_structure    Recreate the test database from the
development structure


rake db:test:load   Recreate the test database from the current schema.rb


rake db:test:prepare    Check for pending migrations and load the test schema

我甚至不知道结构和模式之间的区别。加载当前环境的模式和只加载 schema.rb 有什么区别？

这些任务究竟有多相似(或不同) ？

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最佳答案

问得好。我被难住了，所以我潜入轨道源，拉起 database.rake。现在事情变得更加清楚了:

db:test:clone只是 db:schema:dump和 db:test:load的组合:
```
task :clone => %w(db:schema:dump db:test:load)
```

db:test:clone_structure uses the {rails_env}_structure.sql file:

task :clone_structure => [ 'db:structure:dump', 'db:test:purge' ] do
# skipped some code, here's what happens for MySQL:
ActiveRecord::Base.establish_connection(:test)
# ...
IO.readlines("#{Rails.root}/db/#{Rails.env}_structure.sql").join.split("\n\n").each do |table|
ActiveRecord::Base.connection.execute(table)
end
end

db:test:load is the same as db:schema:load, but invokes it on the test database:

task :load => 'db:test:purge' do
ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations['test'])
# ...
db_namespace['schema:load'].invoke
end

db:test:prepare alerts you if any migrations are pending, and if not, either runs db:test:clone_structure (using the {rails_env}_structure.sql file) or db:test:load (using the schema.rb file), depending on the schema format (this is a little confusing to me, maybe someone else can expand on it):
```
task :prepare => 'db:abort_if_pending_migrations' do
# ...
db_namespace[{ :sql  => 'test:clone_structure', :ruby => 'test:load' }[ActiveRecord::Base.schema_format]].invoke
end
```

Hope this clears it up! Again, going through the database.rake file is easy and will clear up any other questions you might have. That link goes to the line that is the beginning of the :test namespace.