Membuat aplikasi multi-penyewa menggunakan skema dan Rails PostgreSQL

Perbarui 5 Desember 2011

Terima kasih kepada Brad Robertson dan timnya, ada Permata apartemen . Ini sangat berguna dan melakukan banyak pekerjaan berat.

Namun, jika Anda akan mengutak-atik skema, saya sangat menyarankan untuk mengetahui cara kerjanya. Biasakan diri Anda dengan panduan Jerod Santo , jadi Anda akan tahu apa yang kurang lebih dilakukan oleh permata Apartemen.

Pembaruan 20 Agustus 2011 11:23 GMT+8

Seseorang membuat postingan blog dan berjalan melalui seluruh proses ini dengan cukup baik.

Pembaruan 11 Mei 2010 11:26 GMT+8

Sejak tadi malam saya bisa mendapatkan metode untuk bekerja yang membuat skema baru dan memuat schema.rb ke dalamnya. Tidak yakin apakah yang saya lakukan benar (tampaknya berfungsi dengan baik, sejauh ini) tetapi setidaknya selangkah lebih dekat. Jika ada cara yang lebih baik, beri tahu saya.

  module SchemaUtils
   def self.add_schema_to_path(schema)
    conn = ActiveRecord::Base.connection
    conn.execute "SET search_path TO #{schema}, #{conn.schema_search_path}"
   end

   def self.reset_search_path
    conn = ActiveRecord::Base.connection
    conn.execute "SET search_path TO #{conn.schema_search_path}"
   end

   def self.create_and_migrate_schema(schema_name)
    conn = ActiveRecord::Base.connection

    schemas = conn.select_values("select * from pg_namespace where nspname != 'information_schema' AND nspname NOT LIKE 'pg%'")

    if schemas.include?(schema_name)
     tables = conn.tables
     Rails.logger.info "#{schema_name} exists already with these tables #{tables.inspect}"
    else
     Rails.logger.info "About to create #{schema_name}"
     conn.execute "create schema #{schema_name}"
    end

    # Save the old search path so we can set it back at the end of this method
    old_search_path = conn.schema_search_path

    # Tried to set the search path like in the methods above (from Guy Naor)
    # [METHOD 1]: conn.execute "SET search_path TO #{schema_name}"
    # But the connection itself seems to remember the old search path.
    # When Rails executes a schema it first asks if the table it will load in already exists and if :force => true. 
    # If both true, it will drop the table and then load it. 
    # The problem is that in the METHOD 1 way of setting things, ActiveRecord::Base.connection.schema_search_path still returns $user,public.
    # That means that when Rails tries to load the schema, and asks if the tables exist, it searches for these tables in the public schema.
    # See line 655 in Rails 2.3.5 activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
    # That's why I kept running into this error of the table existing when it didn't (in the newly created schema).
    # If used this way [METHOD 2], it works. ActiveRecord::Base.connection.schema_search_path returns the string we pass it.
    conn.schema_search_path = schema_name

    # Directly from databases.rake. 
    # In Rails 2.3.5 databases.rake can be found in railties/lib/tasks/databases.rake
    file = "#{Rails.root}/db/schema.rb"
    if File.exists?(file)
     Rails.logger.info "About to load the schema #{file}"
     load(file)
    else
     abort %{#{file} doesn't exist yet. It's possible that you just ran a migration!}
    end

    Rails.logger.info "About to set search path back to #{old_search_path}."
    conn.schema_search_path = old_search_path
   end
  end