Revert "Merge pull request #23366 from maclover7/add-configuation-ar-docs"

This reverts commit 96355e87cba247246234386b0af9273cc5d59db9, reversing
changes made to a00c36feea6c0271b5ad48a949ef294514fdef52.

See https://github.com/rails/rails/pull/23366#issuecomment-177714429

1 files changed, 0 insertions, 102 deletions

diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index 0932cc4829..fba89f9d13 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -375,105 +375,3 @@ and to roll it back, `rails db:rollback`.
 Note that the above code is database-agnostic: it will run in MySQL,
 PostgreSQL, Oracle and others. You can learn more about migrations in the
 [Active Record Migrations guide](migrations.html).
-
-Connecting to the Database
-----------------------
-
-### `config/database.yml`
-
-When managing connections to the database, the `config/database.yml` file is
-your best friend. This file helps to keep track of the adapter and
-authentication parameters you are using for every database
-environment in your application. This file is automatically
-generated in all new Rails applications that have Active Record
-enabled.
-
-Here's an example of what this file looks like:
-
-```yaml
-default: &default
-  adapter: sqlite3
-  pool: 5
-  timeout: 5000
-
-development:
-  <<: *default
-  database: db/development.sqlite3
-
-test:
-  <<: *default
-  database: db/test.sqlite3
-
-production:
-  <<: *default
-  database: db/production.sqlite3
-```
-
-As you can see, there are 3 different database configurations listed
-above. One for each of the Rails environments for this application
--- development, test, and production. As well, all three
-environments are sharing the same adapter, pool, and timeout
-settings, so this was extracted out to the "default" group. This
-extraction helps to keep your `config/database.yml` file DRY and easy
-to read.
-
-A small side note before the next topic -- the test database
-configured above will be deleted and restored both before and after
-every test run, so make sure you keep your environments' databases
-separated and siloed.
-
-### Connecting Manually
-
-In some special cases, you may want to establish connections for you
-Active Record models directly inside the model file itself. For this
-purpose, the `establish_connection` function was created. Say for
-example you have a `Message` model, like below:
-
-```ruby
-class Message < ActiveRecord::Base
-end
-```
-
-Also, say you want to have this `Message` model connect to a
-special "msg" database, instead of the one that the rest of the
-application is using. In this case, you would do as follows:
-
-Step 1: Add the `establish_connection` helper method to your model
-file:
-
-```ruby
-class Message < ActiveRecord::Base
-  establish_connection()
-end
-```
-
-Step 2: Add the configuration for this new database to your
-`config/database.yml` file, under the `msg` (or whichever name you
-choose) database name.
-
-Step 3: Turn this database name into a symbol. Remember, using string
-keys here is not supported! In this case, `msg`
-converts simply to `:msg`. If you are unsure of what the symbolized
-database name would be, simply boot up either an `irb` or `rails c`
-session, and type in the name of your database as a String, with a
-`.to_sym` at the end, as follows:
-
-```bash
-irb(main):001:0> "msg".to_sym
-=> :msg
-```
-
-Step 4: The last and final step! Simply use this symbolized
-database name as the sole parameter for the `establish_connection`
-method.
-
-```ruby
-class Message < ActiveRecord::Base
-  establish_connection(:msg)
-end
-```
-
-That's all there is to it! When configuring your database via the
-`config/database.yml` file, or connecting manually in your model,
-connecting to your database and making changes is easy when using Active
-Record.