README.md in scenic-1.7.0 vs README.md in scenic-1.8.0
- old
+ new
@@ -2,11 +2,10 @@
[](https://github.com/scenic-views/scenic/actions/workflows/ci.yml)
[](http://inch-ci.org/github/scenic-views/scenic)
-[](https://houndci.com)
Scenic adds methods to `ActiveRecord::Migration` to create and manage database
views in Rails.
Using Scenic, you can bring the power of SQL views to your Rails application
@@ -84,40 +83,37 @@
update to the version 2 schema. All that's left for you to do is tweak the
schema in the new definition and run the `update_view` migration.
## What if I want to change a view without dropping it?
-The `update_view` statement used by default will drop your view then create
-a new version of it.
+The `update_view` statement used by default will drop your view then create a
+new version of it. This may not be desirable when you have complicated
+hierarchies of dependent views.
-This is not desirable when you have complicated hierarchies of views, especially
-when some of those views may be materialized and take a long time to recreate.
+Scenic offers a `replace_view` schema statement, resulting in a `CREATE OR
+REPLACE VIEW` SQL query which will update the supplied view in place, retaining
+all dependencies. Materialized views cannot be replaced in this fashion.
-You can use `replace_view` to generate a CREATE OR REPLACE VIEW SQL statement
-instead by adding the `--replace` option to the generate command:
+You can generate a migration that uses the `replace_view` schema statement by
+passing the `--replace` option to the `scenic:view` generator:
```sh
$ rails generate scenic:view search_results --replace
create db/views/search_results_v02.sql
create db/migrate/[TIMESTAMP]_update_search_results_to_version_2.rb
```
-See Postgres documentation on how this works:
-http://www.postgresql.org/docs/current/static/sql-createview.html
-
The migration will look something like this:
```ruby
class UpdateSearchResultsToVersion2 < ActiveRecord::Migration
def change
replace_view :search_results, version: 2, revert_to_version: 1
end
end
```
-You can run the migration and the view will be replaced instead.
-
## Can I use this view to back a model?
You bet! Using view-backed models can help promote concepts hidden in your
relational data to first-class domain objects and can clean up complex
ActiveRecord or ARel queries. As far as ActiveRecord is concerned, a view is
@@ -125,10 +121,15 @@
```ruby
class SearchResult < ApplicationRecord
belongs_to :searchable, polymorphic: true
+ # If you want to be able to call +Model.find+, you
+ # must declare the primary key. It can not be
+ # inferred from column information.
+ # self.primary_key = :id
+
# this isn't strictly necessary, but it will prevent
# rails from calling save, which would fail anyway.
def readonly?
true
end
@@ -246,9 +247,14 @@
* [`scenic-sqlserver-adapter`](<https://github.com/ClickMechanic/scenic_sqlserver_adapter>)
* [`scenic-oracle_adapter`](<https://github.com/cdinger/scenic-oracle_adapter>)
Please note that the maintainers of Scenic make no assertions about the
quality or security of the above adapters.
+
+**Related projects**
+
+- [`fx`](<https://github.com/teoljungberg/fx>) Versioned database functions and
+ triggers for Rails
## About
Scenic is used by some popular open source Rails apps:
[Mastodon](<https://github.com/mastodon/mastodon/>),