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Diffstat (limited to 'guides/source/active_record_migrations.md')
| -rw-r--r-- | guides/source/active_record_migrations.md | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md index 6e7e29ed60..ab3af438f5 100644 --- a/guides/source/active_record_migrations.md +++ b/guides/source/active_record_migrations.md @@ -21,7 +21,7 @@ Migration Overview ------------------ Migrations are a convenient way to -[alter your database schema over time](http://en.wikipedia.org/wiki/Schema_migration) +[alter your database schema over time](https://en.wikipedia.org/wiki/Schema_migration) in a consistent and easy way. They use a Ruby DSL so that you don't have to write SQL by hand, allowing your schema and changes to be database independent. @@ -353,8 +353,7 @@ create_table :products, options: "ENGINE=BLACKHOLE" do |t| end ``` -will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table -(when using MySQL or MariaDB, the default is `ENGINE=InnoDB`). +will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table. Also you can pass the `:comment` option with any description for the table that will be stored in database itself and can be viewed with database administration @@ -972,11 +971,11 @@ on. Because this is database-independent, it could be loaded into any database that Active Record supports. This could be very useful if you were to distribute an application that is able to run against multiple databases. -There is however a trade-off: `db/schema.rb` cannot express database specific -items such as triggers, stored procedures or check constraints. While in a -migration you can execute custom SQL statements, the schema dumper cannot -reconstitute those statements from the database. If you are using features like -this, then you should set the schema format to `:sql`. +NOTE: `db/schema.rb` cannot express database specific items such as triggers, +sequences, stored procedures or check constraints, etc. Please note that while +custom SQL statements can be run in migrations, these statements cannot be reconstituted +by the schema dumper. If you are using features like this, then you +should set the schema format to `:sql`. Instead of using Active Record's schema dumper, the database's structure will be dumped using a tool specific to the database (via the `db:structure:dump` |