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docs, refactor docs about column modifiers. [ci skip] [Matthew Draper & Yves Senn]
This is a follow up to #15602 which rendered the guides in a weird state: > You can also specify some options just after the field type between curly braces. You can use the following modifiers: > `null` Allows or disallows `NULL` values in the column. > NOTE: `null` and `default` cannot be specified via command line. The modifiers are now moved into a separate section. The generator simply referes to that section. Related to #15583. /cc @JuanitoFatas Conflicts: guides/source/migrations.md
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@ -292,18 +292,10 @@ end
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You can append as many column name/type pairs as you want.
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### Supported Type Modifiers
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### Passing Modifiers
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You can also specify some options just after the field type between curly
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braces. You can use the following modifiers:
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* `limit` Sets the maximum size of the `string/text/binary/integer` fields.
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* `precision` Defines the precision for the `decimal` fields, representing the total number of digits in the number.
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* `scale` Defines the scale for the `decimal` fields, representing the number of digits after the decimal point.
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* `polymorphic` Adds a `type` column for `belongs_to` associations.
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* `null` Allows or disallows `NULL` values in the column.
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NOTE: `null` and `default` cannot be specified via command line.
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Some commonly used [type modifiers](#column-modifiers) can be passed directly on
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the command line. They are enclosed by curly braces and follow the field type:
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For instance, running:
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@ -322,6 +314,8 @@ class AddDetailsToProducts < ActiveRecord::Migration
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end
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```
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TIP: Have a look at the generators help output for further details.
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Writing a Migration
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-------------------
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@ -416,6 +410,21 @@ end
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removes the `description` and `name` columns, creates a `part_number` string
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column and adds an index on it. Finally it renames the `upccode` column.
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### Column Modifiers
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Column modifiers can be applied when creating or changing a column:
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* `limit` Sets the maximum size of the `string/text/binary/integer` fields.
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* `precision` Defines the precision for the `decimal` fields, representing the total number of digits in the number.
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* `scale` Defines the scale for the `decimal` fields, representing the number of digits after the decimal point.
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* `polymorphic` Adds a `type` column for `belongs_to` associations.
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* `null` Allows or disallows `NULL` values in the column.
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* `default` Allows to set a default value on the column. NOTE: If using a dynamic value (such as date), the default will only be calculated the first time (e.g. on the date the migration is applied.)
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* `index` Adds an index for the column.
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Some adapters may support additional options; see the adapter specific API docs
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for further information.
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### When Helpers aren't Enough
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If the helpers provided by Active Record aren't enough you can use the `execute`
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