Question

在我的Rails应用程序中，我有一个名为Rutinas的模型。一段时间后，我需要在表格中添加一些列，以便生成迁移20171116094810_add_votos_y_veces_asignada_to_rutinas.rb：

class AddVotosYVecesAsignadaToRutinas < ActiveRecord::Migration[5.1]
  def change
    add_column :rutinas, :votos_pos, :integer, :default => 0
    add_column :rutinas, :votos_neg, :integer, :default => 0
    add_column :rutinas, :veces_asig, :integer, :default => 0
  end
end

在进行其他一些迁移之后，我需要删除我不再需要的两列votos_pos和votos_neg，因此我生成了另一个迁移20171117092026_remove_votos_from_rutinas.rb：

class RemoveVotosFromRutinas < ActiveRecord::Migration[5.1]
  def change
    remove_column :rutinas, :votos_pos, :integer
    remove_column :rutinas, :votos_neg, :integer
  end
end

问题在于，当我运行rails db:migrate来迁移最后一次迁移时，它会抛出一些奇怪的错误：

== 20171117092026 RemoveVotosFromRutinas: migrating ===========================
-- remove_column(:rutinas, :votos_pos)
rails aborted!
StandardError: An error has occurred, this and all later migrations canceled:

SQLite3::ConstraintException: FOREIGN KEY constraint failed: DROP TABLE "rutinas"
C:/Users/pepe/Dropbox/pepe/KeepMeFit/KeepMeFit-git/db/migrate/20171117092026_remove_votos_from_rutinas.rb:3:in `change'
bin/rails:4:in `require'
bin/rails:4:in `<main>'

Caused by:
ActiveRecord::InvalidForeignKey: SQLite3::ConstraintException: FOREIGN KEY constraint failed: DROP TABLE "rutinas"
C:/Users/pepe/Dropbox/pepe/KeepMeFit/KeepMeFit-git/db/migrate/20171117092026_remove_votos_from_rutinas.rb:3:in `change'
bin/rails:4:in `require'
bin/rails:4:in `<main>'

Caused by:
SQLite3::ConstraintException: FOREIGN KEY constraint failed
C:/Users/pepe/Dropbox/pepe/KeepMeFit/KeepMeFit-git/db/migrate/20171117092026_remove_votos_from_rutinas.rb:3:in `change'
bin/rails:4:in `require'
bin/rails:4:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

我的Rutinas模型如下：

class Rutina < ActiveRecord::Base    
  validates_presence_of :nombre

  belongs_to :user
  has_many :repeticions
  has_many :entrenos, dependent: :destroy
  has_many :votos

  has_many :days, dependent: :destroy

  def get_array_dias
    (1..self.repeticions.last.dia).to_a
  end

  def get_number_of_days
    days.count
  end

end

用户，repeticion，entreno，voto和day是与我试图删除的列无关的其他表。也就是说，这些列不是外键，任何外键都引用这些列。

Answer 1

似乎问题是SQLite的限制。如果您查看了您将看到的文档，它只允许添加列，但不能删除一列：https://sqlite.org/lang_altertable.html

当删除列时，迁移实际上可能会删除整个表并重新创建它。这将解释DROP TABLE "rutinas"消息。当然，如果删除了while表，那么某些外键约束就会失败。

删除列Rails时出错

1 个答案: