Ruby-on-rails 如何通过迁移向现有索引添加“唯一”约束
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How to add `unique` constraint to already existing index by migration
提问by ironsand
How can I add unique: trueconstraint to already existing index in Rails database?
如何unique: true向 Rails 数据库中现有的索引添加约束？
I tried to migrate by
我试图通过
def change
add_index :editabilities, [:user_id, :list_id], unique: true
end
but migration fails with a error like this.
但是迁移失败并出现这样的错误。
Index name 'index_editabilities_on_user_id_and_list_id' on table 'editabilities' already exists
表 'editabilities' 上的索引名称 'index_editabilities_on_user_id_and_list_id' 已经存在
I'm using rails4 and postgresql.
我正在使用 rails4 和 postgresql。
回答by Baldrick
Remove the old index and add it again with the new constraint:
删除旧索引并使用新约束再次添加它：
def change
remove_index :editabilities, [:user_id, :list_id]
add_index :editabilities, [:user_id, :list_id], unique: true
end
回答by asiniy
Faster way using add_index_options:
使用add_index_options 的更快方法：
def change
add_index_options :editabilities, [:user_id, :list_id], unique: true
end
