已存在的Rails自动分配ID [英] Rails auto-assigning id that already exists
问题描述
我这样创建新记录:
truck = Truck.create(:name=>name, :user_id=>2)
我的数据库当前有数千个卡车实体，但是我以一些可用的方式将ID分配给了其中的几个.因此，发生的事情是rails创建id = 150的项目，并且工作正常.但是随后它尝试创建一个项目并将其分配为id = 151，但是该id可能已经存在，所以我看到此错误:
My database currently has several thousand entities for truck, but I assigned the id's to several of them, in a way that left some id's available. So what's happening is rails creates item with id = 150 and it works fine. But then it tries to create an item and assign it id = 151, but that id may already exist, so I'm seeing this error:
ActiveRecord::RecordNotUnique (PG::Error: ERROR: duplicate key value violates unique constraint "companies_pkey"
DETAIL: Key (id)=(151) already exists.
ActiveRecord::RecordNotUnique (PG::Error: ERROR: duplicate key value violates unique constraint "companies_pkey"
DETAIL: Key (id)=(151) already exists.
下次我执行该操作时，它将简单地分配ID 152，如果尚未使用该值，它将很好地工作.如何在分配ID之前让Rails检查ID是否已经存在?
And the next time I run the action, it will simply assign the id 152, which will work fine if that value isn't already taken. How can I get rails to check whether an ID already exists before it assigns it?
谢谢！
编辑
卡车ID是要重复的内容.用户已经存在，并且在这种情况下为常数.实际上，这是我必须处理的遗留问题.一种选择是重新创建表，此时让rails自动分配每个id.我开始认为这可能是最好的选择，因为我还有其他一些问题，但是这样做的迁移将非常复杂，因为Truck是许多其他表中的外键.是否有一种简单的方法可以使Rails创建一个具有已存储在Truck下的相同数据，具有自动分配的ID并维护所有现有关系的新表?
The Truck id is what is being duplicated. The user already exists and is a constant in this case. It actually is a legacy issue that I have to deal with. One option, is to re-create the table at let rails auto assign every id this time around. I'm beginning to think this may be the best choice because I'm have a few other problems, but the migration for doing this would be very complicated because Truck is a foreign key in so many other tables. Would there be a simple way to have rails create a new table with the same data already stored under Truck, with auto-assigned ID's and maintaining all existing relationships?
推荐答案
Rails可能使用了内置的PostgreSQL序列.序列的想法是只能使用一次.
Rails is probably using the built-in PostgreSQL sequence. The idea of a sequence is that it is only used once.
最简单的解决方案是使用以下查询将company.id列的序列设置为表中的最高值:
The simplest solution is to set the sequence for your company.id column to the highest value in the table with a query like this:
SELECT setval('company_id_seq', (SELECT max(id) FROM company));
我猜您的序列名称为"company_id_seq"，表名称为"company"和列名称为"id" ...请用正确的名称替换它们.您可以使用SELECT pg_get_serial_sequence('tablename', 'columname');获取序列名称，或使用\d tablename查看表定义.
I am guessing at your sequence name "company_id_seq", table name "company", and column name "id" ... please replace them with the correct ones. You can get the sequence name with SELECT pg_get_serial_sequence('tablename', 'columname'); or look at the table definition with \d tablename.
另一种解决方案是覆盖公司类中的save()方法，以便在保存之前手动为新行设置公司ID.
An alternate solution is to override the save() method in your company class to manually set the company id for new rows before saving.
这篇关于已存在的Rails自动分配ID的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
