Firstly, I'd keep this display ID (maybe "member ID") separate from users.id.
Any non-standard behaviour there is asking for trouble. There's a lot of
convention built up in activerecord around having a single artificial
integer PK, and veering from this standard isn't worth the trouble it
causes. (We used some composite PKs for a time at TC as part of a migration
strategy, and they were very inconvenient to work with.)
I'd recommend having a unique users.id column like normal, and then a
separate member_id that you use for routing, which is unique within each
tenant (enforced in the DB).
I'd add a unique index to the users table on (tenant_id, member_id):
add_index :users, [:tenant_id, :member_id], unique: true
Then I'd add a validation in the model, for reasonable error messages (the
real "validation" is done by the DB's unique index):
validates :member_id, presence: true, uniqueness: {scope: :tenant_id}
Then I'd auto-populate that field before the model's validation happens.
before_validation :assign_member_id_if_required
def assign_member_id_if_required
self.member_id ||= begin
max_member_id = tenant.users.order('member_id
DESC').limit(1).pluck(:member_id).first
(max_member_id || 0) + 1
end
end
That will query efficiently:
SELECT "users"."member_id" FROM "users" WHERE "users"."tenant_id" =
12345 ORDER BY member_id DESC LIMIT 1
- Ben
On 3 April 2013 20:29, Rich Buggy <r...@zoombugmedia.com> wrote:
> Hi everyone,
>
> I'm building a multi-tenant application and I'd like some of the ID's to
> be per tenant. It's using the path based multi-tenant approach. For example
> - /:account/invoices/:id
>
> I've got the routing working correctly but the ID's are being generated
> automatically so they are unique across the application, not just the
> tenant. This isn't ideal because each tenant should start from 1.
>
> I already store the next id in the tenant table so they can choose to
> start from a number other than 1. This is important as someone with
> existing data may decide to not start from 1. I think there are a number of
> ways I can deal with this.
>
> 1. If I was doing this without rails I'd make the tenant_id + id a
> composite field and set the id manually when creating the record. Is there
> are an easy way to do this with rails?
>
> 2. I could add number field and accept that number != id. This is easy but
> ugly because /demo/invoices/123456 could be invoice 1
>
> 3. I could add a number field and try to muck with the routing so it used
> number instead of id
>
> Does anyone know of a good guide or blog post on how to do this?
>
> Rich
>
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Cheers
Ben
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