Question

I have a database used by several clients. I don’t really want surrogate incremental key values to bleed between clients. I want the numbering to start from 1 and be client specific.

I’ll use a two-part composite key of the tenant_id as well as an incremental id.

What is the best way to create an incremental key per tenant?

I am using SQL Server Azure. I’m concerned about locking tables, duplicate keys, etc. I’d typically set the primary key to IDENTITY and move on.

Thanks

Answer 1

Are you planning on using SQL Azure Federations in the future? If so, the current version of SQL Azure Federations does not support the use of IDENTITY as part of a clustered index. See this What alternatives exist to using guid as clustered index on tables in SQL Azure (Federations) for more details.

If you haven’t looked at Federations yet, you might want to check it out as it provides an interesting way to both shard the database and for tenant isolation within the database.

Depending upon your end goal, using Federations you might be able to use a GUID as the primary clustered index on the table and also use an incremental INT IDENTITY field on the table. This INT IDENTITY field could be shown to end-users. If you are federating on the TenantID each “Tenant table” effectively becomes a silo (as I understand it at least) so the use of IDENTITY on a field within that table would effectively be an ever increasing auto generated value which increments within a given Tenant.

When \ if data is merged together (combining data from multiple Tenants) you would wind up with collisions on this INT IDENTITY field (hence why IDENTITY isn’t supported as a primary key in federations) but as long as you aren’t using this field as a unique identifier within the system at large you should be ok.