Multitenancy

AshClickhouse supports Ash's multitenancy feature. Two strategies are available, configured on the resource via Ash's multitenancy DSL:

• Database-based — the tenant becomes part of the table qualifier ("tenant_db"."table").
• Attribute-based — the tenant is applied as a filter on a tenant column.

Multitenancy is reported as supported by the data layer (can?(:multitenancy)).

Enabling multitenancy

defmodule MyApp.Post do
  use Ash.Resource,
    data_layer: AshClickhouse.DataLayer,
    domain: MyApp.Domain

  import AshClickhouse.DataLayer.Dsl.Macros

  clickhouse do
    table "posts"
    repo MyApp.Repo
  end

  multitenancy do
    strategy :attribute
    attribute :tenant_id
  end

  attributes do
    uuid_primary_key :id
    attribute :tenant_id, :string
    attribute :title, :string
  end
end

Setting the tenant

The data layer applies the tenant through set_tenant/3:

MyApp.Post
|> Ash.Query.set_tenant("org_123")
|> Ash.read!()

For database-based multitenancy, the tenant is resolved into the qualified table name at query time. For attribute-based multitenancy, a filter on the tenant column is added to every query (and combined with any base_filter).

Interaction with base_filter and default_context

• base_filter (resource DSL) is always applied on top of tenant scoping.
• default_context (resource DSL) is merged into every query/changeset, so you can seed tenant-like context there if needed.

Notes

• ClickHouse has no row-level security; attribute-based multitenancy is enforced by the data layer adding filters, not by the database.
• Ensure the tenant column exists in your schema (it is a normal attribute).