Wallaby

Appearance

Multi-tenancy (per-row scoping) ​

Sometimes the enrichment DbContext and/or destination must be derived from the changed row's own data. The canonical case is multi-tenancy: a row carries a TenantId, enrichment must run against a context scoped to that tenant (a tenant connection, or a global query filter), and the result must land in a per-tenant destination (e.g. an index per tenant).

API ​

csharp
cdc.UseScopedContext((scopeKey, services) => new AppDbContext(OptionsForTenant(scopeKey)))
   .Map<Order>()
       .ScopedBy(o => o.TenantId)                  // derive the scope key from the change
       .UsingTransform<OrderTransform>()           // transform receives the tenant-scoped DbContext
       .ScopedDestination(key => $"orders_{key}"); // per-tenant destination (optional)
  • ScopedBy(o => o.TenantId) extracts a scope key from each change.
  • UseScopedContext((key, services) => ...) builds the enrichment DbContext for a scope key - point it at a tenant connection string, or hand the context the tenant so a global query filter applies.
  • ScopedDestination(key => ...) computes the destination per scope key. Without it, the scope only affects the enrichment context and the fixed ToSink(...) destination is used.

Each is opt-in and independent; with neither, behavior is exactly as normal (one shared context per batch).

Internals ​

For each transaction, Wallaby will sub-group the changes by scope key and invoke the transform once per scope with a DbContext built for that scope. Backfill operations flow through the same router, so the scope will apply too.

Deletes and REPLICA IDENTITY ​

Deletes never reach a transform, but a scoped destination still needs the scope key to target the right destination, and a default delete only carries the primary key. So ScopedDestination marks its table to require REPLICA IDENTITY FULL. With full replica identity the old-row values carry the scope key on delete. Enrichment-only scoping (ScopedBy without ScopedDestination) has no such requirement, since non-delete changes carry the full new row.