Weasel.SqlServer: managed dynamic per-tenant partitioning API (parity with Weasel.Postgresql ManagedListPartitions)

[jeremydmiller]

Background

Weasel.SqlServer currently ships only RangePartitioning (ISqlServerPartitioning) with static, migration-time boundaries (additive ALTER PARTITION FUNCTION ... SPLIT RANGE). There is no managed/dynamic per-tenant partitioning API analogous to Weasel.Postgresql's ManagedListPartitions (Weasel.Postgresql/Tables/Partitioning/ManagedListPartitions.cs), which Marten relies on for per-tenant LIST partitions that grow as tenants are registered at runtime.

Why

Polecat (the SQL Server event store / "Marten for SQL Server") is implementing per-tenant event partitioning — JasperFx/polecat#163. The bounded-scan win comes from per-tenant sequences, but the issue also calls for physical per-tenant partitioning of pc_events / pc_streams. Without a managed-partition API in Weasel.SqlServer, Polecat would have to hand-roll runtime CREATE PARTITION FUNCTION / ALTER PARTITION FUNCTION ... SPLIT RANGE DDL as tenants join, which violates the "use Weasel for all schema management" principle and duplicates logic Weasel already owns for PostgreSQL.

Proposal

Add a managed per-tenant partitioning strategy to Weasel.SqlServer mirroring ManagedListPartitions:

• A ManagedRangePartitions (or ManagedTenantPartitions) ISqlServerPartitioning implementation that:
  • tracks the desired set of tenant boundary values (e.g. a tenant-ordinal column),
  • emits CREATE PARTITION FUNCTION + CREATE PARTITION SCHEME for the initial set,
  • computes an additive delta and emits SPLIT RANGE for newly-added tenants at migration time,
  • exposes a runtime "add tenant/boundary" operation (idempotent SPLIT RANGE) so a store can register a new tenant partition without a full migration.
• Consider a small registry-table convention (tenant_id → ordinal) so the partition column is a compact int rather than a varchar tenant id.

Acceptance

• Weasel.SqlServer exposes a managed per-tenant partitioning strategy with additive migration + runtime add-boundary
• Round-trip / delta tests (initial create, additive split, no-op, rebuild detection)
• Consumable by Polecat Making the foreign key correction for partition columns be a little s… #163's physical-partitioning follow-up

Related

• Per-tenant event partitioning + per-tenant daemon (#209 — SQL Server track) polecat#163 — per-tenant event partitioning (SQL Server track)
• Weasel.Postgresql/Tables/Partitioning/ManagedListPartitions.cs — the PostgreSQL reference