Multi-Tenanted Documents

Polecat supports isolating document data by tenant using conjoined tenancy (shared tables with a tenant_id column) or separate database tenancy.

Conjoined Tenancy

When conjoined tenancy is enabled, all document tables include a tenant_id column and use a composite primary key of (tenant_id, id):

Conjoined document tenancy can be turned on three ways, from narrowest to widest:

var store = DocumentStore.For(opts =>
{
    opts.Connection("...");

    // 1. One document type at a time. Mirrors Marten's Schema.For<T>().MultiTenanted().
    opts.Schema.For<Order>().MultiTenanted();

    // 2. ...or through a policy, which is the same switch in the policy's spelling.
    opts.Policies.ForDocument<Invoice>(p => p.MultiTenanted = true);

    // 3. ...or every document type in the store.
    opts.Policies.AllDocumentsAreMultiTenanted();
});

A conjoined event store still makes every document conjoined, which is how document tenancy worked before the per-type opt-in existed:

var store = DocumentStore.For(opts =>
{
    opts.Connection("...");
    opts.Events.TenancyStyle = TenancyStyle.Conjoined;
});

Events.TenancyStyle is the fallback, so the two combine the way you would expect: the opt-ins above can make a document conjoined in a store whose events are not, and nothing you have already configured changes shape. The opt-in only ever widens tenancy — there is deliberately no per-type way to make a document single-tenanted inside a conjoined event store, because that would retype a primary key under stores that never asked for it.

Tenancy is a schema decision

Turning MultiTenanted() on for a document type whose table already exists changes its primary key from (id) to (tenant_id, id). That is a migration, not a setting — plan it like one.

Querying

All queries automatically filter by the session's tenant ID:

await using var session = store.LightweightSession(new SessionOptions
{
    TenantId = "tenant-a"
});

// Only returns documents belonging to "tenant-a"
var orders = await session.Query<Order>().ToListAsync();

Loading by ID

// Only loads if the document belongs to the session's tenant
var order = await session.LoadAsync<Order>(orderId);

Separate Database Tenancy

Each tenant gets a completely separate SQL Server database:

var store = DocumentStore.For(opts =>
{
    opts.MultiTenantedDatabases(databases =>
    {
        databases.AddTenant("tenant-a", "Server=localhost;Database=tenant_a;...");
        databases.AddTenant("tenant-b", "Server=localhost;Database=tenant_b;...");
    });
});

Sessions are automatically routed to the correct database.

No default tenant — and no top level connection string

MultiTenantedDatabases() (and MultiTenantedMasterTable()) sets StoreOptions.DefaultTenantUsageEnabled to false. Do not register a placeholder *DEFAULT* tenant, and you do not need to set StoreOptions.ConnectionString — the tenancy supplies one. Opening a session or building a daemon without a tenant throws DefaultTenantUsageDisabledException rather than quietly using whichever database happened to be first.

The async daemon starts one daemon per tenant database with the default tenant disabled, and ApplyAllDatabaseChangesOnStartup() migrates every tenant database. See No default tenant is required.

ITenanted Interface

Documents implementing ITenanted have their TenantId property automatically synced:

public class Order : ITenanted
{
    public Guid Id { get; set; }
    public string TenantId { get; set; } = "";
    public string Description { get; set; } = "";
}

// When stored, order.TenantId is automatically set to the session's tenant

See Multi-Tenancy Configuration for complete setup details.