Multi-Tenancy with Database per Tenant

Polecat supports multiple multi-tenancy strategies for isolating data between tenants.

Tenancy Styles

Single Tenant (Default)

All data lives in one set of tables with no tenant isolation:

var store = DocumentStore.For(opts =>
{
    opts.Connection("...");
    // This is the default -- no tenant isolation
});

Conjoined Tenancy

All tenants share the same database and tables, but data is isolated by a tenant_id column:

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

    // Enable conjoined tenancy for events
    opts.Events.TenancyStyle = TenancyStyle.Conjoined;
});

With conjoined tenancy:

• All document tables get a tenant_id column
• Document primary keys become composite: (tenant_id, id)
• All queries automatically filter by the session's tenant ID
• Event streams are isolated per tenant

Specify the tenant when creating a session:

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

See Multi-Tenanted Documents and Event Multi-Tenancy for more details.

Separate Database Tenancy

Each tenant gets their own isolated SQL Server database:

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

With separate database tenancy:

• Each tenant has completely isolated data
• Schema management runs independently per database
• Sessions automatically route to the correct database based on tenant ID
• The async daemon runs independently per tenant database

Setting the Tenant ID

The tenant ID is set when opening a session:

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

WARNING

If no tenant ID is specified, Polecat uses "DEFAULT" as the tenant ID. In conjoined tenancy mode, this means documents and events will be stored with tenant_id = 'DEFAULT'.

ITenanted Interface

Documents that implement ITenanted will have their TenantId property automatically synced from the session:

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