ActiveRecord::StatementInvalid: PG::InternalError: ERROR: virtual tuple table slot does not have system attributes

Code:

class WebSession < ActiveRecord::Base
  self.primary_key = :id
  upsert_keys [:tenant_id, :session_id]
  belongs_to :tenant
end

WebSession.upsert!(tenant: tenant_id, session_id: session_id, value: {})

SQL generated:

INSERT INTO "web_sessions" 
("tenant_id", "session_id", "value", "created_at", "updated_at") VALUES ('9b893bf4-bb94-4721-a6e8-03b2bd55d81e', '893f5cc3-d31a-4751-8daa-7c9acfd23ad9', '{}', '2020-09-30 07:57:45.535047', '2020-09-30 07:57:45.535047') 
ON CONFLICT  ("tenant_id","session_id")  
DO UPDATE  SET "tenant_id" = '9b893bf4-bb94-4721-a6e8-03b2bd55d81e', "session_id" = '893f5cc3-d31a-4751-8daa-7c9acfd23ad9', "value" = '{}', "updated_at" = '2020-09-30 07:57:45.535047' 
RETURNING *, (xmax = 0) AS _upsert_created_record

Error from PG:

ActiveRecord::StatementInvalid: PG::InternalError: ERROR:  virtual tuple table slot does not have system attributes

Removing the (xmax = 0) AS _upsert_created_record solves the issue.

Reasons why my setup is weird:

I'm using a composite primary (id, tenant_id)
The table is partitioned by tenant_id

      CREATE TABLE web_sessions (
        id uuid NOT NULL DEFAULT uuid_generate_v4(),
        tenant_id uuid NOT NULL,
        session_id uuid NOT NULL,
        value jsonb NOT NULL,

        created_at timestamp without time zone NOT NULL,
        updated_at timestamp without time zone NOT NULL,

        PRIMARY KEY (id, tenant_id)
      ) PARTITION BY LIST (tenant_id);

      CREATE UNIQUE INDEX idx_session_ids ON web_sessions (tenant_id, session_id);

Version: 0.9.5 Rails: 5.2.4.4 Ruby 2.7.1p83 Postgres: 12.2

jesjos / active_record_upsert

ActiveRecord::StatementInvalid: PG::InternalError: ERROR: virtual tuple table slot does not have system attributes #106