EPIC: Multi field id criterion (Multi column PKs)

[janpio]

Spec: The relevant part of the spec on the Prisma Schema Language can be found here.

Description: The Prisma Schema Language allows the user to define a combination of fields as the id criterion. It is an implementation detail of a connector how this is implemented.

Example:
The following example shows a User model where the combination of firstName and lastName is the id criterion.

model User {
  firstName String
  lastName  String
  @@id([firstName, lastName])
}

Affected Components

• Datamodel Parser
• Migration Engine
• Query Engine
• Introspection Engine

Links to actual Work Packages

• Datamodel Parser
• Migration Engine
• Query Engine: Multi field unique #60
• Query Engine
• Introspection Engine

[mavilein]

Initial break down of Work Packages

• Datamodel Parser
  • extend Model data structure in dml module to store informations on multi field ids
  • implement new DirectiveValidator for @@id
  • test cases:
    • basic happy path
    • name arg must not be optional
    • the directive must not refer to undefined fields
    • a model must either have @id or @@id
• Migration Engine
  • core: implement new migration steps for indexes (diffing + applying)
  • sql connector:
    • calculation of sql schema
    • diffing of sql schemas
    • add SQL rendering to database step applier
• Query Engine
  • core:
    • adapt Schema so it can accept a combination fields as id criteria=on
    • adapt all places that expect an id to be a single PrismaValue
  • connector:
    • adapt all places that expect an id to be a single PrismaValue
• Introspection Engine:
  • core: no work required
  • connector:
    • verify that the sql-schema-describer can handle compound ids
    • adapt Datamodel calculation so that compound ids are translated to @@id in a model

[mavilein]

Open Questions

• the GraphQL protocol for the communication between photon client and query engine must be defined

[mavilein]

I asked for a spec for the Photon API in this issue.