persistent-3.0.0

This issue tracks features and bug fixes that will be released as part of persistent-3.0.0. I want to bump the major-major version number because I want to implement a Big Breaking Change:

The Desolation of Entity

There are many problems in persistent relating to the design of Entity:

data Entity record = Entity 
  { entityKey :: Key record
  , entityVal :: record
  }

This works very well in the common case of "I want a datatype record with an autogenerated surrogate Key record," but it doesn't handle composite primary keys or non-autogenerated primary keys particularly well. It also special cases the primary key, when really any number of columns could have database specified defaults.

#1035, #1016, #994, #992, #985, #973, #974,

The solution that I want to implement is detailed in #995. I'll open a new issue to focus on gutting Entity and further conversation can go there.

Moar Breaking Changes

Because this is a big change, I'd like to roll up as many other big changes as possible. If you have something you'd like to change or break about the library, now is a great time to mention it.

I want to roll up the functional/bug fix breaking changes and do persistent-2.11. After that, I'll start working onpersistent-3.0, which will be a bigger change.

The milestone 3.0 is in place for this update.

Start with the Entity definition in the issue and read the proposed solution in #995, along with related issues #1035, #1016, #994, #992, #985, #973, and #974. The issue is an umbrella for a major redesign and does not define a focused entry point or completion criteria; follow-up scope would need to be established before implementation.