Rewrite models

[fredemmott]

• refactor to have a unified 'get from memcached or mysql' function on the base that takes both a key (or calls ->getID()) and queryf params
• refactor to have a unified 'update mysql and invalidate memcache' function that takes both a key and (or calls ->getID()) and queryf params

In most cases, there should be no direct usages of the async mysql objects in the models after this.

Bonus points:Use codegen to create the models from a declarative schema - see https://github.com/hhvm/hack-codegen/tree/master/examples/dorm

[fredemmott]

I'll probably do this in a few months if no one else does it or closes it as wontfix first :p

[fredemmott]

I should probably 'just' turn that dorm example into a reusable library :/

Adding performance label as it will make it easier to revisit caching etc across the whole project.

[fredemmott]

I'm thinking of basically having a stack of some new IStorage interface:

• RequestCacheStorage: always used
• MemcachedCacheStorage: used in multi-server setup
• APCStorage: used in single-server setup instead of Memcached
• MySQLStorage

These could all operate on non-nested shapes; e.g. either handwritten in the model, or in some kind of schema (like the dorm example):

<?hh
class Foo extends Model {
  const type TRow = shape(
    'id' => int,
    'name' => string,
  );

  public function getName(): string {
    return $this->data['name'];
  }

  // initialization of $this->data handled by the base class, as is getID() function
}

[justinwray]

Noting the stop-gap provided by PR #574 here. Obviously not the end-goal solution, but it provides a performance improvement based on the current implementation.