couchx

# Couchx
### CouchDB Adapter for Ecto3.
The Adapter supports 1 main Repo, but also dynamic repos where you can querie on multiple Dbs with a dynamic supervisor.
To create a Repo follow the Ecto default instructions, but we will need to add returning true option in the Repo module,
this is in order to have the _rev value updated into the documents.
```
defmodule MyApp.Repo do
  use Ecto.Repo,
    otp_app: :my_app,
    adapter: Couchx.Adapter
  def default_options(_), do: [returning: true]
end
```
The supported functions in this version are:
```
Repo.get Struct, doc_id
Repo.all(Struct)
Repo.all from doc in Struct, where: doc._id in ^doc_ids_list
Repo.all from doc in Struct, where: doc.field == ^field
Repo.one from doc in Struct, where doc.field == ^field
Repo.one from doc in Struct, where doc.field == ^field, select: ~w[field1 field2]a
Repo.insert Struct, doc
Repo.insert_all Struct, docs
Repo.delete Struct, %{_id: doc_id}
Repo.update changeset
```
To limit a query you can use:
```
Repo.all from doc in Struct, where: doc.field == ^field, limit: 1
```
A very basic version of sort is supported depending on the CouchDB version.
On version 1.x
The sort will only work with `desc` or `asc` on the results of `_all_docs` queries,
which are the ones done by `Repo.all`
```
Repo.all from doc in Struct, order_by: [desc: doc._id]
```
On version >= 2.x
The sort will depend on the type of query being done, if it is an `_all_docs` query, the same rules as 1.x apply.
But for simple field lookups depending on an index, it will follow the rules from Mango, where the `order_by` values will be parsed.
```
order_by [desc: doc.field]
```
will be parsed as
```
{"sort": [{"field": "desc"}]
```
It adds a simple way to execute JS view queries with:
```
  def query(name, design, view_map, key, opts \\ []) do
    {adapter, meta} = Ecto.Repo.Registry.lookup(name)
    adapter.execute(:view, meta, design, view_map, key, opts)
  end
```
Not ideal, so open to suggestions here.
### Mango support
Currently support for mango is limited to do queries on single property, on previously created indexes.
The selector is a map with the `type` property preset to the model namespace, such as:
```
%{
  selector: %{
    type: "user",
    email: "email@email.com"
  }
}
```
This will be the query generated by:
```
import Ecto.Query
Repo.all from u in User, where: u.email == "email@email.com"
```
It will also work with:
```
import Ecto.Query
email = "email@email.com"
Repo.all from u in User, where: u.email == ^email
```
## Mango Index
Couchx have a couple of tasks to handle database indexing:
```
$ mix couchx.gen.mango_index -r MyApp.Repo -n my-mango-index -f name,email
```
This command will generate a index file on `priv/my_app/repo/index/my-mango-index.exs`
It rely on repos declared under `config.exs`
```
import Config
config :my_app, ecto_repos: [MyApp.Repo]
...
```
And build a file with contents such as:
```
defmodule MyApp.Repo.Index.MyMangoIndex do
  use Couchx.MangoIndex, repo_name: MyApp.Repo
  def up do
    create_index "my-mango-index" do
      %{fields: ~w[name email]}
    end
  end
  def down do
    drop_index("my-mango-index")
  end
```
This file will be executed with
```
$ mix couchx.mango_index
```
which will persist the index document in the database defined by the repo.
And if you want to remove the index you can call:
`$ mix couch.mango_index.down -r MyApp.Repo, -n my-mango-index`
Mango indexes could be run in the release like this:
```elixir
defmodule MyApp.Release do
  @moduledoc """
  Used for executing DB release tasks when run in production without Mix
  installed.
  """
  @app :my_app
  def migrate do
    Application.ensure_all_started(@app)
    Couchx.Migrator.run(MyApp.Repo, :up)
  end
end
```
## TODO:
* Repo.insert_all
* Repo.delete_all
* Bulk doc updates
* Better error handling
* More Mango Queries
* A better view query pattern
* Auto indexing requested JS queries
* JS view index management
* Add tests
## Installation
The package can be installed by adding `couchx` to your list of dependencies in `mix.exs`:
```elixir
def deps do
  [
    {:couchx, "~> 0.1.0"}
  ]
end
```
Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
be found at [https://hexdocs.pm/couchx](https://hexdocs.pm/couchx).