Sqlite.Ecto2

Sqlite.Ecto2 is a SQLite3 Adapter for Ecto 2.x.

IMPORTANT!!!! This is an experimental port and does not work yet. It's entirely possible that I'll play with this for a while and abandon it; it's also entirely possible that it will lead to a viable adapter for Ecto 2.x.

If you're able to use Ecto 1.x, please look at sqlite_ecto, on which this project is based.

The remainder of this README is held over from the 1.x version of this project. If this project is ultimately successful, we'll revise the documentation accordingly. For now, consider it inaccurate. Such is life on the bleeding edge.

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Read the tutorial for a detailed example of how to setup and use a SQLite repo with Ecto, or just check-out the CliffsNotes in the sections below if you want to get started quickly.

A WARNING About OTP 19.0.x

OTP 19.0.x appears to have a bug that causes it to misinterpret certain pattern matches. This causes the unit tests for sqlite_ecto to fail on some platforms when hosted on OTP 19.0.x. This bug did not appear in OTP 18.0 and appears to have been fixed for OTP 19.1. Consequently, we strongly advise you to avoid using OTP 19.0.x when running sqlite_ecto, especially if using decimal value types.

Note that the Travis configuration for this repo specifically excludes OTP 19.0 for this reason.

Dependencies

Sqlite.Ecto relies on Sqlitex and esqlite. Since esqlite uses Erlang NIFs, you will need a valid C compiler to build the library.

Example

Here is an example usage:

# In your config/config.exs file
config :my_app, Repo,
  adapter: Sqlite.Ecto,
  database: "ecto_simple.sqlite3"

# In your application code
defmodule Repo do
  use Ecto.Repo,
    otp_app: :my_app,
    adapter: Sqlite.Ecto
end

defmodule Weather do
  use Ecto.Model

  schema "weather" do
    field :city     # Defaults to type :string
    field :temp_lo, :integer
    field :temp_hi, :integer
    field :prcp,    :float, default: 0.0
  end
end

defmodule Simple do
  import Ecto.Query

  def sample_query do
    query = from w in Weather,
          where: w.prcp > 0 or is_nil(w.prcp),
         select: w
    Repo.all(query)
  end
end

Usage

Add Sqlite.Ecto as a dependency in your mix.exs file.

def deps do
  [{:sqlite_ecto2, "~> 2.0.0"}]
end

You should also update your applications list to include both projects:

def application do
  [applications: [:logger, :sqlite_ecto2, :ecto]]
end

To use the adapter in your repo:

defmodule MyApp.Repo do
  use Ecto.Repo,
    otp_app: :my_app,
    adapter: Sqlite.Ecto
end

Unsupported Ecto Constraints

The changeset functions foreign_key_constraint/3 and unique_constraint/3 are not supported by Sqlite.Ecto because the underlying SQLite database does not provide enough information when such constraints are violated to support the features.

Note that SQLite does support both unique and foreign key constraints via unique_index/3 and references/2, respectively. When such constraints are violated, they will raise Sqlite.Ecto.Error exceptions.

Silently Ignored Options

There are a few Ecto options which Sqlite.Ecto silently ignores because SQLite does not support them and raising an error on them does not make sense:

• Most column options will ignore size, precision, and scale constraints on types because columns in SQLite have no types, and SQLite will not coerce any stored value. Thus, all "strings" are TEXT and "numerics" will have arbitrary precision regardless of the declared column constraints. The lone exception to this rule are Decimal types which accept precision and scale options because these constraints are handled in the driver software, not the SQLite database.
• If we are altering a table to add a DATETIME column with a NOT NULL constraint, SQLite will require a default value to be provided. The only default value which would make sense in this situation is CURRENT_TIMESTAMP; however, when adding a column to a table, defaults must be constant values. Therefore, in this situation the NOT NULL constraint will be ignored so that a default value does not need to be provided.
• When creating an index, concurrently and using values are silently ignored since they do not apply to SQLite.