Current

Current provides more powerful streaming mechanisms than those offered by Ecto. Forked from Bourne which is inactive.

Summary

Keyset:

• Iterates by monotonic key say BIGSERIAL identifier.
• Either ascending or descending order.
• Essentially performs repeated SELECT * FROM table WHERE id > N LIMIT 1000 statements, feeding N from the last seen key.
• Does not require a transaction.

Cursor:

• Iterates using a cursor - leveraging server functionality for streaming large row sets.
• You can read more here.
• Essentially a SELECT * FROM table that is streamed in sets of rows.
• Requires a transaction.

Example

defmodule My.Repo do
  use Ecto.Repo, otp_app: :mine
  use Current
end

import Ecto.Query
q = from(actor in Actor, where: actor.born <= 1980)

# You can stream through an `Enumerable`:
My.Repo.stream(q, method: :keyset) |> Stream.each(&IO.inspect) |> Stream.run
My.Repo.stream(q, method: :cursor) |> Stream.each(&IO.inspect) |> Stream.run

Installation

1. Add current to your list of dependencies in mix.exs:

  def deps do
    [{:current, "~> 2.0"}]
  end

1. Fetch and compile your new dependency:

  mix do deps.get current, deps.compile

1. Drink your :tea:

2. That's it!

Usage

Refer to the documentation.

ASDF

Using Bash:

git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch v0.7.6
echo -e '\n. $HOME/.asdf/asdf.sh' >> ~/.bash_profile
echo -e '\n. $HOME/.asdf/completions/asdf.bash' >> ~/.bash_profile
source ~/.bash_profile
asdf plugin-add erlang https://github.com/asdf-vm/asdf-erlang.git
asdf plugin-add elixir https://github.com/asdf-vm/asdf-elixir.git
# cd path/to/current
asdf install
asdf reshim
mix local.hex --if-missing
mix local.rebar --force
mix do deps.get, compile

Testing

The test suite relies on a locally running postgres insatnce. You can use docker to create one quickly:

docker run --name postgres -p 5432:5432 -e POSTGRES_PASSWORD=postgres -d postgres

License

Current is free and unencumbered software released into the public domain, with fallback provisions for jurisdictions that don't recognize the public domain.

For details, see LICENSE.md.