Mnemonics

Read only data store for Elixir: fast, concurrently, for large data & hot reloadable.

Mnemonics is analogous to Ruby's ActiveHash in it's usecase.

Document.

Installation

Add mnemonics to your list of dependencies in mix.exs.

def deps do
  [
    {:mnemonics, "~> 0.5"}
  ]
end

Start under your application.

defmodule Your.Application do
  use Application

  def start(_type, _args) do
    children = [
      {Mnemonics, [name: Your.Mnemonics, ets_dir: "/tmp"]}
    ]

    opts = [strategy: :one_for_one, name: Your.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

Usage

Create an example.ets by :ets.tab2file/3. Then put it into the ets_dir. The examples.ets stores {:example1, %{id: :example1}}.

priv/
└repo/
  └seeds/
    └examples.ets

Create an Example module, use Mnemonics & load.

defmodule Example do
  use Mnemonics, table_name: :examples, sup_name: Your.Mnemonics
end

Example.load(1)

We can lookup the table.

:ets.lookup(Example.table_name(1), :example1)

Let's reload a new table. Put a new examples.ets into the ets_dir & load it with a new version number.

Example.load(2)

We can lookup the new table.

:ets.lookup(Example.table_name(2), :example1)

snap = Mnemonics.Snap.snap(Mnemonics.Snap.new(), 2, %{})
:ets.lookup(Example.table_name(snap), :example1)

Mnemonics has cache function named Mnemonics.Snap.

snap = Mnemonics.Snap.snap(Mnemonics.Snap.new(), 2, %{})
get_and_update_in(snap[:examples].cache[:example1], fn
  nil ->
    example = :ets.lookup Example.table_name(snap), :example1
    {example, example}

  example ->
    {example, example}
end)

:ets.new/2 Option

• Should :public or :protected. :protected (default) is recommended.
• Can't :named_table.
• {:read_concurrency, true} is recommended.

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