[](https://github.com/evntd/fact/actions/workflows/elixir.yml)
<div style="display: flex; justify-content: center;">
<img alt="logo" src=".github/assets/logo.png" width="424">
</div>
## About
*Fact* is an **Elixir library** that provides a file system based event store database.
## Features
- Traditional event sourcing capabilities:
- Append events to event streams
- Read events from specific event streams or all events in the event store
- Subscribe to specific event streams or all events in the event store
- [Optimistic concurrency control](https://en.wikipedia.org/wiki/Optimistic_concurrency_control)
- Compliant with the [Dynamic Consistency Boundary specification](https://dcb.events/specification/)
- Just-in-time indexing for event data queries.
- Supports multiple instances for siloed isolation in multi-tenancy setups
- Configurable [Content-Addressable Storage (CAS)](https://en.wikipedia.org/wiki/Content-addressable_storage)
- Backup store contents to compressed file
- Supported on Elixir 1.13+ and OTP 25+
## Installation
The package can be installed by adding `fact` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:fact, "~> 0.0.1"}
]
end
```
Then create a database instance.
```sh
$ mix fact.create -p data/mydb
```
## Basic Usage
```elixir
# Start a database instance
iex> {:ok, mydb} = Fact.open("data/mydb")
# Append an event to a stream
iex> {:ok, pos} = Fact.append_stream(mydb, %{type: "EventSourcingJourneyStarted"}, "journey-1")
# Read the event stream
iex> Fact.read(mydb, "journey-1") |> Enum.to_list()
[
%{
"event_data" => %{},
"event_id" => "3bb4808303c847fd9ceb0a1251ef95da",
"event_tags" => []
"event_type" => "EventSourcingJourneyStarted",
"event_metadata" => %{},
"store_position" => 1,
"store_timestamp" => 1765039106962264,
"stream_id" => "journey-1",
"stream_position" => 1
}
]
```
