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Getting Started.md

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Getting started

EventStore is available in Hex and can be installed as follows:

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

    def deps do
  [{:eventstore, "~> 0.16"}]
end

  2. Add an eventstore config entry containing the PostgreSQL database connection details to each environment's mix config file (e.g. config/dev.exs):

    config :eventstore, EventStore.Storage,
  serializer: EventStore.TermSerializer,
  username: "postgres",
  password: "postgres",
  database: "eventstore_dev",
  hostname: "localhost",
  pool_size: 10,
  pool_overflow: 5

The database connection pool configuration options are:

  • :pool_size - The number of connections (default: 10).
  • :pool_overflow - The maximum number of overflow connections to start if all connections are checked out (default: 0).

  1. Create the EventStore database and tables using the mix task:

    $ mix do event_store.create, event_store.init

Initialize an existing database

You can use an existing PostgreSQL database with EventStore by running the mix task:

$ mix event_store.init

Reset an existing database

To drop an existing EventStore database and recreate it you can run the following mix tasks:

$ mix do event_store.drop, event_store.create, event_store.init

Warning this will delete all EventStore data.

Event data and metadata data type

EventStore has support for persisting event data and metadata as either:

  • Binary data, using the bytea data type, designed for storing binary strings.
  • JSON data, using the jsonb data type, specifically designed for storing JSON encoded data.

The default data type is bytea. This can be used with any binary serializer, such as the Erlang Term format, JSON data encoded to binary, and other serialization formats.

Using the jsonb data type

The advantage of using this format is that it allows you to execute ad-hoc SQL queries against the event data or metadata.

If you want to use PostgreSQL's native JSON support you need to configure EventStore to use the jsonb data type. You must also use the EventStore.JsonbSerializer serializer to ensure event data and metadata is correctly serialized to JSON and include the Postgres types module (EventStore.PostgresTypes) for the Postgrex library to support JSON.

# config/config.exs
config :eventstore, column_data_type: "jsonb"
config :eventstore, EventStore.Storage,
  serializer: EventStore.JsonbSerializer,
  types: EventStore.PostgresTypes

Finally, you need to include the Jason library in mix.exs to enable Postgrex type with JSON support.

# mix.exs
defp deps do
  [{:jason, "~> 1.1"}]
end

These settings must be configured before creating the EventStore database. It's not possible to migrate between bytea and jsonb data types once you've created the database. This must be decided in advance.