# PgLargeObjects

An Elixir library for working with [large
objects](https://www.postgresql.org/docs/current/largeobjects.html) in
PostgreSQL databases.

## Features

* Easy and memory-efficient streaming of large amounts of data (up to 4TB) using `PgLargeObjects` high-level API.
* Random-access reads and writes to data objects via low-level `PgLargeObjects.LargeObject` API.
* Extensions to Ecto query DSL for interacting with large objects as part of
  Ecto queries.

## Installation

Install the package by adding `pg_large_objects` to your list of dependencies
in `mix.exs`:

```elixir
def deps do
  [
    {:pg_large_objects, "~> 0.1"}
  ]
end
```

Optional, but recommended: include `PgLargeObjects.Repo` in your `Ecto.Repo`
module to define convenience API:

```elixir
defmodule MyApp.Repo do
  use Ecto.Repo,
    otp_app: :my_app,
    adapter: Ecto.Adapters.Postgres

  use PgLargeObjects.Repo
end
```

## Database Configuration

Large objects are referenced by object IDs, modelled using the `oid` type in
PostgreSQL. `Ecto.Migration` has support for this type built-in, e.g.

```
defmodule MyApp.Repo.Migrations.CreateUploadsTable do
  use Ecto.Migration

  def change do
    create table(:uploads) do
      add :user_id, references(:users), null: false
      add :object_id, :oid, null: false

      timestamps()
    end
  end
end
```

In the Ecto schema, use plain `:integer` fields for object IDs:

```
defmodue MyApp.Upload do
  use Ecto.Schema

  schema "uploads" do
    belongs_to :user, MyApp.User
    field :object_id, :integer

    timestamps()
  end
end
```

## Usage

Use the high-level APIs `PgLargeObjects.import/3` and `PgLargeObjects.export/3`
(exposed as `import_large_object/2` and `export_large_object/2` on the
 applications' repository module) for importing data into or exporting data out
of the database:

```elixir
# Import binary into large object
{:ok, object_id} = Repo.import_large_object("My payload.")

# Stream data into large object
{:ok, object_id} =
  "/tmp/recording.mov"
  |> File.stream!()
  |> Repo.import_large_object()

# ...store object_id somewhere to maintain reference to data.
```

```elixir
# Export binary from large object
{:ok, data} = Repo.export_large_object(object_id)

# Stream data of large object into Collectable
:ok =
  "/tmp/recording.mov"
  |> File.stream!()
  |> Repo.export_large_object(object_id)
```

Use the lower-level API in `PgLargeObjects.LargeObject` to interact with
individual object files on a more granular level.

## License

Copyright (c) 2025 Frerich Raabe.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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