# Lidarr Database Research Summary

## Overview

Lidarr is a music collection manager that uses a **Release-based** system. Key design principles:

1. **Metadata Separation** - Artist metadata separated from configuration
2. **Release-Centric** - Works with releases, not loose tracks
3. **Monitoring Hierarchy** - Artist → Album → Release (only one release monitored per album)
4. **Quality Profiles** - Separate profiles for quality and metadata preferences
5. **Download Lifecycle** - Pending → Queue → Imported → History/Blocklist

## Core Entity Hierarchy

```
ArtistMetadata (1) ←→ (1) Artist (1) ←→ (N) Albums
                                              ↓
                                        (N) AlbumReleases (only 1 monitored)
                                              ↓
                                        (N) Tracks (N) ←→ (1) TrackFile
```

## Key Entities

### Music Entities
- **Artists** - Configuration (path, monitoring, profiles)
- **ArtistMetadata** - Metadata (name, images, genres, members)
- **Albums** - Album info with monitoring and search tracking
- **AlbumReleases** - Physical releases (CD, Vinyl, Digital) - only ONE monitored per album
- **Tracks** - Individual tracks linked to releases
- **TrackFiles** - Actual files on disk with quality info

### Configuration
- **QualityProfiles** - Acceptable formats and upgrade cutoff
- **MetadataProfiles** - Which album types to include (Studio, EP, Live, etc.)
- **RootFolders** - Storage locations with defaults

### Download Tracking
- **PendingReleases** - Delayed downloads (waiting for better quality)
- **DownloadHistory** - Download lifecycle events
- **Blocklist** - Failed/rejected releases (prevent re-download)
- **History** - Complete audit trail of all events

### System
- **Indexers** - Search sources (Newznab/Torznab)
- **DownloadClients** - Torrent/Usenet clients
- **ImportLists** - Auto-import from Spotify, Last.fm, etc.
- **Tags** - Categorization

## Monitoring States

### Artist Level
- `monitored` - Is artist being tracked
- `monitor_new_items` - Policy for new releases (All/Future/Missing/Existing/None)

### Album Level
- `monitored` - Should we look for this album
- `any_release_ok` - Auto-switch releases during import

### Release Level
- `monitored` - Is this the release we want (exactly ONE per album)

## Download States

```
TrackedDownloadState:
  Downloading → ImportPending → Importing → Imported
                                         → Ignored
            → DownloadFailed → DownloadFailedPending
```

## History Event Types

- Grabbed - Download started
- TrackFileImported - File imported to library
- DownloadFailed - Download failed
- TrackFileDeleted - File removed
- TrackFileRenamed - File renamed
- TrackFileRetagged - Metadata updated
- AlbumImportIncomplete - Partial import
- DownloadIgnored - Download skipped

## Sources

- GitHub: Lidarr/Lidarr
- Key files:
  - `src/NzbDrone.Core/Music/Model/Artist.cs`
  - `src/NzbDrone.Core/Music/Model/Album.cs`
  - `src/NzbDrone.Core/Music/Model/Release.cs` (AlbumRelease)
  - `src/NzbDrone.Core/Music/Model/Track.cs`
  - `src/NzbDrone.Core/MediaFiles/TrackFile.cs`
  - `src/NzbDrone.Core/Datastore/Migration/001_initial_setup.cs`
  - `src/NzbDrone.Core/Datastore/Migration/023_add_release_groups_etc.cs`