# AcoustID Data Model

## Database Architecture

AcoustID uses a multi-database PostgreSQL architecture with separate databases for different concerns.

### Database Instances

| Database | Purpose | Tables | Extensions |
|----------|---------|--------|------------|
| `acoustid_app` | Application data (accounts, apps, stats) | 8 | pgcrypto |
| `acoustid_fingerprint` | Fingerprint and track data | 19 | intarray, acoustid, cube |
| `acoustid_ingest` | Submission processing | 3 | - |
| `musicbrainz` | MusicBrainz mirror (read-only) | Many | - |

### PostgreSQL Extensions

**intarray**: Integer array operations
- Used for fingerprint array queries
- Provides `&&` (overlap) and `@>` (contains) operators

**pgcrypto**: Cryptographic functions
- UUID generation (`gen_random_uuid()`)
- API key hashing

**acoustid** (custom): Fingerprint similarity functions
- `acoustid_compare(int[], int[])`: Compare two fingerprints
- `acoustid_extract_query(int[])`: Extract query terms
- Source: `acoustid-ext` C extension

**cube**: Multi-dimensional cube data type
- Used for simhash-based fingerprint indexing
- Enables fast approximate nearest neighbor search

## Core Tables

### Account Management (acoustid_app)

#### `account`

User accounts for API access.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Account ID |
| `name` | VARCHAR(255) | NOT NULL | Display name |
| `apikey` | VARCHAR(40) | UNIQUE, NOT NULL | API key (user key) |
| `mbuser` | VARCHAR(64) | UNIQUE | MusicBrainz username |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `lastlogin` | TIMESTAMP | | Last login timestamp |
| `submission_count` | INTEGER | DEFAULT 0 | Total submissions |
| `application_id` | INTEGER | FOREIGN KEY | Default application |
| `application_version` | VARCHAR(255) | | Application version |
| `created_from` | INET | | Registration IP |
| `is_admin` | BOOLEAN | DEFAULT FALSE | Admin flag |

**Indexes**:
- `account_pkey` (PRIMARY KEY on `id`)
- `account_apikey_key` (UNIQUE on `apikey`)
- `account_mbuser_key` (UNIQUE on `mbuser`)

#### `application`

API client applications.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Application ID |
| `name` | VARCHAR(255) | NOT NULL | Application name |
| `version` | VARCHAR(255) | | Version string |
| `apikey` | VARCHAR(40) | UNIQUE, NOT NULL | API key (client key) |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `active` | BOOLEAN | DEFAULT TRUE | Active status |
| `account_id` | INTEGER | FOREIGN KEY | Owner account |
| `email` | VARCHAR(255) | | Contact email |
| `website` | VARCHAR(1000) | | Website URL |
| `rate_limit` | INTEGER | | Custom rate limit (req/s) |

**Indexes**:
- `application_pkey` (PRIMARY KEY on `id`)
- `application_apikey_key` (UNIQUE on `apikey`)

#### `account_openid`

OpenID authentication links.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `openid` | VARCHAR(255) | PRIMARY KEY | OpenID identifier |
| `account_id` | INTEGER | FOREIGN KEY | Linked account |

#### `account_google`

Google OAuth authentication links.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `google_user_id` | VARCHAR(255) | PRIMARY KEY | Google user ID |
| `account_id` | INTEGER | FOREIGN KEY | Linked account |

### Fingerprint Data (acoustid_fingerprint)

#### `track`

Unique audio tracks identified by fingerprints.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Track ID |
| `gid` | UUID | UNIQUE, NOT NULL | Public track UUID |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `new_id` | INTEGER | FOREIGN KEY | Merge target (if merged) |
| `disabled` | BOOLEAN | DEFAULT FALSE | Disabled flag |

**Indexes**:
- `track_pkey` (PRIMARY KEY on `id`)
- `track_gid_key` (UNIQUE on `gid`)
- `track_new_id_idx` (on `new_id`)

**Notes**:
- `gid` is the public-facing AcoustID track ID
- `new_id` points to merged track (for deduplication)
- Disabled tracks excluded from search results

#### `fingerprint`

Audio fingerprints linked to tracks.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Fingerprint ID |
| `track_id` | INTEGER | FOREIGN KEY | Linked track |
| `fingerprint` | INTEGER[] | NOT NULL | Chromaprint hash array |
| `length` | SMALLINT | NOT NULL | Duration in seconds |
| `bitrate` | SMALLINT | | Audio bitrate (kbps) |
| `format_id` | INTEGER | FOREIGN KEY | Audio format |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `submission_count` | INTEGER | DEFAULT 1 | Number of submissions |

**Indexes**:
- `fingerprint_pkey` (PRIMARY KEY on `id`)
- `fingerprint_track_id_idx` (on `track_id`)
- `fingerprint_length_idx` (on `length`)
- `fingerprint_fingerprint_idx` (GIN on `fingerprint` using `intarray`)

**Notes**:
- `fingerprint` is an array of 32-bit integers (Chromaprint hashes)
- GIN index enables fast similarity search
- `submission_count` tracks popularity

#### `fingerprint_data`

Extended fingerprint data with simhash.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `fingerprint_id` | INTEGER | PRIMARY KEY, FOREIGN KEY | Fingerprint ID |
| `fingerprint` | BYTEA | NOT NULL | Raw fingerprint data |
| `simhash` | CUBE | | Locality-sensitive hash |

**Indexes**:
- `fingerprint_data_pkey` (PRIMARY KEY on `fingerprint_id`)
- `fingerprint_data_simhash_idx` (GIST on `simhash`)

**Notes**:
- `fingerprint` stores compressed Chromaprint data
- `simhash` enables approximate nearest neighbor search
- GIST index for fast similarity queries

#### `track_mbid`

Links tracks to MusicBrainz recordings.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Link ID |
| `track_id` | INTEGER | FOREIGN KEY | AcoustID track |
| `mbid` | UUID | NOT NULL | MusicBrainz recording MBID |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `submission_count` | INTEGER | DEFAULT 1 | Number of submissions |
| `disabled` | BOOLEAN | DEFAULT FALSE | Disabled flag |

**Indexes**:
- `track_mbid_pkey` (PRIMARY KEY on `id`)
- `track_mbid_track_id_mbid_key` (UNIQUE on `track_id, mbid`)
- `track_mbid_mbid_idx` (on `mbid`)

**Notes**:
- Multiple MBIDs per track possible (different recordings)
- `submission_count` indicates confidence
- Disabled links excluded from results

#### `meta`

User-submitted metadata.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Metadata ID |
| `track` | VARCHAR(255) | | Track title |
| `artist` | VARCHAR(255) | | Artist name |
| `album` | VARCHAR(255) | | Album title |
| `album_artist` | VARCHAR(255) | | Album artist |
| `track_no` | INTEGER | | Track number |
| `disc_no` | INTEGER | | Disc number |
| `year` | INTEGER | | Release year |

**Indexes**:
- `meta_pkey` (PRIMARY KEY on `id`)

#### `track_meta`

Links tracks to user metadata.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Link ID |
| `track_id` | INTEGER | FOREIGN KEY | AcoustID track |
| `meta_id` | INTEGER | FOREIGN KEY | Metadata record |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `submission_count` | INTEGER | DEFAULT 1 | Number of submissions |

**Indexes**:
- `track_meta_pkey` (PRIMARY KEY on `id`)
- `track_meta_track_id_meta_id_key` (UNIQUE on `track_id, meta_id`)

#### `format`

Audio file formats.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Format ID |
| `name` | VARCHAR(20) | UNIQUE, NOT NULL | Format name (mp3, flac, etc.) |

**Indexes**:
- `format_pkey` (PRIMARY KEY on `id`)
- `format_name_key` (UNIQUE on `name`)

**Common Values**:
- `mp3`, `flac`, `ogg`, `m4a`, `wma`, `ape`, `wav`

#### `source`

Submission sources (applications).

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Source ID |
| `application_id` | INTEGER | FOREIGN KEY | Application |
| `account_id` | INTEGER | FOREIGN KEY | User account |
| `version` | VARCHAR(255) | | Application version |

**Indexes**:
- `source_pkey` (PRIMARY KEY on `id`)
- `source_application_id_account_id_version_key` (UNIQUE on `application_id, account_id, version`)

### Foreign IDs (acoustid_fingerprint)

#### `foreignid_vendor`

External ID providers.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Vendor ID |
| `name` | VARCHAR(255) | UNIQUE, NOT NULL | Vendor name |

**Indexes**:
- `foreignid_vendor_pkey` (PRIMARY KEY on `id`)
- `foreignid_vendor_name_key` (UNIQUE on `name`)

**Common Values**:
- `musicbrainz`, `musicip`, `discogs`, `spotify`

#### `foreignid`

External identifiers.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Foreign ID |
| `vendor_id` | INTEGER | FOREIGN KEY | Vendor |
| `name` | VARCHAR(255) | NOT NULL | External ID value |

**Indexes**:
- `foreignid_pkey` (PRIMARY KEY on `id`)
- `foreignid_vendor_id_name_key` (UNIQUE on `vendor_id, name`)

#### `track_foreignid`

Links tracks to external IDs.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Link ID |
| `track_id` | INTEGER | FOREIGN KEY | AcoustID track |
| `foreignid_id` | INTEGER | FOREIGN KEY | External ID |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `submission_count` | INTEGER | DEFAULT 1 | Number of submissions |

**Indexes**:
- `track_foreignid_pkey` (PRIMARY KEY on `id`)
- `track_foreignid_track_id_foreignid_id_key` (UNIQUE on `track_id, foreignid_id`)

#### `track_puid`

Legacy MusicIP PUID links.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Link ID |
| `track_id` | INTEGER | FOREIGN KEY | AcoustID track |
| `puid` | UUID | NOT NULL | MusicIP PUID |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |
| `submission_count` | INTEGER | DEFAULT 1 | Number of submissions |

**Indexes**:
- `track_puid_pkey` (PRIMARY KEY on `id`)
- `track_puid_track_id_puid_key` (UNIQUE on `track_id, puid`)
- `track_puid_puid_idx` (on `puid`)

### Statistics (acoustid_app)

#### `stats`

General statistics.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Stat ID |
| `name` | VARCHAR(255) | UNIQUE, NOT NULL | Stat name |
| `value` | INTEGER | NOT NULL | Stat value |
| `date` | DATE | NOT NULL | Stat date |

**Indexes**:
- `stats_pkey` (PRIMARY KEY on `id`)
- `stats_name_date_key` (UNIQUE on `name, date`)

**Common Stats**:
- `lookup.count`, `submission.count`, `track.count`, `fingerprint.count`

#### `stats_lookups`

Lookup statistics by hour.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Stat ID |
| `hour` | TIMESTAMP | NOT NULL | Hour timestamp |
| `application_id` | INTEGER | FOREIGN KEY | Application |
| `count_hits` | INTEGER | DEFAULT 0 | Successful lookups |
| `count_misses` | INTEGER | DEFAULT 0 | Failed lookups |

**Indexes**:
- `stats_lookups_pkey` (PRIMARY KEY on `id`)
- `stats_lookups_hour_application_id_key` (UNIQUE on `hour, application_id`)

#### `stats_user_agents`

User agent statistics.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Stat ID |
| `date` | DATE | NOT NULL | Date |
| `application_id` | INTEGER | FOREIGN KEY | Application |
| `user_agent` | VARCHAR(1000) | NOT NULL | User agent string |
| `ip` | INET | NOT NULL | IP address |
| `count` | INTEGER | DEFAULT 0 | Request count |

**Indexes**:
- `stats_user_agents_pkey` (PRIMARY KEY on `id`)
- `stats_user_agents_date_application_id_user_agent_ip_key` (UNIQUE on `date, application_id, user_agent, ip`)

#### `stats_top_accounts`

Top submitter accounts.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Stat ID |
| `account_id` | INTEGER | FOREIGN KEY | Account |
| `count` | INTEGER | NOT NULL | Submission count |

**Indexes**:
- `stats_top_accounts_pkey` (PRIMARY KEY on `id`)
- `stats_top_accounts_account_id_key` (UNIQUE on `account_id`)

### Submission Processing (acoustid_ingest)

#### `submission`

Pending fingerprint submissions.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Submission ID |
| `fingerprint` | INTEGER[] | NOT NULL | Chromaprint hash array |
| `length` | SMALLINT | NOT NULL | Duration in seconds |
| `bitrate` | SMALLINT | | Audio bitrate |
| `format_id` | INTEGER | | Audio format |
| `created` | TIMESTAMP | NOT NULL | Submission timestamp |
| `source_id` | INTEGER | FOREIGN KEY | Submission source |
| `mbid` | UUID | | MusicBrainz MBID (if provided) |
| `handled` | BOOLEAN | DEFAULT FALSE | Processing status |
| `meta_id` | INTEGER | FOREIGN KEY | User metadata |

**Indexes**:
- `submission_pkey` (PRIMARY KEY on `id`)
- `submission_handled_idx` (on `handled` WHERE `handled = FALSE`)

**Notes**:
- Worker processes unhandled submissions
- `handled = TRUE` after processing

#### `submission_result`

Processing results for submissions.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Result ID |
| `submission_id` | INTEGER | FOREIGN KEY | Submission |
| `track_id` | INTEGER | FOREIGN KEY | Matched/created track |
| `created` | TIMESTAMP | NOT NULL | Processing timestamp |

**Indexes**:
- `submission_result_pkey` (PRIMARY KEY on `id`)
- `submission_result_submission_id_key` (UNIQUE on `submission_id`)

#### `pending_submission`

Queue for async submission processing.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Queue ID |
| `submission_id` | INTEGER | FOREIGN KEY | Submission |
| `created` | TIMESTAMP | NOT NULL | Queue timestamp |

**Indexes**:
- `pending_submission_pkey` (PRIMARY KEY on `id`)
- `pending_submission_submission_id_key` (UNIQUE on `submission_id`)

**Notes**:
- Replaced by NATS queue in newer deployments
- Legacy table, may be deprecated

### Provenance Tables (acoustid_fingerprint)

Track data lineage and changes.

#### `fingerprint_source`

Links fingerprints to submission sources.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Link ID |
| `fingerprint_id` | INTEGER | FOREIGN KEY | Fingerprint |
| `source_id` | INTEGER | FOREIGN KEY | Source |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |

#### `track_mbid_source`

Links track-MBID associations to sources.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Link ID |
| `track_mbid_id` | INTEGER | FOREIGN KEY | Track-MBID link |
| `source_id` | INTEGER | FOREIGN KEY | Source |
| `created` | TIMESTAMP | NOT NULL | Creation timestamp |

#### `track_mbid_change`

Audit log for track-MBID changes.

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| `id` | SERIAL | PRIMARY KEY | Change ID |
| `track_mbid_id` | INTEGER | FOREIGN KEY | Track-MBID link |
| `account_id` | INTEGER | FOREIGN KEY | Account that made change |
| `disabled` | BOOLEAN | NOT NULL | New disabled status |
| `created` | TIMESTAMP | NOT NULL | Change timestamp |
| `note` | TEXT | | Change reason |

## ORM Layer (SQLAlchemy)

### Multi-Database Configuration

**File**: `acoustid/db.py`

```python
# Database bind keys
BIND_KEYS = {
    'app': 'acoustid_app',
    'fingerprint': 'acoustid_fingerprint',
    'ingest': 'acoustid_ingest',
    'musicbrainz': 'musicbrainz'
}
```

**Model Binding**:

```python
class Account(Base):
    __bind_key__ = 'app'
    __tablename__ = 'account'
    # ...

class Track(Base):
    __bind_key__ = 'fingerprint'
    __tablename__ = 'track'
    # ...
```

### Connection Pooling

**Configuration** (`acoustid.conf`):

```ini
[database]
name = acoustid_app
user = acoustid
password_file = /run/secrets/db_password
host = postgres
port = 5432
pool_size = 20
pool_recycle = 3600
```

**Pool Settings**:
- `pool_size`: Maximum connections per process
- `pool_recycle`: Recycle connections after N seconds
- `pool_pre_ping`: Test connections before use

### Query Patterns

**Fingerprint Search** (legacy, pre-index):

```python
# Find similar fingerprints using intarray overlap
query = db.session.query(Fingerprint).filter(
    Fingerprint.fingerprint.op('&&')(query_fingerprint),
    Fingerprint.length.between(duration - 5, duration + 5)
).order_by(
    func.acoustid_compare(Fingerprint.fingerprint, query_fingerprint).desc()
).limit(10)
```

**Track Lookup with MBIDs**:

```python
# Fetch track with all linked MBIDs
track = db.session.query(Track).options(
    joinedload(Track.mbids)
).filter(Track.gid == track_gid).first()
```

**Submission Processing**:

```python
# Find unhandled submissions
submissions = db.session.query(Submission).filter(
    Submission.handled == False
).order_by(Submission.created).limit(100).all()
```

## Database Migrations

### Alembic Configuration

**File**: `alembic.ini`

**Migration Directories**:
- `alembic/versions/app/`: acoustid_app migrations
- `alembic/versions/fingerprint/`: acoustid_fingerprint migrations
- `alembic/versions/ingest/`: acoustid_ingest migrations

**Multi-Database Support**:

```python
# alembic/env.py
def run_migrations_online():
    for bind_key in ['app', 'fingerprint', 'ingest']:
        engine = get_engine(bind_key)
        with engine.connect() as connection:
            context.configure(
                connection=connection,
                target_metadata=get_metadata(bind_key)
            )
            with context.begin_transaction():
                context.run_migrations()
```

### Migration Commands

```bash
# Create new migration
alembic revision --autogenerate -m "Add new column"

# Apply migrations
alembic upgrade head

# Rollback migration
alembic downgrade -1

# Show current version
alembic current

# Show migration history
alembic history
```

## Redis Data Structures

### Rate Limiting

**Key Pattern**: `rl:bucket:{scope}:{identifier}:{timestamp}`

**Example Keys**:
```
rl:bucket:global:1714305600
rl:bucket:app:8XaBELgH:1714305600
rl:bucket:ip:192.168.1.1:1714305600
```

**Value**: Integer (request count)  
**TTL**: 25 seconds (window duration + buffer)

**Algorithm**:
```python
# Increment bucket for current window
bucket_key = f"rl:bucket:{scope}:{identifier}:{current_window}"
count = redis.incr(bucket_key)
redis.expire(bucket_key, 25)

# Sum counts across all windows in sliding window
total = sum(redis.get(f"rl:bucket:{scope}:{identifier}:{w}") 
            for w in windows)
```

### Task Queue (Legacy)

**Key Pattern**: `queue:{queue_name}`

**Operations**:
```python
# Push task
redis.rpush('queue:submissions', json.dumps(task_data))

# Pop task
task_data = redis.lpop('queue:submissions')
```

**Note**: Being replaced by NATS in newer deployments

### API Key Cache

**Implementation**: In-memory TTLCache (not Redis)

```python
from cachetools import TTLCache

api_key_cache = TTLCache(maxsize=1000, ttl=60)
```

**Purpose**: Reduce database queries for API key validation

### Backfill State

**Key Pattern**: `backfill:{index_name}:{state_key}`

**Example Keys**:
```
backfill:fingerprints:last_id
backfill:fingerprints:batch_size
backfill:fingerprints:completed
```

**Purpose**: Track progress of index backfill operations

### Unknown MBID Cache

**Key Pattern**: `unknown_mbid:{mbid}`

**Value**: Boolean (1 if MBID not found in MusicBrainz)  
**TTL**: 3600 seconds (1 hour)

**Purpose**: Avoid repeated MusicBrainz queries for non-existent MBIDs

## Data Integrity

### Constraints

**Foreign Keys**:
- All foreign keys have `ON DELETE CASCADE` or `ON DELETE SET NULL`
- Orphaned records cleaned up automatically

**Unique Constraints**:
- Prevent duplicate fingerprints per track
- Prevent duplicate MBID links per track
- Ensure API key uniqueness

**Check Constraints**:
- Duration must be positive
- Bitrate must be positive
- Submission count must be non-negative

### Triggers

**Update Submission Count**:
```sql
CREATE TRIGGER update_fingerprint_submission_count
AFTER INSERT ON fingerprint_source
FOR EACH ROW
EXECUTE FUNCTION increment_submission_count();
```

**Track Merge Propagation**:
```sql
CREATE TRIGGER propagate_track_merge
AFTER UPDATE OF new_id ON track
FOR EACH ROW
EXECUTE FUNCTION update_merged_track_references();
```

### Indexes for Performance

**Covering Indexes**:
```sql
-- Lookup by fingerprint and duration
CREATE INDEX fingerprint_lookup_idx 
ON fingerprint (length, track_id) 
INCLUDE (fingerprint);
```

**Partial Indexes**:
```sql
-- Only index unhandled submissions
CREATE INDEX submission_unhandled_idx 
ON submission (created) 
WHERE handled = FALSE;
```

**GIN Indexes**:
```sql
-- Fast fingerprint array queries
CREATE INDEX fingerprint_fingerprint_idx 
ON fingerprint USING GIN (fingerprint gin__int_ops);
```

## Data Lifecycle

### Fingerprint Submission

1. Insert into `submission` table (acoustid_ingest)
2. Publish to NATS queue
3. Worker processes submission
4. Insert into `fingerprint` table (acoustid_fingerprint)
5. Link to `track` (create or match)
6. Insert into `fingerprint_source` (provenance)
7. Update index via HTTP API
8. Insert into `submission_result`
9. Mark `submission.handled = TRUE`

### Track Merging

1. Identify duplicate tracks (manual or automated)
2. Set `track.new_id` to target track
3. Trigger updates all references
4. Merge fingerprints, MBIDs, metadata
5. Disable old track (`track.disabled = TRUE`)

### Data Cleanup

**Cron Jobs**:
- Delete old handled submissions (>30 days)
- Clean up orphaned metadata records
- Remove disabled tracks with no references
- Archive old statistics

## Performance Optimization

### Query Optimization

**Materialized Views**:
```sql
CREATE MATERIALIZED VIEW track_stats AS
SELECT 
    track_id,
    COUNT(DISTINCT fingerprint_id) AS fingerprint_count,
    COUNT(DISTINCT mbid) AS mbid_count,
    SUM(submission_count) AS total_submissions
FROM fingerprint
LEFT JOIN track_mbid USING (track_id)
GROUP BY track_id;
```

**Partitioning** (future):
```sql
-- Partition submissions by month
CREATE TABLE submission_2025_04 PARTITION OF submission
FOR VALUES FROM ('2025-04-01') TO ('2025-05-01');
```

### Caching Strategy

**Application-Level**:
- API key validation (TTLCache, 60s)
- Format ID lookup (permanent cache)
- MusicBrainz MBID existence (Redis, 1h)

**Database-Level**:
- Shared buffers (PostgreSQL config)
- Connection pooling (SQLAlchemy)
- Query result caching (pg_stat_statements)

### Bulk Operations

**Batch Inserts**:
```python
# Insert multiple fingerprints efficiently
db.session.bulk_insert_mappings(Fingerprint, fingerprint_dicts)
db.session.commit()
```

**Bulk Updates**:
```python
# Update submission counts in batch
db.session.execute(
    update(Fingerprint).where(
        Fingerprint.id.in_(fingerprint_ids)
    ).values(
        submission_count=Fingerprint.submission_count + 1
    )
)
```

## Backup and Recovery

### Backup Strategy

**PostgreSQL**:
- Daily full backups (pg_dump)
- Continuous WAL archiving
- Point-in-time recovery enabled

**Index**:
- Daily snapshots via `/:index/_snapshot`
- Incremental backups of Oplog
- Segment files backed up separately

### Disaster Recovery

**Database Restore**:
```bash
# Restore from dump
pg_restore -d acoustid_app acoustid_app_backup.dump

# Point-in-time recovery
pg_restore --target-time='2025-04-28 12:00:00'
```

**Index Rebuild**:
```bash
# Rebuild from database
python manage.py run import --rebuild-index
```