# Module: Database layer (`src/Database`)

## Purpose

PostgreSQL schema and Linq2DB mapping for annotations, media, detections, queue buffer, settings, and `detection_classes`. Underpins every HTTP module in `01_annotations.md`.

## Public interface

- `AppDataConnection` — `ITable<>` for all mapped entities.
- `DatabaseMigrator.Migrate` — embedded SQL: `CREATE TABLE IF NOT EXISTS` / `ALTER … IF NOT EXISTS`, seed detection classes.

## Entities (summary)

- `Annotation`, `Media`, `Detection` — core annotation + YOLO row model (`time` stored as BIGINT ticks).
- `AnnotationsQueueRecord` — failsafe outbox (`operation`, `annotation_ids`).
- `SystemSettings` — includes `GenerateAnnotatedImage`, `SilentDetection` (suite §Annotated Image / Silent Detection).
- `DirectorySettings` — `/data/...` roots consumed by `PathResolver`.
- `DetectionClass`, `UserSettings`, `CameraSettings`.

## Dependencies

Wire enums on columns.

## Consumers

All services and `ClassesController`.

## Suite doc

Annotation identity and ER-level behavior; cross-check `00_database_schema.md` in suite when entities evolve.