feat: cache geojson data for vector files

internal/repository/postgres/dataset.go

@@ -31,6 +31,7 @@ const datasetColumns = `id, category_id, name, description, unit, filename, stor
 	CASE WHEN file_type = 'raster' AND geometry IS NOT NULL
 	     THEN ARRAY[ST_XMin(geometry), ST_YMin(geometry), ST_XMax(geometry), ST_YMax(geometry)]
 	     ELSE NULL END AS bbox,
+	geojson,
 	created_at, updated_at`
 
 func scanDataset(row pgx.Row) (domain.Dataset, error) {
@@ -40,7 +41,7 @@ func scanDataset(row pgx.Row) (domain.Dataset, error) {
 		&d.Filename, &d.StorageKey, &d.CogStorageKey, &d.FileType, &d.SizeBytes, &d.ContentType,
 		&d.Properties, &d.Meta, &d.Automated, &d.Status,
 		&d.AttributeColumns, &d.KatoColumn, &d.YearColumns, &d.ParseError,
-		&d.Geometry, &d.BBox, &d.CreatedAt, &d.UpdatedAt,
+		&d.Geometry, &d.BBox, &d.GeoJSON, &d.CreatedAt, &d.UpdatedAt,
 	)
 	return d, err
 }
@@ -193,6 +194,23 @@ func (r *DatasetRepository) MarkReady(ctx context.Context, id uuid.UUID, geometr
 	return nil
 }
 
+// SetGeoJSON stores the pre-assembled GeoJSON FeatureCollection for a dataset
+// (nil -> NULL). It is written at processing time and served verbatim by the
+// .geojson endpoint.
+func (r *DatasetRepository) SetGeoJSON(ctx context.Context, id uuid.UUID, geojson []byte) error {
+	tag, err := r.pool.Exec(ctx,
+		`UPDATE datasets SET geojson = $2, updated_at = now() WHERE id = $1`,
+		id, nullableJSON(json.RawMessage(geojson)),
+	)
+	if err != nil {
+		return mapError(err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
 // ReplaceObservations atomically replaces all observations for a dataset.
 func (r *DatasetRepository) ReplaceObservations(ctx context.Context, datasetID uuid.UUID, obs []domain.Observation) error {
 	tx, err := r.pool.Begin(ctx)