Backend: Produktliste gebuendelt laden (N+1 weg, deutlich schneller)

list_products rief product_to_out je Artikel auf - pro Artikel mehrere Abfragen
(Bestand, abgelaufene Chargen, Codes, Bild, Lazy-Relationen). Bei vielen
Artikeln = hunderte Queries und mehrere Sekunden. Neu: products_to_out_bulk holt
Bestand/Abgelaufen/Codes/Bild je einmal fuer alle und laedt Relationen eager
(joinedload/selectinload). Ergebnis identisch (Test), aber nur noch wenige Queries.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/crud.py

@@ -2,12 +2,14 @@
 
 from __future__ import annotations
 
+from collections import defaultdict
 from datetime import date
 
 from fastapi import HTTPException, status
+from sqlalchemy import func
 from sqlalchemy.orm import Session
 
-from .models import Barcode, Category, CategoryTracking, Lot, Product, ProductImage
+from .models import Barcode, Category, CategoryTracking, Item, Lot, Product, ProductImage
 from .schemas import BarcodeOut, LocationMinStockOut, ProductOut
 from .services.conversion import KIND_OF_BASE, display_unit_info
 from .services.stock import current_stock
@@ -89,6 +91,87 @@ def product_to_out(db: Session, product: Product) -> ProductOut:
     return out
 
 
+def products_to_out_bulk(db: Session, products: list[Product]) -> list[ProductOut]:
+    """Wie ``product_to_out``, aber für viele Artikel mit **gebündelten** Abfragen
+    statt N+1 – für die Listen-Ansichten. Bestand, abgelaufene Chargen, Codes und
+    Bild-Version werden je einmal für alle Artikel geholt; Relationen (Kategorie,
+    Shop, Einheiten, Bedarfe, Feldwerte) sollten vom Aufrufer eager-geladen sein.
+    """
+    if not products:
+        return []
+    ids = [p.id for p in products]
+
+    # Bestand: Lot-Summen (Nicht-Einzelstücke) bzw. Item-Anzahl (Einzelstücke).
+    lot_sums = dict(
+        db.query(Lot.product_id, func.coalesce(func.sum(Lot.quantity), 0.0))
+        .filter(Lot.product_id.in_(ids)).group_by(Lot.product_id).all()
+    )
+    item_counts = dict(
+        db.query(Item.product_id, func.count(Item.id))
+        .filter(Item.product_id.in_(ids)).group_by(Item.product_id).all()
+    )
+    # Abgelaufene Chargen je Artikel.
+    heute = date.today()
+    expired = dict(
+        db.query(Lot.product_id, func.count(Lot.id))
+        .filter(
+            Lot.product_id.in_(ids),
+            Lot.best_before.isnot(None),
+            Lot.best_before < heute,
+            Lot.quantity > 0,
+        )
+        .group_by(Lot.product_id).all()
+    )
+    # Zusätzliche EAN-Codes je Artikel.
+    codes: dict[int, list[Barcode]] = defaultdict(list)
+    for b in db.query(Barcode).filter(Barcode.product_id.in_(ids)).order_by(Barcode.id).all():
+        codes[b.product_id].append(b)
+    # Bild-Version (Epoch der letzten Bildänderung) je Artikel.
+    imgs = dict(
+        db.query(ProductImage.product_id, ProductImage.updated_at)
+        .filter(ProductImage.product_id.in_(ids)).all()
+    )
+
+    out: list[ProductOut] = []
+    for product in products:
+        o = ProductOut.model_validate(product)
+        o.stock = (
+            float(item_counts.get(product.id, 0)) if product.individual
+            else float(lot_sums.get(product.id, 0.0))
+        )
+        o.expired_count = expired.get(product.id, 0)
+        o.barcodes = [BarcodeOut.model_validate(b) for b in codes.get(product.id, [])]
+        o.category_name = product.category.name if product.category else None
+        ts = imgs.get(product.id)
+        o.image_version = int(ts.timestamp()) if ts is not None else None
+        o.tracking = CategoryTracking(product_tracking(db, product))
+        o.shop_name = product.shop.name if product.shop else None
+        o.kind = KIND_OF_BASE[product.base_unit].value
+        name, factor = display_unit_info(product)
+        o.unit_name = name
+        o.unit_factor = factor
+        if product.min_stock is not None:
+            if product.min_stock_in_packages and product.package_size:
+                o.min_stock_display = product.min_stock / product.package_size
+                o.min_stock_unit_label = "Pkg"
+            elif product.min_stock_unit is not None:
+                o.min_stock_display = product.min_stock / product.min_stock_unit.factor
+                o.min_stock_unit_label = product.min_stock_unit.name
+            else:
+                o.min_stock_display = product.min_stock / factor
+                o.min_stock_unit_label = name
+        o.location_min_stocks = [
+            LocationMinStockOut(
+                location_id=e.location_id,
+                location_name=e.location.name if e.location else None,
+                min_stock=e.min_stock,
+            )
+            for e in sorted(product.location_min_stocks, key=lambda x: x.id)
+        ]
+        out.append(o)
+    return out
+
+
 def resolve_product(
     db: Session, product_id: int | None, barcode: str | None
 ) -> Product: