From 84fc2785d6d5c9144e39f1342fbd324caff3aa29 Mon Sep 17 00:00:00 2001
From: Oliver <oliver.henry.walters@gmail.com>
Date: Tue, 20 Jul 2021 21:26:51 +1000
Subject: [PATCH] Create a custom Manager class for the Part model

- Always perform prefetch_related calls
---
 InvenTree/part/models.py      | 19 +++++++++++++++++++
 InvenTree/part/serializers.py | 19 -------------------
 2 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index 72d388746b..95a8e407b9 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -284,6 +284,23 @@ def match_part_names(match, threshold=80, reverse=True, compare_length=False):
     return matches
 
 
+class PartManager(models.Manager):
+    """
+    Defines a custom object manager for the Part model.
+
+    The main purpose of this manager is to reduce the number of database hits,
+    as the Part model has a large number of ForeignKey fields!
+    """
+
+    def get_queryset(self):
+
+        return super().get_queryset().prefetch_related(
+            'category',
+            'stock_items',
+            'builds',    
+        )
+
+
 @cleanup.ignore
 class Part(MPTTModel):
     """ The Part object represents an abstract part, the 'concept' of an actual entity.
@@ -321,6 +338,8 @@ class Part(MPTTModel):
         responsible: User who is responsible for this part (optional)
     """
 
+    objects = PartManager()
+
     class Meta:
         verbose_name = _("Part")
         verbose_name_plural = _("Parts")
diff --git a/InvenTree/part/serializers.py b/InvenTree/part/serializers.py
index 92dda58590..db543b8602 100644
--- a/InvenTree/part/serializers.py
+++ b/InvenTree/part/serializers.py
@@ -215,25 +215,6 @@ class PartSerializer(InvenTreeModelSerializer):
         if category_detail is not True:
             self.fields.pop('category_detail')
 
-    @staticmethod
-    def prefetch_queryset(queryset):
-        """
-        Prefetch related database tables,
-        to reduce database hits.
-        """
-
-        return queryset.prefetch_related(
-            'category',
-            'category__parts',
-            'category__parent',
-            'stock_items',
-            'bom_items',
-            'builds',
-            'supplier_parts',
-            'supplier_parts__purchase_order_line_items',
-            'supplier_parts__purchase_order_line_items__order',
-        )
-
     @staticmethod
     def annotate_queryset(queryset):
         """