optimise some dicom manipulations

generic/models.py

@@ -568,41 +568,35 @@ class SeriesBase(models.Model):
             n = n + 1
 
     def order_by_dicom(self, field="SliceLocation"):
+        """
+        Orders images in the series by the given DICOM field (default: SliceLocation).
+        Only keeps minimal data in memory and uses bulk_update for efficiency.
+        """
         images = self.images.filter(removed=False)
+        sortable = []
 
+        for img in images:
+            try:
+                ds = pydicom.dcmread(img.image.path, stop_before_pixels=True)
+                value = getattr(ds, field, None)
+                if value is not None:
+                    sortable.append((value, img))
+            except Exception:
+                continue  # Skip unreadable or invalid DICOMs
 
-        files = []
-
-        for i in images:
-            files.append((i, pydicom.dcmread(i.image.path)))
-
-        # print("file count: {}".format(len(files)))
-
-        # skip files with no SliceLocation (eg scout views)
-        slices = []
-        map = {}
-        skipcount = 0
-        for i, f in files:
-            if hasattr(f, field):
-                slices.append(f)
-                # map[f.SliceLocation] = i
-                map[f[field].value] = i
-            else:
-                skipcount = skipcount + 1
-
-        if not slices:
+        if not sortable:
             return
 
-        # ensure they are in the correct order
-        slices = sorted(slices, key=lambda s: s[field].value)
+        # Sort by the DICOM field value
+        sortable.sort(key=lambda x: x[0])
 
-        # print(slices)
-        n = 1
-        for f in slices:
-            i = map[f[field].value]
-            i.position = n
-            i.save()
-            n = n + 1
+        # Assign new positions and collect for bulk update
+        for idx, (value, img) in enumerate(sortable, start=1):
+            img.position = idx
+
+        # Bulk update all changed images
+        SeriesImage = self.images.model
+        SeriesImage.objects.bulk_update([img for _, img in sortable], ['position'])
 
     def get_total_image_size(self, refresh=False):
         """Returns the total size of all images in the series.