From ced49685221bb71d51c2ed532c7a81e410c866a3 Mon Sep 17 00:00:00 2001
From: Fernando Costa Bertoldi <fcbertoldi@gmail.com>
Date: Wed, 20 Nov 2024 13:40:00 -0300
Subject: [PATCH] Improve performance of the export bookmark service.

Avoid temporary copies in memory of the Bookmark and Tag instances by returning an iterable from services.exporter.export_netscape_html.
---
 bookmarks/services/exporter.py   | 44 +++++++++++++++-----------------
 bookmarks/tests/test_exporter.py |  8 +++---
 bookmarks/views/settings.py      | 10 +++++---
 package-lock.json                |  4 +--
 4 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/bookmarks/services/exporter.py b/bookmarks/services/exporter.py
index fe41bf49..f91dad97 100644
--- a/bookmarks/services/exporter.py
+++ b/bookmarks/services/exporter.py
@@ -1,33 +1,30 @@
 import html
-from typing import List
+import itertools
+from typing import Iterable
 
 from bookmarks.models import Bookmark
 
-BookmarkDocument = List[str]
 
+def export_netscape_html(bookmarks: Iterable[Bookmark]):
+    def _append_bookmarks():
+        for bookmark in bookmarks:
+            yield from append_bookmark(bookmark)
 
-def export_netscape_html(bookmarks: List[Bookmark]):
-    doc = []
-    append_header(doc)
-    append_list_start(doc)
-    [append_bookmark(doc, bookmark) for bookmark in bookmarks]
-    append_list_end(doc)
+    return itertools.chain(append_header(), append_list_start(), _append_bookmarks(), append_list_end())
 
-    return "\n\r".join(doc)
 
+def append_header():
+    yield "<!DOCTYPE NETSCAPE-Bookmark-file-1>"
+    yield '<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8">'
+    yield "<TITLE>Bookmarks</TITLE>"
+    yield "<H1>Bookmarks</H1>"
 
-def append_header(doc: BookmarkDocument):
-    doc.append("<!DOCTYPE NETSCAPE-Bookmark-file-1>")
-    doc.append('<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=UTF-8">')
-    doc.append("<TITLE>Bookmarks</TITLE>")
-    doc.append("<H1>Bookmarks</H1>")
 
+def append_list_start():
+    yield "<DL><p>"
 
-def append_list_start(doc: BookmarkDocument):
-    doc.append("<DL><p>")
 
-
-def append_bookmark(doc: BookmarkDocument, bookmark: Bookmark):
+def append_bookmark(bookmark: Bookmark):
     url = bookmark.url
     title = html.escape(bookmark.resolved_title or "")
     desc = html.escape(bookmark.resolved_description or "")
@@ -42,13 +39,12 @@ def append_bookmark(doc: BookmarkDocument, bookmark: Bookmark):
     added = int(bookmark.date_added.timestamp())
     modified = int(bookmark.date_modified.timestamp())
 
-    doc.append(
-        f'<DT><A HREF="{url}" ADD_DATE="{added}" LAST_MODIFIED="{modified}" PRIVATE="{private}" TOREAD="{toread}" TAGS="{tags}">{title}</A>'
-    )
+    yield  f'<DT><A HREF="{url}" ADD_DATE="{added}" LAST_MODIFIED="{modified}" PRIVATE="{private}" TOREAD="{toread}" TAGS="{tags}">{title}</A>'
+    
 
     if desc:
-        doc.append(f"<DD>{desc}")
+        yield f"<DD>{desc}"
 
 
-def append_list_end(doc: BookmarkDocument):
-    doc.append("</DL><p>")
+def append_list_end():
+    yield "</DL><p>"
diff --git a/bookmarks/tests/test_exporter.py b/bookmarks/tests/test_exporter.py
index 2056bc73..0f9f452a 100644
--- a/bookmarks/tests/test_exporter.py
+++ b/bookmarks/tests/test_exporter.py
@@ -74,7 +74,7 @@ def test_export_bookmarks(self):
                 is_archived=True,
             ),
         ]
-        html = exporter.export_netscape_html(bookmarks)
+        html = "\r\n".join(exporter.export_netscape_html(bookmarks))
 
         lines = [
             '<DT><A HREF="https://example.com/1" ADD_DATE="1" LAST_MODIFIED="11" PRIVATE="1" TOREAD="0" TAGS="">Title 1</A>',
@@ -89,7 +89,7 @@ def test_export_bookmarks(self):
             '<DT><A HREF="https://example.com/7" ADD_DATE="7" LAST_MODIFIED="77" PRIVATE="1" TOREAD="0" TAGS="linkding:archived">Title 7</A>',
             '<DT><A HREF="https://example.com/8" ADD_DATE="8" LAST_MODIFIED="88" PRIVATE="1" TOREAD="0" TAGS="tag4,tag5,linkding:archived">Title 8</A>',
         ]
-        self.assertIn("\n\r".join(lines), html)
+        self.assertIn("\r\n".join(lines), html)
 
     def test_escape_html(self):
         bookmark = self.setup_bookmark(
@@ -97,7 +97,7 @@ def test_escape_html(self):
             description="The <style> HTML element contains style information for a document, or part of a document.",
             notes="Interesting notes about the <style> HTML element.",
         )
-        html = exporter.export_netscape_html([bookmark])
+        html = "\r\n".join(exporter.export_netscape_html([bookmark]))
 
         self.assertIn("&lt;style&gt;: The Style Information element", html)
         self.assertIn(
@@ -111,4 +111,4 @@ def test_handle_empty_values(self):
         bookmark.title = ""
         bookmark.description = ""
         bookmark.save()
-        exporter.export_netscape_html([bookmark])
+        "\r\n".join(exporter.export_netscape_html([bookmark]))
diff --git a/bookmarks/views/settings.py b/bookmarks/views/settings.py
index 2f5f88e9..84de86c3 100644
--- a/bookmarks/views/settings.py
+++ b/bookmarks/views/settings.py
@@ -7,7 +7,6 @@
 from django.contrib import messages
 from django.contrib.auth.decorators import login_required
 from django.core.exceptions import PermissionDenied
-from django.db.models import prefetch_related_objects
 from django.http import HttpResponseRedirect, HttpResponse
 from django.shortcuts import render
 from django.urls import reverse
@@ -233,14 +232,17 @@ def bookmark_import(request):
 def bookmark_export(request):
     # noinspection PyBroadException
     try:
-        bookmarks = Bookmark.objects.filter(owner=request.user)
         # Prefetch tags to prevent n+1 queries
-        prefetch_related_objects(bookmarks, "tags")
+        bookmarks = Bookmark.objects.filter(owner=request.user).prefetch_related("tags")
         file_content = exporter.export_netscape_html(bookmarks)
+        def _newline_appended():
+            for line in file_content:
+                yield line
+                yield "\r\n"
 
         response = HttpResponse(content_type="text/plain; charset=UTF-8")
         response["Content-Disposition"] = 'attachment; filename="bookmarks.html"'
-        response.write(file_content)
+        response.writelines(_newline_appended())
 
         return response
     except:
diff --git a/package-lock.json b/package-lock.json
index 72a0524a..7dae9e37 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "linkding",
-  "version": "1.35.0",
+  "version": "1.36.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "linkding",
-      "version": "1.35.0",
+      "version": "1.36.0",
       "license": "MIT",
       "dependencies": {
         "@hotwired/turbo": "^8.0.6",