Fix item orders and use integrated limit operation;

main.py

@@ -7,7 +7,7 @@ from flask import Flask, request, abort
 from feedgen.feed import FeedGenerator
 
 from pony import orm
-from pony.orm import Required, Optional, Set
+from pony.orm import Required, Optional, Set, desc
 
 config = configparser.ConfigParser()
 config.read('settings.ini')
@@ -146,8 +146,11 @@ def by_feed_name(slug):
     gen.link(href=feed.atom_id)
     gen.description(feed.description)
 
-    count = 0
-    for item in feed.items.order_by(Item.date):
+    # Take the items by reversed date order. When adding them in the RSS feed,
+    # order will be reversed again (first in array will end up last in the
+    # feed), so explicitly reverse one more time.
+    items = reversed(feed.items.order_by(desc(Item.date))[:20])
+    for item in items:
         fe = gen.add_entry()
         fe.id(item.atom_id)
         fe.title(item.title)
@@ -156,10 +159,6 @@ def by_feed_name(slug):
         date = item.date.replace(tzinfo=timezone.utc)
         fe.published(date)
 
-        count += 1
-        if count == 20:
-            break
-
     return gen.rss_str(pretty=True).decode('utf8')