fix: /rss lazy load issue & perf improvements

Some fixes for the /rss endpoints

* Load all data in one go:
Previously data was lazy loaded thus it made several sub-queries per
package (> 200 queries for composing the rss data for a single request).
Now we are performing a single SQL query.
(request time improvement: 550ms -> 130ms)
This also fixes aurweb-errors#510 and alike

* Remove some "dead code":
The fields "source, author, link" were never included in the rss output
(wrong or insufficient data passed to the different entry.xyz functions)
Nobody seems to be missing them anyways, so let's remove em.

* Remove "Last-Modified" header:
Obsolete since nginx can/will only handle "If-Modified-Since" requests
in it's current configuration. All requests are passed to fastapi anyways.

Signed-off-by: moson <moson@archlinux.org>

aurweb/routers/rss.py

@@ -1,5 +1,3 @@
-from datetime import datetime
-
 from fastapi import APIRouter, Request
 from fastapi.responses import Response
 from feedgen.feed import FeedGenerator
@@ -10,12 +8,11 @@ from aurweb.models import Package, PackageBase
 router = APIRouter()
 
 
-def make_rss_feed(request: Request, packages: list, date_attr: str):
+def make_rss_feed(request: Request, packages: list):
     """Create an RSS Feed string for some packages.
 
     :param request: A FastAPI request
     :param packages: A list of packages to add to the RSS feed
-    :param date_attr: The date attribute (DB column) to use
     :return: RSS Feed string
     """
 
@@ -36,18 +33,11 @@ def make_rss_feed(request: Request, packages: list, date_attr: str):
         entry = feed.add_entry(order="append")
         entry.title(pkg.Name)
         entry.link(href=f"{base}/packages/{pkg.Name}", rel="alternate")
-        entry.link(href=f"{base}/rss", rel="self", type="application/rss+xml")
         entry.description(pkg.Description or str())
-
-        attr = getattr(pkg.PackageBase, date_attr)
-        dt = filters.timestamp_to_datetime(attr)
+        dt = filters.timestamp_to_datetime(pkg.Timestamp)
         dt = filters.as_timezone(dt, request.user.Timezone)
         entry.pubDate(dt.strftime("%Y-%m-%d %H:%M:%S%z"))
-
-        entry.source(f"{base}")
-        if pkg.PackageBase.Maintainer:
-            entry.author(author={"name": pkg.PackageBase.Maintainer.Username})
-        entry.guid(f"{pkg.Name} - {attr}")
+        entry.guid(f"{pkg.Name}-{pkg.Timestamp}")
 
     return feed.rss_str()
 
@@ -59,15 +49,15 @@ async def rss(request: Request):
         .join(PackageBase)
         .order_by(PackageBase.SubmittedTS.desc())
         .limit(100)
+        .with_entities(
+            Package.Name,
+            Package.Description,
+            PackageBase.SubmittedTS.label("Timestamp"),
+        )
     )
-    feed = make_rss_feed(request, packages, "SubmittedTS")
 
+    feed = make_rss_feed(request, packages)
     response = Response(feed, media_type="application/rss+xml")
-    package = packages.first()
-    if package:
-        dt = datetime.utcfromtimestamp(package.PackageBase.SubmittedTS)
-        modified = dt.strftime("%a, %d %m %Y %H:%M:%S GMT")
-        response.headers["Last-Modified"] = modified
 
     return response
 
@@ -79,14 +69,14 @@ async def rss_modified(request: Request):
         .join(PackageBase)
         .order_by(PackageBase.ModifiedTS.desc())
         .limit(100)
+        .with_entities(
+            Package.Name,
+            Package.Description,
+            PackageBase.ModifiedTS.label("Timestamp"),
+        )
     )
-    feed = make_rss_feed(request, packages, "ModifiedTS")
 
+    feed = make_rss_feed(request, packages)
     response = Response(feed, media_type="application/rss+xml")
-    package = packages.first()
-    if package:
-        dt = datetime.utcfromtimestamp(package.PackageBase.ModifiedTS)
-        modified = dt.strftime("%a, %d %m %Y %H:%M:%S GMT")
-        response.headers["Last-Modified"] = modified
 
     return response