fix(users/Profpatsch/whatcd-resolver): refresh table on delete

Instead of serving a stale table when a torrent gets deleted, fetch
the whole view again. This is a little wasteful, but torrents
shouldn’t get deleted very often, so it’s fine.

Change-Id: If33d517270421881852158f27dbc3e7d24880d3b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12333
Reviewed-by: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI

users/Profpatsch/whatcd-resolver/src/Transmission.hs

@@ -61,7 +61,7 @@ getAndUpdateTransmissionTorrentsStatus ::
     HasField "torrentId" info Int
   ) =>
   Map (Label "torrentHash" Text) info ->
-  (Transaction m (Map (Label "torrentHash" Text) (Label "percentDone" Percentage)))
+  (Transaction m (Label "knownTorrentsStale" Bool, (Map (Label "torrentHash" Text) (Label "percentDone" Percentage))))
 getAndUpdateTransmissionTorrentsStatus knownTorrents = inSpan' "getAndUpdateTransmissionTorrentsStatus" $ \span -> do
   let fields = ["hashString", "percentDone"]
   actualTorrents <-
@@ -82,7 +82,7 @@ getAndUpdateTransmissionTorrentsStatus knownTorrents = inSpan' "getAndUpdateTran
   if
     | Map.null toDelete -> do
         addEventSimple span "We know about all transmission hashes."
-        pure actualTorrents
+        pure (label @"knownTorrentsStale" False, actualTorrents)
     | otherwise -> inSpan' "Delete outdated transmission hashes" $ \span' -> do
         addAttribute
           span'
@@ -108,7 +108,7 @@ getAndUpdateTransmissionTorrentsStatus knownTorrents = inSpan' "getAndUpdateTran
           WHERE transmission_torrent_hash = ANY (?::text[])
         |]
             $ Only (toDelete & Map.keys <&> (.torrentHash) & PGArray :: PGArray Text)
-        pure actualTorrents
+        pure (label @"knownTorrentsStale" True, actualTorrents)
 
 getTransmissionTorrentsTable ::
   (MonadTransmission m, MonadThrow m, MonadLogger m, MonadOtel m) => m Html