Add StaleDataCleaner and related changes

BackgroundServices/StaleDataCleaner.cs

@@ -0,0 +1,47 @@
+using BirthdayBot.Data;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace BirthdayBot.BackgroundServices
+{
+    /// <summary>
+    /// Automatically removes database information for guilds that have not been accessed in a long time.
+    /// </summary>
+    class StaleDataCleaner : BackgroundService
+    {
+        public StaleDataCleaner(BirthdayBot instance) : base(instance) { }
+
+        public override async Task OnTick()
+        {
+            using var db = await BotInstance.Config.DatabaseSettings.OpenConnectionAsync();
+
+            // Update only for all guilds the bot has cached
+            using (var c = db.CreateCommand())
+            {
+                c.CommandText = $"update {GuildStateInformation.BackingTable} set last_seen = now() "
+                    + "where guild_id = @Gid";
+                var updateGuild = c.Parameters.Add("@Gid", NpgsqlTypes.NpgsqlDbType.Bigint);
+                c.Prepare();
+
+                var list = new List<ulong>(BotInstance.GuildCache.Keys);
+                foreach (var id in list)
+                {
+                    updateGuild.Value = (long)id;
+                    c.ExecuteNonQuery();
+                }
+            }
+
+            // Delete all old values - expecte referencing tables to have 'on delete cascade'
+            using (var t = db.BeginTransaction())
+            {
+                using (var c = db.CreateCommand())
+                {
+                    // Delete data for guilds not seen in 2 weeks
+                    c.CommandText = $"delete from {GuildUserSettings.BackingTable} where (now() - interval '14 days') > last_seen";
+                    var r = c.ExecuteNonQuery();
+                    if (r != 0) Log($"Removed {r} stale guild(s).");
+                }
+            }
+        }
+    }
+}

Data/GuildStateInformation.cs

@@ -316,14 +316,15 @@ namespace BirthdayBot.Data
                     + "moderator_role bigint null, "
                     + "announce_message text null, "
                     + "announce_message_pl text null, "
-                    + "announce_ping boolean not null default FALSE"
+                    + "announce_ping boolean not null default FALSE, "
+                    + "last_seen timestamptz not null default NOW()"
                     + ")";
                 c.ExecuteNonQuery();
             }
             using (var c = db.CreateCommand())
             {
                 c.CommandText = $"create table if not exists {BackingTableBans} ("
-                    + $"guild_id bigint not null references {BackingTable}, "
+                    + $"guild_id bigint not null references {BackingTable} ON DELETE CASCADE, "
                     + "user_id bigint not null, "
                     + "PRIMARY KEY (guild_id, user_id)"
                     + ")";

Data/GuildUserSettings.cs

@@ -126,7 +126,7 @@ namespace BirthdayBot.Data
             using (var c = db.CreateCommand())
             {
                 c.CommandText = $"create table if not exists {BackingTable} ("
-                    + $"guild_id bigint not null references {GuildStateInformation.BackingTable}, "
+                    + $"guild_id bigint not null references {GuildStateInformation.BackingTable} ON DELETE CASCADE, "
                     + "user_id bigint not null, "
                     + "birth_month integer not null, "
                     + "birth_day integer not null, "