optimize sql for getting unknown member ids

src/discord/discord.hpp

@@ -84,6 +84,17 @@ public:
     void GetArchivedPrivateThreads(Snowflake channel_id, sigc::slot<void(DiscordError, const ArchivedThreadsResponseData &)> callback);
     std::vector<Snowflake> GetChildChannelIDs(Snowflake parent_id) const;
 
+    // get ids of given list of members for who we do not have the member data
+    template<typename Iter>
+    std::unordered_set<Snowflake> FilterUnknownMembersFrom(Snowflake guild_id, Iter begin, Iter end) {
+        std::unordered_set<Snowflake> ret;
+        const auto known = m_store.GetMembersInGuild(guild_id);
+        for (auto iter = begin; iter != end; iter++)
+            if (known.find(*iter) == known.end())
+                ret.insert(*iter);
+        return ret;
+    }
+
     bool IsThreadJoined(Snowflake thread_id) const;
     bool HasGuildPermission(Snowflake user_id, Snowflake guild_id, Permission perm) const;
 

src/discord/store.cpp

@@ -576,6 +576,23 @@ std::vector<Snowflake> Store::GetChannelIDsWithParentID(Snowflake channel_id) co
     return ret;
 }
 
+std::unordered_set<Snowflake> Store::GetMembersInGuild(Snowflake guild_id) const {
+    auto &s = m_stmt_get_guild_member_ids;
+
+    s->Bind(1, guild_id);
+
+    std::unordered_set<Snowflake> ret;
+    while (s->FetchOne()) {
+        Snowflake x;
+        s->Get(0, x);
+        ret.insert(x);
+    }
+
+    s->Reset();
+
+    return ret;
+}
+
 void Store::AddReaction(const MessageReactionAddObject &data, bool byself) {
     auto &s = m_stmt_add_reaction;
 
@@ -2134,6 +2151,14 @@ bool Store::CreateStatements() {
         return false;
     }
 
+    m_stmt_get_guild_member_ids = std::make_unique<Statement>(m_db, R"(
+        SELECT user_id FROM members WHERE guild_id = ?
+    )");
+    if (!m_stmt_get_guild_member_ids->OK()) {
+        fprintf(stderr, "failed to prepare get guild member ids statement: %s\n", m_db.ErrStr());
+        return false;
+    }
+
     return true;
 }
 

src/discord/store.hpp

@@ -44,6 +44,8 @@ public:
     std::vector<Message> GetPinnedMessages(Snowflake channel_id) const;
     std::vector<ChannelData> GetActiveThreads(Snowflake channel_id) const; // public
     std::vector<Snowflake> GetChannelIDsWithParentID(Snowflake channel_id) const;
+    std::unordered_set<Snowflake> GetMembersInGuild(Snowflake guild_id) const;
+    // ^ not the same as GetUsersInGuild since users in a guild may include users who do not have retrieved member data
 
     void AddReaction(const MessageReactionAddObject &data, bool byself);
     void RemoveReaction(const MessageReactionRemoveObject &data, bool byself);
@@ -302,5 +304,6 @@ private:
     STMT(sub_reaction);
     STMT(get_reactions);
     STMT(get_chan_ids_parent);
+    STMT(get_guild_member_ids);
 #undef STMT
 };