Speed up writes of events with statekeys to state db

src/Cache.cpp

@@ -37,7 +37,7 @@
 
 //! Should be changed when a breaking change occurs in the cache format.
 //! This will reset client's data.
-static const std::string CURRENT_CACHE_FORMAT_VERSION{"2022.11.06"};
+static const std::string CURRENT_CACHE_FORMAT_VERSION{"2023.03.12"};
 
 //! Keys used for the DB
 static const std::string_view NEXT_BATCH_KEY("next_batch");
@@ -1513,6 +1513,64 @@ Cache::runMigrations()
                QCoreApplication::instance()->processEvents(QEventLoop::AllEvents, 100);
            }
 
+           return true;
+       }},
+      {"2023.03.12",
+       [this]() {
+           try {
+               auto txn      = lmdb::txn::begin(env_, nullptr);
+               auto room_ids = getRoomIds(txn);
+
+               for (const auto &room_id : room_ids) {
+                   try {
+                       auto oldStateskeyDb =
+                         lmdb::dbi::open(txn,
+                                         std::string(room_id + "/state_by_key").c_str(),
+                                         MDB_CREATE | MDB_DUPSORT);
+                       lmdb::dbi_set_dupsort(
+                         txn, oldStateskeyDb, +[](const MDB_val *a, const MDB_val *b) {
+                             auto get_skey = [](const MDB_val *v) {
+                                 return nlohmann::json::parse(
+                                          std::string_view(static_cast<const char *>(v->mv_data),
+                                                           v->mv_size))
+                                   .value("key", "");
+                             };
+
+                             return get_skey(a).compare(get_skey(b));
+                         });
+                       auto newStateskeyDb = getStatesKeyDb(txn, room_id);
+
+                       // convert the dupsort format
+                       {
+                           auto cursor = lmdb::cursor::open(txn, oldStateskeyDb);
+                           std::string_view ev_type, data;
+                           bool start = true;
+                           while (cursor.get(ev_type, data, start ? MDB_FIRST : MDB_NEXT)) {
+                               start = false;
+
+                               auto j =
+                                 nlohmann::json::parse(std::string_view(data.data(), data.size()));
+
+                               newStateskeyDb.put(
+                                 txn, ev_type, j.value("key", "") + '\0' + j.value("id", ""));
+                           }
+                       }
+
+                       // delete old db
+                       lmdb::dbi_drop(txn, oldStateskeyDb, true);
+                   } catch (std::exception &e) {
+                       nhlog::db()->error("While migrating state events from {}, ignoring error {}",
+                                          room_id,
+                                          e.what());
+                   }
+               }
+               txn.commit();
+           } catch (const lmdb::error &) {
+               nhlog::db()->critical("Failed to convert states key database in migration!");
+               return false;
+           }
+
+           nhlog::db()->info("Successfully updated states key database format.");
            return true;
        }},
     };

src/Cache_p.h

@@ -310,9 +310,12 @@ public:
     static int compare_state_key(const MDB_val *a, const MDB_val *b)
     {
         auto get_skey = [](const MDB_val *v) {
-            return nlohmann::json::parse(
+            auto temp = std::string_view(static_cast<const char *>(v->mv_data), v->mv_size);
-                     std::string_view(static_cast<const char *>(v->mv_data), v->mv_size))
+            // allow only passing the state key, in which case no null char will be in it and we
-              .value("key", "");
+            // return the whole string because rfind returns npos.
+            // We search from the back, because state keys could include nullbytes, event ids can
+            // not.
+            return temp.substr(0, temp.rfind('\0'));
         };
 
         return get_skey(a).compare(get_skey(b));
@@ -438,21 +441,12 @@ private:
                           else if (e.state_key.empty())
                               statesdb.del(txn, to_string(e.type));
                           else
-                              stateskeydb.del(txn,
+                              stateskeydb.del(
-                                              to_string(e.type),
+                                txn, to_string(e.type), e.state_key + '\0' + e.event_id);
-                                              nlohmann::json::object({
-                                                                       {"key", e.state_key},
-                                                                       {"id", e.event_id},
-                                                                     })
-                                                .dump());
                       } else if (e.state_key.empty()) {
                           statesdb.put(txn, to_string(e.type), nlohmann::json(e).dump());
                       } else {
-                          auto data = nlohmann::json::object({
+                          auto data = e.state_key + '\0' + e.event_id;
-                                                               {"key", e.state_key},
-                                                               {"id", e.event_id},
-                                                             })
-                                        .dump();
                           auto key  = to_string(e.type);
 
                           // Work around https://bugs.openldap.org/show_bug.cgi?id=8447
@@ -486,8 +480,9 @@ private:
                 }
             } else {
                 auto db = getStatesKeyDb(txn, room_id);
-                std::string d             = nlohmann::json::object({{"key", state_key}}).dump();
+                // we can search using state key, since the compare functions defaults to the whole
-                std::string_view data     = d;
+                // string, when there is no nullbyte
+                std::string_view data     = state_key;
                 std::string_view typeStrV = typeStr;
 
                 auto cursor = lmdb::cursor::open(txn, db);
@@ -496,9 +491,14 @@ private:
 
                 try {
                     auto eventsDb = getEventsDb(txn, room_id);
-                    if (!eventsDb.get(
+                    auto eventid  = data;
-                          txn, nlohmann::json::parse(data)["id"].get<std::string>(), value))
+                    if (auto sep = data.rfind('\0'); sep != std::string_view::npos) {
+                        if (!eventsDb.get(txn, eventid.substr(sep + 1), value))
                             return std::nullopt;
+                    } else {
+                        return std::nullopt;
+                    }
+
                 } catch (std::exception &) {
                     return std::nullopt;
                 }
@@ -537,10 +537,12 @@ private:
                     first = false;
 
                     try {
-                        if (eventsDb.get(
+                        auto eventid = data;
-                              txn, nlohmann::json::parse(data)["id"].get<std::string>(), value))
+                        if (auto sep = data.rfind('\0'); sep != std::string_view::npos) {
+                            if (eventsDb.get(txn, eventid.substr(sep + 1), value))
                                 events.push_back(
                                   nlohmann::json::parse(value).get<mtx::events::StateEvent<T>>());
+                        }
                     } catch (std::exception &e) {
                         nhlog::db()->warn("Failed to parse state event: {}", e.what());
                     }
@@ -636,7 +638,7 @@ private:
     lmdb::dbi getStatesKeyDb(lmdb::txn &txn, const std::string &room_id)
     {
         auto db = lmdb::dbi::open(
-          txn, std::string(room_id + "/state_by_key").c_str(), MDB_CREATE | MDB_DUPSORT);
+          txn, std::string(room_id + "/states_key").c_str(), MDB_CREATE | MDB_DUPSORT);
         lmdb::dbi_set_dupsort(txn, db, compare_state_key);
         return db;
     }