Merge branch 'navmeshdb_sqlite_open_nomutex' into 'master'

Use SQLITE_OPEN_NOMUTEX for navmeshdb

See merge request OpenMW/openmw!1673

apps/openmw_test_suite/sqlite3/request.cpp

@@ -1,7 +1,6 @@
 #include <components/sqlite3/db.hpp>
 #include <components/sqlite3/request.hpp>
 #include <components/sqlite3/statement.hpp>
-#include <components/sqlite3/transaction.hpp>
 
 #include <gtest/gtest.h>
 #include <gmock/gmock.h>

components/sqlite3/db.cpp

@@ -16,7 +16,10 @@ namespace Sqlite3
     Db makeDb(std::string_view path, const char* schema)
     {
         sqlite3* handle = nullptr;
-        const int flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE;
+        // All uses of NavMeshDb are protected by a mutex (navmeshtool) or serialized in a single thread (DbWorker)
+        // so additional synchronization between threads is not required and SQLITE_OPEN_NOMUTEX can be used.
+        // This is unsafe to use NavMeshDb without external synchronization because of internal state.
+        const int flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_NOMUTEX;
         if (const int ec = sqlite3_open_v2(std::string(path).c_str(), &handle, flags, nullptr); ec != SQLITE_OK)
         {
             const std::string message(sqlite3_errmsg(handle));