Added a query plan recorder for debugging purposes

2025-07-11 00:11:02 +02:00
parent 2fd7d9767b
commit 59e85ee424
29 changed files with 546 additions and 44 deletions
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2025 Emeric Poupon
+ *
+ * This file is part of LMS.
+ *
+ * LMS is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * LMS is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with LMS.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "QueryPlanRecorder.hpp"
+
+#include <memory>
+#include <mutex>
+
+#include <Wt/Dbo/SqlStatement.h>
+#include <Wt/Dbo/Transaction.h>
+
+#include "core/ILogger.hpp"
+
+namespace lms::db
+{
+    std::unique_ptr<IQueryPlanRecorder> createQueryPlanRecorder()
+    {
+        return std::make_unique<QueryPlanRecorder>();
+    }
+
+    QueryPlanRecorder::QueryPlanRecorder()
+    {
+        LMS_LOG(DB, INFO, "Recording database query plans");
+    }
+
+    QueryPlanRecorder::~QueryPlanRecorder() = default;
+
+    void QueryPlanRecorder::visitQueryPlans(const QueryPlanVisitor& visitor) const
+    {
+        const std::shared_lock lock{ _mutex };
+
+        for (const auto& [query, plan] : _queryPlans)
+            visitor(query, plan);
+    }
+
+    void QueryPlanRecorder::recordQueryPlanIfNeeded(Wt::Dbo::Session& session, const std::string& query)
+    {
+        {
+            const std::shared_lock lock{ _mutex };
+
+            if (_queryPlans.contains(query))
+                return;
+        }
+
+        Wt::Dbo::Transaction transaction{ session };
+
+        Wt::Dbo::SqlConnection* connection{ transaction.connection() };
+        auto statement{ connection->prepareStatement("EXPLAIN QUERY PLAN " + query) };
+        statement->execute();
+
+        std::map<int, std::string> entries{ { 0, "" } };
+        std::map<int, std::vector<int>> relationships;
+
+        std::string detail;
+        while (statement->nextRow())
+        {
+            detail.clear();
+
+            int id{};
+            int parent{};
+            int unused{};
+
+            if (statement->getResult(0, &id)
+                && statement->getResult(1, &parent)
+                && statement->getResult(2, &unused)
+                && statement->getResult(3, &detail, static_cast<int>(detail.capacity())))
+            {
+                entries.emplace(id, detail);
+                relationships[parent].push_back(id);
+            }
+        }
+
+        // format
+        std::string result;
+        std::function<void(int, unsigned)> formatQuery = [&](int id, unsigned level) -> void {
+            for (std::size_t i{}; i < level; ++i)
+                result += '\t';
+
+            result += entries.at(id);
+            result += '\n';
+            auto itChildren = relationships.find(id);
+            if (itChildren == relationships.end())
+                return;
+
+            for (int child : itChildren->second)
+                formatQuery(child, level + 1);
+        };
+
+        formatQuery(0, 0);
+
+        {
+            const std::unique_lock lock{ _mutex };
+            _queryPlans.try_emplace(query, std::move(result));
+        }
+    }
+} // namespace lms::db