Also switched explain over to own async framework.

explaintreemodelitem.cpp

@@ -51,9 +51,9 @@ namespace {
 
 } // END of unnamed namespace
 
-std::unique_ptr<ExplainRoot> ExplainRoot::createFromJson(Json::Value &json)
+ExplainRoot::SPtr ExplainRoot::createFromJson(Json::Value &json)
 {
-	auto res = std::make_unique<ExplainRoot>();
+	auto res = std::make_shared<ExplainRoot>();
 	// Explain always seems to be an array with one element
 	if (json.isArray()) {
 		if (json.size() > 0) {

explaintreemodelitem.h

@@ -128,7 +128,8 @@ private:
 
 class ExplainRoot {
 public:
-	static std::unique_ptr<ExplainRoot> createFromJson(Json::Value &json);
+	using SPtr = std::shared_ptr<ExplainRoot>;
+	static SPtr createFromJson(Json::Value &json);
 
 	ExplainTreeModelItemPtr plan;
 	float planningTime = 0.f;

mainwindow.cpp

@@ -213,9 +213,10 @@ void MainWindow::performExplain()
 
 	QString command = "EXPLAIN (ANALYZE, VERBOSE, BUFFERS, FORMAT JSON) ";
 	command += ui->queryEdit->toPlainText();
-	explainFuture = std::async(std::launch::async, [this,command]()-> std::unique_ptr<ExplainRoot>
+//	explainFuture = std::async(std::launch::async, [this,command]()-> std::unique_ptr<ExplainRoot>
+   std::thread([this,command]()
 		{
-			std::unique_ptr<ExplainRoot> explain;
+			std::shared_ptr<ExplainRoot> explain;
 			auto res = connection->query(command);
 			if (res.getCols() == 1 && res.getRows() == 1) {
 				std::string s = res.getVal(0, 0);
@@ -226,16 +227,14 @@ void MainWindow::performExplain()
 					explain = ExplainRoot::createFromJson(root);
 				}
 			}
-			QMetaObject::invokeMethod(this, "explain_ready",	 Qt::QueuedConnection); // queues on main thread
+			QueueTask([this, explain]() { explain_ready(explain); });
-			return explain;
+		}).detach();
-		});
 }
 
-void MainWindow::explain_ready()
+void MainWindow::explain_ready(ExplainRoot::SPtr explain)
 {
-	std::unique_ptr<ExplainRoot> explain(explainFuture.get());
 	if (explain) {
-		explainModel.reset(new QueryExplainModel(nullptr, std::move(explain)));
+		explainModel.reset(new QueryExplainModel(nullptr, explain));
 		ui->explainTreeView->setModel(explainModel.get());
 		ui->explainTreeView->expandAll();
 		ui->explainTreeView->setColumnWidth(0, 200);

mainwindow.h

@@ -60,7 +60,7 @@ private:
 	std::unique_ptr<QueryExplainModel> explainModel;
 
 	Pgsql::Canceller queryCancel;
-	std::future<std::unique_ptr<ExplainRoot>> explainFuture;
+
 
 	struct {
 		std::unique_ptr<QSocketNotifier> notifier;
@@ -74,6 +74,7 @@ private:
 
 	void processNotice(const PGresult *result);
 	void query_ready(Pgsql::Result res);
+	void explain_ready(std::shared_ptr<ExplainRoot> explain);
 private slots:
 
 	void startConnect();
@@ -81,7 +82,7 @@ private slots:
 	void performQuery();
 	void performExplain();
 	void socket_activate_connect(int socket);
-	void explain_ready();
+
 	void cancel_query();
 	void receiveNotice(Pgsql::ErrorDetails notice);
 

queryexplainmodel.cpp

@@ -11,8 +11,7 @@ const int c_ColumnLoops = 5;
 const int c_ColumnDetails = 6;
 const int c_NumberOfColumns = 7;
 
-QueryExplainModel::QueryExplainModel(QObject *parent,
+QueryExplainModel::QueryExplainModel(QObject *parent, ExplainRoot::SPtr exp)
-								std::unique_ptr<ExplainRoot> exp)
 	: QAbstractItemModel(parent)
 	, explain(std::move(exp))
 {}

queryexplainmodel.h

@@ -8,7 +8,7 @@ class QueryExplainModel : public QAbstractItemModel
 {
 	Q_OBJECT
 public:
-	explicit QueryExplainModel(QObject *parent, std::unique_ptr<ExplainRoot> exp);
+	explicit QueryExplainModel(QObject *parent, ExplainRoot::SPtr exp);
 
 	QVariant data(const QModelIndex &index, int role) const override;
 
@@ -27,5 +27,5 @@ public:
 	int columnCount(const QModelIndex &parent = QModelIndex()) const override;
 
 private:
-	std::unique_ptr<ExplainRoot> explain;
+	ExplainRoot::SPtr explain;
 };