7 files changed, 13 insertions, 16 deletions
diff --git a/src/sql/kernel/qsqlindex.cpp b/src/sql/kernel/qsqlindex.cpp
index 60b0ef6965..5781f24b5c 100644
--- a/src/sql/kernel/qsqlindex.cpp
+++ b/src/sql/kernel/qsqlindex.cpp
@@ -44,9 +44,6 @@
 
 QT_BEGIN_NAMESPACE
 
-// ### Qt 6: remove the static assertion, the 'sorts' field was changed from QList to QVector in Qt 5.6
-Q_STATIC_ASSERT((sizeof(QList<bool>) == sizeof(QVector<bool>)));
-
 /*!
     \class QSqlIndex
     \brief The QSqlIndex class provides functions to manipulate and
diff --git a/src/sql/kernel/qsqlquery.cpp b/src/sql/kernel/qsqlquery.cpp
index 34a3ba3755..ce6c997919 100644
--- a/src/sql/kernel/qsqlquery.cpp
+++ b/src/sql/kernel/qsqlquery.cpp
@@ -261,7 +261,7 @@ QSqlQuery::QSqlQuery(const QSqlQuery& other)
 /*!
     \internal
 */
-static void qInit(QSqlQuery *q, const QString& query, QSqlDatabase db)
+static void qInit(QSqlQuery *q, const QString& query, const QSqlDatabase &db)
 {
     QSqlDatabase database = db;
     if (!database.isValid())
@@ -281,7 +281,7 @@ static void qInit(QSqlQuery *q, const QString& query, QSqlDatabase db)
 
     \sa QSqlDatabase
 */
-QSqlQuery::QSqlQuery(const QString& query, QSqlDatabase db)
+QSqlQuery::QSqlQuery(const QString& query, const QSqlDatabase &db)
 {
     d = QSqlQueryPrivate::shared_null();
     qInit(this, query, db);
@@ -294,7 +294,7 @@ QSqlQuery::QSqlQuery(const QString& query, QSqlDatabase db)
     \sa QSqlDatabase
 */
 
-QSqlQuery::QSqlQuery(QSqlDatabase db)
+QSqlQuery::QSqlQuery(const QSqlDatabase &db)
 {
     d = QSqlQueryPrivate::shared_null();
     qInit(this, QString(), db);
diff --git a/src/sql/kernel/qsqlquery.h b/src/sql/kernel/qsqlquery.h
index cbbc25c4ec..3be04c492c 100644
--- a/src/sql/kernel/qsqlquery.h
+++ b/src/sql/kernel/qsqlquery.h
@@ -59,8 +59,8 @@ class Q_SQL_EXPORT QSqlQuery
 {
 public:
     explicit QSqlQuery(QSqlResult *r);
-    explicit QSqlQuery(const QString& query = QString(), QSqlDatabase db = QSqlDatabase());
-    explicit QSqlQuery(QSqlDatabase db);
+    explicit QSqlQuery(const QString& query = QString(), const QSqlDatabase &db = QSqlDatabase());
+    explicit QSqlQuery(const QSqlDatabase &db);
     QSqlQuery(const QSqlQuery& other);
     QSqlQuery& operator=(const QSqlQuery& other);
     ~QSqlQuery();
diff --git a/src/sql/models/qsqlrelationaltablemodel.cpp b/src/sql/models/qsqlrelationaltablemodel.cpp
index 20adec6a3b..4f5f00bf96 100644
--- a/src/sql/models/qsqlrelationaltablemodel.cpp
+++ b/src/sql/models/qsqlrelationaltablemodel.cpp
@@ -161,7 +161,7 @@ struct QRelation
 class QRelatedTableModel : public QSqlTableModel
 {
 public:
-    QRelatedTableModel(QRelation *rel, QObject *parent = nullptr, QSqlDatabase db = QSqlDatabase());
+    QRelatedTableModel(QRelation *rel, QObject *parent = nullptr, const QSqlDatabase &db = QSqlDatabase());
     bool select() override;
 private:
     bool firstSelect;
@@ -245,7 +245,7 @@ bool QRelation::isValid()
 
 
 
-QRelatedTableModel::QRelatedTableModel(QRelation *rel, QObject *parent, QSqlDatabase db) :
+QRelatedTableModel::QRelatedTableModel(QRelation *rel, QObject *parent, const QSqlDatabase &db) :
     QSqlTableModel(parent, db), firstSelect(true), relation(rel)
 {
 }
@@ -410,7 +410,7 @@ void QSqlRelationalTableModelPrivate::clearCache()
     and the database connection to \a db. If \a db is not valid, the
     default database connection will be used.
 */
-QSqlRelationalTableModel::QSqlRelationalTableModel(QObject *parent, QSqlDatabase db)
+QSqlRelationalTableModel::QSqlRelationalTableModel(QObject *parent, const QSqlDatabase &db)
     : QSqlTableModel(*new QSqlRelationalTableModelPrivate, parent, db)
 {
 }
diff --git a/src/sql/models/qsqlrelationaltablemodel.h b/src/sql/models/qsqlrelationaltablemodel.h
index 1929bd320a..2ebadaabd1 100644
--- a/src/sql/models/qsqlrelationaltablemodel.h
+++ b/src/sql/models/qsqlrelationaltablemodel.h
@@ -91,7 +91,7 @@ public:
     };
 
     explicit QSqlRelationalTableModel(QObject *parent = nullptr,
-                                      QSqlDatabase db = QSqlDatabase());
+                                      const QSqlDatabase &db = QSqlDatabase());
     virtual ~QSqlRelationalTableModel();
 
     QVariant data(const QModelIndex &item, int role = Qt::DisplayRole) const override;
diff --git a/src/sql/models/qsqltablemodel.cpp b/src/sql/models/qsqltablemodel.cpp
index 4b29492134..4d20915c09 100644
--- a/src/sql/models/qsqltablemodel.cpp
+++ b/src/sql/models/qsqltablemodel.cpp
@@ -291,7 +291,7 @@ bool QSqlTableModelPrivate::exec(const QString &stmt, bool prepStatement,
 
     The default edit strategy is \l OnRowChange.
 */
-QSqlTableModel::QSqlTableModel(QObject *parent, QSqlDatabase db)
+QSqlTableModel::QSqlTableModel(QObject *parent, const QSqlDatabase &db)
     : QSqlQueryModel(*new QSqlTableModelPrivate, parent)
 {
     Q_D(QSqlTableModel);
@@ -300,7 +300,7 @@ QSqlTableModel::QSqlTableModel(QObject *parent, QSqlDatabase db)
 
 /*!  \internal
 */
-QSqlTableModel::QSqlTableModel(QSqlTableModelPrivate &dd, QObject *parent, QSqlDatabase db)
+QSqlTableModel::QSqlTableModel(QSqlTableModelPrivate &dd, QObject *parent, const QSqlDatabase &db)
     : QSqlQueryModel(dd, parent)
 {
     Q_D(QSqlTableModel);
diff --git a/src/sql/models/qsqltablemodel.h b/src/sql/models/qsqltablemodel.h
index eba27e60ec..1ac8bd9b04 100644
--- a/src/sql/models/qsqltablemodel.h
+++ b/src/sql/models/qsqltablemodel.h
@@ -62,7 +62,7 @@ class Q_SQL_EXPORT QSqlTableModel: public QSqlQueryModel
 public:
     enum EditStrategy {OnFieldChange, OnRowChange, OnManualSubmit};
 
-    explicit QSqlTableModel(QObject *parent = nullptr, QSqlDatabase db = QSqlDatabase());
+    explicit QSqlTableModel(QObject *parent = nullptr, const QSqlDatabase &db = QSqlDatabase());
     virtual ~QSqlTableModel();
 
     virtual void setTable(const QString &tableName);
@@ -127,7 +127,7 @@ Q_SIGNALS:
     void beforeDelete(int row);
 
 protected:
-    QSqlTableModel(QSqlTableModelPrivate &dd, QObject *parent = nullptr, QSqlDatabase db = QSqlDatabase());
+    QSqlTableModel(QSqlTableModelPrivate &dd, QObject *parent = nullptr, const QSqlDatabase &db = QSqlDatabase());
 
     virtual bool updateRowInTable(int row, const QSqlRecord &values);
     virtual bool insertRowIntoTable(const QSqlRecord &values);