Optimize performance by adding support for count queries.

src/orm/qormglobal.h

@@ -1,6 +1,6 @@
 /*
- * Copyright (C) 2019-2022 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019-2022 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -108,7 +108,8 @@ namespace QOrm
         Read,
         Update,
         Delete,
-        Merge
+        Merge,
+        Count
     };
     extern Q_ORM_EXPORT QDebug operator<<(QDebug dbg, Operation operation);
 

src/orm/qormquerybuilder.cpp

@@ -1,6 +1,6 @@
 /*
- * Copyright (C) 2019 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -119,11 +119,11 @@ namespace QOrmPrivate
     {
     }
 
-    QueryBuilderHelper::QueryBuilderHelper(QueryBuilderHelper&&) = default;
+    QueryBuilderHelper::QueryBuilderHelper(QueryBuilderHelper&&) noexcept = default;
 
     QueryBuilderHelper::~QueryBuilderHelper() = default;
 
-    QueryBuilderHelper& QueryBuilderHelper::operator=(QueryBuilderHelper&&) = default;
+    QueryBuilderHelper& QueryBuilderHelper::operator=(QueryBuilderHelper&&) noexcept = default;
 
     void QueryBuilderHelper::setInstance(const QMetaObject& qMetaObject, QObject* instance)
     {
@@ -169,7 +169,8 @@ namespace QOrmPrivate
 
             return QOrmQuery{operation, *d->m_relation.mapping(), d->m_entityInstance};
         }
-        else if (operation == QOrm::Operation::Read || operation == QOrm::Operation::Delete)
+        else if (operation == QOrm::Operation::Read || operation == QOrm::Operation::Delete ||
+                 operation == QOrm::Operation::Count)
         {
             FoldedFilters filters = foldFilters(d->m_relation, d->m_filters);
             QOrmQuery query = QOrmQuery{operation,
@@ -196,6 +197,19 @@ namespace QOrmPrivate
     {
         return d->m_session->execute(build(QOrm::Operation::Delete, QOrm::QueryFlags::None));
     }
+
+    QOrmQueryResult<int> QueryBuilderHelper::count() const
+    {
+        QOrmQueryResult<QObject> result =
+            d->m_session->execute(build(QOrm::Operation::Count, QOrm::QueryFlags::None));
+
+        if (result.hasError())
+        {
+            return QOrmQueryResult<int>{result.error(), result.numRowsAffected()};
+        }
+
+        return QOrmQueryResult<int>{result.numRowsAffected()};
+    }
 } // namespace QOrmPrivate
 
 QT_END_NAMESPACE

src/orm/qormquerybuilder.h

@@ -1,6 +1,6 @@
 /*
- * Copyright (C) 2019 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -51,11 +51,11 @@ namespace QOrmPrivate
     public:
         QueryBuilderHelper(QOrmSession* session, const QOrmRelation& relation);
         QueryBuilderHelper(const QueryBuilderHelper&) = delete;
-        QueryBuilderHelper(QueryBuilderHelper&&);
+        QueryBuilderHelper(QueryBuilderHelper&&) noexcept;
         ~QueryBuilderHelper();
 
         QueryBuilderHelper& operator=(const QueryBuilderHelper&) = delete;
-        QueryBuilderHelper& operator=(QueryBuilderHelper&&);
+        QueryBuilderHelper& operator=(QueryBuilderHelper&&) noexcept;
 
         void setInstance(const QMetaObject& qMetaObject, QObject* instance);
         void addFilter(const QOrmFilter& filter);
@@ -66,10 +66,9 @@ namespace QOrmPrivate
         Q_REQUIRED_RESULT
         QOrmQuery build(QOrm::Operation operation, QOrm::QueryFlags flags) const;
 
-        Q_REQUIRED_RESULT
-        QOrmQueryResult<QObject> select(QOrm::QueryFlags flags) const;
-
+        [[nodiscard]] QOrmQueryResult<QObject> select(QOrm::QueryFlags flags) const;
         [[nodiscard]] QOrmQueryResult<QObject> remove() const;
+        [[nodiscard]] QOrmQueryResult<int> count() const;
 
     private:
         std::unique_ptr<QueryBuilderHelperPrivate> d;
@@ -150,6 +149,8 @@ class QOrmQueryBuilder
 
     [[nodiscard]] QOrmQueryResult<Projection> remove() { return m_helper.remove(); }
 
+    [[nodiscard]] QOrmQueryResult<int> count() const { return m_helper.count(); }
+
     Q_REQUIRED_RESULT
     QOrmQuery build(QOrm::Operation operation, QOrm::QueryFlags flags = QOrm::QueryFlags::None) const { return m_helper.build(operation, flags); }
 

src/orm/qormqueryresult.h

@@ -1,6 +1,6 @@
 /*
- * Copyright (C) 2019 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -240,6 +240,29 @@ class QOrmQueryResult<void> : public QtOrmPrivate::QOrmQueryResultBase<void>
     }
 };
 
+template<>
+class QOrmQueryResult<int> : public QtOrmPrivate::QOrmQueryResultBase<int>
+{
+    using Base = QOrmQueryResultBase<int>;
+
+public:
+    explicit QOrmQueryResult(int value)
+        : Base{QOrmError{QOrm::ErrorType::None, QString{}}, QVariant{}, 0}
+        , m_value{value}
+    {
+    }
+
+    explicit QOrmQueryResult(const QOrmError& error, int numRowsAffected)
+        : Base{error, QVariant{}, numRowsAffected}
+    {
+    }
+
+    [[nodiscard]] int value() const { return m_value; }
+
+private:
+    int m_value{0};
+};
+
 QT_END_NAMESPACE
 
 #endif

src/orm/qormsqliteprovider.cpp

@@ -1,7 +1,7 @@
 /*
  * Copyright (C) 2020-2024 Dmitriy Purgin <dpurgin@gmail.com>
- * Copyright (C) 2019-2024 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019-2024 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -103,6 +103,7 @@ class QOrmSqliteProviderPrivate
     QOrmQueryResult<QObject> merge(const QOrmQuery& query);
     QOrmQueryResult<QObject> remove(const QOrmQuery& query,
                                     QOrmEntityInstanceCache& entityInstanceCache);
+    QOrmQueryResult<QObject> count(const QOrmQuery& query);
 
     [[nodiscard]] bool foreignKeysEnabled();
     [[nodiscard]] QOrmError setForeignKeysEnabled(bool enabled);
@@ -981,6 +982,26 @@ QOrmQueryResult<QObject> QOrmSqliteProviderPrivate::remove(
     return QOrmQueryResult<QObject>{resultSet, sqlQuery.numRowsAffected()};
 }
 
+QOrmQueryResult<QObject> QOrmSqliteProviderPrivate::count(const QOrmQuery& query)
+{
+    Q_ASSERT(query.operation() == QOrm::Operation::Count);
+
+    auto [statement, boundParameters] = m_statementGenerator.generate(query);
+
+    QSqlQuery sqlQuery = prepareAndExecute(statement, boundParameters);
+
+    if (sqlQuery.lastError().type() != QSqlError::NoError || !sqlQuery.next())
+    {
+        return QOrmQueryResult<QObject>{QOrmError{QOrm::ErrorType::Provider,
+                                                  sqlQuery.lastError().text()},
+                                        sqlQuery.numRowsAffected()};
+    }
+
+    int count = sqlQuery.value(0).toInt();
+
+    return QOrmQueryResult{QVector<QObject*>{}, count};
+}
+
 bool QOrmSqliteProviderPrivate::foreignKeysEnabled()
 {
     QSqlQuery query{m_database};
@@ -1208,6 +1229,9 @@ QOrmQueryResult<QObject> QOrmSqliteProvider::execute(const QOrmQuery& query,
         case QOrm::Operation::Delete:
             return d->remove(query, entityInstanceCache);
 
+        case QOrm::Operation::Count:
+            return d->count(query);
+
         case QOrm::Operation::Merge:
             Q_ORM_UNEXPECTED_STATE;
     }

src/orm/qormsqlitestatementgenerator_p.cpp

@@ -1,6 +1,6 @@
 /*
- * Copyright (C) 2019-2022 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019-2022 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -102,6 +102,7 @@ QString QOrmSqliteStatementGenerator::generate(const QOrmQuery& query, QVariantM
                                            boundParameters);
 
         case QOrm::Operation::Read:
+        case QOrm::Operation::Count:
             return generateSelectStatement(query, boundParameters);
 
         case QOrm::Operation::Delete:
@@ -211,9 +212,17 @@ QString QOrmSqliteStatementGenerator::generateUpdateStatement(const QOrmMetadata
 QString QOrmSqliteStatementGenerator::generateSelectStatement(const QOrmQuery& query,
                                                               QVariantMap& boundParameters)
 {
-    Q_ASSERT(query.operation() == QOrm::Operation::Read);
+    Q_ASSERT(query.operation() == QOrm::Operation::Read ||
+             query.operation() == QOrm::Operation::Count);
 
-    QStringList parts = {"SELECT *", generateFromClause(query.relation(), boundParameters)};
+    QString projection = query.operation() == QOrm::Operation::Read
+                             ? QString{"*"}
+                             : QString{"COUNT(*) AS %1"}.arg(escapeIdentifier("count"));
+    ;
+
+    QStringList parts = {"SELECT",
+                         projection,
+                         generateFromClause(query.relation(), boundParameters)};
 
     if (query.expressionFilter().has_value())
         parts += generateWhereClause(*query.expressionFilter(), boundParameters);

tests/auto/qormsession/tst_ormsession.cpp

@@ -1,7 +1,7 @@
 /*
  * Copyright (C) 2020-2021 Dmitriy Purgin <dpurgin@gmail.com>
- * Copyright (C) 2019-2022 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019-2022 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -65,6 +65,9 @@ private slots:
     void testSelectWithLimitOffset();
     void testSelectWithOverwriteCachedInstances();
 
+    void testCount();
+    void testCountWithFilter();
+
     void testMergeFailsWithInconsistentReferences();
     void testMergeOfExistingUncachedEntitiesWithExplicitIdsUpdates();
     void testMergeNewEntitiesNoAutogeneratedIds();
@@ -543,6 +546,33 @@ void SqliteSessionTest::testSelectWithOverwriteCachedInstances()
     QVERIFY(!session.entityInstanceCache()->isModified(upperAustria));
 }
 
+void SqliteSessionTest::testCount()
+{
+    QOrmSession session;
+    session.merge(new Province(QString::fromUtf8("Oberösterreich")),
+                  new Province(QString::fromUtf8("Niederösterreich")),
+                  new Province(QString::fromUtf8("Salzburg")));
+
+    auto result = session.from<Province>().count();
+
+    QCOMPARE(result.error().type(), QOrm::ErrorType::None);
+    QCOMPARE(result.value(), 3);
+}
+
+void SqliteSessionTest::testCountWithFilter()
+{
+    QOrmSession session;
+    session.merge(new Province(QString::fromUtf8("Oberösterreich")),
+                  new Province(QString::fromUtf8("Niederösterreich")),
+                  new Province(QString::fromUtf8("Salzburg")));
+
+    auto result =
+        session.from<Province>().filter(Q_ORM_CLASS_PROPERTY(name).contains("österreich")).count();
+
+    QCOMPARE(result.error().type(), QOrm::ErrorType::None);
+    QCOMPARE(result.value(), 2);
+}
+
 void SqliteSessionTest::testMergeFailsWithInconsistentReferences()
 {
     QOrmSession session;
@@ -953,7 +983,7 @@ void SqliteSessionTest::testRemoveInstance()
     Province* upperAustria = new Province{QString::fromUtf8("Oberösterreich")};
     QVERIFY(session.merge(upperAustria));
     QVERIFY(session.remove(upperAustria));
-    QVERIFY(session.from<Province>().select().toVector().empty());    
+    QVERIFY(session.from<Province>().select().toVector().empty());
 }
 
 void SqliteSessionTest::testRemoveWithFilter()

tests/auto/qormsqlitestatementgenerator/tst_sqlitestatementgenerator.cpp

@@ -1,7 +1,7 @@
 /*
  * Copyright (C) 2020-2021 Dmitriy Purgin <dpurgin@gmail.com>
- * Copyright (C) 2019-2022 Dmitriy Purgin <dmitriy.purgin@sequality.at>
- * Copyright (C) 2019-2022 sequality software engineering e.U. <office@sequality.at>
+ * Copyright (C) 2019-2025 Dmitriy Purgin <dmitriy.purgin@sequality.at>
+ * Copyright (C) 2019-2025 sequality software engineering e.U. <office@sequality.at>
  *
  * This file is part of QtOrm library.
  *
@@ -78,6 +78,8 @@ private slots:
     void testSelectWithNamespace();
     void testLimitOffset();
     void testLimitOffset_data();
+
+    void testCount();
 };
 
 void SqliteStatementGenerator::init()
@@ -550,6 +552,28 @@ void SqliteStatementGenerator::testLimitOffset_data()
         << QVariant{} << QVariant{42} << "LIMIT :limit OFFSET :offset";
 }
 
+void SqliteStatementGenerator::testCount()
+{
+    QOrmMetadataCache cache;
+
+    QOrmRelation relation{cache.get<Town>()};
+    QOrmMetadata projection{cache.get<Town>()};
+
+    QOrmQuery query{QOrm::Operation::Count,
+                    relation,
+                    projection,
+                    std::nullopt,
+                    std::nullopt,
+                    {},
+                    QOrm::QueryFlags::None};
+    QMap<QString, QVariant> boundParameters;
+    QString actual = QOrmSqliteStatementGenerator{}.generate(query, boundParameters).simplified();
+    QString expected{R"(SELECT COUNT(*) AS "count" FROM "Town")"};
+
+    QCOMPARE(actual, expected);
+    QVERIFY(boundParameters.empty());
+}
+
 QTEST_APPLESS_MAIN(SqliteStatementGenerator)
 
 #include "tst_sqlitestatementgenerator.moc"