delete with custom predicate

Author: jkalias

include/database.h

@@ -147,7 +147,8 @@ namespace sqlite_reflection {
 		void Delete(const T& model) const {
 			const auto type_id = typeid(T).name();
 			const auto& record = GetRecord(type_id);
-			Delete(model.id, record);
+            const auto equal_id_predicate = Equal(&T::id, model.id);
+			Delete(record, &equal_id_predicate);
 		}
 
 		/// Deletes a given record from the database, which matches a given id.
@@ -156,8 +157,18 @@ namespace sqlite_reflection {
 		void Delete(int64_t id) const {
 			const auto type_id = typeid(T).name();
 			const auto& record = GetRecord(type_id);
-			Delete(id, record);
+            const auto equal_id_predicate = Equal(&T::id, id);
+			Delete(record, &equal_id_predicate);
 		}
+        
+        /// Deletes multiple records of a given type from the database, which match a given predicate.
+        /// This corresponds to an DELETE query in the SQL syntax, with an additional WHERE clause
+        template <typename T>
+        void Delete(const QueryPredicateBase* predicate) const {
+            const auto type_id = typeid(T).name();
+            const auto& record = GetRecord(type_id);
+            Delete(record, predicate);
+        }
 
 	private:
 		explicit Database(const char* path);
@@ -189,7 +200,7 @@ namespace sqlite_reflection {
 		void Update(void* p, const Reflection& record) const;
 
 		/// Deletes a single record from the database
-		void Delete(int64_t id, const Reflection& record) const;
+		void Delete(const Reflection& record, const QueryPredicateBase* predicate) const;
 
 		static Database* instance_;
 		sqlite3* db_;

include/queries.h

@@ -95,11 +95,11 @@ namespace sqlite_reflection {
 	{
 	public:
 		~DeleteQuery() override = default;
-		explicit DeleteQuery(sqlite3* db, const Reflection& record, int64_t id);
+		explicit DeleteQuery(sqlite3* db, const Reflection& record, const QueryPredicateBase* predicate);
 
 	protected:
 		std::string PrepareSql() const override;
-		int64_t id_;
+        const QueryPredicateBase* predicate_;
 	};
 
 	/// A query to insert a given record to the database, by supplying a given type-erased struct instance

include/reflection.h

@@ -35,8 +35,6 @@
 #include <stddef.h>
 #endif
 
-// todo: delete with custom predicate
-
 // todo: BETWEEN / IN / NOT IN predicate
 // todo: raw sql queries
 // todo: save with automatic id

src/database.cc

@@ -91,8 +91,8 @@ namespace sqlite_reflection {
 		query.Execute();
 	}
 
-	void Database::Delete(int64_t id, const Reflection& record) const {
-		DeleteQuery query(db_, record, id);
+	void Database::Delete(const Reflection& record, const QueryPredicateBase* predicate) const {
+		DeleteQuery query(db_, record, predicate);
 		query.Execute();
 	}
 }

src/queries.cc

@@ -146,12 +146,12 @@ std::string CreateTableQuery::CustomizedColumnName(size_t index) const {
 		       : name;
 }
 
-DeleteQuery::DeleteQuery(sqlite3* db, const Reflection& record, int64_t id)
-	: ExecutionQuery(db, record), id_(id) {}
+DeleteQuery::DeleteQuery(sqlite3* db, const Reflection& record, const QueryPredicateBase* predicate)
+	: ExecutionQuery(db, record), predicate_(predicate) {}
 
 std::string DeleteQuery::PrepareSql() const {
 	std::string sql("DELETE FROM ");
-	sql += record_.name + " WHERE id = " + StringUtilities::FromInt(id_) + ";";
+	sql += record_.name + " WHERE " + predicate_->Evaluate() + ";";
 	return sql;
 }
 

src/query_predicates.cc

@@ -60,6 +60,11 @@ std::string QueryPredicate::GetStringForValue(void* v, SqliteStorageClass storag
 			auto value = *(int64_t*)(v);
 			return StringUtilities::FromInt(value);
 		}
+    case SqliteStorageClass::kBool:
+        {
+            auto value = *(bool*)(v);
+            return StringUtilities::FromInt(value ? 1 : 0);
+        }
 	case SqliteStorageClass::kReal:
 		{
 			auto value = *(double*)(v);
@@ -115,4 +120,4 @@ OrPredicate::OrPredicate(const QueryPredicateBase& left, const QueryPredicateBas
 
 QueryPredicateBase* OrPredicate::Clone() const {
 	return new OrPredicate(*left_.get(), *right_.get());
-}
+}

tests/database_test.cc

@@ -205,6 +205,31 @@ TEST_F(DatabaseTest, DeleteWithId) {
 	EXPECT_EQ(20, saved_persons[i].age);
 }
 
+TEST_F(DatabaseTest, DeleteWithPredicate) {
+    const auto& db = Database::Instance();
+
+    std::vector<Person> persons;
+
+    persons.push_back({3, L"παναγιώτης", L"ανδριανόπουλος", 28, true});
+    persons.push_back({5, L"peter", L"meier", 32, false});
+    persons.push_back({13, L"mary", L"poppins", 20, true});
+
+    db.Save(persons);
+
+    const auto age_match_predicate = SmallerThan(&Person::age, 30)
+        .And(Equal(&Person::isVaccinated, true));
+
+    db.Delete<Person>(&age_match_predicate);
+    const auto fetched_persons = db.FetchAll<Person>();
+    EXPECT_EQ(1, fetched_persons.size());
+
+    EXPECT_EQ(5, fetched_persons[0].id);
+    EXPECT_EQ(L"peter", fetched_persons[0].first_name);
+    EXPECT_EQ(L"meier", fetched_persons[0].last_name);
+    EXPECT_EQ(32, fetched_persons[0].age);
+    EXPECT_EQ(false, fetched_persons[0].isVaccinated);
+}
+
 TEST_F(DatabaseTest, SingleFetch) {
 	const auto& db = Database::Instance();