Merge pull request #386 from LASTRADA-Software/improvement/exist_api

[DataMapper] Add Exist api that reuse First() implementation

Author: Yaraslaut

src/Lightweight/DataMapper/DataMapper.hpp

@@ -628,6 +628,26 @@ size_t SqlCoreDataMapperQueryBuilder<Record, Derived, QueryOptions>::Count()
     return 0;
 }
 
+template <typename Record, typename Derived, DataMapperOptions QueryOptions>
+bool SqlCoreDataMapperQueryBuilder<Record, Derived, QueryOptions>::Exist()
+{
+    auto stmt = SqlStatement { _dm.Connection() };
+
+    auto const query = _formatter.SelectFirst(this->_query.distinct,
+                                              _fields,
+                                              RecordTableName<Record>,
+                                              this->_query.searchCondition.tableAlias,
+                                              this->_query.searchCondition.tableJoins,
+                                              this->_query.searchCondition.condition,
+                                              this->_query.orderBy,
+                                              1);
+
+    stmt.ExecuteDirect(query);
+    if (SqlResultCursor reader = stmt.GetResultCursor(); reader.FetchRow())
+        return true;
+    return false;
+}
+
 template <typename Record, typename Derived, DataMapperOptions QueryOptions>
 std::vector<Record> SqlCoreDataMapperQueryBuilder<Record, Derived, QueryOptions>::All()
 {

src/Lightweight/DataMapper/QueryBuilders.hpp

@@ -52,6 +52,10 @@ class [[nodiscard]] SqlCoreDataMapperQueryBuilder: public SqlBasicSelectQueryBui
     LIGHTWEIGHT_FORCE_INLINE explicit SqlCoreDataMapperQueryBuilder(DataMapper& dm, std::string fields) noexcept;
 
   public:
+    /// Executes a SELECT 1 ... query and returns true if a record exists
+    /// We do not provide db specific syntax to check this but reuse the First() implementation
+    [[nodiscard]] bool Exist();
+
     /// Executes a SELECT COUNT query and returns the number of records found.
     [[nodiscard]] size_t Count();
 

src/tests/DataMapper/CreateTests.cpp

@@ -62,6 +62,19 @@ TEST_CASE_METHOD(SqlTestFixture, "Create table with default values", "[DataMappe
     CHECK(actual.int2 == record.int2);
 }
 
+TEST_CASE_METHOD(SqlTestFixture, "Check that record exist", "[DataMapper]")
+{
+    auto dm = DataMapper::Create();
+    dm->CreateTable<RecordWithDefaults>();
+
+    auto record = RecordWithDefaults {};
+    dm->Create(record);
+
+    CHECK(
+        dm->Query<RecordWithDefaults>().Where(FieldNameOf<Member(RecordWithDefaults::id)>, "=", record.id.Value()).Exist());
+    CHECK(!dm->Query<RecordWithDefaults>().Where(FieldNameOf<Member(RecordWithDefaults::id)>, "=", -1).Exist());
+}
+
 struct TestRecord
 {
     Field<uint64_t, PrimaryKey::AutoAssign> id {};

src/tests/DataMapper/ReadTests.cpp

@@ -47,6 +47,15 @@ TEST_CASE_METHOD(SqlTestFixture, "Query", "[DataMapper]")
         CHECK(countAll == 4);
     }
 
+    SECTION("Exist()")
+    {
+        auto const existSome = dm->Query<Person>().Where(FieldNameOf<Member(Person::is_active)>, "=", true).Exist();
+        CHECK(existSome);
+
+        auto const notExist = dm->Query<Person>().Where(FieldNameOf<Member(Person::id)>, SqlGuid::Create()).Exist();
+        CHECK(!notExist);
+    }
+
     SECTION("All()")
     {
         auto const records = dm->Query<Person>()