Add SQL dialect support to StatementOptions

src/fb-cpp/Statement.cpp

@@ -51,7 +51,7 @@ Statement::Statement(
 		flags |= fb::IStatement::PREPARE_PREFETCH_DETAILED_PLAN;
 
 	statementHandle.reset(attachment.getHandle()->prepare(&statusWrapper, transaction.getHandle().get(),
-		static_cast<unsigned>(sql.length()), sql.data(), SQL_DIALECT_CURRENT, flags));
+		static_cast<unsigned>(sql.length()), sql.data(), options.getDialect(), flags));
 
 	if (options.getCursorName().has_value())
 		statementHandle->setCursorName(&statusWrapper, options.getCursorName()->c_str());

src/fb-cpp/Statement.h

@@ -164,11 +164,31 @@ namespace fbcpp
 			return *this;
 		}
 
+		///
+		/// @brief Returns the SQL dialect used when preparing the statement.
+		///
+		unsigned getDialect() const
+		{
+			return dialect;
+		}
+
+		///
+		/// @brief Sets the SQL dialect used when preparing the statement.
+		/// @param value SQL dialect number (1 for InterBase compatibility, 3 for current).
+		/// @return Reference to this instance for fluent configuration.
+		///
+		StatementOptions& setDialect(unsigned value)
+		{
+			dialect = value;
+			return *this;
+		}
+
 	private:
 		bool prefetchLegacyPlan = false;
 		bool prefetchPlan = false;
 		std::optional<std::string> cursorName;
 		CursorType cursorType = CursorType::FORWARD_ONLY;
+		unsigned dialect = SQL_DIALECT_CURRENT;
 	};
 
 	///

src/test/Statement.cpp

@@ -158,6 +158,57 @@ BOOST_AUTO_TEST_CASE(unsupportedStatementsThrow)
 	BOOST_CHECK_THROW(Statement(attachment, transaction, "rollback"), FbCppException);
 }
 
+BOOST_AUTO_TEST_CASE(dialectDefaultIsCurrent)
+{
+	StatementOptions options;
+	BOOST_CHECK_EQUAL(options.getDialect(), SQL_DIALECT_CURRENT);
+}
+
+BOOST_AUTO_TEST_CASE(dialectSetterGetter)
+{
+	StatementOptions options;
+	options.setDialect(1u);
+	BOOST_CHECK_EQUAL(options.getDialect(), 1u);
+}
+
+BOOST_AUTO_TEST_CASE(constructorWithExplicitDialect)
+{
+	const auto database = getTempFile("Statement-constructorWithExplicitDialect.fdb");
+
+	// Firebird 5 requires that statement dialect matches the database dialect, so
+	// the test database must be created with dialect 1.
+	const std::vector<std::uint8_t> dialect1Dpb = {
+		isc_dpb_version1,
+		isc_dpb_sql_dialect,
+		4,
+		1,
+		0,
+		0,
+		0,
+	};
+
+	Attachment attachment{CLIENT, database, AttachmentOptions().setCreateDatabase(true).setDpb(dialect1Dpb)};
+	FbDropDatabase attachmentDrop{attachment};
+
+	Transaction transaction{attachment};
+
+	// SQL_DIALECT_CURRENT (3) does not match database dialect 1 and is rejected,
+	// proving statement dialect controls the behavior.
+	BOOST_CHECK_THROW(
+		Statement(attachment, transaction, "select cast(1234.56 as numeric(18, 2)) from rdb$database"), FbCppException);
+
+	// With dialect 1 explicitly set, NUMERIC(18,2) is described as DOUBLE
+	// PRECISION and the value is retrieved via getDouble().
+	Statement stmt{attachment, transaction, "select cast(1234.56 as numeric(18, 2)) from rdb$database",
+		StatementOptions().setDialect(1u)};
+	BOOST_CHECK(stmt.isValid());
+	BOOST_CHECK(stmt.getOutputDescriptors()[0].adjustedType == DescriptorAdjustedType::DOUBLE);
+	BOOST_REQUIRE(stmt.execute(transaction));
+	auto value = stmt.getDouble(0);
+	BOOST_REQUIRE(value.has_value());
+	BOOST_CHECK_CLOSE(*value, 1234.56, 0.001);
+}
+
 BOOST_AUTO_TEST_SUITE_END()