From 52b3a899949501322e60b3d14580ca0f6c300cca Mon Sep 17 00:00:00 2001
From: "Dr. Patrick Urbanke" <patrick@getml.com>
Date: Sun, 30 Nov 2025 15:46:18 +0100
Subject: [PATCH 1/2] Make sure that Transaction also work with iterators and
 expand the is_connection concept

---
 include/sqlgen/Session.hpp               |  2 +-
 include/sqlgen/Transaction.hpp           | 11 ++++++++++-
 include/sqlgen/duckdb/Connection.hpp     | 12 +++++++-----
 include/sqlgen/internal/to_container.hpp |  1 +
 include/sqlgen/is_connection.hpp         |  8 ++++++++
 include/sqlgen/mysql/Connection.hpp      | 13 ++++++++-----
 include/sqlgen/postgres/Connection.hpp   | 13 ++++++++-----
 include/sqlgen/sqlite/Connection.hpp     | 12 +++++++-----
 8 files changed, 50 insertions(+), 22 deletions(-)

diff --git a/include/sqlgen/Session.hpp b/include/sqlgen/Session.hpp
index 4e079d74..353f0d25 100644
--- a/include/sqlgen/Session.hpp
+++ b/include/sqlgen/Session.hpp
@@ -65,7 +65,7 @@ class Session {
   }
 
   template <class ContainerType>
-  Result<ContainerType> read(const dynamic::SelectFrom& _query) {
+  auto read(const dynamic::SelectFrom& _query) {
     return conn_->template read<ContainerType>(_query);
   }
 
diff --git a/include/sqlgen/Transaction.hpp b/include/sqlgen/Transaction.hpp
index 7d1ae5bc..b980dcae 100644
--- a/include/sqlgen/Transaction.hpp
+++ b/include/sqlgen/Transaction.hpp
@@ -2,6 +2,7 @@
 #define SQLGEN_TRANSACTION_HPP_
 
 #include "Ref.hpp"
+#include "internal/iterator_t.hpp"
 #include "is_connection.hpp"
 
 namespace sqlgen {
@@ -74,7 +75,7 @@ class Transaction {
   }
 
   template <class ContainerType>
-  Result<ContainerType> read(const dynamic::SelectFrom& _query) {
+  auto read(const dynamic::SelectFrom& _query) {
     return conn_->template read<ContainerType>(_query);
   }
 
@@ -111,4 +112,12 @@ class Transaction {
 
 }  // namespace sqlgen
 
+namespace sqlgen::internal {
+
+template <class ValueType, class Connection>
+struct IteratorType<ValueType, sqlgen::Transaction<Connection>> {
+  using Type = typename IteratorType<ValueType, Connection>::Type;
+};
+
+}  // namespace sqlgen::internal
 #endif
diff --git a/include/sqlgen/duckdb/Connection.hpp b/include/sqlgen/duckdb/Connection.hpp
index 19d9b7af..988c91fc 100644
--- a/include/sqlgen/duckdb/Connection.hpp
+++ b/include/sqlgen/duckdb/Connection.hpp
@@ -192,11 +192,6 @@ class SQLGEN_API Connection {
   ConnPtr conn_;
 };
 
-static_assert(is_connection<Connection>,
-              "Must fulfill the is_connection concept.");
-static_assert(is_connection<Transaction<Connection>>,
-              "Must fulfill the is_connection concept.");
-
 }  // namespace sqlgen::duckdb
 
 namespace sqlgen::internal {
@@ -205,6 +200,13 @@ struct IteratorType<ValueType, duckdb::Connection> {
   using Type = duckdb::Iterator<ValueType>;
 };
 
+static_assert(is_connection<duckdb::Connection>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Session<duckdb::Connection>>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Transaction<duckdb::Connection>>,
+              "Must fulfill the is_connection concept.");
+
 }  // namespace sqlgen::internal
 
 #endif
diff --git a/include/sqlgen/internal/to_container.hpp b/include/sqlgen/internal/to_container.hpp
index ceaacbc1..4f7262f3 100644
--- a/include/sqlgen/internal/to_container.hpp
+++ b/include/sqlgen/internal/to_container.hpp
@@ -6,6 +6,7 @@
 #include "../Result.hpp"
 #include "../transpilation/value_t.hpp"
 #include "is_range.hpp"
+#include "iterator_t.hpp"
 
 namespace sqlgen::internal {
 
diff --git a/include/sqlgen/is_connection.hpp b/include/sqlgen/is_connection.hpp
index e526a7f5..1aa7b6dc 100644
--- a/include/sqlgen/is_connection.hpp
+++ b/include/sqlgen/is_connection.hpp
@@ -6,12 +6,14 @@
 #include <string>
 #include <vector>
 
+#include "Range.hpp"
 #include "Ref.hpp"
 #include "Result.hpp"
 #include "dynamic/SelectFrom.hpp"
 #include "dynamic/Statement.hpp"
 #include "dynamic/Write.hpp"
 #include "internal/MockTable.hpp"
+#include "internal/iterator_t.hpp"
 
 namespace sqlgen {
 
@@ -41,6 +43,12 @@ concept is_connection = requires(
     c.template read<std::vector<internal::MockTable>>(_select_from)
   } -> std::same_as<Result<std::vector<internal::MockTable>>>;
 
+  /// Reads the results of a SelectFrom statement as a Range.
+  {
+    c.template read<Range<internal::MockTable>>(_select_from)
+  } -> std::same_as<
+        Result<Range<internal::iterator_t<internal::MockTable, ConnType>>>>;
+
   /// Commits a transaction.
   { c.rollback() } -> std::same_as<Result<Nothing>>;
 
diff --git a/include/sqlgen/mysql/Connection.hpp b/include/sqlgen/mysql/Connection.hpp
index 4bf62d5a..323162e7 100644
--- a/include/sqlgen/mysql/Connection.hpp
+++ b/include/sqlgen/mysql/Connection.hpp
@@ -11,6 +11,7 @@
 #include "../Iterator.hpp"
 #include "../Ref.hpp"
 #include "../Result.hpp"
+#include "../Session.hpp"
 #include "../Transaction.hpp"
 #include "../dynamic/Column.hpp"
 #include "../dynamic/Insert.hpp"
@@ -112,11 +113,6 @@ class SQLGEN_API Connection {
   ConnPtr conn_;
 };
 
-static_assert(is_connection<Connection>,
-              "Must fulfill the is_connection concept.");
-static_assert(is_connection<Transaction<Connection>>,
-              "Must fulfill the is_connection concept.");
-
 }  // namespace sqlgen::mysql
 
 namespace sqlgen::internal {
@@ -126,6 +122,13 @@ struct IteratorType<ValueType, mysql::Connection> {
   using Type = Iterator<ValueType, mysql::Iterator>;
 };
 
+static_assert(is_connection<mysql::Connection>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Session<mysql::Connection>>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Transaction<mysql::Connection>>,
+              "Must fulfill the is_connection concept.");
+
 }  // namespace sqlgen::internal
 
 #endif
diff --git a/include/sqlgen/postgres/Connection.hpp b/include/sqlgen/postgres/Connection.hpp
index 77924f1d..abaee344 100644
--- a/include/sqlgen/postgres/Connection.hpp
+++ b/include/sqlgen/postgres/Connection.hpp
@@ -13,6 +13,7 @@
 #include "../Iterator.hpp"
 #include "../Ref.hpp"
 #include "../Result.hpp"
+#include "../Session.hpp"
 #include "../Transaction.hpp"
 #include "../dynamic/Column.hpp"
 #include "../dynamic/Insert.hpp"
@@ -104,11 +105,6 @@ class SQLGEN_API Connection {
   Conn conn_;
 };
 
-static_assert(is_connection<Connection>,
-              "Must fulfill the is_connection concept.");
-static_assert(is_connection<Transaction<Connection>>,
-              "Must fulfill the is_connection concept.");
-
 }  // namespace sqlgen::postgres
 
 namespace sqlgen::internal {
@@ -118,6 +114,13 @@ struct IteratorType<ValueType, postgres::Connection> {
   using Type = Iterator<ValueType, postgres::Iterator>;
 };
 
+static_assert(is_connection<postgres::Connection>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Session<postgres::Connection>>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Transaction<postgres::Connection>>,
+              "Must fulfill the is_connection concept.");
+
 }  // namespace sqlgen::internal
 
 #endif
diff --git a/include/sqlgen/sqlite/Connection.hpp b/include/sqlgen/sqlite/Connection.hpp
index ec04dd08..670f2769 100644
--- a/include/sqlgen/sqlite/Connection.hpp
+++ b/include/sqlgen/sqlite/Connection.hpp
@@ -12,6 +12,7 @@
 #include "../Iterator.hpp"
 #include "../Ref.hpp"
 #include "../Result.hpp"
+#include "../Session.hpp"
 #include "../Transaction.hpp"
 #include "../dynamic/SelectFrom.hpp"
 #include "../dynamic/Union.hpp"
@@ -110,11 +111,6 @@ class SQLGEN_API Connection {
   ConnPtr conn_;
 };
 
-static_assert(is_connection<Connection>,
-              "Must fulfill the is_connection concept.");
-static_assert(is_connection<Transaction<Connection>>,
-              "Must fulfill the is_connection concept.");
-
 }  // namespace sqlgen::sqlite
 
 namespace sqlgen::internal {
@@ -124,6 +120,12 @@ struct IteratorType<ValueType, sqlite::Connection> {
   using Type = Iterator<ValueType, sqlite::Iterator>;
 };
 
+static_assert(is_connection<sqlite::Connection>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Session<sqlite::Connection>>,
+              "Must fulfill the is_connection concept.");
+static_assert(is_connection<Transaction<sqlite::Connection>>,
+              "Must fulfill the is_connection concept.");
 }  // namespace sqlgen::internal
 
 #endif

From 66f83ef69e32bd508a2c7f598e9e4b702a090649 Mon Sep 17 00:00:00 2001
From: "Dr. Patrick Urbanke" <patrick@getml.com>
Date: Sat, 6 Dec 2025 21:39:17 +0100
Subject: [PATCH 2/2] Added missing include

---
 include/sqlgen/duckdb/Connection.hpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/sqlgen/duckdb/Connection.hpp b/include/sqlgen/duckdb/Connection.hpp
index 45c431ed..b348bbc4 100644
--- a/include/sqlgen/duckdb/Connection.hpp
+++ b/include/sqlgen/duckdb/Connection.hpp
@@ -15,6 +15,7 @@
 #include "../Range.hpp"
 #include "../Ref.hpp"
 #include "../Result.hpp"
+#include "../Session.hpp"
 #include "../Transaction.hpp"
 #include "../dynamic/Operation.hpp"
 #include "../dynamic/SelectFrom.hpp"
@@ -138,8 +139,10 @@ class SQLGEN_API Connection {
               .as = std::nullopt};
         }));
 
-    const auto select_from = dynamic::SelectFrom{
-        .table_or_query = _table, .fields = fields, .limit = dynamic::Limit{0}, .offset = dynamic::Offset{0}};
+    const auto select_from = dynamic::SelectFrom{.table_or_query = _table,
+                                                 .fields = fields,
+                                                 .limit = dynamic::Limit{0},
+                                                 .offset = dynamic::Offset{0}};
 
     return DuckDBResult::make(to_sql(select_from), conn_)
         .transform([&](const auto &_res) {