From 73abd61eba4c01c202aa158bf48022696a4bd9cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sascha=20K=C3=BChl?= <skuehl1972@gmail.com>
Date: Tue, 3 Feb 2026 07:26:37 +0100
Subject: [PATCH] has many to many collection resolver progress

---
 include/matador/query/schema.hpp | 18 +++++--
 test/backends/QueryTest.cpp      | 82 +++++++++++++++++++++++++++++++-
 2 files changed, 94 insertions(+), 6 deletions(-)

diff --git a/include/matador/query/schema.hpp b/include/matador/query/schema.hpp
index 283dc88..f33235b 100644
--- a/include/matador/query/schema.hpp
+++ b/include/matador/query/schema.hpp
@@ -69,10 +69,6 @@ public:
   static void on_belongs_to(const char * /*id*/, Pointer & /*x*/, const utils::foreign_attributes &/*attr*/) {}
   template<class Pointer>
   static void on_has_one(const char * /*id*/, Pointer & /*x*/, const utils::foreign_attributes &/*attr*/) {}
-  template<class ContainerType>
-  static void on_has_many_to_many(const char *, ContainerType &, const char * /*join_column*/, const char * /*inverse_join_column*/, const utils::foreign_attributes &/*attr*/) {}
-  template<class ContainerType>
-  static void on_has_many_to_many(const char *, ContainerType &, const utils::foreign_attributes &/*attr*/) {}
 
   template<class CollectionType>
   void on_has_many(const char * /*id*/, CollectionType &/*cont*/, const char *join_column, const utils::foreign_attributes &/*attr*/, std::enable_if_t<object::is_object_ptr<typename CollectionType::value_type>::value> * = nullptr) {
@@ -99,6 +95,20 @@ public:
 
   }
 
+  template<class CollectionType>
+  void on_has_many_to_many(const char *, CollectionType &, const char * /*join_column*/, const char * /*inverse_join_column*/, const utils::foreign_attributes &/*attr*/) {
+    const auto it = schema_.find(typeid(typename CollectionType::value_type::value_type));
+    if (it == schema_.end()) {
+      throw query_builder_exception{query_build_error::UnknownType};
+    }
+    if (!it->second.node().info().has_primary_key()) {
+      throw query_builder_exception{query_build_error::MissingPrimaryKey};
+    }
+
+  }
+  template<class ContainerType>
+  static void on_has_many_to_many(const char *, ContainerType &, const utils::foreign_attributes &/*attr*/) {}
+
 private:
   basic_schema& schema_;
   const std::type_index root_type_;
diff --git a/test/backends/QueryTest.cpp b/test/backends/QueryTest.cpp
index 69104bb..3b9b77e 100644
--- a/test/backends/QueryTest.cpp
+++ b/test/backends/QueryTest.cpp
@@ -740,8 +740,6 @@ TEST_CASE_METHOD(QueryFixture, "Test load entity with lazy belongs to relation",
 }
 
 TEST_CASE_METHOD(QueryFixture, "Test load entity with eager belongs to relation", "[query][belongs_to][eager]") {
-  // auto result = repo.attach<author>("authors")
-  // .and_then( [this] { return repo.attach<book>("books"); } )
   auto result = repo.attach<book>("books")
     .and_then( [this] { return repo.attach<author>("authors"); })
     .and_then([this] { return repo.create(db); });
@@ -816,4 +814,84 @@ TEST_CASE_METHOD(QueryFixture, "Test load entity with eager belongs to relation"
     REQUIRE(b->published_in == books.at(index)->published_in);
     ++index;
   }
+}
+
+TEST_CASE_METHOD(QueryFixture, "Test load entity with eager has many to many relation", "[query][has_many_to_many][eager]") {
+  auto result = repo.attach<ingredient>("ingredients")
+    .and_then( [this] { return repo.attach<recipe>("recipes"); } )
+    .and_then([this] {return repo.create(db); });
+
+  REQUIRE(db.exists(RECIPE.table_name()));
+  REQUIRE(db.exists(INGREDIENT.table_name()));
+  REQUIRE(db.exists(RECIPE_INGREDIENT.table_name()));
+
+  std::vector<ingredient> ingredients {
+        {1, "Apple"},
+        {2, "Strawberry"},
+        {3, "Pineapple"},
+        {4, "Sugar"},
+        {5, "Flour"},
+        {6, "Butter"},
+        {7, "Beans"}
+  };
+
+  for (const auto &i: ingredients) {
+    auto res = query::insert()
+    .into(INGREDIENT, {INGREDIENT.id, INGREDIENT.name})
+    .values(i)
+    .execute(db);
+    REQUIRE(res.is_ok());
+    REQUIRE(*res == 1);
+  }
+
+  std::vector<recipe> recipes{
+        {7, "Apple Crumble"},
+        {8, "Beans Chili"},
+        {9, "Fruit Salad"}
+  };
+
+  for (const auto &r: recipes) {
+    auto res = query::insert()
+    .into(RECIPE, {RECIPE.id, RECIPE.name})
+    .values(r)
+    .execute(db);
+    REQUIRE(res.is_ok());
+    REQUIRE(*res == 1);
+  }
+
+  std::vector<std::pair<int, int>> recipe_ingredients {
+        { 7, 1 },
+        { 7, 4 },
+        { 7, 5 },
+        { 8, 6 },
+        { 8, 7 },
+        { 9, 1 },
+        { 9, 2 },
+        { 9, 3 }
+  };
+
+  for (const auto & [recipe_id, ingredient_id]: recipe_ingredients) {
+    auto res = query::insert()
+    .into(RECIPE_INGREDIENT, {RECIPE_INGREDIENT.recipe_id, RECIPE_INGREDIENT.ingredient_id})
+    .values({recipe_id, ingredient_id})
+    .execute(db);
+    REQUIRE(res.is_ok());
+    REQUIRE(*res == 1);
+  }
+
+  const auto r = RECIPE.as("r");
+  const auto ri= RECIPE_INGREDIENT.as("ri");
+  const auto i = INGREDIENT.as("i");
+
+  auto ingredients_result = query::select({r.id, r.name, ri.ingredient_id, i.name})
+    .from(r)
+    .join_left(ri).on(r.id == ri.recipe_id)
+    .join_left(i).on(ri.ingredient_id == i.id)
+    .order_by({i.id, r.id}).asc()
+    .fetch_all<ingredient>(db);
+  REQUIRE(ingredients_result.is_ok());
+
+  for (const auto &ing : *ingredients_result) {
+    REQUIRE(!ing->recipes.empty());
+  }
 }
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