Schema support for nesting collection

src/realm/object-store/object_schema.cpp

@@ -151,6 +151,15 @@ ObjectSchema::ObjectSchema(Group const& group, StringData name, TableKey key)
         property.is_fulltext_indexed = table->search_index_type(col_key) == IndexType::Fulltext;
         property.column_key = col_key;
 
+        // account for nesting collections
+        const auto nesting_levels = table->get_nesting_levels(col_key);
+        if (nesting_levels > 0) {
+            property.nested_types.reserve(nesting_levels);
+            for (size_t i = 0; i < nesting_levels; ++i) {
+                property.nested_types.push_back(table->get_nested_column_type(col_key, i));
+            }
+        }
+
         if (property.type == PropertyType::Object) {
             // set link type for objects and arrays
             ConstTableRef linkTable = table->get_link_target(col_key);

src/realm/object-store/object_schema.hpp

@@ -88,6 +88,7 @@ class ObjectSchema {
 
     static PropertyType from_core_type(ColumnType type);
     static PropertyType from_core_type(ColKey col);
+    static PropertyType from_core_type(CollectionType type);
 
 private:
     void set_primary_key_property() noexcept;

src/realm/object-store/object_store.cpp

@@ -98,6 +98,30 @@ DataType to_core_type(PropertyType type)
     }
 }
 
+std::vector<CollectionType> process_nested_collection(const Property& property)
+{
+    std::vector<CollectionType> collection_types;
+    // process the list of nested levels
+    for (const auto& prop_type : property.nested_types) {
+        collection_types.push_back(prop_type);
+    }
+
+    // check if the final type is itself a collection.
+    if (is_array(property.type)) {
+        collection_types.push_back(CollectionType::List);
+    }
+    else if (is_set(property.type)) {
+        collection_types.push_back(CollectionType::Set);
+    }
+    else if (is_dictionary(property.type)) {
+        collection_types.push_back(CollectionType::Dictionary);
+    }
+    else if (!collection_types.empty()) {
+        throw InvalidColumnKey("Not a valid nested collection type");
+    }
+    return collection_types;
+}
+
 ColKey add_column(Group& group, Table& table, Property const& property)
 {
     // Cannot directly insert a LinkingObjects column (a computed property).
@@ -110,37 +134,16 @@ ColKey add_column(Group& group, Table& table, Property const& property)
             return col;
         }
     }
+    auto collection_types = process_nested_collection(property);
     if (property.type == PropertyType::Object) {
         auto target_name = ObjectStore::table_name_for_object_type(property.object_type);
         TableRef link_table = group.get_table(target_name);
         REALM_ASSERT(link_table);
-        if (is_array(property.type)) {
-            return table.add_column_list(*link_table, property.name);
-        }
-        else if (is_set(property.type)) {
-            return table.add_column_set(*link_table, property.name);
-        }
-        else if (is_dictionary(property.type)) {
-            return table.add_column_dictionary(*link_table, property.name);
-        }
-        else {
-            return table.add_column(*link_table, property.name);
-        }
-    }
-    else if (is_array(property.type)) {
-        return table.add_column_list(to_core_type(property.type & ~PropertyType::Flags), property.name,
-                                     is_nullable(property.type));
-    }
-    else if (is_set(property.type)) {
-        return table.add_column_set(to_core_type(property.type & ~PropertyType::Flags), property.name,
-                                    is_nullable(property.type));
-    }
-    else if (is_dictionary(property.type)) {
-        return table.add_column_dictionary(to_core_type(property.type & ~PropertyType::Flags), property.name,
-                                           is_nullable(property.type));
+        return table.add_column(*link_table, property.name, collection_types);
     }
     else {
-        auto key = table.add_column(to_core_type(property.type), property.name, is_nullable(property.type));
+        auto key = table.add_column(to_core_type(property.type), property.name, is_nullable(property.type),
+                                    collection_types);
         if (property.requires_index())
             table.add_search_index(key);
         if (property.requires_fulltext_index())

src/realm/object-store/property.hpp

@@ -27,7 +27,6 @@
 #include <realm/util/tagged_bool.hpp>
 
 #include <string>
-
 namespace realm {
 class BinaryData;
 class Decimal128;
@@ -59,6 +58,7 @@ enum class PropertyType : unsigned short {
     Required = 0,
     Nullable = 64,
     Array = 128,
+
     Set = 256,
     Dictionary = 512,
 
@@ -96,6 +96,8 @@ struct Property {
     IsPrimary is_primary = false;
     IsIndexed is_indexed = false;
     IsFulltextIndexed is_fulltext_indexed = false;
+    using NestedTypes = std::vector<CollectionType>;
+    NestedTypes nested_types;
 
     ColKey column_key;
 
@@ -107,9 +109,14 @@ struct Property {
     // Text property with fulltext index
     Property(std::string name, IsFulltextIndexed indexed, std::string public_name = "");
 
+    // Link to another object
     Property(std::string name, PropertyType type, std::string object_type, std::string link_origin_property_name = "",
              std::string public_name = "");
 
+    // Nested collections
+    Property(std::string name, PropertyType type, const NestedTypes& nested_types, std::string object_type = "",
+             std::string public_name = "");
+
     Property(Property const&) = default;
     Property(Property&&) noexcept = default;
     Property& operator=(Property const&) = default;
@@ -127,6 +134,7 @@ struct Property {
 
     bool type_is_indexable() const noexcept;
     bool type_is_nullable() const noexcept;
+    size_t type_nesting_levels() const noexcept;
 
     std::string type_string() const;
 };
@@ -336,6 +344,18 @@ inline Property::Property(std::string name, PropertyType type, std::string objec
 {
 }
 
+inline Property::Property(std::string name, PropertyType type, const NestedTypes& nested_types,
+                          std::string target_type, std::string public_name)
+    : name(std::move(name))
+    , public_name(std::move(public_name))
+    , type(type)
+    , object_type(std::move(target_type))
+    , nested_types(nested_types)
+{
+    REALM_ASSERT(is_collection(type));
+    REALM_ASSERT((type == PropertyType::Object) == (object_type.size() != 0));
+}
+
 inline bool Property::type_is_indexable() const noexcept
 {
     return !is_collection(type) &&
@@ -350,26 +370,52 @@ inline bool Property::type_is_nullable() const noexcept
            type != PropertyType::LinkingObjects;
 }
 
+inline size_t Property::type_nesting_levels() const noexcept
+{
+    return nested_types.size();
+}
+
 inline std::string Property::type_string() const
 {
+    std::string nested;
+    std::string closing_brackets;
+    for (auto& type : nested_types) {
+        switch (type) {
+            case CollectionType::List:
+                nested += "array<";
+                break;
+            case CollectionType::Dictionary:
+                nested += "dictionary<string,";
+                break;
+            case CollectionType::Set:
+                REALM_UNREACHABLE();
+                break;
+        }
+        closing_brackets += ">";
+    }
+
     if (is_array(type)) {
         if (type == PropertyType::Object)
             return "array<" + object_type + ">";
         if (type == PropertyType::LinkingObjects)
             return "linking objects<" + object_type + ">";
-        return std::string("array<") + string_for_property_type(type & ~PropertyType::Flags) + ">";
+        const auto str = std::string("array<") + string_for_property_type(type & ~PropertyType::Flags) + ">";
+        return nested + str + closing_brackets;
     }
     if (is_set(type)) {
         REALM_ASSERT(type != PropertyType::LinkingObjects);
         if (type == PropertyType::Object)
             return "set<" + object_type + ">";
-        return std::string("set<") + string_for_property_type(type & ~PropertyType::Flags) + ">";
+        const auto str = std::string("set<") + string_for_property_type(type & ~PropertyType::Flags) + ">";
+        return nested + str + closing_brackets;
     }
     if (is_dictionary(type)) {
         REALM_ASSERT(type != PropertyType::LinkingObjects);
         if (type == PropertyType::Object)
             return "dictionary<string, " + object_type + ">";
-        return std::string("dictionary<string, ") + string_for_property_type(type & ~PropertyType::Flags) + ">";
+        const auto str =
+            std::string("dictionary<string, ") + string_for_property_type(type & ~PropertyType::Flags) + ">";
+        return nested + str + closing_brackets;
     }
     switch (auto base_type = (type & ~PropertyType::Flags)) {
         case PropertyType::Object:
@@ -388,7 +434,8 @@ inline bool operator==(Property const& lft, Property const& rgt)
     return to_underlying(lft.type) == to_underlying(rgt.type) && lft.is_primary == rgt.is_primary &&
            lft.requires_index() == rgt.requires_index() &&
            lft.requires_fulltext_index() == rgt.requires_fulltext_index() && lft.name == rgt.name &&
-           lft.object_type == rgt.object_type && lft.link_origin_property_name == rgt.link_origin_property_name;
+           lft.object_type == rgt.object_type && lft.link_origin_property_name == rgt.link_origin_property_name &&
+           lft.nested_types == rgt.nested_types;
 }
 } // namespace realm
 

src/realm/object-store/schema.cpp

@@ -250,6 +250,10 @@ static void compare(ObjectSchema const& existing_schema, ObjectSchema const& tar
             changes.emplace_back(schema_change::RemoveProperty{&existing_schema, &current_prop});
             continue;
         }
+        if (current_prop.nested_types != target_prop->nested_types) {
+            changes.emplace_back(schema_change::ChangePropertyType{&existing_schema, &current_prop, target_prop});
+            continue;
+        }
         if (current_prop.type != target_prop->type || current_prop.object_type != target_prop->object_type ||
             is_array(current_prop.type) != is_array(target_prop->type) ||
             is_set(current_prop.type) != is_set(target_prop->type) ||

test/object-store/CMakeLists.txt

@@ -28,6 +28,7 @@ set(SOURCES
     thread_safe_reference.cpp
     transaction_log_parsing.cpp
     uuid.cpp
+    nested_collections.cpp
     c_api/c_api.cpp
     c_api/c_api.c
 

test/object-store/migrations.cpp

@@ -2651,3 +2651,126 @@ TEST_CASE("migration: Manual") {
                           Catch::Matchers::ContainsSubstring("Property 'object.value' has been removed."));
     }
 }
+
+TEST_CASE("migration nested collection automatic") {
+    TestFile config;
+    config.schema_mode = SchemaMode::Automatic;
+    auto realm = Realm::get_shared_realm(config);
+
+    Schema schema = {
+        {"nested_object", {{"nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}}}}};
+    REQUIRE_UPDATE_SUCCEEDS(*realm, schema, 0);
+
+    SECTION("Remove nested list") {
+        Schema new_schema = remove_property(schema, "nested_object", "nested_list");
+        REQUIRE_UPDATE_SUCCEEDS(*realm, schema, 1);
+    }
+
+    SECTION("Add nested collection") {
+        Schema new_schema =
+            add_property(schema, "nested_object",
+                         {"another_nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}});
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+    }
+
+    SECTION("Reorder property") {
+        Schema new_schema =
+            add_property(schema, "nested_object",
+                         {"another_nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}});
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+        auto& properties = new_schema.find("nested_object")->persisted_properties;
+        std::swap(properties[0], properties[1]);
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 2);
+    }
+
+    SECTION("Change property type should fail with schema in automatic mode") {
+        Schema new_schema = set_type(schema, "nested_object", "nested_list", PropertyType::Int);
+        REQUIRE_UPDATE_FAILS(
+            *realm, new_schema,
+            "Property 'nested_object.nested_list' has been changed from 'array<array<int>>' to 'int'.");
+    }
+
+    SECTION("add nested collection to same object") {
+        Schema new_schema =
+            add_property(schema, "nested_object",
+                         {"another_nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}});
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+    }
+
+    SECTION("add nested collection with nullable type") {
+        Schema schema = {
+            {"nested_object", {{"nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}}}},
+            {"nested_object2",
+             {{"nested_list_optional",
+               PropertyType::Array | PropertyType::Int | PropertyType::Nullable,
+               {CollectionType::List}}}},
+        };
+        REQUIRE_UPDATE_SUCCEEDS(*realm, schema, 1);
+    }
+
+    SECTION("change inner type") {
+        Schema new_schema = {
+            {"nested_object",
+             {{"nested_list",
+               PropertyType::Array | PropertyType::Mixed | PropertyType::Nullable,
+               {CollectionType::List}}}},
+        };
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+    }
+
+    SECTION("change type of nested collection") {
+        Schema new_schema = {
+            {"nested_object",
+             {{"nested_list",
+               PropertyType::Array | PropertyType::Mixed | PropertyType::Nullable,
+               {CollectionType::Dictionary}}}},
+        };
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+    }
+}
+
+TEST_CASE("migration nested collection additive") {
+
+    TestFile config;
+    config.schema_mode = SchemaMode::AdditiveExplicit;
+    config.schema_subset_mode = SchemaSubsetMode::Strict; // ignore reporting complete schema
+    auto realm = Realm::get_shared_realm(config);
+
+    Schema schema = {
+        {"nested_object", {{"nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}}}}};
+    REQUIRE_UPDATE_SUCCEEDS(*realm, schema, 0);
+
+    SECTION("Add new column") {
+        Schema new_schema =
+            add_property(schema, "nested_object",
+                         {"another_nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::List}});
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+    }
+
+    SECTION("Remove column") {
+        auto new_schema = remove_property(schema, "nested_object", "nested_list");
+        REQUIRE_UPDATE_SUCCEEDS(*realm, new_schema, 1);
+    }
+
+    SECTION("Change inner type") {
+        Schema new_schema = {
+            {"nested_object",
+             {{"nested_list",
+               PropertyType::Array | PropertyType::Mixed | PropertyType::Nullable,
+               {CollectionType::List}}}},
+        };
+        INVALID_SCHEMA_CHANGE(*realm, new_schema,
+                              "Property 'nested_object.nested_list' has been changed from 'array<array<int>>' to "
+                              "'array<array<mixed>>'");
+    }
+
+    SECTION("Change type of nested collection") {
+        Schema new_schema = {
+            {"nested_object",
+             {{"nested_list", PropertyType::Array | PropertyType::Int, {CollectionType::Dictionary}}}},
+        };
+        INVALID_SCHEMA_CHANGE(*realm, new_schema,
+                              "Property 'nested_object.nested_list' has been changed from 'array<array<int>>' to "
+                              "'dictionary<string,array<int>>'");
+    }
+}