evindj commented on code in PR #561:
URL: https://github.com/apache/iceberg-cpp/pull/561#discussion_r2814027596
##########
src/iceberg/name_mapping.cc:
##########
@@ -323,6 +323,158 @@ class CreateMappingVisitor {
}
};
+// Visitor class for updating name mappings with schema changes
+class UpdateMappingVisitor {
+ public:
+ UpdateMappingVisitor(const std::map<int32_t, SchemaField>& updates,
+ const std::multimap<int32_t, int32_t>& adds)
+ : updates_(updates), adds_(adds) {}
+
+ Result<std::unique_ptr<MappedFields>> VisitMapping(const NameMapping&
mapping) {
+ auto fields_result = VisitFields(mapping.AsMappedFields());
+ ICEBERG_RETURN_UNEXPECTED(fields_result);
+ return AddNewFields(std::move(*fields_result),
+ -1 /* parent ID for top-level fields */);
+ }
+
+ private:
+ Result<std::unique_ptr<MappedFields>> VisitFields(const MappedFields&
fields) {
+ // Recursively visit all fields
+ std::vector<MappedField> field_results;
+ field_results.reserve(fields.Size());
+
+ for (const auto& field : fields.fields()) {
+ auto field_result = VisitField(field);
+ ICEBERG_RETURN_UNEXPECTED(field_result);
+ field_results.push_back(std::move(*field_result));
+ }
+
+ // Build update assignments map for removing reassigned names
+ std::unordered_map<std::string, int32_t> update_assignments;
+ std::ranges::for_each(field_results, [&](const auto& field) {
+ if (field.field_id.has_value()) {
+ auto update_it = updates_.find(field.field_id.value());
+ if (update_it != updates_.end()) {
+ update_assignments.emplace(std::string(update_it->second.name()),
+ field.field_id.value());
+ }
+ }
+ });
+
+ // Remove reassigned names from all fields
+ for (auto& field : field_results) {
+ field = RemoveReassignedNames(field, update_assignments);
+ }
+
+ return MappedFields::Make(std::move(field_results));
+ }
+
+ Result<MappedField> VisitField(const MappedField& field) {
+ // Update this field's names
+ std::unordered_set<std::string> field_names = field.names;
+ if (field.field_id.has_value()) {
+ auto update_it = updates_.find(field.field_id.value());
+ if (update_it != updates_.end()) {
+ field_names.insert(std::string(update_it->second.name()));
+ }
+ }
+
+ std::unique_ptr<MappedFields> nested_mapping = nullptr;
+ if (field.nested_mapping != nullptr) {
+ auto nested_result = VisitFields(*field.nested_mapping);
+ ICEBERG_RETURN_UNEXPECTED(nested_result);
+ nested_mapping = std::move(*nested_result);
+ }
+
+ // Add a new mapping for any new nested fields
+ if (field.field_id.has_value()) {
+ auto nested_result =
+ AddNewFields(std::move(nested_mapping), field.field_id.value());
+ ICEBERG_RETURN_UNEXPECTED(nested_result);
+ nested_mapping = std::move(*nested_result);
+ }
+
+ return MappedField{
+ .names = std::move(field_names),
+ .field_id = field.field_id,
+ .nested_mapping = std::move(nested_mapping),
+ };
+ }
+
+ Result<std::unique_ptr<MappedFields>> AddNewFields(
+ std::unique_ptr<MappedFields> mapping, int32_t parent_id) {
+ auto range = adds_.equal_range(parent_id);
+ std::vector<const SchemaField*> fields_to_add;
+ for (auto it = range.first; it != range.second; ++it) {
+ auto update_it = updates_.find(it->second);
+ if (update_it != updates_.end()) {
+ fields_to_add.push_back(&update_it->second);
+ }
+ }
+
+ if (fields_to_add.empty()) {
+ return std::move(mapping);
+ }
+
+ std::vector<MappedField> new_fields;
+ CreateMappingVisitor create_visitor;
+ for (const auto* field_to_add : fields_to_add) {
+ auto nested_result = VisitType(
+ *field_to_add->type(),
+ [&create_visitor](const auto& type) { return
create_visitor.Visit(type); });
+ ICEBERG_RETURN_UNEXPECTED(nested_result);
+
+ new_fields.emplace_back(MappedField{
+ .names = {std::string(field_to_add->name())},
+ .field_id = field_to_add->field_id(),
+ .nested_mapping = std::move(*nested_result),
+ });
+ }
+
+ if (mapping == nullptr || mapping->Size() == 0) {
+ return MappedFields::Make(std::move(new_fields));
+ }
+
+ // Build assignments map for removing reassigned names
+ std::unordered_map<std::string, int32_t> assignments;
+ for (const auto* field_to_add : fields_to_add) {
+ assignments.emplace(std::string(field_to_add->name()),
field_to_add->field_id());
+ }
+
+ // create a copy of fields that can be updated (append new fields, replace
existing
+ // for reassignment)
+ std::vector<MappedField> fields;
+ fields.reserve(mapping->Size() + new_fields.size());
+ for (const auto& field : mapping->fields()) {
+ fields.push_back(RemoveReassignedNames(field, assignments));
+ }
+
+ fields.insert(fields.end(), std::make_move_iterator(new_fields.begin()),
+ std::make_move_iterator(new_fields.end()));
+
+ return MappedFields::Make(std::move(fields));
+ }
+
+ static MappedField RemoveReassignedNames(
+ const MappedField& field,
+ const std::unordered_map<std::string, int32_t>& assignments) {
+ std::unordered_set<std::string> updated_names = field.names;
+ std::erase_if(updated_names, [&](const std::string& name) {
+ auto assign_it = assignments.find(name);
+ return assign_it != assignments.end() &&
+ (!field.field_id.has_value() || assign_it->second !=
field.field_id.value());
+ });
+ return MappedField{
+ .names = std::move(updated_names),
+ .field_id = field.field_id,
+ .nested_mapping = field.nested_mapping,
+ };
+ }
+
+ const std::map<int32_t, SchemaField>& updates_;
Review Comment:
do we want these to be sorted or an unordered_map enough
##########
src/iceberg/json_serde.cc:
##########
@@ -1270,6 +1270,24 @@ Result<std::unique_ptr<NameMapping>>
NameMappingFromJson(const nlohmann::json& j
return NameMapping::Make(std::move(mapped_fields));
}
+std::optional<std::string> UpdateMappingFromJsonString(
Review Comment:
This probably works but it seems the pattern in this file is to use
Result<T>() for *FromJson. It is also unclear what the intend of the method is,
it seems from reading the code that we are trying to update the initial json
representation with updates.
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