refactor: use contains() for membership checks

src/iceberg/metadata_columns.cc

@@ -58,12 +58,11 @@ const std::set<int32_t>& MetadataColumns::MetadataFieldIds() {
 }
 
 bool MetadataColumns::IsMetadataColumn(std::string_view name) {
-  return name == kPartitionColumnName ||
-         GetMetadataColumnMap().find(name) != GetMetadataColumnMap().end();
+  return name == kPartitionColumnName || GetMetadataColumnMap().contains(name);
 }
 
 bool MetadataColumns::IsMetadataColumn(int32_t id) {
-  return GetMetadataFieldIdSet().find(id) != GetMetadataFieldIdSet().end();
+  return GetMetadataFieldIdSet().contains(id);
 }
 
 bool MetadataColumns::IsRowLineageColumn(int32_t id) {

src/iceberg/table_metadata.cc

@@ -792,7 +792,7 @@ Status TableMetadataBuilder::Impl::SetDefaultSortOrder(int32_t order_id) {
 Result<int32_t> TableMetadataBuilder::Impl::AddSortOrder(const SortOrder& order) {
   int32_t new_order_id = ReuseOrCreateNewSortOrderId(order);
 
-  if (sort_orders_by_id_.find(new_order_id) != sort_orders_by_id_.end()) {
+  if (sort_orders_by_id_.contains(new_order_id)) {
     // update last_added_order_id if the order was added in this set of changes (since it
     // is now the last)
     bool is_new_order =

src/iceberg/util/content_file_util.cc

@@ -105,7 +105,7 @@ template <typename V>
 void DropUnselectedColumnStats(std::map<int32_t, V>& map,
                                const std::unordered_set<int32_t>& columns) {
   for (auto it = map.begin(); it != map.end();) {
-    if (columns.find(it->first) == columns.end()) {
+    if (!columns.contains(it->first)) {
       it = map.erase(it);
     } else {
       ++it;

src/iceberg/util/struct_like_set.cc

@@ -584,7 +584,7 @@ Result<bool> StructLikeSet<kValidate>::Contains(const StructLike& row) const {
   if constexpr (kValidate) {
     ICEBERG_RETURN_UNEXPECTED(ValidateRowAgainstTypes(row, field_types_));
   }
-  return set_.find(row) != set_.end();
+  return set_.contains(row);
 }
 
 template <bool kValidate>