Method AddField

cpp/src/arrow/type.cc:2524–2568

        field_merge_options_(field_merge_options) {}

  Status AddField(const std::shared_ptr<Field>& field) {
    DCHECK_NE(field, nullptr);

    // Short-circuit, no lookup needed.
    if (policy_ == CONFLICT_APPEND) {
      return AppendField(field);
    }

    auto name = field->name();
    constexpr int kNotFound = -1;
    constexpr int kDuplicateFound = -2;
    auto i = LookupNameIndex<kNotFound, kDuplicateFound>(name_to_index_, name);

    if (i == kNotFound) {
      return AppendField(field);
    }

    // From this point, there's one or more field in the builder that exists with
    // the same name.

    if (policy_ == CONFLICT_IGNORE) {
      // The ignore policy is more generous when there's duplicate in the builder.
      return Status::OK();
    } else if (policy_ == CONFLICT_ERROR) {
      return Status::Invalid("Duplicate found, policy dictate to treat as an error");
    }

    if (i == kDuplicateFound) {
      // Cannot merge/replace when there's more than one field in the builder
      // because we can't decide which to merge/replace.
      return Status::Invalid("Cannot merge field ", name,
                             " more than one field with same name exists");
    }

    DCHECK_GE(i, 0);

    if (policy_ == CONFLICT_REPLACE) {
      fields_[i] = field;
    } else if (policy_ == CONFLICT_MERGE) {
      ARROW_ASSIGN_OR_RAISE(fields_[i],
                            fields_[i]->MergeWith(field, field_merge_options_));
    }

    return Status::OK();
  }

  Status AppendField(const std::shared_ptr<Field>& field) {
    name_to_index_.emplace(field->name(), static_cast<int>(fields_.size()));