Move key_begin and key_end members from scan_context to scan_info

[YoshiakiNishimura]

https://github.com/project-tsurugi/tsurugi-issues/issues/991

改造

scan_context

以下のメンバーを取り除く
data::aligned_buffer key_begin_{};
data::aligned_buffer key_end_{};

scan_info

以下のメンバーを追加する
data::aligned_buffer key_begin_{};
data::aligned_buffer key_end_{};
std::size_t blen_{};
std::size_t elen_{};
status status_result_{};

scan::open

機能のほとんどをflow::create_task_contextにもっていく
残す機能は

• secondaryの設定
• エラーメッセージの処理
• iteratorの設定

status scan::open(scan_context& ctx) {  //NOLINT(readability-make-member-function-const)
    auto& stg = use_secondary_ ? *ctx.secondary_stg_ : *ctx.stg_;
    if (auto status = ctx.scan_info_->status_result(); status != status::ok) {
        return status;
    }
    if(auto res = stg.content_scan(
            *ctx.tx_,
            ctx.scan_info_->begin_key(),
            ctx.scan_info_->begin_kind(use_secondary_),
            ctx.scan_info_->end_key(),
            ctx.scan_info_->end_kind(use_secondary_),
            ctx.it_
        ); res != status::ok) {
        handle_kvs_errors(*ctx.req_context(), res);
        handle_generic_error(*ctx.req_context(), res, error_code::sql_execution_exception);
        return res;
    }
    return status::ok;
}

flow::create_task_context

scan::operatorの設定はimpl:task_contextに新設のencode_keyメンバ関数を行う

std::shared_ptr<impl::task_context> flow::create_task_context(
    std::size_t partition,
    impl::ops::operator_container const& operators,
    std::size_t sink_index
) {
...
    if (ctx->scan_info() != nullptr){
        ctx->encode_key();
    }
...

impl::task_context

void task_context::encode_key(){
    std::size_t blen{};
    std::string msg{};
    executor::process::impl::variable_table vars{};
    if(auto res = impl::ops::details::encode_key(
        request_context_,
        scan_info_->begin_columns(),
        vars,
        *getImplWorkContext().varlen_resource(),
        scan_info_->key_begin(),
        blen,
        msg
      );
       res != status::ok) {
        if(res == status::err_type_mismatch) {
            // only on err_type_mismatch, msg is filled with error message. use it to create the error info in request context
            set_error(*request_context_, error_code::unsupported_runtime_feature_exception, msg, res);
        }
        scan_info_->status_result(res);
        return;
    }
    scan_info_->blen(blen);
    std::size_t elen{};
    if(auto res = impl::ops::details::encode_key(
        request_context_,
        scan_info_->end_columns(),
        vars,
        *getImplWorkContext().varlen_resource(),
        scan_info_->key_end(),
        elen,
        msg
       );
       res != status::ok) {
        if(res == status::err_type_mismatch) {
            // only on err_type_mismatch, msg is filled with error message. use it to create the error info in request context
            set_error(*request_context_, error_code::unsupported_runtime_feature_exception, msg, res);
        }
        scan_info_->status_result(res);
    }
    scan_info_->elen(elen);
    scan_info_->status_result(status::ok);
    return;
}