Re: Force streaming every change in logical decoding

On Fri, Dec 23, 2022 at 10:48 AM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>
> ```
> + * If logical_decoding_mode is immediate, loop until there's no change.
> + * Otherwise, loop until we reach under the memory limit. One might think
> + * that just by evicting the largest (sub)transaction we will come under
> + * the memory limit based on assumption that the selected transaction is
> + * at least as large as the most recent change (which caused us to go over
> + * the memory limit). However, that is not true because a user can reduce
> + * the logical_decoding_work_mem to a smaller value before the most recent
> * change.
> */
> ```
>
> Do we need to pick the largest (sub)transaciton even if we are in the immediate mode?
> It seems that the liner search is done in ReorderBufferLargestStreamableTopTXN()
> to find the largest transaction, but in this case we can choose the arbitrary one.
>

In immediate mode, we will stream/spill each change, so ideally, we
don't need to perform any search. Otherwise, also, I think changing
those functions will complicate the code without serving any purpose.

--
With Regards,
Amit Kapila.