Re: POC: make mxidoff 64 bits
| От | Maxim Orlov |
|---|---|
| Тема | Re: POC: make mxidoff 64 bits |
| Дата | |
| Msg-id | CACG=ezaCc4bFfua-VA1NB6wppMPwuMmZiGdrkb-iYK9ZmQa6gg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: POC: make mxidoff 64 bits (Alexander Korotkov <aekorotkov@gmail.com>) |
| Ответы |
Re: POC: make mxidoff 64 bits
|
| Список | pgsql-hackers |
On Sat, 13 Sept 2025 at 16:34, Alexander Korotkov <aekorotkov@gmail.com> wrote:
Therefore, we can change from each 8 of 32-bit multixact offsets
(takes 32-bytes) to one 64-bit offset + 7 of 24-bit offset increments
(takes 29-bytes). The actual multixact offsets can be calculated at
the fly, overhead shouldn't be significant. What do you think?
Thank you for your review; I'm pleased to hear from you again.
Yes, because the maximum number of mxoff is limited by the number of
running transactions, we may do it that way.
However, it is a bit wired to have offsets with the 7-byte "base".
I believe we may take advantage of the 64XID patch's notion of putting a
Yes, because the maximum number of mxoff is limited by the number of
running transactions, we may do it that way.
However, it is a bit wired to have offsets with the 7-byte "base".
I believe we may take advantage of the 64XID patch's notion of putting a
8 byte base followed by 4 byte offsets for particular page.
32kB page may contain then 2^13-2 offsets, each is maxed by 2^18+1.
Therefore, offset from base will never overflow 2^31 and will always
fit uint32.
It appears logical to me.
--
Best regards,
Maxim Orlov.
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