| From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
|---|---|
| To: | Maxim Orlov <orlovmg(at)gmail(dot)com>, Postgres hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: POC: make mxidoff 64 bits |
| Date: | 2024-04-23 09:37:40 |
| Message-ID: | ff143b24-a093-40da-9833-d36b83726bdf@iki.fi |
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| Lists: | pgsql-hackers |
On 23/04/2024 11:23, Maxim Orlov wrote:
> PROPOSAL
> Make multixact offsets 64 bit.
+1, this is a good next step and useful regardless of 64-bit XIDs.
> @@ -156,7 +148,7 @@
> ((uint32) ((0xFFFFFFFF % MULTIXACT_MEMBERS_PER_PAGE) + 1))
>
> /* page in which a member is to be found */
> -#define MXOffsetToMemberPage(xid) ((xid) / (TransactionId) MULTIXACT_MEMBERS_PER_PAGE)
> +#define MXOffsetToMemberPage(xid) ((xid) / (MultiXactOffset) MULTIXACT_MEMBERS_PER_PAGE)
> #define MXOffsetToMemberSegment(xid) (MXOffsetToMemberPage(xid) / SLRU_PAGES_PER_SEGMENT)
>
> /* Location (byte offset within page) of flag word for a given member */
This is really a bug fix. It didn't matter when TransactionId and
MultiXactOffset were both typedefs of uint32, but it was always wrong.
The argument name 'xid' is also misleading.
I think there are some more like that, MXOffsetToFlagsBitShift for example.
--
Heikki Linnakangas
Neon (https://neon.tech)
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