Hi Maxim Orlov
Thank you so much for your tireless work on this. Increasing the WAL size by a few bytes should have very little impact with today's disk performance(Logical replication of this feature wal log is also increased a lot, logical replication is a milestone new feature, and the community has been improving the logical replication of functions),I believe removing troubled postgresql Transaction ID Wraparound was also a milestone new feature adding a few bytes is worth it!
Best regards
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)