Re: POC: make mxidoff 64 bits

wenhui qiu <qiuwenhuifx@gmail.com>

From: wenhui qiu <qiuwenhuifx@gmail.com>

To: Maxim Orlov <orlovmg@gmail.com>

Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Alexander Korotkov <aekorotkov@gmail.com>, Postgres hackers <pgsql-hackers@lists.postgresql.org>

Date: 2024-10-25T03:38:57Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Fix partial read handling in pg_upgrade's multixact conversion
- ac94ce8194e5 19 (unreleased) landed
Increase timeout in multixid_conversion upgrade test
- bd43940b02b2 19 (unreleased) landed
Improve sanity checks on multixid members length
- ecb553ae8211 19 (unreleased) landed
Clarify comment on multixid offset wraparound check
- 170361d7b869 14.21 landed
- b0b52b7123ae 15.16 landed
- 7d42e2367c6b 16.12 landed
- cd1a887fe9bf 17.8 landed
- 3fbad030a24d 18.2 landed
- 366dcdaf5779 19 (unreleased) landed
Never store 0 as the nextMXact
- 87a350e1f284 19 (unreleased) landed
Add runtime checks for bogus multixact offsets
- d4b7bde4183b 19 (unreleased) landed
Widen MultiXactOffset to 64 bits
- bd8d9c9bdfa0 19 (unreleased) landed
Move pg_multixact SLRU page format definitions to a separate header
- bb3b1c4f6462 19 (unreleased) landed
Convert confusing macros in multixact.c to static inline functions
- 0099b9408e8c 17.0 landed
Index SLRUs by 64-bit integers rather than by 32-bit integers
- 4ed8f0913bfd 17.0 cited
Cope with possible failure of the oldest MultiXact to exist.
- b6a3444fa635 9.4.4 cited

HI Maxim Orlov
> After a bit of thought, I've realized that to be conservative here is the
way to go.
>We can reuse a maximum of existing logic. I mean, we can remove offset
wraparound "error logic" and reuse "warning logic". But set the threshold
for "warning >logic" to a much higher value. For now, I choose 2^32-1. In
other world, legit logic, in my view, here would be to trigger autovacuum
if the number of offsets (i.e. >difference nextOffset - oldestOffset)
exceeds 2^32-1. PFA patch set.
good point ,Couldn't agree with you more. xid64 is the solution to the
wraparound problem,The previous error log is no longer meaningful ,But we
might want to refine the output waring log a little(For example, checking
the underlying reasons why age has been increasing),Though we don't have to
worry about xid wraparound

+/*
+ * Multixact members warning threshold.
+ *
+ * If difference bettween nextOffset and oldestOffset exceed this value, we
+ * trigger autovacuum in order to release the disk space if possible.
+ */
+#define MULTIXACT_MEMBER_AUTOVAC_THRESHOLD UINT64CONST(0xFFFFFFFF)
Can we refine this annotation a bit? for example
+/*
+ * Multixact members warning threshold.
+ *
+ * If difference bettween nextOffset and oldestOffset exceed this value, we
+ * trigger autovacuum in order to release the disk space ,reduce table
bloat if possible.
+ */
+#define MULTIXACT_MEMBER_AUTOVAC_THRESHOLD UINT64CONST(0xFFFFFFFF)

Thanks

Maxim Orlov <orlovmg@gmail.com> 于2024年10月23日周三 23:55写道：

> After a bit of thought, I've realized that to be conservative here is the
> way to go.
>
> We can reuse a maximum of existing logic. I mean, we can remove offset
> wraparound "error logic" and reuse "warning logic". But set the threshold
> for "warning logic" to a much higher value. For now, I choose 2^32-1. In
> other world, legit logic, in my view, here would be to trigger autovacuum
> if the number of offsets (i.e. difference nextOffset - oldestOffset)
> exceeds 2^32-1. PFA patch set.
>
> --
> Best regards,
> Maxim Orlov.
>