Horton

Re: Add 64-bit XIDs into PostgreSQL 15

Maxim Orlov <orlovmg@gmail.com>

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From: Maxim Orlov <orlovmg@gmail.com>
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2022-01-08T08:48:41Z
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 →

  1. Add SLRU tests for 64-bit page case

  2. Make use FullTransactionId in 2PC filenames

  3. Use larger segment file names for pg_notify

  4. Index SLRUs by 64-bit integers rather than by 32-bit integers

> Is there any documentation or README explaining this whole 64-bit XID
> mechanism?
>
There is none, unfortunately. I would come back to this later.


> Could you tell me what happens if new tuple with XID larger than xid_base
> + 0xFFFFFFFF is inserted into the page? Such new tuple is not allowed to be
> inserted into that page? Or xid_base and xids of all existing tuples in the
> page are increased? Also what happens if one of those xids (of existing
> tuples) cannot be changed because the tuple still can be seen by
> very-long-running transaction?
>
All this mechanism is around heap_insert/heap_update by
calling heap_page_prepare_for_xid() and if it fails (due to tuple still
visible) error is raised. Also If xid_base shift is not viable, it will try
to remove old tuples.

-- 
Best regards,
Maxim Orlov.