| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Tianzhou Chen <tianzhouchen(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Challenges preventing us moving to 64 bit transaction id (XID)? |
| Date: | 2017-11-27 19:56:09 |
| Message-ID: | CA+Tgmob65jf2Mtg9+Z8ddDNR7CjBYK7a-nqUqhZZr5W3xvdKZg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Nov 24, 2017 at 5:33 AM, Alexander Korotkov
<a(dot)korotkov(at)postgrespro(dot)ru> wrote:
> pg_prune_xid makes sense only for heap pages. Once we introduce special
> area for heap pages, we can move pg_prune_xid there and save some bytes in
> index pages. However, this is an optimization not directly related to
> 64-bit xids. Idea is that if we anyway change page format, why don't apply
> this optimization as well? But if we have any doubts in this, it can be
> removed with no problem.
My first reaction is that changing the page format seems like a
non-starter, because it would break pg_upgrade. If we get the heap
storage API working, then we could have a heap AM that works as it
does today and a newheap AM with such changes, but I have a bit of a
hard time imagining a patch that causes a hard compatibility break
ever being accepted.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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