| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Erik Rijkers <er(at)xs4all(dot)nl>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: testing HS/SR - 1 vs 2 performance |
| Date: | 2010-04-17 15:25:46 |
| Message-ID: | y2u603c8f071004170825zc8ae5f0fv19f999fe72e6f666@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sat, Apr 17, 2010 at 11:13 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
>> AFAICS the example you give isn't correct.
>
>> We would lay out the values like this
>
>> W-3 W-2 W-1 W 3 4 5
>
>> where W is the wrap value
>
> Stop right there, you're already failing to think clearly. There is no
> unique "wrap value", all values act the same in circular XID space.
Or to put it a different way, what happens when the "wrap value"
changes? An array that was in order under one wrap value can cease to
be in order under another.
...Robert
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