Re: testing HS/SR - 1 vs 2 performance - Mailing list pgsql-hackers

From Robert Haas
Subject Re: testing HS/SR - 1 vs 2 performance
Date
Msg-id y2u603c8f071004170825zc8ae5f0fv19f999fe72e6f666@mail.gmail.com
Whole thread Raw
In response to Re: testing HS/SR - 1 vs 2 performance  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
On Sat, Apr 17, 2010 at 11:13 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Simon Riggs <simon@2ndQuadrant.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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