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Re: xlog location arithmetic

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Peter Eisentraut <peter_e(at)gmx(dot)net>, Magnus Hagander <magnus(at)hagander(dot)net>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Euler Taveira de Oliveira <euler(at)timbira(dot)com>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: xlog location arithmetic
Date: 2012-03-09 19:39:26
Message-ID: CA+TgmobFsPgc=tNH-c1ak0jCOF5m=5oanyb7gx1oONv2ipVBmQ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Fri, Mar 9, 2012 at 2:34 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Mar 9, 2012 at 2:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
>>>> Yeah, the use of XLogFile to mean something other than, well a file in
>>>> the xlog, is greatly annoying.. I guess we could change it, but it
>>>> goes pretty deep in the system so it's not a small change...
>>
>>> The whole thing was built around the lack of 64 bit integers.  If we bit
>>> the bullet and changed the whole thing to be just a single 64-bit
>>> counter, we could probably delete thousands of lines of code.
>>
>> Hm.  I think "thousands" is an overestimate, but yeah the logic could be
>> greatly simplified.  However, I'm not sure we could avoid breaking the
>> existing naming convention for WAL files.  How much do we care about
>> that?
>
> Probably not very much, since WAL files aren't portable across major
> versions anyway.  But I don't see why you couldn't keep the naming
> convention - there's nothing to prevent you from converting a 64-bit
> integer back into two 32-bit integers if and where needed.

On further reflection, this seems likely to break quite a few
third-party tools.  Maybe it'd be worth it anyway, but it definitely
seems like it would be worth going to at least some minor trouble to
avoid it.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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