From: | Magnus Hagander <magnus(at)hagander(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Jaime Casanova <jaime(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Updated version of pg_receivexlog |
Date: | 2011-10-27 14:57:22 |
Message-ID: | CABUevEziv=ejN1XmQM6EWuc_4q=30dUZu2=PJtkajgfxQVF8yQ@mail.gmail.com |
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On Thu, Oct 27, 2011 at 16:54, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Magnus Hagander <magnus(at)hagander(dot)net> writes:
>> On Thu, Oct 27, 2011 at 13:19, Heikki Linnakangas
>> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>>> On 27.10.2011 14:09, Fujii Masao wrote:
>>>> Yes. But that sounds unuserfriendly. Padding the WAL file manually
>>>> is easy-to-do for a user?
>
>> I'd definitely want to avoid anything that requires pg_receivexlog to
>> actually *parse* the WAL. That'll make it way more complex than I'd
>> like.
>
> What parsing? Just pad to 16MB with zeroes. In fact, I think the
I'm just sayihng that *if* parsing is required, it would be bad.
> receiver should just create the file that size to start with, and then
> write received data into it, much like normal WAL creation does.
So when pg_receivexlog starts up, how would it know if the last file
represents a completed file, or a half-full file, without actually
parsing it? It could be a 16Mb file with 10 bytes of valid data, or a
complete file with 16Mb of valid data.
We could always ask for a retransmit of the whole file, but if that
file is gone on the master, we won't be able to do that, and will
error out in a situation that's not actually an error.
Though I guess if we leave the file as .partial up until this point
(per my other patch just posted), I guess this doesn't actually apply
- if the file is called .partial, we'll overwrite into it. If it's
not, then we assume it's a complete segment.
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
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