From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org, Bruce Momjian <bruce(at)momjian(dot)us> |
Subject: | Re: Creation of temporary tables on read-only standby servers |
Date: | 2010-10-18 20:27:59 |
Message-ID: | AANLkTikE7Zib0hiXO10C89sm=43bXM4p-qGS_XkX-rk9@mail.gmail.com |
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Lists: | pgsql-hackers |
On Mon, Oct 18, 2010 at 3:55 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Mon, Oct 18, 2010 at 3:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Andres Freund <andres(at)anarazel(dot)de> writes:
>>>> Hm. Wouldnt it be possible to use virtual xids for that purpose? They are
>>>> never seen outside of that session anyway...
>>>
>>> Well, maybe, but then you need infrastructure to track whether VXIDs
>>> committed or aborted.
>
>> Seems like this would wreak havoc with the HeapTupleSatisfies* functions.
>
> Yeah, it would be messy all over. This reminds me of last week's
> discussion about mysql-style storage engines --- by the time you made
> this work, you'd have something darn close to a separate storage engine
> for temp tables. It'd need its own parallel infrastructure covering
> everything to do with tuple visibility determination.
>
> It'd be kinda cool if we had it, but the work required to get there
> seems far out of proportion to the benefits ...
I agree. I think that's backing into the problem from the wrong end.
The limiting factor here is that we require the entire cluster to be
replicated. If you could replicate individual tables/schemas, then
this problem disappears. Of course, that's not easy either, but if
you're going to solve a really hard problem, you might as well pick
that one.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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