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Re: idea: global temp tables

From: "A(dot)M(dot)" <agentm(at)themactionfaction(dot)com>
To: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: idea: global temp tables
Date: 2009-04-28 01:39:48
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Lists: pgsql-hackers
On Apr 27, 2009, at 6:01 PM, Kevin Grittner wrote:

> "A.M." <agentm(at)themactionfaction(dot)com> wrote:
>> On Apr 27, 2009, at 5:39 PM, Dimitri Fontaine wrote:
>>> Le 27 avr. 09 à 23:32, A.M. a écrit :
>>>> When will postgresql offer "global" temporary tables with data
>>>> which are shared among sessions? Such tables are great for
>>>> transient data such as web session data where writing to the WAL is
>>>> a waste. (On DB startup, the tables would simply be empty.) We're
>>>> currently stuck with the memcached plugin which makes it impossible
>>>> to use database constructs such as foreign keys against the
>>>> temporary data.
>>> If using 8.3 you can SET LOCAL synchronous_commit TO off; for web
>>> session management transactions, it'll skip the WAL fsync'ing, which
>>> is already a good start.
>> That's pretty close, but it's not table specific and wouldn't let us
>> to reliably mix transient data changes with real data changes.
> Yeah, we have a dozen or so tables we use with the pattern you
> describe; so the feature you describe would also have some value for
> us.  To avoid confusion, we don't refer to these as "temporary
> tables", but rather as "permanent work tables".  Again, I can't
> comment on practical issues regarding implementation; but it would be
> a "nice feature" to add some day.  The tricky bit would be to figure
> out how to ensure that it got cleaned up properly, especially if the
> PostgreSQL went down or client processes wend down before tidying up.

Actually, for our usage, that's the easiest part- truncate all the  
"permanent work tables" whenever the db starts. That's really the  
only sane thing to do anyway. That's what I mean by "transient" data-  
if it's there, that's great, if not, I can re-generate it (cache) or  
I don't care because, if the database goes down, then the data is  
useless on restart anyway.


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