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Re: Clarification on a Time travel feature

From: "Gokulakannan Somasundaram" <gokul007(at)gmail(dot)com>
To: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Clarification on a Time travel feature
Date: 2007-10-31 11:44:16
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
There is only one condition under which this would be useful.

Current Scenario:


Select x into var from inventory where y=const;

update inventory..

some more DMLs.

some select into var2;

if (condition based on var2)
   use the var;


here i have to fire the first select query all the 100% of the time. Say if
i have a feature to time travel within a transaction, i need to fire that
select query on the probability of the condition based on var2 getting true.

After that implementation

store command id and increment it into cid;
some DMLS
some select into var2
if(condition based on var2)
     select into :var as of  cid;

I know this is a small use-case. But if you think about it, the
implementation is very easy. It wouldn't take much time to implement it.


On 10/31/07, Heikki Linnakangas <heikki(at)enterprisedb(dot)com> wrote:
> Gokulakannan Somasundaram wrote:
> > a) Is there a proposal in place for going back in time within a
> transaction?
> Within a transaction? No, can't remember one. Doesn't sound very useful.
> --
>    Heikki Linnakangas
>    EnterpriseDB

CertoSQL Project,
Allied Solution Groups.

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