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From: NikhilS <[email protected]>
To: Tom Lane <[email protected]>
Cc: Neil Conway <[email protected]>
Cc: Hannu Krosing <[email protected]>
Cc: Josh Berkus <[email protected]>
Cc: [email protected]
Cc: Simon Riggs <[email protected]>
Subject: Re: VLDB Features
Date: Mon, 17 Dec 2007 13:05:35 +0530
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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	<[email protected]>
	<1197636530.7974.16.camel@hannu-laptop>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

Hi,

On Dec 15, 2007 1:14 PM, Tom Lane <[email protected]> wrote:

> NikhilS <[email protected]> writes:
> > Any errors which occur before doing the heap_insert should not require
> > any recovery according to me.
>
> A sufficient (though far from all-encompassing) rejoinder to that is
> "triggers and CHECK constraints can do anything".
>
> > The overhead of having a subtransaction per row is a very valid concern.
> But
> > instead of using a per insert or a batch insert substraction, I am
> > thinking that we can start off a subtraction and continue it till we
> > encounter a failure.The moment an error is encountered, since we have
> the offending >(already in heap) tuple around, we can call a
> simple_heap_delete on the same and commit >(instead of aborting) this
> subtransaction
>
> What of failures that occur only at (sub)transaction commit, such as
> foreign key checks?
>

What if we identify and define a subset where we could do subtransactions
based COPY? The following could be supported:

* A subset of triggers and CHECK constraints which do not move the tuple
around. (Identifying this subset might be an issue though?)
* Primary/unique key indexes

As Hannu mentioned elsewhere in this thread, there should not be very many
instances of complex triggers/CHECKs around? And  may be in those instances
(and also the foreign key checks case), the behaviour could default to use a
per-subtransaction-per-row or even the existing single transaction model?

Regards,
Nikhils
-- 
EnterpriseDB               http://www.enterprisedb.com

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