Re: Doubt in mvcc - Mailing list pgsql-general

From Laurenz Albe
Subject Re: Doubt in mvcc
Date
Msg-id c754e62e3b88aeef133ef9816227bec80f335230.camel@cybertec.at
Whole thread Raw
In response to Doubt in mvcc  (Rama Krishnan <raghuldrag@gmail.com>)
List pgsql-general
On Mon, 2020-07-13 at 13:01 +0530, Rama Krishnan wrote:
> I m preparing for interview one of the recruiter asked me mvcc drawbacks as i told due
> to mvcc it use more space and need to perform maintenance activity.

Yes.  Generally speaking, you have to pay a price for keeping old versions of the
data around, no matter how you implement it.

> Another one is the same data causes an update conflict because two different transactions
> can update the same version of the row.
>  he told its wrong, kindly tell me will you please tell me its correct or wrong?

There is always a certain version (the latest) that can be updated, so this is
the same no matter if you have MVCC or not: if two sessions want to update the same
row, one has to wait until the other is done.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com




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