Re: Proposal for CSN based snapshots

On Tue, May 13, 2014 at 1:59 PM, Heikki Linnakangas
<hlinnakangas@vmware.com> wrote:
> On 05/13/2014 09:44 AM, Amit Kapila wrote:
>>
>> To accomplish this won't XID-CSN map table be required and how will
>> it be maintained (means when to clear and add a entry to that map table)?
>
>
> Not sure I understand. The clog is a mapping from XID to CSN.

The case I was referring is for xmin < XID < xmax, which you have
mentioned below that you are planing to directly refer pg_clog.  This
is I think one of the main place where new design can have impact
on performance, but as you said it is better to first do the implementation
based on pg_clog rather than directly jumping to optimize by maintaining
XID to CSN mapping.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com