Re: Proposal: Incremental Backup - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Proposal: Incremental Backup
Date
Msg-id CA+TgmobUXtVj=Mu+9d_PEF=zp+1bV+3VDbs+Ni7UyHXqZPfOSA@mail.gmail.com
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In response to Re: Proposal: Incremental Backup  (Amit Kapila <amit.kapila16@gmail.com>)
List pgsql-hackers
On Thu, Jul 31, 2014 at 2:00 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> On Wed, Jul 30, 2014 at 11:32 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> IMV, the way to eventually make this efficient is to have a background
>> process that reads the WAL and figures out which data blocks have been
>> modified, and tracks that someplace.
>
> Nice idea, however I think to make this happen we need to ensure
> that WAL doesn't get deleted/overwritten before this process reads
> it (may be by using some existing param or mechanism) and
> wal_level has to be archive or more.

That should be a problem; logical decoding added a mechanism for
retaining WAL until decoding is done with it, and if it needs to be
extended a bit further, so be it.

> One more thing, what will happen for unlogged tables with such a
> mechanism?

As Michael Paquier points out, it doesn't matter, because that data
will be gone anyway.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company



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