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
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