On Wed, Oct 5, 2016 at 3:23 PM, Vitaly Burovoy <vitaly.buro...@gmail.com> wrote:
On 10/5/16, Andres Freund <and...@anarazel.de> wrote:
> On 2016-10-05 11:58:33 -0700, Serge Rielau wrote:
>> Dear Hackers,
>> I’m working on a patch that expands PG’s ability to add columns to a table
>> without a table rewrite (i.e. at O(1) cost) from the
>> nullable-without-default to a more general case.
> If I understand this proposal correctly, altering a column default will
> still have trigger a rewrite unless there's previous default?
No, "a second “exist default"" was mentioned, i.e. it is an additional
column in a system table (pg_attribute) as default column values of
the "pre-alter" era. It solves changing of the default expression of
the same column later. Correct and good guess on pg_attribute. That’s where 
it’s living in my proposal.
Cheers Serge

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