Re: Fast AT ADD COLUMN with DEFAULTs

On 6 October 2016 at 04:43, Serge Rielau <serge(at)rielau(dot)com> wrote:

>>> Or should I compose some sort of a design document?

Having read this thread, I'm a little unclear as to what you're
writing now, though there's definitely good ideas here.

I think it would be beneficial to write up a single coherent
description of this, including behaviour and a small sketch of
implementation, just so everyone knows what this is. No design doc,
but a summary.

It would be very useful to be able to do this...
ALTER TABLE foo ADD last_updated_timestamp timestamp default current_timestamp
so that it generates a constant value and stores that for all prior
rows, but then generates a new value for future rows.

Which makes me think we should call this missing_value or absent_value
so its clear that it is not a "default" it is the value we use for
rows that do not have any value stored for them.

--
Simon Riggs http://www.2ndQuadrant.com/
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