Re: [HACKERS] generated columns - Mailing list pgsql-hackers

From Simon Riggs
Subject Re: [HACKERS] generated columns
Date
Msg-id CANP8+jJVK82tHfzHKz7w7oN_q1T1gPFMW+13LY4RuytfTr=3+g@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] generated columns  (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>)
List pgsql-hackers
On Tue, 6 Nov 2018 at 13:16, Peter Eisentraut <peter.eisentraut@2ndquadrant.com> wrote:
 
> Stored generated columns should be treated just like we'd treat a column
> value added by a trigger.
>
> e.g. if we had a Timestamp column called LastUpdateTimestamp we would
> want to send that value

Generated columns cannot have volatile expression results in them, so
this case cannot happen.

Also, we don't know whether the generation expression on the target is
the same (or even if it looks the same, consider locale issues etc.), so
we need to recompute the generated columns on the target anyway, so it's
pointless to send the already computed stored values.

Makes sense. 

--
Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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