Michael Paquier wrote:
> On Fri, Jan 19, 2018 at 11:33:43AM -0500, Tom Lane wrote:
> > It means reading the whole table and writing it out in some modified
> > form (for instance, with some column transformed into a new datatype).
> > It's not "dangerous" in any way ... but if you've got many GB of data in
> > the table and you can't afford to have the table locked for a long time,
> > then it's something to avoid.
>
> Yeah that can be costly. Note that WAL corresponding to this data needs
> to be generated as well.
Maybe we need to document this somewhere, particularly now that we have
a "table_rewrite" event item.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
