On Wed, Aug 9, 2017 at 3:39 AM, Michael Paquier <michael.paqu...@gmail.com>
> This triggers a table rewrite and makes sure that all the data gets
> WAL-logged. The cost to pay for durability.
> > Is there a way to get my cake and eat it too?
> Not completely. Making data durable will have a cost at the end, but
> you can leverage it.
Aren't you over-playing the role of the WAL in providing durability. An
unlogged table remains intact after a clean shutdown and so is "durable" if
one considers the primary "permanence" aspect of the word.
The trade-off the OP wishes for is "lose crash-safety to gain write-once
(to the data files) performance". Seeming having this on a per-table basis
would be part of the desirability. It sounds like OP would be willing to
place the table into "read only" mode in order to ensure this - which is
something that is not presently possible. I could envision that putting an
unlogged table into read-only mode would cause the system to ensure that
the data files are fully populated and then set a flag in the catalog that
informs the crash recovery process to go ahead and omit truncating that
particular unlogged table since the data files are known to be accurate.