On Wed, Apr 24, 2024 at 03:36:35PM -0700, David G. Johnston wrote: > On Wed, Apr 24, 2024 at 1:26 PM Nathan Bossart <nathandboss...@gmail.com> > wrote: >> On Wed, Apr 24, 2024 at 04:17:44PM +0900, Michael Paquier wrote: >>> - CREATE TABLE PARTITION OF would make a new partition inherit the >>> logged ness of the parent if UNLOGGED is not directly specified. >> >> This one seems generally reasonable to me, provided it's properly noted in >> the docs. > > I don't see this being desirable at this point. And especially not by > itself. It is an error to not specify TEMP on the partition create table > command when the parent is temporary, and that one is a no-brainer for > having the persistence mode of the child be derived from the parent. The > current policy of requiring the persistence of the child to be explicitly > specified seems perfectly reasonable. Or, put differently, the specific > current persistence of the parent doesn't get copied or even considered > when creating children.
I disagree here, actually. Temporary tables are a different beast
because they require automated cleanup which would include interacting
with the partitionining information if temp and non-temp relations are
mixed. That's why the current restrictions are in place: you should
be able to mix them. Mixing unlogged and logged is OK, they retain a
state in their catalogs.
> In any case we aren't going to be able to do exactly what it means by
> marking a partitioned table unlogged - namely that we execute the truncate
> command on it after a crash. Forcing the implementation here just so that
> our existing decision to ignore unlogged on the parent table is, IMO,
> letting optics corrupt good design.
It depends on retention policies, for one. I could imagine an
application where partitioning is used based on a key where we
classify records based on their persistency, and one does not care
about a portion of them, still would like some retention as long as
the application is healthy.
> I do agree with having an in-core way for the DBA to communicate that they
> wish for partitions to be created with a known persistence unless the
> create table command specifies something different. The way I would
> approach this is to add something like the following to the syntax/system:
>
> CREATE [ persistence_mode ] TABLE ...
> ...
> WITH (partition_default_persistence = { logged, unlogged, temporary }) --
> storage_parameter, logged is effectively the default
While we have keywords to drive that at query level for TEMP and
UNLOGGED? Not sure to be on board with this idea. pg_dump may need
some changes to reflect the loggedness across the partitions, now that
I think about it even if there should be an ATTACH once the table is
created to link it to its partitioned table. There should be no
rewrites at restore.
> I do agree with adding LOGGED to the list of optional persistence_mode
> specifiers, possibly regardless of whether any of this happens. Seems
> desirable to give our default mode a name.
Yeah, at least it looks like Nathan and you are OK with this addition.
--
Michael
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