Re: [HACKERS] CLUSTER command progress monitor

On Fri, Sep 06, 2019 at 08:10:58AM -0400, Robert Haas wrote:
> It's fine if things are updated as well -- it's just you need to make
> sure that those places know whether or not they are supposed to be
> doing those updates. Again, why can't we just pass down a value
> telling them "do reindex-style progress updates" or "do cluster-style
> progress updates" or "do no progress updates"?

That's invasive.  CREATE INDEX reporting goes pretty deep into the
tree, with steps dedicated to the builds and scans of btree (nbtsort.c
for example) and hash index AMs.  In this case we have something that
does somewhat what you are looking for with report_progress which gets
set to true only for VACUUM.  If we were to do something like that, we
would also need to keep some sort of mapping regarding which command
ID (as defined by ProgressCommandType) is able to use which set of
parameter flags (as defined by the arguments of
pgstat_progress_update_param() and its multi_* cousin).  Then comes
the issue that some parameters may be used by multiple command types,
while other don't (REINDEX and CREATE INDEX have some shared
mapping).
--
Michael