On Sat, Jul 26, 2025 at 07:47:47AM -0700, David G. Johnston wrote: > On Sat, Jul 26, 2025, 07:23 Bruce Momjian <br...@momjian.us> wrote: > > On Wed, Jul 23, 2025 at 02:45:10PM +0200, Frédéric Yhuel wrote: > > > > > > On 3/18/25 22:37, Nathan Bossart wrote: > > > Committed with the following small changes: > > > > Hi, I don't really understand this sentence in > > doc/src/sgml/ref/vacuumdb.sgml: > > > > > This option prevents vacuumdb from deleting existing statistics so > that > > the query optimizer's choices do not become transiently worse. > > > > I thought that the point was to avoid unnecessary post-upgrade analyzes? > > So, the full paragraph is: > > + Only analyze relations that are missing statistics for a column, > index > + expression, or extended statistics object. This option prevents > + <application>vacuumdb</application> from deleting existing > statistics > + so that the query optimizer's choices do not become transiently > worse. > > What it is trying to say is that if you run vacuumedb without this > option, not only will it analyze all tables, including ones that already > have statistics, but will drop statistics on this tables that already > have statistics for a brief period while it installs new statistics. > During that period, the optimizer will not have any statistics for the > table. Is there a clearer way to state this? > > Statistics are transactional. Without this option specified are we really > removing them and commiting prior to computing and saving new ones? And we > are > opposed to just changing this behavior and instead prefer to add an option > that > at first glance seems like everyone should use?
Yes, I thought it was transactional too, but the doc patch suggests is isn't, so maybe I am wrong. > "If not specified the system will analyze all statistics-capable objects in > alphabetical order. Specifying this option then limits the result to only > those objects that do not already have statistics.". That may not be how the > feature strictly behaves but that would seem to be all one would expect it to > do. Yes, I would prefer the simpler text, if it is accurate. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com Do not let urgent matters crowd out time for investment in the future.
