two cents: On Wed, Mar 25, 2026 at 9:21 AM Bruce Momjian <[email protected]> wrote: > > On Wed, Mar 25, 2026 at 07:03:01AM +0100, Laurenz Albe wrote: > > On Tue, 2026-03-24 at 14:11 -0400, Bruce Momjian wrote: > > > On Tue, Mar 24, 2026 at 05:53:27PM +0100, Laurenz Albe wrote: > > > > Bruce, you are confusing me. Your first sentence suggests that you > > > > (erroneously) thought that upgrading statistics only works when > > > > upgrading > > > > > > Right. > > > > > > > *from* v18 or better. But your last sentence suggests that you'd rather > > > > not add anything to the documentation that could dispel that > > > > misconception. > > > > > > So, we don't normally document cases where a limitation does not exist.
I see it rather as an undocumented feature, not an undocumented "limitation that doesn't exist". > > > I think the logical place to document this is in the PG 18 release > > > notes. I am still confused why people, like myself, got this wrong. > > > What is the source of the confusion? Just unclear release notes? > > > > I understand now, thanks. I agree with you in principle, but I wouldn't > > see that as a hard rule that should stand in the way of clarity. > > > > Let me quote a precedent from > > https://www.postgresql.org/docs/current/upgrading.html > > > > Minor releases never change the internal storage format and are always > > compatible with earlier and later minor releases of the same major > > version number. For example, version 10.1 is compatible with version 10.0 > > and version 10.6. > > > > To me, that clarifies that there is no limitation to performing minor > > updates with a simple restart. I think that is useful information. > > Right. > > > Perhaps you'd feel better if we phrase it as a limitation: > > > > Transferring optimizer statistics only work when upgrading to PostgreSQL > > version v18 or later, but there is no such limitation to the version of > > the old cluster. > > > > I like my original suggestion better, though. > > Uh, we added the feature in PG 18, so why would we say it only works in > PG 18 --- that is kind of obvious. I am still asking, why did people, > like me, think it only worked for _old_ PG 18 servers. If we find where > that was communicated, we can clarify it _there_. If you don't know anything about implementation, it is natural to expect that something new will work only when both old and new clusters support it. That's why I started with words that I see everyone (includfing both of us) were originally confused. I bumped into it in some blog posts and LinkedIn discussions after which decided to clarify [1] since I couldn't find clarification anywhere on surface – only in source code, diving into implementation, and the depth of discussions [2] [3] [4]. It would be great to get it covered in the 2nd (after source code) source of truth-- the docs. [1] https://postgres.ai/blog/20260324-pg18-stats-upgrade-across-versions [2] https://www.postgresql.org/message-id/flat/aC5F1LX6-uL0wRV1%40nathan#f71f3dcd5fd88ee970f0b1ea0a779298 [3] https://www.postgresql.org/message-id/flat/1322262.1741643606%40sss.pgh.pa.us#d666e5e99bbd955a4f258338b44389da [4] https://www.postgresql.org/message-id/flat/Z_BcWVMvlUIJ_iuZ%40nathan#1f6ae665591cb5e5371552761aa90615
