Re: OS system version upgrade (glibc / libicu version change)

On Wed, 2026-10-28 at 14:32 +0100, Alexey Shishkin wrote:
> On the other hand it should not be only for PG20, but rather for all previous PG versions too.

Yes, perhaps.

> About the structure:
> - first, we should refer to Locale Providers chapter
> - then mention that icu/libc locale providers are backed by libicu/glibc libraries which
> versions might change from time to time (even within the lifecycle of the same major version of OS)
> - libicu/glibc version changes might lead to changes of SQL-queries which use affected indexes, so
> it's important to keep an eye on such changes

Simpler said, an index can become corrupted, leading to bad query results
and in due course to violated unique constraints.

> - the next item should describe what to do in case of libicu/glibc version changes - mainly about
> rebuilding the indexes, but not only
> - finally, we should provide the list of commands to identify affected indexes, to rebuild them
> online/offline, concurrently etc.

There are several strategies to deal with the problem:

- rebuild all indexes (simple, slow)
- identify all indexes that involve strings (a bit more complicated, faster)
- check all indexes with amcheck and rebuild only those with a problem
(leaves a window where users couls get bad query results
- perform a test upgrade and find the affected indexes ahead of time

Yours,
Laurenz Albe