Re: format of pg_upgrade loadable_libraries warning

On Wed, Oct  2, 2019 at 12:23:37PM -0500, Justin Pryzby wrote:
> Regarding the previous thread and commit here:
> https://www.postgresql.org/message-id/flat/20180713162815.GA3835%40momjian.us
> https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=60e3bd1d7f92430b24b710ecf0559656eb8ed499
> 
> I'm suggesting to reformat the warning, which I found to be misleading:
> 
> |could not load library "$libdir/pgfincore": ERROR:  could not access file "$libdir/pgfincore": No such file or
directory
> |Database: postgres
> |Database: too
> 
> To me that reads as "error message" followed by successful processing of two,
> named database, and not "error message followed by list of databases for which
> that error was experienced".  Essentially, the database names are themselves
> the "error", and the message is a prefix indicating the library version; but
> normally, error-looking things are output without a "prefix", since they
> weren't anticipated.
> 
> The existing check is optimized to check each library once, but then outputs
> each database which would try to load it.  That's an implementation detail, but
> adds to confusion, since it shows a single error-looking thing which might
> apply to multiple DBs (not obvious to me that it's associated with an DB at
> all).  That leads me to believe that after I "DROP EXTENSION" once, I can
> reasonably expect the upgrade to complete, which has a good chance of being
> wrong, and is exactly what the patch was intended to avoid :(

Understood.  This is a general problem with the way pg_upgrade displays
errors and the databases/objects associated with them.  The attached
patch fixes the output text to say "in database", e.g.:

  Could not load library "$libdir/pgfincore": ERROR:  could not access file "$libdir/pgfincore": No such file or
directory
  in database: postgres
  in database: too

Would intenting help too?  I am inclined to fix this only head, and not
to backpatch the change.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
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