Further adjust guidance for running vacuumdb after pg_upgrade.

Since pg_upgrade does not transfer the cumulative statistics used
to trigger autovacuum and autoanalyze, the server may take much
longer than expected to process them post-upgrade.  Currently, we
recommend analyzing only relations for which optimizer statistics
were not transferred by using the --analyze-in-stages and
--missing-stats-only options.  This commit appends another
recommendation to analyze all relations to update the relevant
cumulative statistics by using the --analyze-only option.  This is
similar to the recommendation for pg_stat_reset().

Reported-by: Christoph Berg <[email protected]>
Reviewed-by: Christoph Berg <[email protected]>
Discussion: https://postgr.es/m/aAfxfKC82B9NvJDj%40msg.df7cb.de

Author: nathan-bossart

doc/src/sgml/ref/pgupgrade.sgml

@@ -833,17 +833,19 @@ psql --username=postgres --file=script.sql postgres
 
     <para>
      Because not all statistics are not transferred by
-     <command>pg_upgrade</command>, you will be instructed to run a command to
+     <command>pg_upgrade</command>, you will be instructed to run commands to
      regenerate that information at the end of the upgrade.  You might need to
      set connection parameters to match your new cluster.
     </para>
 
     <para>
-     Using <command>vacuumdb --all --analyze-only --missing-stats-only</command>
-     can efficiently generate such statistics.  Alternatively,
+     First, use
      <command>vacuumdb --all --analyze-in-stages --missing-stats-only</command>
-     can be used to generate minimal statistics quickly.  For either command,
-     the use of <option>--jobs</option> can speed it up.
+     to quickly generate minimal optimizer statistics for relations without
+     any.  Then, use <command>vacuumdb --all --analyze-only</command> to ensure
+     all relations have updated cumulative statistics for triggering vacuum and
+     analyze.  For both commands, the use of <option>--jobs</option> can speed
+     it up.
      If <varname>vacuum_cost_delay</varname> is set to a non-zero
      value, this can be overridden to speed up statistics generation
      using <envar>PGOPTIONS</envar>, e.g., <literal>PGOPTIONS='-c

src/bin/pg_upgrade/check.c

@@ -814,9 +814,12 @@ output_completion_banner(char *deletion_script_file_name)
 	}
 
 	pg_log(PG_REPORT,
-		   "Some optimizer statistics may not have been transferred by pg_upgrade.\n"
-		   "Once you start the new server, consider running:\n"
-		   "    %s/vacuumdb %s--all --analyze-in-stages --missing-stats-only", new_cluster.bindir, user_specification.data);
+		   "Some statistics are not transferred by pg_upgrade.\n"
+		   "Once you start the new server, consider running these two commands:\n"
+		   "    %s/vacuumdb %s--all --analyze-in-stages --missing-stats-only\n"
+		   "    %s/vacuumdb %s--all --analyze-only",
+		   new_cluster.bindir, user_specification.data,
+		   new_cluster.bindir, user_specification.data);
 
 	if (deletion_script_file_name)
 		pg_log(PG_REPORT,