pgsql: Further adjust guidance for running vacuumdb after pg_upgrade.

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 <myon@debian.org>
Reviewed-by: Christoph Berg <myon@debian.org>
Discussion: https://postgr.es/m/aAfxfKC82B9NvJDj%40msg.df7cb.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d5f1b6a75ba3f55a78959c957c3fd25d9569057c

Modified Files
--------------
doc/src/sgml/ref/pgupgrade.sgml | 12 +++++++-----
src/bin/pg_upgrade/check.c      |  9 ++++++---
2 files changed, 13 insertions(+), 8 deletions(-)