This function generates the commands that preserve the OIDs and
relfilenodes of relations during pg_upgrade. It is called once per
relevant relation, and each such call executes a relatively
expensive query to retrieve information for a single pg_class_oid.
This can cause pg_dump to take significantly longer when
--binary-upgrade is specified, especially when there are many
tables.
This commit improves the performance of this function by gathering
all the required pg_class information with a single query at the
beginning of pg_dump. This information is stored in a sorted array
that binary_upgrade_set_pg_class_oids() can bsearch() for what it
needs. This follows a similar approach as commit d5e8930f50, which
introduced a sorted array for role information.
With this patch, 'pg_dump --binary-upgrade' will use more memory,
but that isn't expected to be too egregious. Per the mailing list
discussion, folks feel that this is worth the trade-off.
Reviewed-by: Corey Huinker, Michael Paquier, Daniel Gustafsson
Discussion: https://postgr.es/m/20240418041712.GA3441570%40nathanxps13
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