pgsql: doc: Document overflow handling of pg_class.relpages etc.

doc: Document overflow handling of pg_class.relpages etc.

The pg_class fields relpages, relallvisible, and relallfrozen are
stored as int32 in the catalog but block numbers are internally of
type uint32. This all works correctly because the values are
implicitly converted back and forth according to C conversion rules.
But this was apparently never explicitly documented, so add this.

Reviewed-by: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/db993f34-e3e1-4e6e-85c3-4f248d2ff29b%40eisentraut.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e63961d7c16f7df5ba4b881f4bfa7a7920c628bd

Modified Files
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doc/src/sgml/catalogs.sgml | 12 ++++++++++++
1 file changed, 12 insertions(+)