pgsql: Reject non-finite reltuples when restoring stats

Reject non-finite reltuples when restoring stats

When restoring relation stats, pg_restore_relation_stats() rejected
calls with (reltuples < -1.0). But that is insufficient - Infinity and
NaN values both pass that check, and get stored in pg_class verbatim.
This can have various undesirable consequences.

Fixed by rejecting non-finite reltuple values, in the same non-fatal way
as for the existing checks (emit WARNING and skip the update). Adds a
regression test to stats_import for these non-finite values, and to
check the -1.0 special value is still accepted.

Backpatch to 18, where pg_restore_relation_stats() was introduced.

Patch by Jan Nidzwetzki, minor commit message tweaks by me.

Author: Jan Nidzwetzki <jan(at)planetscale(dot)com>
Discussion: https://postgr.es/m/518BA772-8026-412A-AA8F-A7FE4C6B3717@planetscale.com
Backpatch-through: 18

Branch
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REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a0369dd8448fba99d22068f533764bf2fb001278

Modified Files
--------------
src/backend/statistics/relation_stats.c | 11 ++++-
src/test/regress/expected/stats_import.out | 79 ++++++++++++++++++++++++++++++
src/test/regress/sql/stats_import.sql | 43 ++++++++++++++++
3 files changed, 132 insertions(+), 1 deletion(-)