pgsql: Correct on-access VM setting heuristic

Correct on-access VM setting heuristic

The heuristic to avoid setting the VM during on-access pruning when
doing so would emit an extra FPI missed a few cases. First it missed
temp and unlogged tables. Those will never emit an FPI, so they can
always set the VM if the page is all-visible. It also missed that if
hint bits are not WAL-logged, setting only the VM passes REGBUF_NO_IMAGE
for an already WAL-logged heap page, forbidding a heap FPI in the WAL
record. A page that has never been WAL-logged still requires a heap FPI.

The third is more subtle: If the page is all-visible, the new prune xid
will be InvalidTransactionId. On-access pruning only executes when the
current pd_prune_xid is valid and visible. So, when on-access pruning
finds the page all-visible, it will always clear pd_prune_xid, modifying
the page.

Knowing this means we can set the VM without emitting an extra heap FPI
in more cases. When hint bits are WAL-logged, if the heap buffer is
clean, modifying pd_prune_xid will emit an FPI if one is required. There
is no reason to try to avoid an FPI by not setting the VM. So, set the
VM in this case. However, when the heap buffer is already dirty,
modifying pd_prune_xid can avoid an FPI; so if the page hasn't been
logged since the last checkpoint, setting it all-visible will emit an
extra heap page FPI. We will still avoid setting the VM in this case.

This is being backpatched to 19 because since 378a216187ae pd_prune_xid
is set on insert, and if we execute a prune cycle and skip setting the
VM because of an incorrect heuristic, we have added new wasted work in
PG 19.

This commit adds some tests covering these cases. It also updates one of
the existing temp table tests to avoid exceeding the pin limit. Setting
the VM and FSM on-access when querying temp tables takes more local pins
and can run into the limit with fewer heap buffers pinned.

Reported-by: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Author: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Reviewed-by: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Discussion: https://postgr.es/m/CAAKRu_amj7qLF4c=9ijd=708Fu2G8gg-2EqwBu=aCdAHU2sPHg@mail.gmail.com
Backpatch-through: 19

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4a2f5533f3ceb20727686ed5ef38107d6b295e33

Modified Files
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contrib/pg_visibility/expected/pg_visibility.out | 78 ++++++++++++++++++++++++
contrib/pg_visibility/sql/pg_visibility.sql | 36 +++++++++++
src/backend/access/heap/pruneheap.c | 37 ++++++++---
src/test/regress/expected/temp.out | 2 +-
src/test/regress/sql/temp.sql | 2 +-
5 files changed, 146 insertions(+), 9 deletions(-)