pgsql: amcheck: Allow interrupting the child-level rightlink walk

amcheck: Allow interrupting the child-level rightlink walk

bt_child_highkey_check() walks right along the child level following
btpo_next links, reading a page on each iteration, but its loop lacked a
CHECK_FOR_INTERRUPTS(). Every other page-traversal loop in
verify_nbtree.c already has one.

The loop's existing checks do not guarantee a timely exit on a corrupt
index. The in-loop cycle check only fires when a rightlink points back
through the block the walk started from, or to a page whose btpo_prev
points to itself, so a cycle further downstream can go undetected -- for
example a run of pages all flagged P_INCOMPLETE_SPLIT, which skips both
the high-key comparison and bt_downlink_missing_check() and so never
reaches an error. Such an index, or simply a very long rightlink chain,
makes the walk effectively uninterruptible. Since amcheck exists to be
run against possibly-corrupt indexes, make this walk respond to query
cancellation and shutdown requests like the sibling loops do.

Author: Paul Kim <mok03127(at)gmail(dot)com>
Reviewed-by: shihao zhong <zhong950419(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/20260717151437.10713-1-mok03127@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a846ee9854ee9994935d697e1f9c2a0d70f328f1

Modified Files
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contrib/amcheck/verify_nbtree.c | 2 ++
1 file changed, 2 insertions(+)