[PATCH v1] 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 circular-link detection only catches an immediate two-page
cycle, so a corrupt index whose rightlink chain forms a larger cycle, or
simply a very long forward chain, makes this loop effectively
uninterruptible. As amcheck is specifically meant to be run against
possibly-corrupt indexes, make this walk respond to query cancellation
and shutdown requests the same way the sibling loops do.
---
Hi,

While reading verify_nbtree.c I noticed bt_child_highkey_check()'s
rightlink walk is the only page-traversal loop in the file without a
CHECK_FOR_INTERRUPTS(). Patch attached.

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

diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c
index 3ef2d66f826..486bd7a87cc 100644
--- a/contrib/amcheck/verify_nbtree.c
+++ b/contrib/amcheck/verify_nbtree.c
@@ -2191,6 +2191,8 @@ bt_child_highkey_check(BtreeCheckState *state,
/* Move to the right on the child level */
while (true)
{
+ CHECK_FOR_INTERRUPTS();
+
/*
* Did we traverse the whole tree level and this is check for pages to
* the right of rightmost downlink?
--
2.50.1 (Apple Git-155)