From 54fa16e3e35683f65bbb7277363451f9f2b7c8e5 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Thu, 26 Sep 2024 08:32:44 -0700
Subject: [PATCH] Added safety check [skip ci]

---
 src/hnswutils.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/hnswutils.c b/src/hnswutils.c
index ac1e7de..d807248 100644
--- a/src/hnswutils.c
+++ b/src/hnswutils.c
@@ -759,9 +759,16 @@ HnswLoadUnvisitedFromDisk(HnswElement element, HnswUnvisited * unvisited, int *u
 	page = BufferGetPage(buf);
 
 	ntup = (HnswNeighborTuple) PageGetItem(page, PageGetItemId(page, element->neighborOffno));
-	start = (element->level - lc) * m;
+
+	/* Ensure expected neighbors */
+	if (ntup->count != (element->level + 2) * m)
+	{
+		UnlockReleaseBuffer(buf);
+		return;
+	}
 
 	/* Copy to minimize lock time */
+	start = (element->level - lc) * m;
 	memcpy(&indextids, ntup->indextids + start, lm * sizeof(ItemPointerData));
 
 	UnlockReleaseBuffer(buf);