From 90a042e5aa0379263b57c76de726285af73ce495 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Mon, 21 Aug 2023 02:24:53 -0700
Subject: [PATCH] Wait for selects to complete

---
 src/hnswscan.c   | 3 +++
 src/hnswutils.c  | 4 +---
 src/hnswvacuum.c | 4 ++++
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/hnswscan.c b/src/hnswscan.c
index 4a5c7f9..040738b 100644
--- a/src/hnswscan.c
+++ b/src/hnswscan.c
@@ -4,6 +4,7 @@
 #include "hnsw.h"
 #include "pgstat.h"
 #include "storage/bufmgr.h"
+#include "storage/lmgr.h"
 #include "utils/memutils.h"
 
 /*
@@ -144,7 +145,9 @@ hnswgettuple(IndexScanDesc scan, ScanDirection dir)
 				HnswNormValue(so->normprocinfo, so->collation, &value, NULL);
 		}
 
+		LockPage(scan->indexRelation, HNSW_HEAD_BLKNO, ShareLock);
 		so->w = GetScanItems(scan, value);
+		UnlockPage(scan->indexRelation, HNSW_HEAD_BLKNO, ShareLock);
 		so->first = false;
 	}
 
diff --git a/src/hnswutils.c b/src/hnswutils.c
index 4e7f7eb..e1bd17c 100644
--- a/src/hnswutils.c
+++ b/src/hnswutils.c
@@ -625,9 +625,7 @@ HnswSearchLayer(Datum q, List *ep, int ef, int lc, Relation index, FmgrInfo *pro
 				else
 					HnswLoadElement(e->element, &eDistance, &q, index, procinfo, collation, inserting);
 
-				/* Skip if fully deleted */
-				if (e->element->deleted)
-					continue;
+				Assert(!e->element->deleted);
 
 				/* Skip self for vacuuming update */
 				if (skipElement != NULL && e->element->neighborPage == skipElement->neighborPage && e->element->neighborOffno == skipElement->neighborOffno)
diff --git a/src/hnswvacuum.c b/src/hnswvacuum.c
index 43b63de..425e737 100644
--- a/src/hnswvacuum.c
+++ b/src/hnswvacuum.c
@@ -404,6 +404,10 @@ MarkDeleted(HnswVacuumState * vacuumstate)
 	Relation	index = vacuumstate->index;
 	BufferAccessStrategy bas = vacuumstate->bas;
 
+	/* Wait for selects to complete */
+	LockPage(index, HNSW_HEAD_BLKNO, ExclusiveLock);
+	UnlockPage(index, HNSW_HEAD_BLKNO, ExclusiveLock);
+
 	while (BlockNumberIsValid(blkno))
 	{
 		Buffer		buf;