From c01e76f2faf65410979a2071e45d571da4847727 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Sat, 28 Sep 2024 11:31:03 -0700
Subject: [PATCH] Added strict ordering [skip ci]

---
 src/hnsw.h     | 1 +
 src/hnswscan.c | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/src/hnsw.h b/src/hnsw.h
index 0e1aa54..400eaa0 100644
--- a/src/hnsw.h
+++ b/src/hnsw.h
@@ -371,6 +371,7 @@ typedef struct HnswScanOpaqueData
 	Datum		q;
 	int			m;
 	int64		tuples;
+	double		previousDistance;
 	MemoryContext tmpCtx;
 
 	/* Support functions */
diff --git a/src/hnswscan.c b/src/hnswscan.c
index a2f6f8b..7b5c3d7 100644
--- a/src/hnswscan.c
+++ b/src/hnswscan.c
@@ -1,5 +1,7 @@
 #include "postgres.h"
 
+#include <float.h>
+
 #include "access/relscan.h"
 #include "hnsw.h"
 #include "pgstat.h"
@@ -149,6 +151,7 @@ hnswrescan(IndexScanDesc scan, ScanKey keys, int nkeys, ScanKey orderbys, int no
 
 	so->first = true;
 	so->tuples = 0;
+	so->previousDistance = -INFINITY;
 	MemoryContextReset(so->tmpCtx);
 
 	if (keys && scan->numberOfKeys > 0)
@@ -296,6 +299,11 @@ hnswgettuple(IndexScanDesc scan, ScanDirection dir)
 
 		heaptid = &element->heaptids[--element->heaptidsLength];
 
+		if (hc->distance < so->previousDistance)
+			continue;
+
+		so->previousDistance = hc->distance;
+
 		MemoryContextSwitchTo(oldCtx);
 
 		scan->xs_heaptid = *heaptid;