From 029c336c62d832b2ca52825b37c457204c1f50d7 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Fri, 4 Aug 2023 13:51:16 -0700
Subject: [PATCH] Fixed results for NULL and NaN distances [skip ci]

---
 src/hnswscan.c                | 46 ++++++++++++++++++++++++++---------
 test/expected/hnsw_cosine.out | 17 ++++++++++---
 test/expected/hnsw_ip.out     | 10 +++++---
 test/expected/hnsw_l2.out     | 10 +++++---
 test/sql/hnsw_cosine.sql      |  1 +
 5 files changed, 63 insertions(+), 21 deletions(-)

diff --git a/src/hnswscan.c b/src/hnswscan.c
index 3dca1ce..a178b60 100644
--- a/src/hnswscan.c
+++ b/src/hnswscan.c
@@ -35,6 +35,29 @@ GetScanItems(IndexScanDesc scan, Datum q)
 	so->w = SearchLayer(q, ep, hnsw_ef_search, 0, index, procinfo, collation, false, NULL, NULL);
 }
 
+/*
+ * Get dimensions from metapage
+ */
+static int
+GetDimensions(Relation index)
+{
+	Buffer		buf;
+	Page		page;
+	HnswMetaPage metap;
+	int			dimensions;
+
+	buf = ReadBuffer(index, HNSW_METAPAGE_BLKNO);
+	LockBuffer(buf, BUFFER_LOCK_SHARE);
+	page = BufferGetPage(buf);
+	metap = HnswPageGetMeta(page);
+
+	dimensions = metap->dimensions;
+
+	UnlockReleaseBuffer(buf);
+
+	return dimensions;
+}
+
 /*
  * Prepare for an index scan
  */
@@ -107,19 +130,18 @@ hnswgettuple(IndexScanDesc scan, ScanDirection dir)
 
 		/* No items will match if null */
 		if (scan->orderByData->sk_flags & SK_ISNULL)
-			return false;
-
-		value = scan->orderByData->sk_argument;
-
-		/* Value should not be compressed or toasted */
-		Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
-		Assert(!VARATT_IS_EXTENDED(DatumGetPointer(value)));
-
-		if (so->normprocinfo != NULL)
+			value = PointerGetDatum(InitVector(GetDimensions(scan->indexRelation)));
+		else
 		{
-			/* No items will match if normalization fails */
-			if (!HnswNormValue(so->normprocinfo, so->collation, &value, NULL))
-				return false;
+			value = scan->orderByData->sk_argument;
+
+			/* Value should not be compressed or toasted */
+			Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
+			Assert(!VARATT_IS_EXTENDED(DatumGetPointer(value)));
+
+			/* Fine if normalization fails */
+			if (so->normprocinfo != NULL)
+				HnswNormValue(so->normprocinfo, so->collation, &value, NULL);
 		}
 
 		GetScanItems(scan, value);
diff --git a/test/expected/hnsw_cosine.out b/test/expected/hnsw_cosine.out
index eec40d9..9bf8f59 100644
--- a/test/expected/hnsw_cosine.out
+++ b/test/expected/hnsw_cosine.out
@@ -11,9 +11,20 @@ SELECT * FROM t ORDER BY val <=> '[3,3,3]';
  [1,2,4]
 (3 rows)
 
+SELECT * FROM t ORDER BY val <=> '[0,0,0]';
+   val   
+---------
+ [1,1,1]
+ [1,2,4]
+ [1,2,3]
+(3 rows)
+
 SELECT * FROM t ORDER BY val <=> (SELECT NULL::vector);
- val 
------
-(0 rows)
+   val   
+---------
+ [1,1,1]
+ [1,2,4]
+ [1,2,3]
+(3 rows)
 
 DROP TABLE t;
diff --git a/test/expected/hnsw_ip.out b/test/expected/hnsw_ip.out
index 85a4648..d6ae2ea 100644
--- a/test/expected/hnsw_ip.out
+++ b/test/expected/hnsw_ip.out
@@ -13,8 +13,12 @@ SELECT * FROM t ORDER BY val <#> '[3,3,3]';
 (4 rows)
 
 SELECT * FROM t ORDER BY val <#> (SELECT NULL::vector);
- val 
------
-(0 rows)
+   val   
+---------
+ [1,1,1]
+ [1,2,4]
+ [1,2,3]
+ [0,0,0]
+(4 rows)
 
 DROP TABLE t;
diff --git a/test/expected/hnsw_l2.out b/test/expected/hnsw_l2.out
index 4136b82..e8a16c8 100644
--- a/test/expected/hnsw_l2.out
+++ b/test/expected/hnsw_l2.out
@@ -13,9 +13,13 @@ SELECT * FROM t ORDER BY val <-> '[3,3,3]';
 (4 rows)
 
 SELECT * FROM t ORDER BY val <-> (SELECT NULL::vector);
- val 
------
-(0 rows)
+   val   
+---------
+ [0,0,0]
+ [1,1,1]
+ [1,2,3]
+ [1,2,4]
+(4 rows)
 
 SELECT COUNT(*) FROM t;
  count 
diff --git a/test/sql/hnsw_cosine.sql b/test/sql/hnsw_cosine.sql
index 4398150..9b84d09 100644
--- a/test/sql/hnsw_cosine.sql
+++ b/test/sql/hnsw_cosine.sql
@@ -7,6 +7,7 @@ CREATE INDEX ON t USING hnsw (val vector_cosine_ops);
 INSERT INTO t (val) VALUES ('[1,2,4]');
 
 SELECT * FROM t ORDER BY val <=> '[3,3,3]';
+SELECT * FROM t ORDER BY val <=> '[0,0,0]';
 SELECT * FROM t ORDER BY val <=> (SELECT NULL::vector);
 
 DROP TABLE t;