From f4b67b078f8dc158b4d88a125d7043cc6cc6ac65 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Wed, 9 Oct 2024 17:01:49 -0700
Subject: [PATCH] DRY HNSW distance calculations

---
 src/hnswutils.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/src/hnswutils.c b/src/hnswutils.c
index 3d0b484..a7eb819 100644
--- a/src/hnswutils.c
+++ b/src/hnswutils.c
@@ -482,6 +482,15 @@ HnswLoadElementFromTuple(HnswElement element, HnswElementTuple etup, bool loadHe
 	}
 }
 
+/*
+ * Calculate the distance between values
+ */
+static inline float
+HnswGetDistance(Datum a, Datum b, FmgrInfo *procinfo, Oid collation)
+{
+	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, a, b));
+}
+
 /*
  * Load an element and optionally get its distance from q
  */
@@ -507,7 +516,7 @@ HnswLoadElementImpl(BlockNumber blkno, OffsetNumber offno, double *distance, Dat
 		if (DatumGetPointer(*q) == NULL)
 			*distance = 0;
 		else
-			*distance = DatumGetFloat8(FunctionCall2Coll(procinfo, collation, *q, PointerGetDatum(&etup->data)));
+			*distance = HnswGetDistance(*q, PointerGetDatum(&etup->data), procinfo, collation);
 	}
 
 	/* Load element */
@@ -539,7 +548,7 @@ GetElementDistance(char *base, HnswElement element, Datum q, FmgrInfo *procinfo,
 {
 	Datum		value = HnswGetValue(base, element);
 
-	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, q, value));
+	return HnswGetDistance(q, value, procinfo, collation);
 }
 
 /*
@@ -921,18 +930,6 @@ CompareCandidateDistancesOffset(const ListCell *a, const ListCell *b)
 	return 0;
 }
 
-/*
- * Calculate the distance between elements
- */
-static float
-HnswGetDistance(char *base, HnswElement a, HnswElement b, FmgrInfo *procinfo, Oid collation)
-{
-	Datum		aValue = HnswGetValue(base, a);
-	Datum		bValue = HnswGetValue(base, b);
-
-	return DatumGetFloat8(FunctionCall2Coll(procinfo, collation, aValue, bValue));
-}
-
 /*
  * Check if an element is closer to q than any element from R
  */
@@ -940,13 +937,15 @@ static bool
 CheckElementCloser(char *base, HnswCandidate * e, List *r, FmgrInfo *procinfo, Oid collation)
 {
 	HnswElement eElement = HnswPtrAccess(base, e->element);
+	Datum		eValue = HnswGetValue(base, eElement);
 	ListCell   *lc2;
 
 	foreach(lc2, r)
 	{
 		HnswCandidate *ri = lfirst(lc2);
 		HnswElement riElement = HnswPtrAccess(base, ri->element);
-		float		distance = HnswGetDistance(base, eElement, riElement, procinfo, collation);
+		Datum		riValue = HnswGetValue(base, riElement);
+		float		distance = HnswGetDistance(eValue, riValue, procinfo, collation);
 
 		if (distance <= e->distance)
 			return false;