Revert "Remove offsethash"

This reverts commit 1cbd204f52.

src/hnsw.h

@@ -445,4 +445,17 @@ typedef struct PointerHashEntry
 #define SH_DECLARE
 #include "lib/simplehash.h"
 
+typedef struct OffsetHashEntry
+{
+	Size		offset;
+	char		status;
+}			OffsetHashEntry;
+
+#define SH_PREFIX offsethash
+#define SH_ELEMENT_TYPE OffsetHashEntry
+#define SH_KEY_TYPE Size
+#define SH_SCOPE extern
+#define SH_DECLARE
+#include "lib/simplehash.h"
+
 #endif

src/hnswutils.c

@@ -81,9 +81,31 @@ hash_pointer(uintptr_t ptr)
 #define SH_DEFINE
 #include "lib/simplehash.h"
 
+/* Offset hash table */
+static uint32
+hash_offset(Size offset)
+{
+#if SIZEOF_SIZE_T == 8
+	return murmurhash64((uint64) offset);
+#else
+	return murmurhash32((uint32) offset);
+#endif
+}
+
+#define SH_PREFIX		offsethash
+#define SH_ELEMENT_TYPE	OffsetHashEntry
+#define SH_KEY_TYPE		Size
+#define	SH_KEY			offset
+#define SH_HASH_KEY(tb, key)	hash_offset(key)
+#define SH_EQUAL(tb, a, b)		(a == b)
+#define	SH_SCOPE		extern
+#define SH_DEFINE
+#include "lib/simplehash.h"
+
 typedef union
 {
 	pointerhash_hash *pointers;
+	offsethash_hash *offsets;
 	tidhash_hash *tids;
 }			visited_hash;
 
@@ -636,6 +658,8 @@ InitVisited(char *base, visited_hash * v, Relation index, int ef, int m)
 {
 	if (index != NULL)
 		v->tids = tidhash_create(CurrentMemoryContext, ef * m * 2, NULL);
+	else if (base != NULL)
+		v->offsets = offsethash_create(CurrentMemoryContext, ef * m * 2, NULL);
 	else
 		v->pointers = pointerhash_create(CurrentMemoryContext, ef * m * 2, NULL);
 }
@@ -644,21 +668,34 @@ InitVisited(char *base, visited_hash * v, Relation index, int ef, int m)
  * Add to visited
  */
 static inline void
-AddToVisited(char *base, visited_hash * v, HnswElement element, Relation index, bool *found)
+AddToVisited(char *base, visited_hash * v, HnswCandidate * hc, Relation index, bool *found)
 {
 	if (index != NULL)
 	{
+		HnswElement element = HnswPtrAccess(base, hc->element);
 		ItemPointerData indextid;
 
 		ItemPointerSet(&indextid, element->blkno, element->offno);
 		tidhash_insert(v->tids, indextid, found);
 	}
+	else if (base != NULL)
+	{
+#if PG_VERSION_NUM >= 130000
+		HnswElement element = HnswPtrAccess(base, hc->element);
+
+		offsethash_insert_hash(v->offsets, HnswPtrOffset(hc->element), element->hash, found);
+#else
+		offsethash_insert(v->offsets, HnswPtrOffset(hc->element), found);
+#endif
+	}
 	else
 	{
 #if PG_VERSION_NUM >= 130000
-		pointerhash_insert_hash(v->pointers, (uintptr_t) element, element->hash, found);
+		HnswElement element = HnswPtrAccess(base, hc->element);
+
+		pointerhash_insert_hash(v->pointers, (uintptr_t) HnswPtrPointer(hc->element), element->hash, found);
 #else
-		pointerhash_insert(v->pointers, (uintptr_t) element, found);
+		pointerhash_insert(v->pointers, (uintptr_t) HnswPtrPointer(hc->element), found);
 #endif
 	}
 }
@@ -711,7 +748,7 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 		HnswCandidate *hc = (HnswCandidate *) lfirst(lc2);
 		bool		found;
 
-		AddToVisited(base, &v, HnswPtrAccess(base, hc->element), index, &found);
+		AddToVisited(base, &v, hc, index, &found);
 
 		pairingheap_add(C, &(CreatePairingHeapNode(hc)->ph_node));
 		pairingheap_add(W, &(CreatePairingHeapNode(hc)->ph_node));
@@ -755,14 +792,14 @@ HnswSearchLayer(char *base, Datum q, List *ep, int ef, int lc, Relation index, F
 		for (int i = 0; i < neighborhood->length; i++)
 		{
 			HnswCandidate *e = &neighborhood->items[i];
-			HnswElement eElement = HnswPtrAccess(base, e->element);
 			bool		visited;
 
-			AddToVisited(base, &v, eElement, index, &visited);
+			AddToVisited(base, &v, e, index, &visited);
 
 			if (!visited)
 			{
 				float		eDistance;
+				HnswElement eElement = HnswPtrAccess(base, e->element);
 
 				f = ((HnswPairingHeapNode *) pairingheap_first(W))->inner;
 
@@ -1143,7 +1180,14 @@ RemoveElements(char *base, List *w, HnswElement skipElement)
 static void
 PrecomputeHash(char *base, HnswElement element)
 {
-	element->hash = hash_pointer((uintptr_t) element);
+	HnswElementPtr ptr;
+
+	HnswPtrStore(base, ptr, element);
+
+	if (base == NULL)
+		element->hash = hash_pointer((uintptr_t) HnswPtrPointer(ptr));
+	else
+		element->hash = hash_offset(HnswPtrOffset(ptr));
 }
 #endif