From 02f4e0ec8b0acd0401b9b86fb0b8fb967b19b800 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Mon, 21 Aug 2023 02:47:27 -0700
Subject: [PATCH] Revert "Added version to reduce stale reads and writes and
 prepare for optimistic locking"

This reverts commit ef1209eaf48ba3b5827b4c7e9f198504f089e1af.
---
 src/hnsw.h       | 5 ++---
 src/hnswinsert.c | 9 +++------
 src/hnswutils.c  | 6 +-----
 src/hnswvacuum.c | 2 --
 4 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/src/hnsw.h b/src/hnsw.h
index ae2476f..7495e40 100644
--- a/src/hnsw.h
+++ b/src/hnsw.h
@@ -85,7 +85,6 @@ typedef struct HnswNeighborArray HnswNeighborArray;
 typedef struct HnswElementData
 {
 	List	   *heaptids;
-	uint8		version;
 	uint8		level;
 	uint8		deleted;
 	HnswNeighborArray *neighbors;
@@ -186,9 +185,9 @@ typedef HnswPageOpaqueData * HnswPageOpaque;
 typedef struct HnswElementTupleData
 {
 	uint8		type;
-	uint8		version;
 	uint8		level;
 	uint8		deleted;
+	uint8		unused;
 	ItemPointerData heaptids[HNSW_HEAPTIDS];
 	ItemPointerData neighbortid;
 	uint16		unused2;
@@ -200,7 +199,7 @@ typedef HnswElementTupleData * HnswElementTuple;
 typedef struct HnswNeighborTupleData
 {
 	uint8		type;
-	uint8		version;
+	uint8		unused;
 	uint16		count;
 	ItemPointerData indextids[FLEXIBLE_ARRAY_MEMBER];
 }			HnswNeighborTupleData;
diff --git a/src/hnswinsert.c b/src/hnswinsert.c
index 19f2fee..f0c3d2a 100644
--- a/src/hnswinsert.c
+++ b/src/hnswinsert.c
@@ -359,11 +359,8 @@ HnswUpdateNeighborPages(Relation index, FmgrInfo *procinfo, Oid collation, HnswE
 			/* Calculate index for update */
 			startIdx = (hc->element->level - lc) * m;
 
-			/* TODO Skip when deleting */
-			/* TODO Resolve issue with connections from element neighbor tuple */
-			if (ntup->version != hc->element->version)
-				idx = -1;
-			else if (checkExisting && ConnectionExists(e, ntup, startIdx, lm))
+			/* Check for existing connection */
+			if (checkExisting && ConnectionExists(e, ntup, startIdx, lm))
 				idx = -1;
 			else if (idx == -2)
 			{
@@ -477,7 +474,7 @@ HnswAddDuplicate(Relation index, HnswElement element, HnswElement dup)
 	}
 
 	/* Either being deleted or we lost our chance to another backend */
-	if (i == 0 || i == HNSW_HEAPTIDS || etup->version != dup->version)
+	if (i == 0 || i == HNSW_HEAPTIDS)
 	{
 		GenericXLogAbort(state);
 		UnlockReleaseBuffer(buf);
diff --git a/src/hnswutils.c b/src/hnswutils.c
index e1bd17c..4ca1cc2 100644
--- a/src/hnswutils.c
+++ b/src/hnswutils.c
@@ -160,7 +160,6 @@ HnswInitElement(ItemPointer heaptid, int m, double ml, int maxLevel)
 	element->heaptids = NIL;
 	HnswAddHeapTid(element, heaptid);
 
-	element->version = 1;
 	element->level = level;
 	element->deleted = 0;
 
@@ -289,7 +288,6 @@ void
 HnswSetElementTuple(HnswElementTuple etup, HnswElement element)
 {
 	etup->type = HNSW_ELEMENT_TUPLE_TYPE;
-	etup->version = element->version;
 	etup->level = element->level;
 	etup->deleted = 0;
 	for (int i = 0; i < HNSW_HEAPTIDS; i++)
@@ -311,7 +309,6 @@ HnswSetNeighborTuple(HnswNeighborTuple ntup, HnswElement e, int m)
 	int			idx = 0;
 
 	ntup->type = HNSW_NEIGHBOR_TUPLE_TYPE;
-	ntup->version = e->version;
 
 	for (int lc = e->level; lc >= 0; lc--)
 	{
@@ -351,7 +348,7 @@ LoadNeighborsFromPage(HnswElement element, Relation index, Page page)
 	HnswInitNeighbors(element, m);
 
 	/* Ensure expected neighbors */
-	if (ntup->version != element->version || ntup->count != neighborCount)
+	if (ntup->count != neighborCount)
 		return;
 
 	for (int i = 0; i < neighborCount; i++)
@@ -404,7 +401,6 @@ HnswLoadNeighbors(HnswElement element, Relation index)
 void
 HnswLoadElementFromTuple(HnswElement element, HnswElementTuple etup, bool loadHeaptids, bool loadVec)
 {
-	element->version = etup->version;
 	element->level = etup->level;
 	element->deleted = etup->deleted;
 	element->neighborPage = ItemPointerGetBlockNumber(&etup->neighbortid);
diff --git a/src/hnswvacuum.c b/src/hnswvacuum.c
index 425e737..c6dd91b 100644
--- a/src/hnswvacuum.c
+++ b/src/hnswvacuum.c
@@ -485,12 +485,10 @@ MarkDeleted(HnswVacuumState * vacuumstate)
 			ntup = (HnswNeighborTuple) PageGetItem(npage, PageGetItemId(npage, neighborOffno));
 
 			/* Overwrite element */
-			etup->version++;
 			etup->deleted = 1;
 			MemSet(&etup->vec.x, 0, etup->vec.dim * sizeof(float));
 
 			/* Overwrite neighbors */
-			ntup->version = etup->version;
 			for (int i = 0; i < ntup->count; i++)
 				ItemPointerSetInvalid(&ntup->indextids[i]);