From 8c5a4bfb6cf9601b01f8b2cab2e986c33e49e758 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Fri, 19 Jul 2024 13:54:36 -0700
Subject: [PATCH] Fixed failed to add index item error with sparsevec - fixes
 #625

---
 CHANGELOG.md                               |  1 +
 src/hnswinsert.c                           | 28 ++++++++++++----
 test/t/038_hnsw_sparsevec_vacuum_insert.pl | 38 ++++++++++++++++++++++
 3 files changed, 60 insertions(+), 7 deletions(-)
 create mode 100644 test/t/038_hnsw_sparsevec_vacuum_insert.pl

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80826c8..44ef23f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## 0.7.3 (unreleased)
 
+- Fixed `failed to add index item` error with `sparsevec`
 - Fixed compilation error with FreeBSD ARM
 - Fixed compilation warning with MSVC and Postgres 16
 
diff --git a/src/hnswinsert.c b/src/hnswinsert.c
index 0023024..04a10f9 100644
--- a/src/hnswinsert.c
+++ b/src/hnswinsert.c
@@ -36,14 +36,15 @@ GetInsertPage(Relation index)
  * Check for a free offset
  */
 static bool
-HnswFreeOffset(Relation index, Buffer buf, Page page, HnswElement element, Size ntupSize, Buffer *nbuf, Page *npage, OffsetNumber *freeOffno, OffsetNumber *freeNeighborOffno, BlockNumber *newInsertPage)
+HnswFreeOffset(Relation index, Buffer buf, Page page, HnswElement element, Size etupSize, Size ntupSize, Buffer *nbuf, Page *npage, OffsetNumber *freeOffno, OffsetNumber *freeNeighborOffno, BlockNumber *newInsertPage)
 {
 	OffsetNumber offno;
 	OffsetNumber maxoffno = PageGetMaxOffsetNumber(page);
 
 	for (offno = FirstOffsetNumber; offno <= maxoffno; offno = OffsetNumberNext(offno))
 	{
-		HnswElementTuple etup = (HnswElementTuple) PageGetItem(page, PageGetItemId(page, offno));
+		ItemId		eitemid = PageGetItemId(page, offno);
+		HnswElementTuple etup = (HnswElementTuple) PageGetItem(page, eitemid);
 
 		/* Skip neighbor tuples */
 		if (!HnswIsElementTuple(etup))
@@ -54,7 +55,9 @@ HnswFreeOffset(Relation index, Buffer buf, Page page, HnswElement element, Size
 			BlockNumber elementPage = BufferGetBlockNumber(buf);
 			BlockNumber neighborPage = ItemPointerGetBlockNumber(&etup->neighbortid);
 			OffsetNumber neighborOffno = ItemPointerGetOffsetNumber(&etup->neighbortid);
-			ItemId		itemid;
+			ItemId		nitemid;
+			Size		pageFree;
+			Size		npageFree;
 
 			if (!BlockNumberIsValid(*newInsertPage))
 				*newInsertPage = elementPage;
@@ -73,10 +76,21 @@ HnswFreeOffset(Relation index, Buffer buf, Page page, HnswElement element, Size
 				*npage = BufferGetPage(*nbuf);
 			}
 
-			itemid = PageGetItemId(*npage, neighborOffno);
+			nitemid = PageGetItemId(*npage, neighborOffno);
 
-			/* Check for space on neighbor tuple page */
-			if (PageGetFreeSpace(*npage) + ItemIdGetLength(itemid) - sizeof(ItemIdData) >= ntupSize)
+			/*
+			 * Calculate free space individually since tuples are overwritten
+			 * individually (in separate calls to PageIndexTupleOverwrite)
+			 */
+			pageFree = ItemIdGetLength(eitemid) + PageGetExactFreeSpace(page);
+			npageFree = ItemIdGetLength(nitemid);
+			if (neighborPage != elementPage)
+				npageFree += PageGetExactFreeSpace(*npage);
+			else if (pageFree >= etupSize)
+				npageFree += pageFree - etupSize;
+
+			/* Check for space */
+			if (pageFree >= etupSize && npageFree >= ntupSize)
 			{
 				*freeOffno = offno;
 				*freeNeighborOffno = neighborOffno;
@@ -184,7 +198,7 @@ AddElementOnDisk(Relation index, HnswElement e, int m, BlockNumber insertPage, B
 		}
 
 		/* Next, try space from a deleted element */
-		if (HnswFreeOffset(index, buf, page, e, ntupSize, &nbuf, &npage, &freeOffno, &freeNeighborOffno, &newInsertPage))
+		if (HnswFreeOffset(index, buf, page, e, etupSize, ntupSize, &nbuf, &npage, &freeOffno, &freeNeighborOffno, &newInsertPage))
 		{
 			if (nbuf != buf)
 			{
diff --git a/test/t/038_hnsw_sparsevec_vacuum_insert.pl b/test/t/038_hnsw_sparsevec_vacuum_insert.pl
new file mode 100644
index 0000000..28e71c7
--- /dev/null
+++ b/test/t/038_hnsw_sparsevec_vacuum_insert.pl
@@ -0,0 +1,38 @@
+use strict;
+use warnings;
+use PostgresNode;
+use TestLib;
+use Test::More;
+
+# Initialize node
+my $node = get_new_node('node');
+$node->init;
+$node->start;
+
+# Create table and index
+$node->safe_psql("postgres", "CREATE EXTENSION vector;");
+$node->safe_psql("postgres", "CREATE TABLE tst (i serial, v sparsevec(100000));");
+$node->safe_psql("postgres", "CREATE INDEX ON tst USING hnsw (v sparsevec_l2_ops);");
+
+for (1 .. 3) {
+    for (1 .. 100) {
+        my @elements;
+        my %indices;
+        for (1 .. int(rand() * 100)) {
+            my $index = int(rand() * (100000 - 1)) + 1;
+            if (!exists($indices{$index})) {
+                my $value = rand();
+                push(@elements, "$index:$value");
+                $indices{$index} = 1;
+            }
+        }
+        my $embedding = "{" . join(",", @elements) . "}/100000";
+        $node->safe_psql("postgres", "INSERT INTO tst (v) VALUES ('$embedding');");
+    }
+
+    $node->safe_psql("postgres", "DELETE FROM tst WHERE i % 2 = 0;");
+    $node->safe_psql("postgres", "VACUUM tst;");
+    is(1, 1);
+}
+
+done_testing();