From a2a0b377f06e1122dcfb6eb40b5c0312bf604009 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Mon, 28 Oct 2024 13:46:49 -0700
Subject: [PATCH] Removed memory limit debug message from HNSW index scans
 (EXPLAIN ANALYZE can be used instead)

---
 README.md      | 13 +------------
 src/hnswscan.c | 19 ++-----------------
 2 files changed, 3 insertions(+), 29 deletions(-)

diff --git a/README.md b/README.md
index a9aff94..4851120 100644
--- a/README.md
+++ b/README.md
@@ -537,18 +537,7 @@ Specify the max amount of memory to use, as a multiple of `work_mem` (1 by defau
 SET hnsw.scan_mem_multiplier = 2;
 ```
 
-You can see when increasing this is needed by enabling debug messages
-
-```sql
-SET client_min_messages = debug1;
-```
-
-which will show when a scan reaches the memory limit
-
-```text
-DEBUG:  hnsw index scan reached memory limit after 20000 tuples
-HINT:  Increase hnsw.scan_mem_multiplier to scan more tuples.
-```
+Note: Try increasing this if increasing `hnsw.max_scan_tuples` does not improve recall
 
 #### IVFFlat
 
diff --git a/src/hnswscan.c b/src/hnswscan.c
index f38057b..955998a 100644
--- a/src/hnswscan.c
+++ b/src/hnswscan.c
@@ -240,8 +240,8 @@ hnswgettuple(IndexScanDesc scan, ScanDirection dir)
 			if (so->discarded == NULL)
 				break;
 
-			/* Reached max number of tuples */
-			if (so->tuples >= hnsw_max_scan_tuples)
+			/* Reached max number of tuples or memory limit */
+			if (so->tuples >= hnsw_max_scan_tuples || MemoryContextMemAllocated(so->tmpCtx, false) > so->maxMemory)
 			{
 				if (pairingheap_is_empty(so->discarded))
 					break;
@@ -249,21 +249,6 @@ hnswgettuple(IndexScanDesc scan, ScanDirection dir)
 				/* Return remaining tuples */
 				so->w = lappend(so->w, HnswGetSearchCandidate(w_node, pairingheap_remove_first(so->discarded)));
 			}
-			/* Prevent scans from consuming too much memory */
-			else if (MemoryContextMemAllocated(so->tmpCtx, false) > so->maxMemory)
-			{
-				if (pairingheap_is_empty(so->discarded))
-				{
-					ereport(DEBUG1,
-							(errmsg("hnsw index scan reached memory limit after " INT64_FORMAT " tuples", so->tuples),
-							 errhint("Increase hnsw.scan_mem_multiplier to scan more tuples.")));
-
-					break;
-				}
-
-				/* Return remaining tuples */
-				so->w = lappend(so->w, HnswGetSearchCandidate(w_node, pairingheap_remove_first(so->discarded)));
-			}
 			else
 			{
 				/*