From: Alexander Korotkov <akorotkov@postgresql.org>
Date: Mon, 15 Apr 2019 17:20:43 +0000 (+0300)
Subject: Fix division by zero in _bt_vacuum_needs_cleanup()
X-Git-Tag: REL_12_BETA1~229
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1e871981823a68ec9e0174b652e8d27e05ce08bb;p=thirdparty%2Fpostgresql.git

Fix division by zero in _bt_vacuum_needs_cleanup()

Checks inside _bt_vacuum_needs_cleanup() allow division by zero to happen when
metad->btm_last_cleanup_num_heap_tuples == 0.  This commit adjusts the
expression so that no division by zero might happen.

Reported-by: Piotr Stefaniak
Discussion: https://postgr.es/m/DB8PR03MB5931C41F7787A95313F08322F22A0%40DB8PR03MB5931.eurprd03.prod.outlook.com
Reviewed-by: Masahiko Sawada
Backpatch-through: 11
---

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 7370379c6a1..02fb352b94a 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -835,7 +835,7 @@ _bt_vacuum_needs_cleanup(IndexVacuumInfo *info)
 		prev_num_heap_tuples = metad->btm_last_cleanup_num_heap_tuples;
 
 		if (cleanup_scale_factor <= 0 ||
-			prev_num_heap_tuples < 0 ||
+			prev_num_heap_tuples <= 0 ||
 			(info->num_heap_tuples - prev_num_heap_tuples) /
 			prev_num_heap_tuples >= cleanup_scale_factor)
 			result = true;