commit a576ddcbb81554aad8c79d28b05d396ed378417b
Author: Alexander Korotkov <a.korotkov@postgrespro.ru>
Date:   Mon May 7 19:10:41 2018 +0300

    Fix condition for B-tree index cleanup
    
    Zero value of vacuum_cleanup_index_scale_factor means that user wants B-tree
    index cleanup to be never skipped.

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index e5dce00876..d894ba0374 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -829,7 +829,7 @@ _bt_vacuum_needs_cleanup(IndexVacuumInfo *info)
 			? relopts->vacuum_cleanup_index_scale_factor
 			: vacuum_cleanup_index_scale_factor;
 
-		if (cleanup_scale_factor < 0 ||
+		if (cleanup_scale_factor <= 0 ||
 			metad->btm_last_cleanup_num_heap_tuples < 0 ||
 			info->num_heap_tuples > (1.0 + cleanup_scale_factor) *
 			metad->btm_last_cleanup_num_heap_tuples)