From f24174ebf1d0493aa3d6bbb2721d69ce2b486f8a Mon Sep 17 00:00:00 2001
From: minghong <englefly@gmail.com>
Date: Wed, 29 Mar 2023 19:03:53 +0800
Subject: [PATCH] when estimated rowCount is 0, adjust to 1 (#18174)

---
 .../org/apache/doris/nereids/stats/FilterEstimation.java    | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java
index c906490cb5..6bc3bc96c6 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/FilterEstimation.java
@@ -319,10 +319,8 @@ public class FilterEstimation extends ExpressionVisitor<Statistics, EstimationCo
     @Override
     public Statistics visitNot(Not not, EstimationContext context) {
         Statistics childStats = new FilterEstimation().estimate(not.child(), context.statistics);
-        double rowCount = Math.max(context.statistics.getRowCount() - childStats.getRowCount(), 0);
-        if (rowCount == 0.0) {
-            return Statistics.zero(context.statistics);
-        }
+        //if estimated rowCount is 0, adjust to 1 to make upper join reorder reasonable.
+        double rowCount = Math.max(context.statistics.getRowCount() - childStats.getRowCount(), 1);
         StatisticsBuilder statisticsBuilder = new StatisticsBuilder(context.statistics).setRowCount(rowCount);
         for (Entry<Expression, ColumnStatistic> entry : context.statistics.columnStatistics().entrySet()) {
             Expression expr = entry.getKey();