From e1214f14b49229947ca43ad7cafdf80afad56248 Mon Sep 17 00:00:00 2001
From: minghong <englefly@gmail.com>
Date: Fri, 6 Sep 2024 16:36:01 +0800
Subject: [PATCH] when table.rows > topn.limit+topn.offset, do not generate
 topn-filter

---
 .../post/TopnFilterPushDownVisitor.java       |  6 ++-
 .../nereids_tpch_p0/tpch/topn_filter.groovy   | 40 +++++++++++++++++++
 2 files changed, 44 insertions(+), 2 deletions(-)
 create mode 100644 regression-test/suites/nereids_tpch_p0/tpch/topn_filter.groovy

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopnFilterPushDownVisitor.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopnFilterPushDownVisitor.java
index a6ec5a70353c96a..95cdbd9cc96af0b 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopnFilterPushDownVisitor.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopnFilterPushDownVisitor.java
@@ -218,8 +218,10 @@ public Boolean visitPhysicalNestedLoopJoin(PhysicalNestedLoopJoin<? extends Plan
     public Boolean visitPhysicalRelation(PhysicalRelation relation, PushDownContext ctx) {
         if (supportPhysicalRelations(relation)
                 && relation.getOutputSet().containsAll(ctx.probeExpr.getInputSlots())) {
-            topnFilterContext.addTopnFilter(ctx.topn, relation, ctx.probeExpr);
-            return true;
+            if (relation.getStats().getRowCount() > ctx.topn.getLimit() + ctx.topn.getOffset()) {
+                topnFilterContext.addTopnFilter(ctx.topn, relation, ctx.probeExpr);
+                return true;
+            }
         }
         return false;
     }
diff --git a/regression-test/suites/nereids_tpch_p0/tpch/topn_filter.groovy b/regression-test/suites/nereids_tpch_p0/tpch/topn_filter.groovy
new file mode 100644
index 000000000000000..cb752332cd51fce
--- /dev/null
+++ b/regression-test/suites/nereids_tpch_p0/tpch/topn_filter.groovy
@@ -0,0 +1,40 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+suite("topn_filter") {
+    String db = context.config.getDbNameByFile(new File(context.file.parent))
+    sql "use ${db}"
+    sql "set topn_opt_limit_threshold=1024"
+    sql "analyze table nation with sync"
+    // limit + offset > table.rows, do not generate topn filter
+    explain{
+        sql "select * from nation order by n_nationkey limit 40;"
+        notContains ("TOPN OPT:")
+    }
+    explain{
+        sql "select * from nation order by n_nationkey limit 4 offset 21;"
+        notContains ("TOPN OPT:")
+    }
+
+    explain{
+        sql "select * from nation order by n_nationkey limit 4 offset 20;"
+        contains ("TOPN OPT:1")
+    }
+
+}
\ No newline at end of file