From 18d69e521f06d46d9917dec6d5d2e418e2861694 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Mon, 28 Jun 2021 16:31:25 +0800
Subject: [PATCH] executor: fix incorrect rows returned by `TABLESAMPLE` 
 (#25357) (#25795)

---
 executor/sample.go      |  2 +-
 executor/sample_test.go | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/executor/sample.go b/executor/sample.go
index 2edd189c02cc9..a2447557d6342 100644
--- a/executor/sample.go
+++ b/executor/sample.go
@@ -220,7 +220,7 @@ func splitIntoMultiRanges(store kv.Storage, startKey, endKey kv.Key) ([]kv.KeyRa
 		if kv.Key(start).Cmp(startKey) < 0 {
 			start = startKey
 		}
-		if kv.Key(end).Cmp(endKey) > 0 {
+		if end == nil || kv.Key(end).Cmp(endKey) > 0 {
 			end = endKey
 		}
 		ranges = append(ranges, kv.KeyRange{StartKey: start, EndKey: end})
diff --git a/executor/sample_test.go b/executor/sample_test.go
index 6760fc5135d35..42aed46448881 100644
--- a/executor/sample_test.go
+++ b/executor/sample_test.go
@@ -119,6 +119,20 @@ func (s *testTableSampleSuite) TestTableSampleMultiRegions(c *C) {
 	tk.MustExec("drop table t2;")
 }
 
+func (s *testTableSampleSuite) TestTableSampleNoSplitTable(c *C) {
+	tk := s.initSampleTest(c)
+	atomic.StoreUint32(&ddl.EnableSplitTableRegion, 0)
+	tk.MustExec("drop table if exists t1;")
+	tk.MustExec("drop table if exists t2;")
+	tk.MustExec("create table t1 (id int primary key);")
+	tk.MustExec("create table t2 (id int primary key);")
+	tk.MustExec("insert into t2 values(1);")
+	rows := tk.MustQuery("select * from t1 tablesample regions();").Rows()
+	rows2 := tk.MustQuery("select * from t2 tablesample regions();").Rows()
+	c.Assert(len(rows), Equals, 0)
+	c.Assert(len(rows2), Equals, 1)
+}
+
 func (s *testTableSampleSuite) TestTableSampleSchema(c *C) {
 	tk := s.initSampleTest(c)
 	tk.Se.GetSessionVars().EnableClusteredIndex = variable.ClusteredIndexDefModeOn