From 17bba4d7a7b7d505697a5815c1e1ccafc379a882 Mon Sep 17 00:00:00 2001
From: tangenta <tangenta@126.com>
Date: Wed, 2 Nov 2022 16:07:59 +0800
Subject: [PATCH] ddl: correct the next key during adding index (#38804)

close pingcap/tidb#38803
---
 ddl/index.go             |  5 ++++-
 ddl/index_modify_test.go | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/ddl/index.go b/ddl/index.go
index 931580e586af0..4404ea4f551bd 100644
--- a/ddl/index.go
+++ b/ddl/index.go
@@ -1293,7 +1293,10 @@ func (w *baseIndexWorker) getNextKey(taskRange reorgBackfillTask, taskDone bool)
 		recordKey := tablecodec.EncodeRecordKey(w.table.RecordPrefix(), lastHandle)
 		return recordKey.Next()
 	}
-	return taskRange.endKey.Next()
+	if taskRange.endInclude {
+		return taskRange.endKey.Next()
+	}
+	return taskRange.endKey
 }
 
 func (w *baseIndexWorker) updateRowDecoder(handle kv.Handle, rawRecord []byte) error {
diff --git a/ddl/index_modify_test.go b/ddl/index_modify_test.go
index 18ff753aee618..00695b3da8f6e 100644
--- a/ddl/index_modify_test.go
+++ b/ddl/index_modify_test.go
@@ -1067,3 +1067,17 @@ func TestAddIndexWithDupIndex(t *testing.T) {
 	err = tk.ExecToErr("alter table test_add_index_with_dup add index idx (a)")
 	require.ErrorIs(t, err, errors.Cause(err2))
 }
+
+func TestAddIndexUniqueFailOnDuplicate(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t (a bigint primary key clustered, b int);")
+	tk.MustExec("set @@global.tidb_ddl_reorg_worker_cnt = 2;")
+	for i := 1; i <= 12; i++ {
+		tk.MustExec("insert into t values (?, ?)", i, i)
+	}
+	tk.MustExec("insert into t values (0, 1);") // Insert a duplicate key.
+	tk.MustQuery("split table t by (0), (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12);").Check(testkit.Rows("13 1"))
+	tk.MustGetErrCode("alter table t add unique index idx (b);", errno.ErrDupEntry)
+}