From 9a3f362639ddeb837246fd9f5d821f49d495b516 Mon Sep 17 00:00:00 2001
From: Ti Chi Robot <ti-community-prow-bot@tidb.io>
Date: Fri, 3 Mar 2023 13:09:10 +0800
Subject: [PATCH] ddl: never write untouched index values to temp index
 (#41879) (#41884)

close pingcap/tidb#41880
---
 ddl/index_merge_tmp_test.go | 41 +++++++++++++++++++++++++++++++++++++
 ddl/ingest/engine.go        |  2 +-
 table/tables/index.go       | 13 +++++++-----
 3 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/ddl/index_merge_tmp_test.go b/ddl/index_merge_tmp_test.go
index 42cf75bb4a2cd..8dd5283d6c3de 100644
--- a/ddl/index_merge_tmp_test.go
+++ b/ddl/index_merge_tmp_test.go
@@ -870,3 +870,44 @@ func TestAddIndexMultipleDelete(t *testing.T) {
 	tk.MustQuery("select * from t;").Check(testkit.Rows())
 	require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/ddl/mockDMLExecution"))
 }
+
+func TestAddIndexUpdateUntouchedValues(t *testing.T) {
+	store, dom := testkit.CreateMockStoreAndDomain(t)
+
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t(id int primary key, b int, k int);")
+	tk.MustExec("insert into t values (1, 1, 1);")
+
+	tk1 := testkit.NewTestKit(t, store)
+	tk1.MustExec("use test")
+
+	d := dom.DDL()
+	originalCallback := d.GetHook()
+	defer d.SetHook(originalCallback)
+	callback := &ddl.TestDDLCallback{}
+	var runDML bool
+	callback.OnJobRunBeforeExported = func(job *model.Job) {
+		if t.Failed() || runDML {
+			return
+		}
+		switch job.SchemaState {
+		case model.StateWriteReorganization:
+			_, err := tk1.Exec("begin;")
+			assert.NoError(t, err)
+			_, err = tk1.Exec("update t set k=k+1 where id = 1;")
+			assert.NoError(t, err)
+			_, err = tk1.Exec("insert into t values (2, 1, 2);")
+			// Should not report "invalid temp index value".
+			assert.NoError(t, err)
+			_, err = tk1.Exec("commit;")
+			assert.NoError(t, err)
+			runDML = true
+		}
+	}
+	d.SetHook(callback)
+
+	tk.MustGetErrCode("alter table t add unique index idx(b);", errno.ErrDupEntry)
+	tk.MustExec("admin check table t;")
+	tk.MustQuery("select * from t;").Check(testkit.Rows("1 1 2", "2 1 2"))
+}
diff --git a/ddl/ingest/engine.go b/ddl/ingest/engine.go
index ac0287b26637a..fce350df09e40 100644
--- a/ddl/ingest/engine.go
+++ b/ddl/ingest/engine.go
@@ -204,7 +204,7 @@ func (ei *engineInfo) newWriterContext(workerID int, unique bool) (*WriterContex
 
 func (ei *engineInfo) closeWriters() error {
 	var firstErr error
-	for wid := range ei.writerCache.Keys() {
+	for _, wid := range ei.writerCache.Keys() {
 		if w, ok := ei.writerCache.Load(wid); ok {
 			_, err := w.Close(ei.ctx)
 			if err != nil {
diff --git a/table/tables/index.go b/table/tables/index.go
index 4b10605535c8f..b8a164a9b2ece 100644
--- a/table/tables/index.go
+++ b/table/tables/index.go
@@ -177,7 +177,12 @@ func (c *index) Create(sctx sessionctx.Context, txn kv.Transaction, indexedValue
 
 	if !distinct || skipCheck || opt.Untouched {
 		val := idxVal
-		if keyIsTempIdxKey && !opt.Untouched { // Untouched key-values never occur in the storage.
+		if opt.Untouched && (keyIsTempIdxKey || len(tempKey) > 0) {
+			// Untouched key-values never occur in the storage and the temp index is not public.
+			// It is unnecessary to write the untouched temp index key-values.
+			return nil, nil
+		}
+		if keyIsTempIdxKey {
 			tempVal := tablecodec.TempIndexValueElem{Value: idxVal, KeyVer: keyVer, Distinct: distinct}
 			val = tempVal.Encode(nil)
 		}
@@ -186,10 +191,8 @@ func (c *index) Create(sctx sessionctx.Context, txn kv.Transaction, indexedValue
 			return nil, err
 		}
 		if len(tempKey) > 0 {
-			if !opt.Untouched { // Untouched key-values never occur in the storage.
-				tempVal := tablecodec.TempIndexValueElem{Value: idxVal, KeyVer: keyVer, Distinct: distinct}
-				val = tempVal.Encode(nil)
-			}
+			tempVal := tablecodec.TempIndexValueElem{Value: idxVal, KeyVer: keyVer, Distinct: distinct}
+			val = tempVal.Encode(nil)
 			err = txn.GetMemBuffer().Set(tempKey, val)
 			if err != nil {
 				return nil, err