Update ddl/index.go

Co-authored-by: djshow832 <zhangming@pingcap.com>

ddl/index.go

@@ -1293,8 +1293,8 @@ func (w *addIndexWorker) batchCheckUniqueKey(txn kv.Transaction, idxRecords []*i
 	return nil
 }
 
-// BackfillDataInTxn will backfill table index in a transaction, lock corresponding rowKey, if the value of rowKey is changed,
-// indicate that index columns values may changed, index is not allowed to be added, so the txn will rollback and retry.
+// BackfillDataInTxn will backfill table index in a transaction. A lock corresponds to a rowKey if the value of rowKey is changed,
+// Note that index columns values may change, and an index is not allowed to be added, so the txn will rollback and retry.
 // BackfillDataInTxn will add w.batchCnt indices once, default value of w.batchCnt is 128.
 func (w *addIndexWorker) BackfillDataInTxn(handleRange reorgBackfillTask) (taskCtx backfillTaskContext, errInTxn error) {
 	failpoint.Inject("errorMockPanic", func(val failpoint.Value) {