lightning: fix panic when table name in source file and target cluste…

…r is different (pingcap#31808)

close pingcap#31771

br/pkg/lightning/restore/tidb.go

@@ -265,13 +265,15 @@ func LoadSchemaInfo(
 			if err != nil {
 				return nil, errors.Trace(err)
 			}
+			// Table names are case-sensitive in mydump.MDTableMeta.
+			// We should always use the original tbl.Name in checkpoints.
 			tableInfo := &checkpoints.TidbTableInfo{
 				ID:   tblInfo.ID,
 				DB:   schema.Name,
-				Name: tableName,
+				Name: tbl.Name,
 				Core: tblInfo,
 			}
-			dbInfo.Tables[tableName] = tableInfo
+			dbInfo.Tables[tbl.Name] = tableInfo
 		}
 
 		result[schema.Name] = dbInfo

br/pkg/lightning/restore/tidb_test.go

@@ -284,7 +284,8 @@ func TestLoadSchemaInfo(t *testing.T) {
 		"CREATE TABLE `t1` (`a` INT PRIMARY KEY);"+
 			"CREATE TABLE `t2` (`b` VARCHAR(20), `c` BOOL, KEY (`b`, `c`));"+
 			// an extra table that not exists in dbMetas
-			"CREATE TABLE `t3` (`d` VARCHAR(20), `e` BOOL);",
+			"CREATE TABLE `t3` (`d` VARCHAR(20), `e` BOOL);"+
+			"CREATE TABLE `T4` (`f` BIGINT PRIMARY KEY);",
 		"", "")
 	require.NoError(t, err)
 	tableInfos := make([]*model.TableInfo, 0, len(nodes))
@@ -309,6 +310,10 @@ func TestLoadSchemaInfo(t *testing.T) {
 					DB:   "db",
 					Name: "t2",
 				},
+				{
+					DB:   "db",
+					Name: "t4",
+				},
 			},
 		},
 	}
@@ -334,13 +339,19 @@ func TestLoadSchemaInfo(t *testing.T) {
 					Name: "t2",
 					Core: tableInfos[1],
 				},
+				"t4": {
+					ID:   103,
+					DB:   "db",
+					Name: "t4",
+					Core: tableInfos[3],
+				},
 			},
 		},
 	}, loaded)
 
 	tableCntAfter := metric.ReadCounter(metric.TableCounter.WithLabelValues(metric.TableStatePending, metric.TableResultSuccess))
 
-	require.Equal(t, 2.0, tableCntAfter-tableCntBefore)
+	require.Equal(t, 3.0, tableCntAfter-tableCntBefore)
 }
 
 func TestLoadSchemaInfoMissing(t *testing.T) {