Data inconsistency after adding indexes with multi-schema optimization

[tangenta]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

	store, dom := testkit.CreateMockStoreAndDomain(t)
	defer ingesttestutil.InjectMockBackendMgr(t, store)()
	tk := testkit.NewTestKit(t, store)
	tk.MustExec("use test")
	tk.MustExec("CREATE TABLE `19bbb05e` (\n  `cca4a823` smallint(6) DEFAULT '7008',\n  `b5244bf8` bigint(20) DEFAULT '6308994588244965155',\n  `32c733ce` bigint(20) DEFAULT '-1343611900857841884',\n  `5c7e9e66` datetime DEFAULT '9052-06-30 13:10:34',\n  `24e1a62a` mediumint(9) DEFAULT '-4378120',\n  `df1a2915` tinyint(4) DEFAULT '-113',\n  `90a87a70` int(11) DEFAULT '-1057258940',\n  KEY `99d84913` (`df1a2915`),\n  KEY `cb679e68` (`24e1a62a`),\n  KEY `eba0c161` (`32c733ce`),\n  KEY `d5ba3944` (`90a87a70`,`32c733ce`,`24e1a62a`)\n) ENGINE=InnoDB DEFAULT CHARSET=gbk COLLATE=gbk_chinese_ci")
	tk.MustExec("ALTER TABLE `19bbb05e` ADD  INDEX `08427bcf` (`cca4a823`), ADD  INDEX `367bc5a4` (`90a87a70`), RENAME INDEX `99d84913` to `06c5d43f`, ADD COLUMN `ae57ec09` SMALLINT NULL DEFAULT '-18721' AFTER `5c7e9e66`;")

2. What did you expect to see? (Required)

Both of temp indexes get merged.

3. What did you see instead (Required)

There are two indexes, but only one "merge temp index" log is observed. It is possible that one of temp index is not merged. That means if there are workload during adding index on the this table, data must be inconsistency.

4. What is your TiDB version? (Required)

47a990e