[Bug](Variant) use lower case name for variant's root, since backend …

[eldenmoon]

…treat parent column as lower case

This PR address the problem as blow:

errCode = 2, detailMessage = (172.16.56.137)[CANCELLED]failed to initialize storage reader. tablet=17136, res=[INTERNAL_ERROR]Not found field_name, field_name:Tags.tag_key1, schema:[Thread(8), Tags(9), Source(5), tags.tag_key1(-1), Title(6), Level(3), Time(2), CreateDate(1), Message(7), IP(4), AppId(0)]

Proposed changes

Issue Number: close #xxx

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[doris-robot]

Thank you for your contribution to Apache Doris.
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Since 2024-03-18, the Document has been moved to doris-website.
See Doris Document.

[eldenmoon]

run buildall

[doris-robot]

TPC-H: Total hot run time: 37777 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 7cf0c2850ec83773ed392f351999141072f1c25f, data reload: false

------ Round 1 ----------------------------------
q1	17790	4310	4248	4248
q2	2432	163	155	155
q3	11529	1097	1182	1097
q4	10241	777	763	763
q5	7479	2948	2952	2948
q6	208	124	123	123
q7	950	528	505	505
q8	9341	2009	2030	2009
q9	7040	6361	6342	6342
q10	8438	3465	3550	3465
q11	427	242	224	224
q12	369	199	195	195
q13	17804	2857	2837	2837
q14	249	204	213	204
q15	512	464	456	456
q16	515	372	366	366
q17	959	591	547	547
q18	7257	6485	6414	6414
q19	1587	1504	1436	1436
q20	552	272	250	250
q21	3555	3033	2906	2906
q22	338	287	296	287
Total cold run time: 109572 ms
Total hot run time: 37777 ms

----- Round 2, with runtime_filter_mode=off -----
q1	4110	4096	4123	4096
q2	336	231	232	231
q3	2980	2827	2866	2827
q4	1865	1505	1611	1505
q5	5190	5249	5229	5229
q6	204	115	117	115
q7	1754	1417	1394	1394
q8	3203	3301	3332	3301
q9	8428	8434	8443	8434
q10	3797	3780	3761	3761
q11	542	442	443	442
q12	732	592	552	552
q13	16925	2840	2862	2840
q14	282	254	255	254
q15	508	452	460	452
q16	477	424	419	419
q17	1748	1490	1468	1468
q18	7457	7108	7006	7006
q19	1620	1518	1483	1483
q20	1898	1705	1706	1705
q21	4644	4682	4754	4682
q22	511	450	448	448
Total cold run time: 69211 ms
Total hot run time: 52644 ms

[doris-robot]

TPC-DS: Total hot run time: 181308 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpcds-tools
TPC-DS sf100 test result on commit 7cf0c2850ec83773ed392f351999141072f1c25f, data reload: false

query1	922	366	354	354
query2	6556	1922	1855	1855
query3	6709	218	226	218
query4	31793	21226	21218	21218
query5	4242	394	409	394
query6	269	179	176	176
query7	4631	286	287	286
query8	232	165	171	165
query9	9271	2278	2250	2250
query10	534	252	256	252
query11	17202	14224	14205	14205
query12	143	95	86	86
query13	1633	422	425	422
query14	10181	7369	7853	7369
query15	254	180	192	180
query16	8206	263	261	261
query17	1956	584	552	552
query18	2125	321	292	292
query19	312	162	157	157
query20	99	89	89	89
query21	205	127	131	127
query22	5119	4951	4847	4847
query23	33759	32874	32837	32837
query24	11717	2900	2857	2857
query25	658	388	393	388
query26	1778	157	153	153
query27	2946	325	321	321
query28	7760	1893	1884	1884
query29	972	613	585	585
query30	301	146	141	141
query31	1034	725	743	725
query32	92	55	52	52
query33	749	263	255	255
query34	1046	483	499	483
query35	908	699	680	680
query36	1032	844	911	844
query37	149	65	60	60
query38	3561	3470	3436	3436
query39	1592	1562	1531	1531
query40	288	112	110	110
query41	48	45	45	45
query42	100	98	92	92
query43	495	442	442	442
query44	1207	730	734	730
query45	279	257	263	257
query46	1109	681	686	681
query47	1921	1835	1875	1835
query48	453	345	364	345
query49	1216	319	329	319
query50	782	361	367	361
query51	6753	6688	6676	6676
query52	102	89	89	89
query53	343	269	278	269
query54	316	242	229	229
query55	82	80	85	80
query56	250	227	227	227
query57	1216	1143	1127	1127
query58	239	202	205	202
query59	2884	2694	2649	2649
query60	254	254	238	238
query61	98	98	94	94
query62	649	449	460	449
query63	301	272	278	272
query64	6357	4065	4165	4065
query65	3049	3030	3041	3030
query66	1433	390	373	373
query67	15216	14840	14769	14769
query68	7159	533	539	533
query69	619	377	394	377
query70	1234	1171	1168	1168
query71	499	266	267	266
query72	6470	2684	2497	2497
query73	754	323	322	322
query74	7985	6459	6371	6371
query75	3605	2222	2261	2222
query76	4712	848	837	837
query77	635	256	262	256
query78	11017	10222	10011	10011
query79	8927	515	541	515
query80	1577	366	361	361
query81	491	211	219	211
query82	819	88	83	83
query83	220	148	141	141
query84	282	79	77	77
query85	1484	305	320	305
query86	431	322	317	317
query87	3719	3586	3549	3549
query88	5206	2375	2391	2375
query89	508	358	362	358
query90	2028	173	175	173
query91	178	138	139	138
query92	71	48	48	48
query93	6878	501	484	484
query94	1119	176	174	174
query95	413	314	301	301
query96	620	271	270	270
query97	2654	2520	2475	2475
query98	232	211	215	211
query99	1247	840	847	840
Total cold run time: 313881 ms
Total hot run time: 181308 ms

[doris-robot]

Load test result on machine: 'aliyun_ecs.c7a.8xlarge_32C64G'

Load test result on commit 7cf0c2850ec83773ed392f351999141072f1c25f with default session variables
Stream load json:         19 seconds loaded 2358488459 Bytes, about 118 MB/s
Stream load orc:          58 seconds loaded 1101869774 Bytes, about 18 MB/s
Stream load parquet:      31 seconds loaded 861443392 Bytes, about 26 MB/s
Insert into select:       13.7 seconds inserted 10000000 Rows, about 729K ops/s

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.