branch-3.1: [fix](variant) change session var for disable_variant_flatten_nested to enable_variant_flatten_nested #54413

[amorynan]

picked from #54413

[Thearas]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[amorynan]

run buildall

[doris-robot]

TPC-H: Total hot run time: 32353 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 76b518c45f983fc77399e1b26c8b86c304ebf392, data reload: false

------ Round 1 ----------------------------------
q1	17603	5454	5403	5403
q2	2070	291	161	161
q3	10465	1263	750	750
q4	10206	871	448	448
q5	7820	2357	2113	2113
q6	182	164	134	134
q7	895	742	599	599
q8	9332	1453	1213	1213
q9	5257	4881	4930	4881
q10	6740	2262	1796	1796
q11	481	281	256	256
q12	333	358	206	206
q13	17789	3615	2982	2982
q14	230	229	212	212
q15	518	479	458	458
q16	414	436	370	370
q17	601	864	356	356
q18	7074	6361	6476	6361
q19	1291	967	538	538
q20	322	351	211	211
q21	2786	2182	1922	1922
q22	1066	1041	983	983
Total cold run time: 103475 ms
Total hot run time: 32353 ms

----- Round 2, with runtime_filter_mode=off -----
q1	5547	5517	5515	5515
q2	246	337	235	235
q3	2219	2619	2320	2320
q4	1389	1781	1318	1318
q5	4393	4830	4933	4830
q6	178	164	128	128
q7	2051	2015	1825	1825
q8	2646	2834	2674	2674
q9	7286	7151	7325	7151
q10	3021	3288	2833	2833
q11	568	496	499	496
q12	644	711	583	583
q13	3450	3790	3173	3173
q14	274	313	274	274
q15	508	484	463	463
q16	457	479	440	440
q17	1239	1720	1254	1254
q18	7650	7603	7635	7603
q19	804	1006	1113	1006
q20	1993	2069	1910	1910
q21	5372	4968	4693	4693
q22	1077	1052	1021	1021
Total cold run time: 53012 ms
Total hot run time: 51745 ms

[doris-robot]

TPC-DS: Total hot run time: 197781 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 76b518c45f983fc77399e1b26c8b86c304ebf392, data reload: false

query1	1303	920	896	896
query2	6256	1884	1920	1884
query3	10932	4391	4594	4391
query4	33056	23718	23416	23416
query5	3676	608	457	457
query6	291	197	176	176
query7	3995	511	326	326
query8	286	242	227	227
query9	9587	2581	2571	2571
query10	477	329	251	251
query11	17919	15455	15469	15455
query12	160	110	109	109
query13	1562	535	418	418
query14	9589	7306	7289	7289
query15	236	208	193	193
query16	8091	675	519	519
query17	1637	809	600	600
query18	2155	422	329	329
query19	218	188	166	166
query20	124	117	120	117
query21	214	127	116	116
query22	4694	4589	4413	4413
query23	35176	34794	34268	34268
query24	7435	2762	2726	2726
query25	550	511	435	435
query26	1168	293	169	169
query27	2294	478	371	371
query28	5326	2258	2221	2221
query29	799	644	481	481
query30	243	205	154	154
query31	990	903	833	833
query32	85	59	58	58
query33	503	346	314	314
query34	740	869	535	535
query35	818	792	740	740
query36	1005	1057	954	954
query37	102	93	71	71
query38	4051	4068	3993	3993
query39	1516	1451	1491	1451
query40	203	119	106	106
query41	50	51	46	46
query42	120	106	102	102
query43	512	510	483	483
query44	1362	803	825	803
query45	185	182	170	170
query46	899	1067	679	679
query47	1982	2018	1952	1952
query48	416	457	349	349
query49	806	493	404	404
query50	670	706	428	428
query51	7420	7341	7254	7254
query52	102	99	90	90
query53	239	254	187	187
query54	557	558	483	483
query55	80	77	81	77
query56	271	276	265	265
query57	1249	1277	1212	1212
query58	242	224	221	221
query59	3088	3200	2974	2974
query60	293	293	271	271
query61	116	135	113	113
query62	821	740	706	706
query63	237	194	192	192
query64	4727	1033	635	635
query65	3490	3283	3198	3198
query66	970	400	306	306
query67	16089	15780	15560	15560
query68	7218	840	536	536
query69	485	306	265	265
query70	1143	1135	1149	1135
query71	388	296	256	256
query72	5870	3816	3864	3816
query73	643	761	348	348
query74	10297	9317	9070	9070
query75	3187	3153	2673	2673
query76	3088	1203	760	760
query77	468	357	287	287
query78	10389	10504	9600	9600
query79	3649	883	588	588
query80	677	519	439	439
query81	502	261	218	218
query82	645	120	87	87
query83	170	164	145	145
query84	254	99	80	80
query85	786	397	318	318
query86	404	315	300	300
query87	4372	4320	4295	4295
query88	4990	2416	2402	2402
query89	414	331	305	305
query90	1753	193	193	193
query91	135	138	119	119
query92	72	57	53	53
query93	2132	888	546	546
query94	692	401	294	294
query95	343	276	272	272
query96	499	606	285	285
query97	3178	3271	3193	3193
query98	237	205	212	205
query99	1572	1434	1339	1339
Total cold run time: 297107 ms
Total hot run time: 197781 ms

[doris-robot]

ClickBench: Total hot run time: 29.51 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit 76b518c45f983fc77399e1b26c8b86c304ebf392, data reload: false

query1	0.03	0.03	0.03
query2	0.07	0.04	0.04
query3	0.24	0.07	0.06
query4	1.62	0.11	0.11
query5	0.53	0.51	0.50
query6	1.13	0.73	0.71
query7	0.03	0.02	0.01
query8	0.04	0.04	0.04
query9	0.56	0.52	0.48
query10	0.55	0.55	0.57
query11	0.14	0.11	0.10
query12	0.14	0.12	0.11
query13	0.62	0.59	0.60
query14	0.78	0.79	0.78
query15	0.84	0.84	0.82
query16	0.37	0.38	0.38
query17	1.11	1.06	1.09
query18	0.24	0.21	0.22
query19	1.93	1.71	1.80
query20	0.01	0.02	0.01
query21	15.41	0.93	0.59
query22	0.73	0.71	0.61
query23	15.21	1.43	0.57
query24	2.95	1.55	1.71
query25	0.18	0.31	0.10
query26	0.20	0.15	0.14
query27	0.06	0.05	0.06
query28	13.82	0.94	0.44
query29	12.55	4.02	3.34
query30	0.26	0.09	0.06
query31	2.82	0.63	0.38
query32	3.23	0.55	0.45
query33	3.00	3.03	3.03
query34	16.62	5.19	4.58
query35	4.57	4.59	4.52
query36	0.66	0.49	0.48
query37	0.09	0.06	0.06
query38	0.05	0.04	0.04
query39	0.03	0.02	0.03
query40	0.16	0.13	0.12
query41	0.08	0.03	0.03
query42	0.04	0.02	0.02
query43	0.04	0.03	0.03
Total cold run time: 103.74 s
Total hot run time: 29.51 s

[amorynan]

run buildall

[doris-robot]

TPC-H: Total hot run time: 32738 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit e5d2b3e2b1455684a1eb87fb857d59b9b90ca40b, data reload: false

------ Round 1 ----------------------------------
q1	17605	5595	5526	5526
q2	2060	264	162	162
q3	10693	1237	751	751
q4	10223	858	455	455
q5	7870	2349	2133	2133
q6	184	168	133	133
q7	882	747	624	624
q8	9334	1388	1127	1127
q9	5224	4894	4936	4894
q10	6797	2259	1814	1814
q11	472	281	260	260
q12	328	347	206	206
q13	17778	3628	3047	3047
q14	234	225	213	213
q15	530	478	475	475
q16	429	424	376	376
q17	583	865	359	359
q18	6851	6436	6354	6354
q19	1289	962	654	654
q20	328	355	212	212
q21	2741	2157	1977	1977
q22	1089	1053	986	986
Total cold run time: 103524 ms
Total hot run time: 32738 ms

----- Round 2, with runtime_filter_mode=off -----
q1	5570	5538	5569	5538
q2	238	329	238	238
q3	2257	2647	2348	2348
q4	1365	1792	1334	1334
q5	4435	4821	4847	4821
q6	169	165	131	131
q7	2018	1986	1791	1791
q8	2642	2855	2730	2730
q9	7240	7190	7149	7149
q10	3041	3326	2787	2787
q11	571	509	496	496
q12	674	808	593	593
q13	3331	3851	3185	3185
q14	296	309	269	269
q15	505	464	473	464
q16	463	496	447	447
q17	1224	1732	1275	1275
q18	7625	7442	7384	7384
q19	828	1133	1083	1083
q20	2004	2064	1931	1931
q21	5361	5067	4788	4788
q22	1133	1061	995	995
Total cold run time: 52990 ms
Total hot run time: 51777 ms

[doris-robot]

TPC-DS: Total hot run time: 196608 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 e5d2b3e2b1455684a1eb87fb857d59b9b90ca40b, data reload: false

query1	1265	915	894	894
query2	6268	1901	1903	1901
query3	10963	4341	4384	4341
query4	33213	24018	23468	23468
query5	4026	611	461	461
query6	290	200	184	184
query7	3993	488	330	330
query8	304	252	249	249
query9	9478	2574	2540	2540
query10	482	332	280	280
query11	18066	15346	15491	15346
query12	164	107	105	105
query13	1568	528	416	416
query14	10401	6607	7320	6607
query15	221	207	192	192
query16	7830	637	504	504
query17	1592	775	597	597
query18	2074	420	331	331
query19	224	189	159	159
query20	125	120	118	118
query21	204	129	106	106
query22	4675	4552	4366	4366
query23	35119	34548	33740	33740
query24	7257	2698	2700	2698
query25	483	468	409	409
query26	788	282	166	166
query27	2068	464	345	345
query28	5551	2175	2136	2136
query29	583	563	439	439
query30	242	186	166	166
query31	1004	909	850	850
query32	65	58	55	55
query33	500	364	337	337
query34	738	856	542	542
query35	777	803	743	743
query36	1006	1066	964	964
query37	101	89	66	66
query38	4004	3960	3963	3960
query39	1533	1652	1511	1511
query40	212	115	106	106
query41	54	52	49	49
query42	123	111	103	103
query43	500	524	496	496
query44	1303	817	805	805
query45	183	172	172	172
query46	887	1050	661	661
query47	1988	1964	1914	1914
query48	397	421	366	366
query49	738	499	414	414
query50	669	707	432	432
query51	7475	7433	7370	7370
query52	99	104	100	100
query53	230	265	181	181
query54	540	535	481	481
query55	81	79	77	77
query56	259	281	260	260
query57	1257	1267	1209	1209
query58	236	217	221	217
query59	3116	3308	3072	3072
query60	289	287	298	287
query61	133	114	134	114
query62	809	769	702	702
query63	234	196	200	196
query64	3334	1067	722	722
query65	3404	3279	3268	3268
query66	826	425	373	373
query67	16166	15749	15550	15550
query68	4534	836	542	542
query69	487	310	263	263
query70	1160	1135	1075	1075
query71	388	297	267	267
query72	5757	3837	3808	3808
query73	636	733	351	351
query74	10153	9350	9254	9254
query75	3188	3147	2667	2667
query76	3046	1173	759	759
query77	493	363	269	269
query78	10340	10348	9524	9524
query79	2686	881	612	612
query80	667	516	436	436
query81	516	261	219	219
query82	210	116	88	88
query83	165	157	146	146
query84	242	102	86	86
query85	763	374	306	306
query86	378	323	314	314
query87	4346	4349	4252	4252
query88	4960	2386	2383	2383
query89	398	326	286	286
query90	1864	190	193	190
query91	142	140	107	107
query92	70	58	50	50
query93	2657	889	533	533
query94	640	382	309	309
query95	346	279	265	265
query96	485	617	287	287
query97	3168	3264	3148	3148
query98	222	209	201	201
query99	1320	1416	1292	1292
Total cold run time: 291214 ms
Total hot run time: 196608 ms

[doris-robot]

ClickBench: Total hot run time: 28.78 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit e5d2b3e2b1455684a1eb87fb857d59b9b90ca40b, data reload: false

query1	0.04	0.03	0.03
query2	0.06	0.03	0.03
query3	0.24	0.07	0.07
query4	1.62	0.11	0.11
query5	0.53	0.49	0.50
query6	1.14	0.74	0.72
query7	0.02	0.01	0.01
query8	0.04	0.03	0.03
query9	0.56	0.50	0.50
query10	0.57	0.55	0.56
query11	0.14	0.10	0.11
query12	0.13	0.10	0.12
query13	0.60	0.59	0.61
query14	0.77	0.82	0.78
query15	0.84	0.83	0.81
query16	0.39	0.38	0.39
query17	1.03	1.05	1.05
query18	0.24	0.23	0.22
query19	1.87	1.89	1.86
query20	0.01	0.01	0.02
query21	15.40	0.91	0.59
query22	0.73	0.87	0.64
query23	15.03	1.43	0.57
query24	3.04	1.78	0.74
query25	0.17	0.17	0.13
query26	0.36	0.14	0.13
query27	0.06	0.05	0.04
query28	13.20	0.98	0.44
query29	12.57	3.98	3.28
query30	0.27	0.09	0.06
query31	2.82	0.59	0.38
query32	3.22	0.54	0.46
query33	3.00	3.02	3.01
query34	16.62	5.24	4.53
query35	4.57	4.59	4.56
query36	0.65	0.49	0.47
query37	0.09	0.06	0.06
query38	0.05	0.04	0.04
query39	0.03	0.02	0.03
query40	0.17	0.13	0.12
query41	0.08	0.02	0.03
query42	0.03	0.03	0.02
query43	0.04	0.03	0.03
Total cold run time: 103.04 s
Total hot run time: 28.78 s

[hello-stephen]

FE UT Coverage Report

Increment line coverage 60.00% (3/5) 🎉
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