[opt](sum0) update sum0 comments

[englefly]

What problem does this PR solve?

the original description of sum0 is hard to understand.

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hello-stephen]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

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?

[englefly]

run buildall

[englefly]

/review

[github-actions]

Codex automated review failed and did not complete.

Error: You've hit your usage limit. Visit https://chatgpt.com/codex/settings/usage to purchase more credits or try again at Jun 24th, 2026 10:56 PM.
Workflow run: https://github.com/apache/doris/actions/runs/27933307310

Please inspect the workflow logs and rerun the review after the underlying issue is resolved.

[github-actions]

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

[github-actions]

PR approved by anyone and no changes requested.

[zclllyybb]

/review

[github-actions]

Automated review complete. I found one documentation accuracy issue in the only changed line.

Critical checkpoint conclusions:

• Goal/test proof: the PR tries to clarify sum0, but the new wording omits the empty-input behavior. Existing regression output for select sum0(kint) over an empty table is 0.
• Scope/focus: the PR is a focused one-line Javadoc change.
• Parallel paths: checked Sum0, MultiDistinctSum0, FE empty-input/subquery handling, BE sum0 alias registration, and aggregate rewrite paths that synthesize sum0; no separate runtime issue found.
• Concurrency, lifecycle, config/session propagation, compatibility, transactions, data writes, observability: not involved by this comment-only change.
• Tests/style: no test files changed, existing tests cover the behavior being documented, git diff --check passed, and GitHub status shows FE CheckStyle and PR title checker succeeded.

User focus: no additional user-provided focus was supplied.

Subagent conclusions: tests-session-config proposed TSC-1, which became inline comment C-1. optimizer-rewrite proposed OR-1 as a duplicate of TSC-1 and found no separate optimizer/rewrite issue. Convergence round 1 ended with both subagents replying NO_NEW_VALUABLE_FINDINGS for the final ledger/comment set.

[hello-stephen]

TPC-H: Total hot run time: 28942 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 4c78505fd91c838225eb6f2371595109208efd26, data reload: false

------ Round 1 ----------------------------------
============================================
q1	17779	4019	3970	3970
q2	1991	309	185	185
q3	10350	1433	834	834
q4	4684	468	340	340
q5	7487	839	573	573
q6	182	169	139	139
q7	767	846	623	623
q8	9539	1562	1632	1562
q9	6229	4496	4488	4488
q10	6841	1773	1538	1538
q11	431	275	243	243
q12	638	421	291	291
q13	18110	3693	2729	2729
q14	274	258	234	234
q15	q16	789	772	709	709
q17	1045	942	909	909
q18	6916	5694	5649	5649
q19	1331	1234	1077	1077
q20	467	403	284	284
q21	5867	2583	2270	2270
q22	425	356	295	295
Total cold run time: 102142 ms
Total hot run time: 28942 ms

----- Round 2, with runtime_filter_mode=off -----
============================================
q1	4360	4269	4281	4269
q2	332	358	225	225
q3	4584	4959	4396	4396
q4	2059	2165	1387	1387
q5	4426	4306	4323	4306
q6	227	174	129	129
q7	1742	1652	1883	1652
q8	2498	2153	2136	2136
q9	7943	7874	7803	7803
q10	4870	4747	4281	4281
q11	581	414	391	391
q12	730	747	533	533
q13	3305	3621	2952	2952
q14	301	314	307	307
q15	q16	715	753	646	646
q17	1364	1317	1314	1314
q18	8018	7375	7001	7001
q19	1108	1066	1145	1066
q20	2226	2208	1942	1942
q21	5277	4608	4469	4469
q22	522	468	416	416
Total cold run time: 57188 ms
Total hot run time: 51621 ms

[hello-stephen]

TPC-DS: Total hot run time: 173351 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 4c78505fd91c838225eb6f2371595109208efd26, data reload: false

query5	4306	639	504	504
query6	439	203	174	174
query7	4795	586	295	295
query8	373	222	200	200
query9	8746	4211	4170	4170
query10	459	313	267	267
query11	5947	2326	2131	2131
query12	162	103	101	101
query13	1299	614	467	467
query14	6383	5419	5061	5061
query14_1	4439	4399	4398	4398
query15	207	196	176	176
query16	1018	470	451	451
query17	1132	728	599	599
query18	2545	487	365	365
query19	204	192	149	149
query20	116	110	106	106
query21	217	143	122	122
query22	13601	13583	13380	13380
query23	17349	16509	16142	16142
query23_1	16310	16502	16534	16502
query24	7613	1829	1342	1342
query24_1	1349	1326	1319	1319
query25	580	462	411	411
query26	1340	315	169	169
query27	2621	552	355	355
query28	4436	2098	2099	2098
query29	1094	628	515	515
query30	315	241	200	200
query31	1125	1083	961	961
query32	117	63	62	62
query33	538	332	262	262
query34	1206	1180	658	658
query35	790	781	676	676
query36	1377	1375	1228	1228
query37	148	104	89	89
query38	1891	1725	1631	1631
query39	935	930	887	887
query39_1	858	884	882	882
query40	218	119	98	98
query41	64	62	60	60
query42	88	86	87	86
query43	323	326	278	278
query44	1486	782	797	782
query45	195	183	176	176
query46	1102	1206	766	766
query47	2371	2333	2271	2271
query48	423	435	309	309
query49	624	456	355	355
query50	1067	354	266	266
query51	4362	4265	4257	4257
query52	83	81	72	72
query53	251	264	187	187
query54	268	219	197	197
query55	75	70	67	67
query56	226	218	211	211
query57	1464	1412	1298	1298
query58	238	219	194	194
query59	1616	1680	1458	1458
query60	295	253	227	227
query61	156	153	153	153
query62	682	646	578	578
query63	228	201	191	191
query64	2514	786	597	597
query65	4881	4788	4812	4788
query66	1804	445	339	339
query67	29762	29732	29621	29621
query68	3013	1564	980	980
query69	422	313	264	264
query70	1018	980	935	935
query71	294	229	211	211
query72	2834	2629	2347	2347
query73	919	784	475	475
query74	5144	4991	4790	4790
query75	2595	2601	2243	2243
query76	2297	1199	786	786
query77	350	377	288	288
query78	12306	12516	11979	11979
query79	1375	1234	834	834
query80	638	474	379	379
query81	468	283	243	243
query82	582	161	125	125
query83	324	276	251	251
query84	258	147	118	118
query85	869	519	425	425
query86	375	296	283	283
query87	1834	1833	1752	1752
query88	3838	2921	2896	2896
query89	432	380	328	328
query90	1934	200	183	183
query91	177	168	139	139
query92	64	60	59	59
query93	1481	1433	876	876
query94	563	348	286	286
query95	686	390	436	390
query96	1110	810	366	366
query97	2696	2703	2537	2537
query98	224	208	199	199
query99	1162	1152	1025	1025
Total cold run time: 258044 ms
Total hot run time: 173351 ms

[hello-stephen]

ClickBench: Total hot run time: 25.19 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit 4c78505fd91c838225eb6f2371595109208efd26, data reload: false

query1	0.01	0.01	0.00
query2	0.10	0.05	0.05
query3	0.25	0.14	0.14
query4	1.61	0.14	0.14
query5	0.24	0.23	0.22
query6	1.24	1.01	1.10
query7	0.04	0.00	0.00
query8	0.06	0.04	0.03
query9	0.39	0.31	0.31
query10	0.56	0.56	0.54
query11	0.19	0.14	0.14
query12	0.18	0.15	0.14
query13	0.48	0.48	0.49
query14	1.02	1.01	1.00
query15	0.62	0.60	0.61
query16	0.31	0.31	0.30
query17	1.13	1.11	1.09
query18	0.22	0.21	0.22
query19	2.04	1.88	1.96
query20	0.02	0.02	0.01
query21	15.45	0.22	0.14
query22	4.89	0.06	0.06
query23	16.13	0.33	0.12
query24	3.01	0.44	0.33
query25	0.10	0.04	0.04
query26	0.73	0.22	0.17
query27	0.05	0.04	0.03
query28	3.47	0.94	0.52
query29	12.51	4.26	3.48
query30	0.27	0.15	0.15
query31	2.77	0.62	0.30
query32	3.22	0.60	0.49
query33	3.21	3.23	3.25
query34	15.63	4.26	3.51
query35	3.53	3.54	3.56
query36	0.56	0.46	0.42
query37	0.11	0.08	0.07
query38	0.05	0.04	0.03
query39	0.03	0.04	0.03
query40	0.17	0.16	0.15
query41	0.09	0.03	0.04
query42	0.04	0.03	0.03
query43	0.04	0.04	0.03
Total cold run time: 96.77 s
Total hot run time: 25.19 s

done