`var_pop` on constant values may produce wrong result.

r33s3n6 commented 2 weeks ago

1. Minimal reproduce step (Required)

Firstly, execute init.sql to create the table. Then executing error.sql yields unexpected results. Note that reproducing these results might not be entirely stable. Typically, it can be completed within three attempts. You can try executing error.sql multiple times or execute init.sql again to rebuild the table.

init.sql.txt error.sql.txt

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

The SQL statement calculates the var_pop value of the constant expression 604102521670485727, and the result should be 0.

3. What did you see instead (Required)

However, the statement results are unstable; in both the multi-node and single-node versions, there are some 0 and non-zero values.

output_re_main2.log output_re_single2.log

4. What is your TiDB version? (Required)

Release Version: v8.0.0
Edition: Community
Git Commit Hash: 8ba1fa452b1ccdbfb85879ea94b9254aabba2916
Git Branch: HEAD
UTC Build Time: 2024-03-28 14:22:15
GoVersion: go1.21.4
Race Enabled: false
Check Table Before Drop: false
Store: tikv

topology:

distributed.yaml:

global:
  user: "tidb"
  ssh_port: 22
  deploy_dir: "/tidb-deploy"
  data_dir: "/tidb-data"

pd_servers:
  - host: 10.0.2.31

tidb_servers:
  - host: 10.0.2.21

tikv_servers:
  - host: 10.0.2.11
  - host: 10.0.2.12
  - host: 10.0.2.13

monitoring_servers:
  - host: 10.0.2.8

grafana_servers:
  - host: 10.0.2.8

alertmanager_servers:
  - host: 10.0.2.8

tiflash_servers:
  - host: 10.0.2.32

single.yaml

global:
  user: "tidb"
  ssh_port: 22
  deploy_dir: "/tidb-deploy"
  data_dir: "/tidb-data"

pd_servers:
  - host: 10.0.2.73

tidb_servers:
  - host: 10.0.2.72

tikv_servers:
  - host: 10.0.2.71

tiflash_servers:
  - host: 10.0.2.74

about us

We are the BASS team from the School of Cyber Science and Technology at Beihang University. Our main focus is on system software security, operating systems, and program analysis research, as well as the development of automated program testing frameworks for detecting software defects. Using our self-developed database vulnerability testing tool, we have identified the above-mentioned vulnerabilities in TiDB that may lead to database logic error.

yibin87 commented 1 week ago

The plan looks all right, var_pop is executed in tidb side, the implementation of var_pop seems incorrect:

mysql> source error.sql.txt
+----------------------------------------+---------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------+
| id                                     | estRows | task         | access object | operator info                                                                                                                |
+----------------------------------------+---------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------+
| HashAgg_15                             | 249.60  | root         |               | group by:Column#17, funcs:var_pop(6.041025216704858e+17)->Column#18                                                          |
| └─TableReader_38                       | 249.60  | root         |               | MppVersion: 2, data:ExchangeSender_37                                                                                        |
|   └─ExchangeSender_37                  | 249.60  | mpp[tiflash] |               | ExchangeType: PassThrough                                                                                                    |
|     └─Projection_33                    | 249.60  | mpp[tiflash] |               | Column#17                                                                                                                    |
|       └─HashAgg_34                     | 249.60  | mpp[tiflash] |               | group by:test.t_ufims7.c__w, funcs:sum(Column#19)->Column#17, stream_count: 4                                                |
|         └─ExchangeReceiver_36          | 249.60  | mpp[tiflash] |               | stream_count: 4                                                                                                              |
|           └─ExchangeSender_35          | 249.60  | mpp[tiflash] |               | ExchangeType: HashPartition, Compression: FAST, Hash Cols: [name: test.t_ufims7.c__w, collate: utf8mb4_bin], stream_count: 4 |
|             └─HashAgg_20               | 249.60  | mpp[tiflash] |               | group by:Column#22, funcs:count(Column#21)->Column#19                                                                        |
|               └─Projection_42          | 312.00  | mpp[tiflash] |               | cast(test.t_ufims7.c_yhcnkidi8, bigint(22) BINARY)->Column#21, test.t_ufims7.c__w->Column#22                                 |
|                 └─TableFullScan_32     | 312.00  | mpp[tiflash] | table:ref_4   | keep order:false, stats:pseudo                                                                                               |
+----------------------------------------+---------+--------------+---------------+------------------------------------------------------------------------------------------------------------------------------+

yibin87 commented 1 week ago

/label affects-5.4

yibin87 commented 1 week ago

/label affects-6.1

yibin87 commented 1 week ago

/label affects-6.5

yibin87 commented 1 week ago

/label affects-7.1

yibin87 commented 1 week ago

/label affects-7.5