float point comparison in WHERE clause produces different result from select list
- Dominant language
- Go
- Stars
- 40.5k
- Forks
- 6.2k
- PR merge metrics
- PR metrics pending
Description
### 1. Minimal reproduce step (Required)
```sql
create table t1 (c1 int primary key);
insert into t1 (c1) values (100000);
WITH
v2 AS (SELECT (1 + (1 / c1)) as w1 FROM t1)
SELECT
w1, w1 <> cast(1.0 as double)
FROM v2 WHERE w1 <> cast(1.0 as double)
ORDER BY 1,2 desc;
```
### 2. What did you expect to see? (Required)
when the second column is `0`, it should not appear:
in TiDB with unistore:
```
mysql> WITH
-> v2 AS (SELECT (1 + (1 / c1)) as w1 FROM t1)
-> SELECT
-> w1, w1 <> cast(1.0 as double)
-> FROM v2 WHERE w1 <> cast(1.0 as double)
-> ORDER BY 1,2 desc;
Empty set (0.01 sec)
```
### 3. What did you see instead (Required)
in TiDB with TiKV
```
mysql> WITH
-> v2 AS (SELECT (1 + (1 / c1)) as w1 FROM t1)
-> SELECT
-> w1, w1 <> cast(1.0 as double)
-> FROM v2 WHERE w1 <> cast(1.0 as double)
-> ORDER BY 1,2 desc;
+--------+---------------------------+
| w1 | w1 <> cast(1.0 as double) |
+--------+---------------------------+
| 1.0000 | 0 |
+--------+---------------------------+
1 row in set (0.00 sec)
```
### 4. What is your TiDB version? (Required)
```
Release Version: v8.5.0-alpha-184-g1c059a1216
Edition: Community
Git Commit Hash: 1c059a1216db711e2cb56ea9f3d1ad8c23db6327
Git Branch: HEAD
UTC Build Time: 2024-11-21 04:56:22
GoVersion: go1.23.3
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"
tidb_servers:
- host: 10.0.2.81
pd_servers:
- host: 10.0.2.82
tikv_servers:
- host: 10.0.2.83
```
### 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.
Contributor guide
Research direction
Run the provided CTE query against TiKV and unistore to reproduce the differing results. Investigate the floating-point comparison and execution path responsible for the WHERE clause, then verify that TiKV returns an empty result while preserving the expected select-list comparison behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- go, sql
- Domain
- databases, distributed-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100