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float point comparison in WHERE clause produces different result from select list #57654

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r33s3n6 opened this issue Nov 23, 2024 · 0 comments
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type/bug The issue is confirmed as a bug.

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@r33s3n6
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r33s3n6 commented Nov 23, 2024

1. Minimal reproduce step (Required)

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.

@r33s3n6 r33s3n6 added the type/bug The issue is confirmed as a bug. label Nov 23, 2024
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