Incompatible error when grouping on join

[kolbe]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

select region_id from information_schema.tikv_region_status join information_schema.tikv_region_peers using (region_id) group by region_id;

create table t1 (id int);
create table t2 (id int);
select id, count(*) from t1 join t2 using (id) group by id;

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

This query should return results, because there cannot be any ambiguity when grouping on a column that is covered by the join condition.

3. What did you see instead (Required)

ERROR 1052 (23000): Column 'region_id' in field list is ambiguous

This type of query can execute without any error in MySQL:

8.0.23 (root) [test]> create table t1 (id int); create table t2 (id int); select id, count(*) from t1 join t2 using (id) group by id;
Query OK, 0 rows affected (0.00 sec)

Query OK, 0 rows affected (0.01 sec)

Empty set (0.00 sec)

4. What is your TiDB version? (Required)

Release Version: v5.0.1
Edition: Community
Git Commit Hash: 1145e347d3469d8e89f88dce86f6926ca44b3cd8
Git Branch: heads/refs/tags/v5.0.1
UTC Build Time: 2021-04-23 05:51:17
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[morgo]

This is specific to the use of using. If you use the alternative join syntax it doesn't work in MySQL:

mysql [localhost:8024] {msandbox} (test) > select id, count(*) from t1 join t2 using (id) group by id;
Empty set (0.00 sec)

mysql [localhost:8024] {msandbox} (test) > select id, count(*) from t1 join t2 on t1.id=t2.id group by id;
ERROR 1052 (23000): Column 'id' in field list is ambiguous

I am not sure how these are different. I would have thought it's functionally the same.

[kolbe]

The behavior of NATURAL JOIN is the same as USING.

I tested this at https://www.db-fiddle.com/ on Postgres and SQLite and they have the same behavior as MySQL, so we're the outlier here. Let's fix it!

[kolbe]

Morgan found that MySQL actually rewrites the query with USING() so that id becomes t1.id in the field list:

https://gist.github.com/morgo/cc229e891c0abd0563b78b93ffb10cca

[eurekaka]

The problem is incurred by #21922 when trying to fix #6712, I have had a patch to fix this issue, but found another related problem on ONLY_FULL_GROUP_BY check, still working on it.

[eurekaka]

Filed a PR #25094 to solve this issue, the related incompatibility problems regarding only_full_group_by check are recorded in a separate issue #25089.

[ti-srebot]

Please edit this comment or add a new comment to complete the following information

Not a bug

1. Remove the 'type/bug' label
2. Add notes to indicate why it is not a bug

Duplicate bug

1. Add the 'type/duplicate' label
2. Add the link to the original bug

Bug

Note: Make Sure that 'component', and 'severity' labels are added
Example for how to fill out the template: #20100

1. Root Cause Analysis (RCA) (optional)

2. Symptom (optional)

3. All Trigger Conditions (optional)

4. Workaround (optional)

5. Affected versions

6. Fixed versions