terrymanu commented on issue #26338:
URL:
https://github.com/apache/shardingsphere/issues/26338#issuecomment-3538689904
This is not a ShardingSphere bug, but rather a compatibility issue between
MySQL Connector version and database configuration.
Analysis Conclusion
1. No GROUP BY TABLE_TYPE Issue in ShardingSphere Code
After a comprehensive code search, I confirm:
- TABLE_TYPE in ShardingSphere code is only used as a table type filtering
parameter for JDBC getTables() method
- ShardingSphere does not generate any SQL statements containing "GROUP BY
TABLE_TYPE"
- ShardingSphere only transparently forwards JDBC metadata queries
2. Root Cause of the Problem
This SQL is generated by ORM frameworks (such as Spring JPA/Hibernate),
ShardingSphere is responsible for transparent forwarding, and the database
reports the error directly.
The complete error chain:
1. Spring JPA startup calls connection.getMetaData().getTables()
2. MySQL Connector 8.x internally generates complex metadata queries
containing GROUP BY
3. ShardingSphere, as a transparent proxy, directly forwards this SQL to
the database
4. The database receives the SQL and detects a violation of functional
dependency rules in ONLY_FULL_GROUP_BY mode
5. The database directly reports the error: "Expression 'TABLE_TYPE' is
not being grouped"
3. MySQL Version Differences Clarification
- Both MySQL 5.7 and 8.0 have ONLY_FULL_GROUP_BY enabled by default in
sql_mode
- The behavior is consistent between these two versions
- The issue is not related to differences in default values between MySQL
versions
Solution
Check the database's sql_mode setting to ensure compatibility with the
application:
-- Check current sql_mode
SELECT @@sql_mode;
-- Adjust configuration as needed
This is not a bug that ShardingSphere needs to fix, but rather a
compatibility issue with SQL generated by ORM under specific database
configurations. ShardingSphere simply performs correct transparent forwarding.
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