terrymanu commented on issue #28469:
URL:
https://github.com/apache/shardingsphere/issues/28469#issuecomment-3540598024
Thank you for your detailed report and verification! After our team's
in-depth analysis, this is indeed a bug in ShardingSphere's implementation that
needs to maintain consistency with MySQL's native behavior.
## Root Cause Confirmed
✅ Your verification is completely correct:
- Standard MySQL: SELECT DATABASE() returns NULL
- Current ShardingSphere: Uses TABLE_SCHEMA = '' filter
- Core Issue: In SQL, NULL != '', causing incorrect query conditions
## Specific Problem in Code
We identified the problematic code in MySQLMetaDataLoader.java:
// Lines 91, 135, 174 - NPE risk exists
String databaseName = "".equals(connection.getCatalog()) ?
GlobalDataSourceRegistry.getInstance().getCachedDatabaseTables().get(tableNames.iterator().next())
:
connection.getCatalog(); // Throws NPE when connection.getCatalog()
returns NULL
## Fix Recommendation
The correct approach should be:
String catalog = connection.getCatalog();
String databaseName = (catalog == null || catalog.isEmpty()) ?
GlobalDataSourceRegistry.getInstance().getCachedDatabaseTables().get(tableNames.iterator().next())
:
catalog;
Or use Guava's Strings.isNullOrEmpty() method.
🌟 Open Invitation to Community Contributors
Since this is a community-owned open-source project, we're extending an
invitation to all community participants to help solve this issue!
Calling All Community Contributors - Let's Fix This Together!
This is an excellent first-time contribution opportunity because:
- ✅ Problem is well-defined with clear root cause
- ✅ Small, controllable fix scope
- ✅ Immediate improvement to user experience
- ✅ Important fix for database behavior consistency
Any community contributor can participate by following these steps:
1. Claim the task: Comment "I'd like to work on this issue" below
2. Set up development environment:
git clone https://github.com/[your-username]/shardingsphere.git
cd shardingsphere
git checkout -b fix/mysql-null-schema-handling-28469
3. Core modifications (File:
database/connector/dialect/mysql/src/main/java/org/apache/shardingsphere/database/connector/mysql/metadata/data/loader/MySQLMetaDataLoader.java):
- Line 91: Modify NULL check logic
- Line 135: Modify NULL check logic
- Line 174: Modify NULL check logic
4. Add tests: Add test cases for NULL catalog scenarios in the
corresponding test file
5. Verify fix:
./mvnw test -Dtest=MySQLMetaDataLoaderTest
./mvnw spotless:apply
./mvnw install -DskipTests
6. Submit PR: Describe the fix in detail and reference issue #28469
We provide support for community contributors:
- 🎯 Clear guidance: We've clearly identified problem locations and fix
solutions
- 📋 Code review: Provide professional and friendly code review services
- 🤝 Technical support: Get help anytime during development
- 🏆 Contribution recognition: All contributors will be recorded in the
project's contributor list
Why this fix is important?
- 🔧 Improve user experience: Solve real-world usage scenarios without
schema connections
- 🎯 Behavior consistency: Ensure ShardingSphere maintains consistency with
MySQL native behavior
- 📈 Community value: Demonstrates Apache project's commitment to user
experience
The strength of community comes from everyone's participation! Even a
small bug fix is an important contribution to the entire ShardingSphere
ecosystem.
Let's improve ShardingSphere together! 🚀
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