terrymanu commented on issue #33921:
URL:
https://github.com/apache/shardingsphere/issues/33921#issuecomment-3497099689
Root Cause Analysis
After analyzing the ShardingSphere codebase, I've identified that this is
not a bug but an Oracle database architecture limitation. The issue stems from
Oracle's schema management mechanism conflicting with
ShardingSphere's metadata loading process.
Key Technical Limitations
1. Oracle Connection Schema Mechanism: In Oracle, connection.getSchema()
returns the current username, limiting access to only the current user's schema.
2. Metadata Query Restriction: OracleMetaDataLoader uses SQL queries with
WHERE OWNER = ?, where the parameter is connection.getSchema(), which only
returns the current user schema.
3. Configuration Parsing Dependency: Single table rule schema parsing
relies on schema information returned by the database connection.
Solutions
Solution 1: Database-Level Authorization (Recommended)
Grant schema1 user access to schema2 objects in Oracle:
-- Grant access to specific tables
GRANT SELECT ON schema2.table_name TO schema1;
-- Or grant access to all tables in schema2
GRANT SELECT ANY TABLE TO schema1;
Solution 2: Configure Multiple DataSources
Configure separate data sources for each schema:
dataSources:
master_schema1:
dataSourceClassName: com.zaxxer.hikari.HikariDataSource
jdbcUrl: jdbc:oracle:thin:@xx.xx.xx.xx:1521:xxxxxx
username: schema1
password:
driverClassName: oracle.jdbc.OracleDriver
maximumPoolSize: 50
master_schema2:
dataSourceClassName: com.zaxxer.hikari.HikariDataSource
jdbcUrl: jdbc:oracle:thin:@xx.xx.xx.xx:1521:xxxxxx
username: schema2
password:
driverClassName: oracle.jdbc.OracleDriver
maximumPoolSize: 50
rules:
- !READWRITE_SPLITTING
dataSourceGroups:
readwrite_ds_schema1:
writeDataSourceName: master_schema1
readDataSourceNames:
- slaver_schema1
readwrite_ds_schema2:
writeDataSourceName: master_schema2
readDataSourceNames:
- slaver_schema2
- !SINGLE
tables:
- "readwrite_ds_schema1.*"
- "readwrite_ds_schema2.*"
Solution 3: Oracle Synonyms (Oracle-Specific)
Create synonyms in schema1 pointing to schema2 tables:
CREATE SYNONYM schema1.table_name FOR schema2.table_name;
Additional Information Required
To provide the most appropriate solution, please clarify the following:
1. Permissions: Does the schema1 user have permissions to access schema2
tables?
2. Business Requirements: Is it necessary to access multiple schemas
through a single data source?
3. Table Structure: Are the table structures in schema1 and schema2
identical?
4. Access Pattern: Is this primarily for queries or does it include
insert/update/delete operations?
Conclusion
This issue is caused by the incompatibility between Oracle's schema
management mechanism and ShardingSphere's metadata loading process. It's not a
ShardingSphere bug but rather an Oracle database architecture design
characteristic. We recommend considering database-level authorization
solutions first, and then adjusting ShardingSphere configuration if necessary.
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