terrymanu commented on issue #25251:
URL:
https://github.com/apache/shardingsphere/issues/25251#issuecomment-3538698218
Hello, I understand your concern about the join performance between single
tables and sharding tables. Let me clarify the root cause and provide solutions.
## Root Cause Analysis
This issue is not a bug in ShardingSphere, but rather a limitation of the
architecture design:
1. Join Limitation: In ShardingSphere, sharding tables cannot directly
join with single tables. This is a designed architectural limitation.
2. Query Optimizer Constraint: When a single table joins with sharding
tables, ShardingSphere cannot perform effective query routing optimization,
leading to scanning all sharding nodes.
## Recommended Solutions
Solution 1: Broadcast Table (Recommended)
Convert your single table to a broadcast table:
spring:
shardingsphere:
rules:
broadcast:
tables:
- your_single_table_name
Pros:
- Aligns with ShardingSphere design patterns
- Excellent join performance
- Simple configuration
Cons:
- Requires maintenance across all sharding databases
- Data synchronization needs to be considered
Solution 2: Federation Query (Not Recommended)
Enable federation queries (experimental feature):
spring:
shardingsphere:
rules:
federation:
type: SQL_FEDERATION
props:
sql-federation-enabled: true
Why not recommended:
- Federation queries are still experimental
- Stability cannot be guaranteed
- Performance is typically not as good as broadcast tables
- Complex configuration and debugging
Solution 3: Application-Level Join
- Query both tables separately at the application layer
- Perform join operations in memory
- Suitable for small data volumes
## Conclusion
According to ShardingSphere best practices:
- Sharding tables cannot directly join with single tables - This is a
design limitation
- Use broadcast tables instead of single tables - This is the standard
approach
- Federation queries are experimental - Not recommended for production use
I recommend using the broadcast table solution. While it has some
maintenance overhead, it provides the best join performance and stability.
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