docs/document/content/user-manual/shardingsphere-jdbc/java-api/rules/sql-federation.en.md
+++ title = "SQL-federation" weight = 13 +++
This function is an experimental one and is currently not suitable for use in core system production environments. When multiple tables in a join query are distributed across different database instances, enabling federated query allows for cross-database join queries, as well as subqueries.
Class: org.apache.shardingsphere.sqlfederation.config.SQLFederationRuleConfiguration
Attributes:
| name | DataType | Description | Default Value |
|---|---|---|---|
| sqlFederationEnabled | boolean | SQL federation enabled configuration | - |
| allQueryUseSQLFederation | boolean | all query use SQL federation configuration | - |
| executionPlanCache | org.apache.shardingsphere.sql.parser.api.CacheOption | execution plan cache configuration | - |
Class: org.apache.shardingsphere.sql.parser.api.CacheOption
Attributes:
| name | DataType | Description | Default Value |
|---|---|---|---|
| initialCapacity | int | Initial capacity of local cache | execution plan local cache default value of 2000 |
| maximumSize | long | Maximum capacity of local cache | execution plan local cache maximum default value 65535 |
private SQLFederationRuleConfiguration createSQLFederationRuleConfiguration() {
CacheOption executionPlanCache = new CacheOption(2000, 65535L);
return new SQLFederationRuleConfiguration(true, false, executionPlanCache);
}