Refactor SetTransactionHandler (#35489)

* Add DistSQLExecutorDatabaseAware interface to ShowShardingTableNodesExecutor

* Refactor SetTransactionHandler

Author: terrymanu

proxy/backend/core/src/main/java/org/apache/shardingsphere/proxy/backend/handler/tcl/SetTransactionHandler.java

@@ -19,6 +19,7 @@
 
 import lombok.RequiredArgsConstructor;
 import org.apache.shardingsphere.infra.database.core.metadata.database.metadata.option.transaction.DialectTransactionOption;
+import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
 import org.apache.shardingsphere.infra.database.core.type.DatabaseTypeRegistry;
 import org.apache.shardingsphere.infra.exception.core.ShardingSpherePreconditions;
 import org.apache.shardingsphere.proxy.backend.handler.ProxyBackendHandler;
@@ -40,6 +41,8 @@ public final class SetTransactionHandler implements ProxyBackendHandler {
 
     private final ConnectionSession connectionSession;
 
+    private final DatabaseType databaseType;
+    
     @Override
     public ResponseHeader execute() {
         ShardingSpherePreconditions.checkState(null != sqlStatement.getScope() || !connectionSession.getTransactionStatus().isInTransaction(), SwitchTypeInTransactionException::new);
@@ -63,7 +66,7 @@ private void setTransactionIsolationLevel() {
         if (!sqlStatement.getIsolationLevel().isPresent()) {
             return;
         }
-        DialectTransactionOption transactionOption = new DatabaseTypeRegistry(sqlStatement.getDatabaseType()).getDialectDatabaseMetaData().getTransactionOption();
+        DialectTransactionOption transactionOption = new DatabaseTypeRegistry(databaseType).getDialectDatabaseMetaData().getTransactionOption();
         connectionSession.setDefaultIsolationLevel(TransactionUtils.getTransactionIsolationLevel(transactionOption.getDefaultIsolationLevel()));
         connectionSession.setIsolationLevel(sqlStatement.getIsolationLevel().get());
     }

proxy/backend/core/src/main/java/org/apache/shardingsphere/proxy/backend/handler/tcl/TCLBackendHandlerFactory.java

@@ -78,7 +78,7 @@ public static ProxyBackendHandler newInstance(final SQLStatementContext sqlState
                     : new TCLBackendHandler(tclStatement, TransactionOperationType.ROLLBACK, connectionSession);
         }
         if (tclStatement instanceof SetTransactionStatement && OperationScope.GLOBAL != ((SetTransactionStatement) tclStatement).getScope()) {
-            return new SetTransactionHandler((SetTransactionStatement) tclStatement, connectionSession);
+            return new SetTransactionHandler((SetTransactionStatement) tclStatement, connectionSession, sqlStatementContext.getDatabaseType());
         }
         if (tclStatement instanceof XAStatement) {
             return new XATCLHandler(sqlStatementContext, sql, connectionSession);