GUACAMOLE-926: Disable batch executor for SQL Server JDBC extension - it doesn't work.

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/JDBCAuthenticationProviderModule.java

@@ -127,10 +127,11 @@ public class JDBCAuthenticationProviderModule extends MyBatisModule {
         // Transaction factory
         bindTransactionFactoryType(JdbcTransactionFactory.class);
         
-        // Set the JDBC Auth provider to use batch execution when possible
-        bindConfigurationSetting(configuration -> {
-            configuration.setDefaultExecutorType(ExecutorType.BATCH);
-        });
+        // Set the JDBC Auth provider to use batch execution if enabled
+        if (environment.shouldUseBatchExecutor())
+            bindConfigurationSetting(configuration -> {
+                configuration.setDefaultExecutorType(ExecutorType.BATCH);
+            });
 
         // Add MyBatis mappers
         addMapperClass(ConnectionMapper.class);

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/JDBCEnvironment.java

@@ -254,4 +254,22 @@ public abstract class JDBCEnvironment extends DelegatingEnvironment {
      */
     public abstract boolean enforceAccessWindowsForActiveSessions() throws GuacamoleException;
 
+    /**
+     * Returns true if the JDBC batch executor should be used by default, false
+     * otherwise. The batch executor allows repeated updates to be batched
+     * together for improved performance. 
+     * See https://mybatis.org/mybatis-3/java-api.html#sqlSessions
+     *
+     * @return
+     *     true if the batch executor should be used by default, false otherwise.
+     */
+    public boolean shouldUseBatchExecutor() {
+
+        // Unless otherwise overwritten due to implementation-specific problems,
+        // all JDBC extensions should use the batch executor if possible to
+        // ensure the best performance for repetitive queries
+        return true;
+
+    }
+
 }

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-sqlserver/src/main/java/org/apache/guacamole/auth/sqlserver/conf/SQLServerEnvironment.java

@@ -295,6 +295,21 @@ public class SQLServerEnvironment extends JDBCEnvironment {
                 true);
     }
 
+    @Override
+    public boolean shouldUseBatchExecutor() {
+
+        // The SQL Server driver does not work when batch execution is enabled.
+        // Specifically, inserts fail with com.microsoft.sqlserver.jdbc.SQLServerException:
+        // The statement must be executed before any results can be obtained.
+        // See https://github.com/microsoft/mssql-jdbc/issues/358 for more.
+        logger.warn(
+                "JDBC batch executor is disabled for SQL Server Connections. "
+                + "Large batched updates may run slower."
+        );
+        return false;
+        
+    }
+
     /**
      * Returns true if all server certificates should be trusted, including
      * those signed by an unknown certificate authority, such as self-signed