diff --git a/frontend/src/components/DataGrid.tsx b/frontend/src/components/DataGrid.tsx
index 80d9433..49458a5 100644
--- a/frontend/src/components/DataGrid.tsx
+++ b/frontend/src/components/DataGrid.tsx
@@ -5,6 +5,7 @@ import { ReloadOutlined, ImportOutlined, ExportOutlined, DownOutlined, PlusOutli
 import { Resizable } from 'react-resizable';
 import { ImportData, ExportTable, ExportData, ApplyChanges } from '../../wailsjs/go/app/App';
 import { useStore } from '../store';
+import { v4 as uuidv4 } from 'uuid';
 import 'react-resizable/css/styles.css';
 
 // --- Helper: Format Value ---
@@ -214,6 +215,7 @@ const DataGrid: React.FC<DataGridProps> = ({
   const addSqlLog = useStore(state => state.addSqlLog);
   const [form] = Form.useForm();
   const [modal, contextHolder] = Modal.useModal();
+  const gridId = useMemo(() => `grid-${uuidv4()}`, []);
   
   // Helper to export specific data
   const exportData = async (rows: any[], format: string) => {
@@ -234,16 +236,26 @@ const DataGrid: React.FC<DataGridProps> = ({
 
   useEffect(() => {
       if (!containerRef.current) return;
+      
+      let rafId: number;
       const resizeObserver = new ResizeObserver(entries => {
-          for (let entry of entries) {
-              // Subtract header height (~40px)
-              // Ensure minimum height to prevent collapse loop
-              const h = Math.max(100, entry.contentRect.height - 42); 
-              setTableHeight(h); 
-          }
+          rafId = requestAnimationFrame(() => {
+              for (let entry of entries) {
+                  // Use boundingClientRect for more accurate render size (including padding if any)
+                  const height = entry.contentRect.height;
+                  if (height < 50) return; 
+                  // Subtract header (~42px) and a buffer
+                  const h = Math.max(100, height - 42); 
+                  setTableHeight(h); 
+              }
+          });
       });
+      
       resizeObserver.observe(containerRef.current);
-      return () => resizeObserver.disconnect();
+      return () => {
+          resizeObserver.disconnect();
+          cancelAnimationFrame(rafId);
+      };
   }, []);
 
   const [selectedRowKeys, setSelectedRowKeys] = useState<React.Key[]>([]);
@@ -685,7 +697,7 @@ const DataGrid: React.FC<DataGridProps> = ({
   const totalWidth = columns.reduce((sum, col) => sum + (col.width as number || 200), 0);
 
   return (
-    <div style={{ height: '100%', overflow: 'hidden', padding: 0, display: 'flex', flexDirection: 'column' }}>
+    <div className={gridId} style={{ height: '100%', overflow: 'hidden', padding: 0, display: 'flex', flexDirection: 'column', minHeight: 0 }}>
        {/* Toolbar */}
        <div style={{ padding: '8px', borderBottom: '1px solid #eee', display: 'flex', gap: 8, alignItems: 'center' }}>
            {onReload && <Button icon={<ReloadOutlined />} onClick={() => {
@@ -747,7 +759,7 @@ const DataGrid: React.FC<DataGridProps> = ({
            </div>
        )}
 
-       <div ref={containerRef} style={{ flex: 1, overflow: 'hidden', position: 'relative' }}>
+       <div ref={containerRef} style={{ flex: 1, overflow: 'hidden', position: 'relative', minHeight: 0 }}>
         {contextHolder}
         <Form component={false} form={form}>
             <DataContext.Provider value={{ selectedRowKeysRef, displayDataRef, handleCopyInsert, handleCopyJson, handleCopyCsv, handleExportSelected, copyToClipboard, tableName }}>
@@ -794,9 +806,9 @@ const DataGrid: React.FC<DataGridProps> = ({
        )}
 
        <style>{`
-           .row-added td { background-color: #f6ffed !important; }
-           .row-modified td { background-color: #e6f7ff !important; }
-           .ant-table-body {
+           .${gridId} .row-added td { background-color: #f6ffed !important; }
+           .${gridId} .row-modified td { background-color: #e6f7ff !important; }
+           .${gridId} .ant-table-body {
                height: ${tableHeight}px !important;
                max-height: ${tableHeight}px !important;
            }
diff --git a/frontend/src/components/DataViewer.tsx b/frontend/src/components/DataViewer.tsx
index baab82a..7b9d4e3 100644
--- a/frontend/src/components/DataViewer.tsx
+++ b/frontend/src/components/DataViewer.tsx
@@ -162,6 +162,7 @@ const DataViewer: React.FC<{ tab: TabData }> = ({ tab }) => {
   }, [tab, sortInfo, filterConditions]); // Initial load and re-load on sort/filter
 
   return (
+    <div style={{ height: '100%', width: '100%', overflow: 'hidden' }}>
       <DataGrid
           data={data}
           columnNames={columnNames}
@@ -178,6 +179,7 @@ const DataViewer: React.FC<{ tab: TabData }> = ({ tab }) => {
           onToggleFilter={handleToggleFilter}
           onApplyFilter={handleApplyFilter}
       />
+    </div>
   );
 };
 
diff --git a/frontend/src/components/Sidebar.tsx b/frontend/src/components/Sidebar.tsx
index bb4c835..2774bbe 100644
--- a/frontend/src/components/Sidebar.tsx
+++ b/frontend/src/components/Sidebar.tsx
@@ -503,13 +503,21 @@ const Sidebar: React.FC<{ onEditConnection?: (conn: SavedConnection) => void }>
                  label: '断开连接',
                  icon: <DisconnectOutlined />,
                  onClick: () => {
+                     // Reset status recursively
                      setConnectionStates(prev => {
                          const next = { ...prev };
-                         delete next[node.key];
+                         Object.keys(next).forEach(k => {
+                             if (k === node.key || k.startsWith(`${node.key}-`)) {
+                                 delete next[k];
+                             }
+                         });
                          return next;
                      });
-                     setExpandedKeys(prev => prev.filter(k => k !== node.key));
-                     setLoadedKeys(prev => prev.filter(k => k !== node.key));
+                     // Collapse node and children
+                     setExpandedKeys(prev => prev.filter(k => k !== node.key && !k.toString().startsWith(`${node.key}-`)));
+                     // Reset loaded state recursively
+                     setLoadedKeys(prev => prev.filter(k => k !== node.key && !k.toString().startsWith(`${node.key}-`)));
+                     // Clear children (undefined to trigger reload)
                      setTreeData(origin => updateTreeData(origin, node.key, undefined));
                      message.success("已断开连接");
                  }
@@ -553,8 +561,8 @@ const Sidebar: React.FC<{ onEditConnection?: (conn: SavedConnection) => void }>
                        delete next[node.key];
                        return next;
                    });
-                   setExpandedKeys(prev => prev.filter(k => k !== node.key));
-                   setLoadedKeys(prev => prev.filter(k => k !== node.key));
+                   setExpandedKeys(prev => prev.filter(k => k !== node.key && !k.toString().startsWith(`${node.key}-`)));
+                   setLoadedKeys(prev => prev.filter(k => k !== node.key && !k.toString().startsWith(`${node.key}-`)));
                    setTreeData(origin => updateTreeData(origin, node.key, undefined));
                }
            },
diff --git a/internal/app/methods_db.go b/internal/app/methods_db.go
index 9c5436a..33cb49b 100644
--- a/internal/app/methods_db.go
+++ b/internal/app/methods_db.go
@@ -10,19 +10,7 @@ import (
 // Generic DB Methods
 
 func (a *App) DBConnect(config connection.ConnectionConfig) connection.QueryResult {
-	key := getCacheKey(config)
-	
-	// Use an anonymous function to scope the lock
-	func() {
-		a.mu.Lock()
-		defer a.mu.Unlock()
-		if oldDB, ok := a.dbCache[key]; ok {
-			oldDB.Close()
-			delete(a.dbCache, key)
-		}
-	}()
-
-	// getDatabase acquires the lock internally, so we must be unlocked here
+	// getDatabase checks cache and Pings. If valid, reuses. If not, connects.
 	_, err := a.getDatabase(config)
 	if err != nil {
 		return connection.QueryResult{Success: false, Message: err.Error()}
@@ -32,17 +20,6 @@ func (a *App) DBConnect(config connection.ConnectionConfig) connection.QueryResu
 }
 
 func (a *App) TestConnection(config connection.ConnectionConfig) connection.QueryResult {
-	// Force close existing cached connection if any to ensure fresh test
-	key := getCacheKey(config)
-	func() {
-		a.mu.Lock()
-		defer a.mu.Unlock()
-		if oldDB, ok := a.dbCache[key]; ok {
-			oldDB.Close()
-			delete(a.dbCache, key)
-		}
-	}()
-
 	_, err := a.getDatabase(config)
 	if err != nil {
 		return connection.QueryResult{Success: false, Message: err.Error()}