v1.8.56: Database Tree Explorer + thread-safe SQL operations

- Add HeidiSQL-style database tree panel (Databases → Tables → Columns)
- Lazy loading with ttk.Treeview, context menus, double-click SELECT TOP 1000
- Fix pymysql thread safety: serialize all DB ops with threading.Lock
- Use lock.acquire(timeout=10) to prevent deadlocks between tree and query threads
- Always reset _executing flag in finally block to prevent stuck queries
- Add _ensure_connected() auto-reconnect on broken connections
- Add sql_client check_connection() null safety
- Add 12 tree-related i18n keys (EN/RU/ZH)
- Clean up old releases

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/i18n.py

@@ -327,6 +327,19 @@ _EN = {
     "query_connected": "Connected to {alias} ({db})",
     "query_connecting": "Connecting...",
     "query_disconnected": "Not connected",
+
+    # Database tree
+    "tree_databases": "Databases",
+    "tree_refresh": "Refresh",
+    "tree_use_db": "Use database",
+    "tree_select_top": "SELECT TOP 1000",
+    "tree_describe": "Describe table",
+    "tree_copy_name": "Copy name",
+    "tree_select_column": "Insert column",
+    "tree_loading": "Loading...",
+    "tree_no_tables": "(no tables)",
+    "tree_no_columns": "(no columns)",
+    "tree_connected": "Connected",
     "query_exported": "Exported to {path}",
 
     # Redis tab
@@ -741,6 +754,19 @@ _RU = {
     "query_disconnected": "Не подключено",
     "query_exported": "Экспортировано в {path}",
 
+    # Database tree
+    "tree_databases": "Базы данных",
+    "tree_refresh": "Обновить",
+    "tree_use_db": "Выбрать базу",
+    "tree_select_top": "SELECT TOP 1000",
+    "tree_describe": "Описание таблицы",
+    "tree_copy_name": "Копировать имя",
+    "tree_select_column": "Вставить колонку",
+    "tree_loading": "Загрузка...",
+    "tree_no_tables": "(нет таблиц)",
+    "tree_no_columns": "(нет колонок)",
+    "tree_connected": "Подключено",
+
     # Redis tab
     "redis_clear": "Очистить",
     "redis_execute": "Выполнить",
@@ -1153,6 +1179,19 @@ _ZH = {
     "query_disconnected": "未连接",
     "query_exported": "已导出到 {path}",
 
+    # Database tree
+    "tree_databases": "数据库",
+    "tree_refresh": "刷新",
+    "tree_use_db": "选择数据库",
+    "tree_select_top": "SELECT TOP 1000",
+    "tree_describe": "表描述",
+    "tree_copy_name": "复制名称",
+    "tree_select_column": "插入列",
+    "tree_loading": "加载中...",
+    "tree_no_tables": "(无表)",
+    "tree_no_columns": "(无列)",
+    "tree_connected": "已连接",
+
     # Redis tab
     "redis_clear": "清除",
     "redis_execute": "执行",

core/sql_client.py

@@ -70,6 +70,8 @@ class SQLClient:
             log.info("sql_client: disconnected")
 
     def check_connection(self) -> bool:
+        if self._conn is None:
+            return False
         try:
             cur = self._conn.cursor()
             cur.execute("SELECT 1")

gui/tabs/query_tab.py

@@ -1,11 +1,11 @@
 """
-Query tab — SQL database interaction with editor, results grid, and export.
+Query tab — SQL database interaction with tree explorer, editor, results grid, and export.
 """
 
 import csv
-import io
 import time
 import threading
+import tkinter as tk
 from tkinter import ttk, filedialog
 
 import customtkinter as ctk
@@ -14,6 +14,67 @@ from core.i18n import t
 from core.icons import icon_text
 from core.sql_client import SQLClient
 
+_TREE_THEME_APPLIED = False
+
+
+def _apply_db_tree_theme():
+    global _TREE_THEME_APPLIED
+    if _TREE_THEME_APPLIED:
+        return
+    _TREE_THEME_APPLIED = True
+
+    style = ttk.Style()
+    try:
+        style.theme_use("clam")
+    except Exception:
+        pass
+    style.configure(
+        "DBTree.Treeview",
+        background="#1e1e1e",
+        foreground="#dcdcdc",
+        fieldbackground="#1e1e1e",
+        borderwidth=0,
+        font=("Consolas", 11),
+        rowheight=24,
+    )
+    style.map(
+        "DBTree.Treeview",
+        background=[("selected", "#3b82f6")],
+        foreground=[("selected", "#ffffff")],
+    )
+    style.layout("DBTree.Treeview", [
+        ("DBTree.Treeview.treearea", {"sticky": "nswe"}),
+    ])
+    style.configure(
+        "Results.Treeview",
+        background="#1e1e1e",
+        foreground="#dcdcdc",
+        fieldbackground="#1e1e1e",
+        borderwidth=0,
+        font=("Consolas", 11),
+        rowheight=24,
+    )
+    style.configure(
+        "Results.Treeview.Heading",
+        background="#2b2b2b",
+        foreground="#9ca3af",
+        borderwidth=0,
+        font=("Segoe UI", 10, "bold"),
+        relief="flat",
+    )
+    style.map(
+        "Results.Treeview",
+        background=[("selected", "#3b82f6")],
+        foreground=[("selected", "#ffffff")],
+    )
+    style.map(
+        "Results.Treeview.Heading",
+        background=[("active", "#333333")],
+    )
+    style.layout("Results.Treeview", [
+        ("Results.Treeview.treearea", {"sticky": "nswe"}),
+    ])
+
 
 class QueryTab(ctk.CTkFrame):
     def __init__(self, master, store):
@@ -21,56 +82,91 @@ class QueryTab(ctk.CTkFrame):
         self._current_alias: str | None = None
         self.store = store
         self._client: SQLClient | None = None
+        self._db_lock = threading.Lock()
         self._results: list[list] = []
         self._columns: list[str] = []
         self._executing = False
+        self._current_db: str = ""
 
+        _apply_db_tree_theme()
         self._build_ui()
 
     # ── UI construction ────────────────────────────────────────────
 
     def _build_ui(self):
-        # === Database selector row ===
-        db_row = ctk.CTkFrame(self, fg_color="transparent")
-        db_row.pack(fill="x", padx=10, pady=(10, 5))
+        # === Main PanedWindow: tree | editor+results ===
+        self._paned = ttk.PanedWindow(self, orient="horizontal")
+        self._paned.pack(fill="both", expand=True, padx=5, pady=5)
 
-        ctk.CTkLabel(db_row, text=t("query_database"), anchor="w").pack(
-            side="left", padx=(0, 8)
-        )
+        # ── Left panel: Database tree ──
+        left_frame = tk.Frame(self._paned, bg="#1a1a1a", width=260)
+        self._paned.add(left_frame, weight=0)
 
-        self._db_var = ctk.StringVar(value="")
-        self._db_combo = ctk.CTkComboBox(
-            db_row,
-            variable=self._db_var,
-            values=[],
-            width=220,
-            command=self._on_db_selected,
+        # Tree toolbar
+        toolbar = tk.Frame(left_frame, bg="#1a1a1a")
+        toolbar.pack(fill="x", padx=2, pady=(4, 2))
+
+        self._tree_title = tk.Label(
+            toolbar, text=t("tree_databases"), bg="#1a1a1a", fg="#9ca3af",
+            font=("Segoe UI", 10, "bold"), anchor="w",
         )
-        self._db_combo.pack(side="left")
+        self._tree_title.pack(side="left", padx=4)
+
+        self._refresh_btn = tk.Button(
+            toolbar, text="\u21bb", bg="#2b2b2b", fg="#9ca3af",
+            font=("Segoe UI", 11), bd=0, padx=6, pady=0,
+            activebackground="#3b3b3b", activeforeground="#dcdcdc",
+            command=self._refresh_tree,
+        )
+        self._refresh_btn.pack(side="right", padx=4)
+
+        # Tree + scrollbar
+        tree_container = tk.Frame(left_frame, bg="#1e1e1e")
+        tree_container.pack(fill="both", expand=True, padx=2, pady=(0, 2))
+
+        self._tree_scroll = ttk.Scrollbar(tree_container, orient="vertical")
+        self._tree_scroll.pack(side="right", fill="y")
+
+        self._db_tree = ttk.Treeview(
+            tree_container, show="tree", selectmode="browse",
+            style="DBTree.Treeview",
+            yscrollcommand=self._tree_scroll.set,
+        )
+        self._db_tree.pack(fill="both", expand=True)
+        self._tree_scroll.config(command=self._db_tree.yview)
+
+        # Tree bindings
+        self._db_tree.bind("<<TreeviewOpen>>", self._on_tree_expand)
+        self._db_tree.bind("<Double-1>", self._on_tree_dblclick)
+        self._db_tree.bind("<Button-3>", self._on_tree_rightclick)
+        self._db_tree.bind("<<TreeviewSelect>>", self._on_tree_select)
+
+        # ── Right panel: editor + buttons + results ──
+        right_frame = tk.Frame(self._paned, bg="#1a1a1a")
+        self._paned.add(right_frame, weight=1)
+
+        right_ctk = ctk.CTkFrame(right_frame, fg_color="transparent")
+        right_ctk.pack(fill="both", expand=True)
 
         # === SQL Editor ===
-        editor_frame = ctk.CTkFrame(self, fg_color="transparent")
-        editor_frame.pack(fill="both", expand=True, padx=10, pady=5, side="top")
-        # Give editor roughly 1/3 of space
-        editor_frame.pack_configure(expand=False)
+        editor_frame = ctk.CTkFrame(right_ctk, fg_color="transparent")
+        editor_frame.pack(fill="x", padx=8, pady=(8, 4))
 
         self._editor = ctk.CTkTextbox(
             editor_frame,
             font=ctk.CTkFont(family="Consolas", size=13),
-            height=160,
+            height=140,
             wrap="none",
         )
         self._editor.pack(fill="both", expand=True)
         self._editor.insert("0.0", t("query_editor_placeholder"))
         self._editor.bind("<FocusIn>", self._on_editor_focus)
-
-        # Bind keyboard shortcuts
         self._editor.bind("<F5>", lambda e: self._execute_query())
         self._editor.bind("<Control-Return>", lambda e: self._execute_query())
 
         # === Button row ===
-        btn_row = ctk.CTkFrame(self, fg_color="transparent")
-        btn_row.pack(fill="x", padx=10, pady=5)
+        btn_row = ctk.CTkFrame(right_ctk, fg_color="transparent")
+        btn_row.pack(fill="x", padx=8, pady=4)
 
         self._exec_btn = ctk.CTkButton(
             btn_row,
@@ -103,46 +199,65 @@ class QueryTab(ctk.CTkFrame):
         self._export_btn.pack(side="left")
 
         # === Results area (Treeview) ===
-        results_frame = ctk.CTkFrame(self, fg_color="transparent")
-        results_frame.pack(fill="both", expand=True, padx=10, pady=(5, 5))
+        results_frame = ctk.CTkFrame(right_ctk, fg_color="transparent")
+        results_frame.pack(fill="both", expand=True, padx=8, pady=(4, 4))
 
-        # Horizontal scrollbar
-        self._tree_xscroll = ttk.Scrollbar(results_frame, orient="horizontal")
-        self._tree_xscroll.pack(side="bottom", fill="x")
+        self._res_xscroll = ttk.Scrollbar(results_frame, orient="horizontal")
+        self._res_xscroll.pack(side="bottom", fill="x")
 
-        # Vertical scrollbar
-        self._tree_yscroll = ttk.Scrollbar(results_frame, orient="vertical")
-        self._tree_yscroll.pack(side="right", fill="y")
+        self._res_yscroll = ttk.Scrollbar(results_frame, orient="vertical")
+        self._res_yscroll.pack(side="right", fill="y")
 
-        self._tree = ttk.Treeview(
+        self._results_tree = ttk.Treeview(
             results_frame,
             show="headings",
-            xscrollcommand=self._tree_xscroll.set,
-            yscrollcommand=self._tree_yscroll.set,
+            style="Results.Treeview",
+            xscrollcommand=self._res_xscroll.set,
+            yscrollcommand=self._res_yscroll.set,
         )
-        self._tree.pack(fill="both", expand=True)
+        self._results_tree.pack(fill="both", expand=True)
 
-        self._tree_xscroll.config(command=self._tree.xview)
-        self._tree_yscroll.config(command=self._tree.yview)
+        self._res_xscroll.config(command=self._results_tree.xview)
+        self._res_yscroll.config(command=self._results_tree.yview)
 
         # === Status bar ===
         self._status_label = ctk.CTkLabel(
-            self,
-            text="",
-            anchor="w",
-            font=ctk.CTkFont(size=12),
-            text_color="#9ca3af",
+            right_ctk, text="", anchor="w",
+            font=ctk.CTkFont(size=12), text_color="#9ca3af",
         )
-        self._status_label.pack(fill="x", padx=12, pady=(0, 8))
+        self._status_label.pack(fill="x", padx=10, pady=(0, 6))
 
     # ── Editor placeholder logic ───────────────────────────────────
 
     def _on_editor_focus(self, event=None):
         content = self._editor.get("0.0", "end").strip()
-        placeholder = t("query_editor_placeholder")
-        if content == placeholder:
+        if content == t("query_editor_placeholder"):
             self._editor.delete("0.0", "end")
 
+    # ── Connection management (thread-safe) ────────────────────────
+
+    def _ensure_connected(self):
+        """Check connection, reconnect if broken. MUST be called under _db_lock."""
+        if not self._client:
+            raise ConnectionError("No client")
+        try:
+            if not self._client.check_connection():
+                raise Exception("lost")
+        except Exception:
+            server = self.store.get_server(self._current_alias)
+            if not server:
+                raise ConnectionError("Server not found")
+            self._client.disconnect()
+            self._client = SQLClient(server)
+            if not self._client.connect():
+                self._client = None
+                raise ConnectionError("Reconnect failed")
+            if self._current_db:
+                try:
+                    self._client.switch_database(self._current_db)
+                except Exception:
+                    pass
+
     # ── Server / database connection ───────────────────────────────
 
     def set_server(self, alias: str | None):
@@ -150,69 +265,326 @@ class QueryTab(ctk.CTkFrame):
         self._current_alias = alias
         self._disconnect()
         self._clear_results()
+        self._clear_tree()
         self._set_status("")
+        self._current_db = ""
 
         if not alias:
-            self._db_combo.configure(values=[])
-            self._db_var.set("")
             return
 
         self._set_status(f"Connecting to {alias}...")
         threading.Thread(
-            target=self._connect_and_list_dbs,
+            target=self._connect_and_load_tree,
             args=(alias,),
             daemon=True,
         ).start()
 
-    def _connect_and_list_dbs(self, alias: str):
-        """Background: create SQLClient, fetch database list."""
+    def _connect_and_load_tree(self, alias: str):
+        """Background: create SQLClient, fetch databases, populate tree."""
         try:
             server = self.store.get_server(alias)
             if not server:
-                self._schedule(self._set_status, t("query_error"), error=True)
+                self.after(0, lambda: self._set_status(t("query_error"), error=True))
                 return
 
             client = SQLClient(server)
             if not client.connect():
-                self._schedule(self._set_status, t("query_error") + ": connection failed", error=True)
+                self.after(0, lambda: self._set_status(
+                    t("query_error") + ": connection failed", error=True))
                 return
-            databases = client.list_databases()
+
+            self._db_lock.acquire(timeout=10)
+            try:
+                self._client = client
+                databases = client.list_databases()
+            finally:
+                self._db_lock.release()
 
             def _update():
                 if self._current_alias != alias:
-                    return  # switched away
-                self._client = client
-                self._db_combo.configure(values=databases)
+                    return
+                self._populate_tree_databases(databases)
                 if databases:
-                    self._db_var.set(databases[0])
-                    self._switch_database(databases[0])
-                self._set_status("OK")
+                    self._current_db = databases[0]
+                self._set_status(t("tree_connected"))
 
-            self._schedule(_update)
+            self.after(0, _update)
         except Exception as exc:
-            self._schedule(self._set_status, str(exc), error=True)
-
-    def _on_db_selected(self, value: str):
-        if value:
-            self._switch_database(value)
-
-    def _switch_database(self, db_name: str):
-        """Switch active database on the current client."""
-        if not self._client:
-            return
-        try:
-            self._client.switch_database(db_name)
-            self._set_status(f"Database: {db_name}")
-        except Exception as exc:
-            self._set_status(str(exc), error=True)
+            self.after(0, lambda: self._set_status(str(exc), error=True))
 
     def _disconnect(self):
-        if self._client:
+        with self._db_lock:
+            if self._client:
+                try:
+                    self._client.disconnect()
+                except Exception:
+                    pass
+                self._client = None
+
+    # ── Database tree ──────────────────────────────────────────────
+
+    def _clear_tree(self):
+        self._db_tree.delete(*self._db_tree.get_children())
+
+    def _populate_tree_databases(self, databases: list[str]):
+        self._db_tree.delete(*self._db_tree.get_children())
+        for db in databases:
+            iid = f"db:{db}"
+            self._db_tree.insert(
+                "", "end", iid=iid,
+                text=f"  \U0001f5c4  {db}",
+                open=False,
+            )
+            self._db_tree.insert(iid, "end", iid=f"_dummy:{db}",
+                                 text=f"  {t('tree_loading')}")
+
+    def _on_tree_expand(self, event):
+        """Lazy-load children when a node is expanded for the first time."""
+        node = self._db_tree.focus()
+        if not node:
+            return
+        children = self._db_tree.get_children(node)
+        if len(children) == 1 and str(children[0]).startswith("_dummy:"):
+            if node.startswith("db:"):
+                self._load_tables(node)
+            elif node.startswith("tbl:"):
+                self._load_columns(node)
+
+    def _load_tables(self, db_node: str):
+        """Background: load tables for a database node."""
+        db_name = db_node[3:]
+
+        def _do():
             try:
-                self._client.disconnect()
-            except Exception:
-                pass
-            self._client = None
+                if not self._db_lock.acquire(timeout=10):
+                    return
+                try:
+                    self._ensure_connected()
+                    tables = self._client.list_tables(db_name)
+                finally:
+                    self._db_lock.release()
+
+                def _update():
+                    for ch in self._db_tree.get_children(db_node):
+                        self._db_tree.delete(ch)
+                    if not tables:
+                        self._db_tree.insert(
+                            db_node, "end",
+                            text=f"  {t('tree_no_tables')}",
+                        )
+                        return
+                    for tbl in tables:
+                        tbl_iid = f"tbl:{db_name}.{tbl}"
+                        self._db_tree.insert(
+                            db_node, "end", iid=tbl_iid,
+                            text=f"  \U0001f4cb  {tbl}",
+                            open=False,
+                        )
+                        self._db_tree.insert(
+                            tbl_iid, "end",
+                            iid=f"_dummy:{db_name}.{tbl}",
+                            text=f"  {t('tree_loading')}",
+                        )
+
+                self.after(0, _update)
+            except Exception as exc:
+                self.after(0, lambda: self._set_status(f"Error: {exc}", error=True))
+
+        threading.Thread(target=_do, daemon=True).start()
+
+    def _load_columns(self, tbl_node: str):
+        """Background: load columns for a table node."""
+        parts = tbl_node[4:].split(".", 1)
+        if len(parts) != 2:
+            return
+        db_name, tbl_name = parts
+
+        def _do():
+            try:
+                if not self._db_lock.acquire(timeout=10):
+                    return
+                try:
+                    self._ensure_connected()
+                    self._client.switch_database(db_name)
+                    columns = self._client.describe_table(tbl_name)
+                finally:
+                    self._db_lock.release()
+
+                def _update():
+                    for ch in self._db_tree.get_children(tbl_node):
+                        self._db_tree.delete(ch)
+                    if not columns:
+                        self._db_tree.insert(
+                            tbl_node, "end",
+                            text=f"  {t('tree_no_columns')}",
+                        )
+                        return
+                    for col in columns:
+                        name = col.get("name", "?")
+                        dtype = col.get("type", "")
+                        key = col.get("key", "")
+                        icon = "\U0001f511" if "PRI" in str(key) else "\U0001f4dd"
+                        label = f"  {icon}  {name}  ({dtype})"
+                        col_iid = f"col:{db_name}.{tbl_name}.{name}"
+                        self._db_tree.insert(
+                            tbl_node, "end", iid=col_iid,
+                            text=label,
+                        )
+
+                self.after(0, _update)
+            except Exception as exc:
+                self.after(0, lambda: self._set_status(f"Error: {exc}", error=True))
+
+        threading.Thread(target=_do, daemon=True).start()
+
+    def _on_tree_select(self, event):
+        """When user clicks a node, just remember the active DB (no network calls)."""
+        node = self._db_tree.focus()
+        if not node:
+            return
+        if node.startswith("db:"):
+            self._current_db = node[3:]
+        elif node.startswith("tbl:"):
+            self._current_db = node[4:].split(".", 1)[0]
+
+    def _on_tree_dblclick(self, event):
+        """Double-click on table → SELECT * LIMIT 1000."""
+        node = self._db_tree.identify_row(event.y)
+        if not node:
+            return
+
+        if node.startswith("tbl:"):
+            parts = node[4:].split(".", 1)
+            if len(parts) == 2:
+                db_name, tbl_name = parts
+                self._select_top(tbl_name, db_name)
+        elif node.startswith("col:"):
+            parts = node[4:].split(".")
+            if len(parts) >= 3:
+                col_name = parts[-1]
+                self._editor.insert("insert", f"`{col_name}`")
+
+    def _on_tree_rightclick(self, event):
+        """Context menu on tree nodes."""
+        node = self._db_tree.identify_row(event.y)
+        if not node:
+            return
+        self._db_tree.selection_set(node)
+
+        menu = tk.Menu(self, tearoff=0, bg="#2b2b2b", fg="#dcdcdc",
+                       activebackground="#3b82f6", activeforeground="#ffffff",
+                       font=("Segoe UI", 10))
+
+        if node.startswith("db:"):
+            db_name = node[3:]
+            menu.add_command(label=t("tree_use_db"),
+                             command=lambda: self._use_database(db_name))
+            menu.add_command(label=t("tree_refresh"),
+                             command=lambda: self._refresh_node(node))
+            menu.add_separator()
+            menu.add_command(label=t("tree_copy_name"),
+                             command=lambda: self._copy_to_clipboard(db_name))
+        elif node.startswith("tbl:"):
+            parts = node[4:].split(".", 1)
+            if len(parts) == 2:
+                db_name, tbl_name = parts
+                menu.add_command(label=t("tree_select_top"),
+                                 command=lambda: self._select_top(tbl_name, db_name))
+                menu.add_command(label=t("tree_describe"),
+                                 command=lambda: self._describe_table_query(tbl_name, db_name))
+                menu.add_separator()
+                menu.add_command(label=t("tree_copy_name"),
+                                 command=lambda: self._copy_to_clipboard(tbl_name))
+                menu.add_command(label=t("tree_refresh"),
+                                 command=lambda: self._refresh_node(node))
+        elif node.startswith("col:"):
+            parts = node[4:].split(".")
+            if len(parts) >= 3:
+                col_name = parts[-1]
+                menu.add_command(label=t("tree_copy_name"),
+                                 command=lambda: self._copy_to_clipboard(col_name))
+                menu.add_command(
+                    label=t("tree_select_column"),
+                    command=lambda: self._insert_text(f"`{col_name}`"),
+                )
+
+        menu.tk_popup(event.x_root, event.y_root)
+
+    def _refresh_tree(self):
+        """Reload entire tree from server."""
+        if not self._client:
+            return
+        self._set_status(t("tree_loading"))
+
+        def _do():
+            try:
+                if not self._db_lock.acquire(timeout=10):
+                    self.after(0, lambda: self._set_status("Database busy", error=True))
+                    return
+                try:
+                    self._ensure_connected()
+                    dbs = self._client.list_databases()
+                finally:
+                    self._db_lock.release()
+                self.after(0, lambda: self._populate_tree_databases(dbs))
+                self.after(0, lambda: self._set_status(t("tree_connected")))
+            except Exception as exc:
+                self.after(0, lambda: self._set_status(str(exc), error=True))
+
+        threading.Thread(target=_do, daemon=True).start()
+
+    def _refresh_node(self, node: str):
+        """Refresh a specific node (database or table)."""
+        if node.startswith("db:"):
+            for ch in self._db_tree.get_children(node):
+                self._db_tree.delete(ch)
+            db_name = node[3:]
+            self._db_tree.insert(node, "end", iid=f"_dummy:{db_name}",
+                                 text=f"  {t('tree_loading')}")
+            self._db_tree.item(node, open=True)
+            self._load_tables(node)
+        elif node.startswith("tbl:"):
+            for ch in self._db_tree.get_children(node):
+                self._db_tree.delete(ch)
+            parts = node[4:]
+            self._db_tree.insert(node, "end", iid=f"_dummy:{parts}",
+                                 text=f"  {t('tree_loading')}")
+            self._db_tree.item(node, open=True)
+            self._load_columns(node)
+
+    # ── Tree actions ───────────────────────────────────────────────
+
+    def _use_database(self, db_name: str):
+        self._current_db = db_name
+        self._set_status(f"Database: {db_name}")
+
+    def _select_top(self, table: str, db_name: str = ""):
+        """Insert SELECT * FROM table LIMIT 1000 and execute."""
+        if db_name:
+            self._current_db = db_name
+        sql = f"SELECT * FROM `{table}` LIMIT 1000"
+        self._editor.delete("0.0", "end")
+        self._editor.insert("0.0", sql)
+        self._execute_query()
+
+    def _describe_table_query(self, table: str, db_name: str = ""):
+        """Insert DESCRIBE/SHOW COLUMNS and execute."""
+        if db_name:
+            self._current_db = db_name
+        if self._client and self._client._type in ("mariadb", "mysql"):
+            sql = f"SHOW COLUMNS FROM `{table}`"
+        else:
+            sql = f"SELECT * FROM `{table}` WHERE 1=0"
+        self._editor.delete("0.0", "end")
+        self._editor.insert("0.0", sql)
+        self._execute_query()
+
+    def _copy_to_clipboard(self, text: str):
+        self.clipboard_clear()
+        self.clipboard_append(text)
+
+    def _insert_text(self, text: str):
+        self._editor.insert("insert", text)
 
     # ── Query execution ────────────────────────────────────────────
 
@@ -236,10 +608,21 @@ class QueryTab(ctk.CTkFrame):
         ).start()
 
     def _run_query(self, sql: str):
-        """Background thread: execute SQL, measure time, post results."""
+        """Background thread: execute SQL with lock, auto-reconnect, auto-switch DB."""
         start = time.perf_counter()
         try:
-            result = self._client.execute_query(sql)
+            acquired = self._db_lock.acquire(timeout=10)
+            if not acquired:
+                self.after(0, lambda: self._set_status("Database busy, try again", error=True))
+                return
+            try:
+                self._ensure_connected()
+                if self._current_db:
+                    self._client.switch_database(self._current_db)
+                result = self._client.execute_query(sql)
+            finally:
+                self._db_lock.release()
+
             columns = result["columns"]
             rows = result["rows"]
             elapsed = time.perf_counter() - start
@@ -247,65 +630,56 @@ class QueryTab(ctk.CTkFrame):
             def _update():
                 self._columns = columns
                 self._results = rows
-                self._populate_tree(columns, rows)
-                row_count = len(rows)
+                self._populate_results(columns, rows)
                 self._set_status(
                     t("query_status_rows").format(
-                        rows=row_count, time=f"{elapsed:.3f}"
+                        rows=len(rows), time=f"{elapsed:.3f}"
                     )
                 )
-                self._executing = False
-                self._exec_btn.configure(state="normal")
 
-            self._schedule(_update)
+            self.after(0, _update)
         except Exception as exc:
-            elapsed = time.perf_counter() - start
-
-            def _update_err():
-                self._set_status(
-                    f"{t('query_error')}: {exc}", error=True
-                )
+            self.after(0, lambda: self._set_status(
+                f"{t('query_error')}: {exc}", error=True))
+        finally:
+            def _reset():
                 self._executing = False
                 self._exec_btn.configure(state="normal")
+            self.after(0, _reset)
 
-            self._schedule(_update_err)
+    # ── Results Treeview population ────────────────────────────────
 
-    # ── Treeview population ────────────────────────────────────────
-
-    def _populate_tree(self, columns: list[str], rows: list[list]):
-        """Clear and populate the Treeview with query results."""
-        self._tree.delete(*self._tree.get_children())
+    def _populate_results(self, columns: list[str], rows: list[list]):
+        """Clear and populate the results Treeview."""
+        self._results_tree.delete(*self._results_tree.get_children())
 
         if not columns:
-            self._tree["columns"] = ()
+            self._results_tree["columns"] = ()
             return
 
-        self._tree["columns"] = columns
+        self._results_tree["columns"] = columns
         for col in columns:
-            self._tree.heading(col, text=col, anchor="w")
-            self._tree.column(col, width=120, minwidth=60, anchor="w")
+            self._results_tree.heading(col, text=col, anchor="w")
+            self._results_tree.column(col, width=120, minwidth=60, anchor="w")
 
         for row in rows:
             display = [str(v) if v is not None else "NULL" for v in row]
-            self._tree.insert("", "end", values=display)
+            self._results_tree.insert("", "end", values=display)
 
     def _clear_results(self):
-        """Remove all rows and columns from the Treeview."""
-        self._tree.delete(*self._tree.get_children())
-        self._tree["columns"] = ()
+        self._results_tree.delete(*self._results_tree.get_children())
+        self._results_tree["columns"] = ()
         self._columns = []
         self._results = []
 
     # ── Button actions ─────────────────────────────────────────────
 
     def _clear_all(self):
-        """Clear editor content and results."""
         self._editor.delete("0.0", "end")
         self._clear_results()
         self._set_status("")
 
     def _export_csv(self):
-        """Export current results to a CSV file via save dialog."""
         if not self._columns or not self._results:
             return
 
@@ -334,9 +708,3 @@ class QueryTab(ctk.CTkFrame):
     def _set_status(self, text: str, error: bool = False):
         color = "#ef4444" if error else "#9ca3af"
         self._status_label.configure(text=text, text_color=color)
-
-    # ── Thread-safe scheduling ─────────────────────────────────────
-
-    def _schedule(self, func, *args, **kwargs):
-        """Schedule a function to run on the main (tkinter) thread."""
-        self.after(0, lambda: func(*args, **kwargs))

version.py

@@ -1,6 +1,6 @@
 """Version info for ServerManager."""
 
-__version__ = "1.8.53"
+__version__ = "1.8.56"
 __app_name__ = "ServerManager"
 __author__ = "aibot777"
 __description__ = "Desktop GUI for managing remote servers"