parallel street-view fetch; thread-local ro connections

app.py

@@ -262,28 +262,51 @@ def render(scene_id: str, show_road_path: bool) -> Tuple[Optional[Image.Image],
 
 
 def node_gallery(scene_id: str) -> List[Tuple[str, str]]:
+    """取本场景每个节点的一张街景。
+
+    数据集模式下每张图都要走一次 CDN，串行拉 38 张要等半分钟。
+    并行拉——单张仍是那个延迟，但总时长压到接近单张。
+    """
     det = load_scene(scene_id)
     if det is None:
         return []
-    out = []
     city = det["scene"]["city"]
     folder = PACKAGE / "ground" / city
-    for n in det["nodes"]:
+
+    def fetch(n: Dict[str, Any]) -> Optional[Tuple[str, str]]:
         cap = (f"{n['label']} · {n['corridor_name'] or '无走廊'}"
                + (" · 孤儿" if n["is_orphan"] else ""))
-        # 街景文件名带朝向，本地包直接 glob；数据集模式下朝向未知，
-        # 逐个试常见朝向取第一张命中的
         if folder.is_dir():
-            hits = sorted(folder.glob(f"{city},{n['panoid']},*.webp"))
+            hits = sorted(folder.rglob(f"{city},{n['panoid']},*.webp"))
             if hits:
-                out.append((str(hits[0]), cap))
-                continue
+                return (str(hits[0]), cap)
         rel = ground_rel(n)
-        if rel:
-            p = asset(rel)
-            if p:
-                out.append((str(p), cap))
-    return out
+        if not rel:
+            return None
+        p = asset(rel)
+        return (str(p), cap) if p else None
+
+    from concurrent.futures import ThreadPoolExecutor
+    with ThreadPoolExecutor(max_workers=12) as ex:
+        got = list(ex.map(fetch, det["nodes"]))
+    return [g for g in got if g]
+
+
+_TLS = __import__("threading").local()
+
+
+def ro_con() -> sqlite3.Connection:
+    """每个线程一个只读连接。
+
+    sqlite3 的连接默认不允许跨线程用，而街景是并行拉的——共用一个连接
+    会抛 ProgrammingError。
+    """
+    c = getattr(_TLS, "con", None)
+    if c is None:
+        c = sqlite3.connect(f"file:{DB}?mode=ro", uri=True)
+        c.row_factory = sqlite3.Row
+        _TLS.con = c
+    return c
 
 
 def ground_rel(node: Dict[str, Any]) -> Optional[str]:
@@ -292,7 +315,7 @@ def ground_rel(node: Dict[str, Any]) -> Optional[str]:
     打包时写了一张 pano -> 文件名 的索引，因为文件名里有 alt/year/heading
     三个字段是数据库里没有的，猜不出来。
     """
-    row = con().execute(
+    row = ro_con().execute(
         "SELECT rel FROM ground_index WHERE panoid = ? LIMIT 1",
         (node["panoid"],)).fetchone()
     return row[0] if row else None