Merge branch '4.0' of github.com:top-think/think-orm into 4.0

Author: liu21st

src/db/Mongo.php

@@ -536,6 +536,16 @@ public function getPk()
         return $this->pk ?: $this->connection->getConfig('pk');
     }
 
+    /**
+     * 执行查询但只返回Cursor对象
+     *
+     * @return Cursor
+     */
+    public function cursor(): Cursor
+    {
+        return $this->getCursor();
+    }
+    
     /**
      * 执行查询但只返回Cursor对象
      *
@@ -545,7 +555,7 @@ public function getCursor(): Cursor
     {
         $this->parseOptions();
 
-        return $this->connection->getCursor($this);
+        return $this->connection->cursor($this);
     }
 
     /**
@@ -637,6 +647,9 @@ public function chunk(int $count, callable $callback, $column = null, string $or
                 [$alias, $key] = explode('.', $column);
             } else {
                 $key = $column;
+                if ($key == '_id' && $this->connection->getConfig('pk_convert_id')) {
+                    $key = 'id';
+                }
             }
         }