cursor.isExhausted()

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cursor.isExhausted()

mongo Shell Method

This page documents the mongo shell method, and does not refer to the MongoDB Node.js driver (or any other driver) method. 本页记录了mongo shell方法，未提及MongoDB Node.js驱动程序（或任何其他驱动程序）方法。For corresponding MongoDB driver API, refer to your specific MongoDB driver documentation instead.有关相应的MongoDB驱动程序API，请参阅特定的MongoDB驱动程序文档。

Returns:Boolean.

cursor.isExhausted() returns true if the cursor is closed and there are no remaining objects in the batch.如果游标已关闭且批处理中没有剩余对象，则cursor.isExhausted()返回true。

Use isExhausted() to support iterating cursors that remain open even if there are no documents remaining in the current batch, such as tailable or change stream cursors.使用isExhausted()支持迭代即使当前批处理中没有剩余文档也保持打开状态的游标，例如tailable游标或change stream游标。

Example示例

Consider the following while loop iterating through updates to a change stream cursor:请考虑以下的while循环，迭代变了对change stream游标的更新：

watchCursor = db.collection.watch();

while (watchCursor.hasNext()) {
   watchCursor.next();
}

A change stream cursor can return an empty batch if no new data changes have occured within a set period of time. 如果在设定的时间段内没有发生新的数据更改，则更改流游标可以返回空批。This causes the while loop to exit prematurely as cursor.hasNext() returns false when it detects the empty batch. 这会导致while循环过早退出，因为cursor.hasNext()在检测到空批时返回false。However, the change stream cursor is still open and able to return more documents in the future.但是，变更流游标仍然处于打开状态，将来可以返回更多文档。

Use cursor.isExhausted() to ensure the while loop only exits when the cursor is closed and there are no documents remaining in the batch:使用cursor.isExhausted()确保while循环仅在游标关闭且批处理中没有剩余文档时退出：

watchCursor = db.collection.watch();

while (!watchCursor.isExhausted()) {
   if (watchCursor.hasNext()){
      watchCursor.next();
   }
}