read only operation 只读操作
Any read-only tree operation is thread-safe as long as there isn't any thread modifying it.
所有只读的树操作都是线程安全的，只要没有线程修改它。
In this example, the memcpy operation is trying to read 20 bytes from PTR, but it has been allocated only 10 bytes.
在本例中，memcpy操作尝试从ptr读取20个字节，但是后者仅被分配了10个字节。
The correct answer here is A. An exception will be thrown, indicating that you are trying to perform an update operation on a read-only connection.
会抛出一个异常，表示您正在试图对一个只读连接执行更新。
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