The following is a true anecdote of an actual event, that happened to have a happy ending. It should not be taken as rational for not visiting a vet should you encounter this situation.
Many years ago, when money was very tight, I had a rescued Bullmastiff, living with me way out in the country. She had a habit of swallowing whole any bits of food that might accidentally come her way. She was well feed, with 'free choice' (all you can eat when ever you want) dry dog food.
We were eating full ears of corn on the cob (6-8 inches long as I recall) while one of the cobs was it's way to the compost pile she grabbed one and swallowed it whole without chewing. It was not in her throat long enough to be a chocking hazard. Lips to belly transit time was like 1 second.
The first day or so she was seemed healthy and fine, the second day she seemed to have a bit of a belly ache, the morning of the third day she seem to be feeling a bit worse. Later on the third day she passed the corn cob undigested and still whole. The morning of the forth day, she appeared fully recovered. As far as I could tell there were no adverse side effects from this event.
This was a 100 pound (50kg) plus dog. Again I am not recommending you do not visit a vet should you encounter this scenario. At the time veterinary intervention for this event was financially impossible.
Edit My in-laws recently a very different experience, with a 50 pound (25kg) lab. Their experience was very similar to Suzie's answer here