I am planning to create my own query cache. I will be looking up the query results from the cache using an MD5 hash of the query string. There will be tens of thousands of queries stored in the cache. What is the likelihood of two different query strings having the same MD5 hash?
The reason I ask is because to my knowledge MySQL's native query cache looks up cached results using the full query string, instead of using a hash of the query string (which would be faster and use less storage), and I wondered if this was due to potential hash conflicts.