Re: ODBC parallel query performance issue using C++

[Bogdan Degtyariov]

There is no limit for the number of threads in ODBC. You can run as many as you like.

It is possible that the bottle neck for the performance is somewhere else. It could be the network bandwidth if the server is running remotely. It could be the MySQL server performance, which depends on many factors. For instance, if each thread inserts large amounts of data in the database the performance can degrade because of disk I/O on the server host or less than optimal configuration of the server.

Depending on the client code the ODBC system can also be a subject to slowing down with many concurrent threads. For instance: the ENVIRONMENT handle for ODBC registers and unregisters new connections. Each such operation is protected by a mutex, which after some number of concurrent requests can cause delays for other threads and make them wait until the operation is completed. This is just one example of how it might happen.

My point is that when something like that happens it is a good idea to try using profiling tools to see where exactly the main delays occur.