One of the most expensive operations that we can do in our applications is to make a remote call. Going beyond our own process is an extremely expensive operation. Going beyond the local machine is more expensive still.
Calling the database, whether to query or to write, is a remote call, and we want to reduce the number of remote calls as much as possible. This warning is raised when the profiler notices that a single request is making an excessive number of calls to the database. This is usually an indication of a potential optimization in the way the sessions are used in the request.
There are several reasons why this can be:
- A large number of queries as a result of a Select N + 1
- Calling the database in a loop
- Updating (or inserting / deleting) a large number of entities
- A large number of (different) queries that we execute to perform our task
For the first reason, you can see the suggestions for Select N + 1.
Calling the database in a loop is generally a bug, and should be avoided. Usually you can restructure the code in such a way that you are not required to call the database in that way.
The last two issues have to be dealt with on an individual basis. Sometimes, using a different approach (such as bulk copy for batching inserts) or a specific query or stored procedure that will get all the data from the database in a single round trip.