Can you explain what is meant by the query partitioning method in working with databases?

Query Splitting in database work is an approach where a complex query is broken down into several simpler ones and executed in parts. This helps improve performance, reduce load on the database, and simplify data processing.

For example, instead of a large JOIN query, you can first retrieve a list of keys from one table, and then perform separate queries to get related data. This approach is often used when complex queries are too slow or cause locking.

In C#, it might look like this:

var userIds = dbContext.Users.Where(u => u.IsActive).Select(u => u.Id).ToList();
var orders = dbContext.Orders.Where(o => userIds.Contains(o.UserId)).ToList();

Here, we first get active users, then separately retrieve their orders.