When querying a large table where you need to access the navigation properties later on in code (I explicitly don't want to use lazy loading) what will perform better
.Load()? Or why use the one over the other?
In this example the included tables all only have about 10 entries and employees has about 200 entries, and it can happen that most of those will be loaded anyway with include because they match the where clause.
Context.Measurements.Include(m => m.Product) .Include(m => m.ProductVersion) .Include(m => m.Line) .Include(m => m.MeasureEmployee) .Include(m => m.MeasurementType) .Where(m => m.MeasurementTime >= DateTime.Now.AddDays(-1)) .ToList();
Context.Products.Load(); Context.ProductVersions.Load(); Context.Lines.Load(); Context.Employees.Load(); Context.MeasurementType.Load(); Context.Measurements.Where(m => m.MeasurementTime >= DateTime.Now.AddDays(-1)) .ToList();
Include(), you get the benefit of loading all of your data in a single call to the underlying data store. If this is a remote SQL Server, for example, that can be a major performance boost.
The downside is that
Include() queries tend to get really complicated, especially if you have any filters (
Where() calls, for example) or try to do any grouping. EF will generate very heavily nested queries using sub-
APPLY statements to get the data you want. It is also much less efficient -- you get back a single row of data with every possible child-object column in it, so data for your top level objects will be repeated a lot of times. (For example, a single parent object with 10 children will product 10 rows, each with the same data for the parent-object's columns.) I've had single EF queries get so complex they caused deadlocks when running at the same time as EF update logic.
Load() method is much simpler. Each query is a single, easy, straightforward
SELECT statement against a single table. These are much easier in every possible way, except you have to do many of them (possibly many times more). If you have nested collections of collections, you may even need to loop through your top level objects and
Load their sub-objects. It can get out of hand.
Try to avoid having any more than three
Include calls in a single query. I find that EF's queries get too ugly to recognize beyond that; it also matches my rule-of-thumb for SQL Server queries, that up to four JOIN statements in a single query works very well, but after that it's time to consider refactoring.
However, all of that is only a starting point.
It depends on your schema, your environment, your data, and many other factors.
In the end, you will just need to try it out each way.
Pick a reasonable "default" pattern to use, see if it's good enough, and if not, optimize to taste.
Include() will be written to SQL as
JOIN: one database roundtrip.
Load()-instruction is "explicitly loading" the requested entities, so one database roundtrip per call.
Include() will most probably be the more sensible choice in this case, but it depends on the database layout, how often this code is called and how long your
DbContext lives. Why don't you try both ways and profile the queries and compare the timings?