Question

Assume the following table MyObjects:

Id (PK, int)
DecimalField (decimal)
TextField (nvarchar)

I have put an additional index on DecimalField.

Consider the following LINQ to Entities query to retrieve an object:

db.MyObjects.FirstOrDefault(r => r.DecimalField == localValue1 && r.TextField == localValue2)

Because of the index, it is important that the EF-generated query keeps the order of the properties in the WHERE clause the same (i.e. DecimalField first and TextField second), otherwise a table scan will occur and the index is useless. How can I enforce EF to keep a certain order in the WHERE clause? And is there a difference between ad hoc and compiled queries?

Answer 1

No, the order of where clause predicates does not matter. SQL Server will use the appropriate index if there is one, even if your where clause specifies the columns in a different order than they appear in the index.