Question

I have a LINQ to SQL query that is something like the following…

return from parent in Context.Parents
       where 
       (
          (parent.SomeProperty != null && parent.SomeProperty != "")
          ||
          (Context.Childs.Count(c => c.ParentID == parent.ID && c.Type == "SomeType") > 0)
       )
       select parent

The idea is that I want to find all the parent records that have either got a value for “SomeProperty” or that have some child records of type “SomeType”.

The problem is that the query is timing out. Is there a quicker (but still easy to read) way of doing the same thing?

Thanks for reading.

Answer 1

Use Any() instead of Count():

return from parent in Context.Parents
       where 
       (
          (parent.SomeProperty != null && parent.SomeProperty != "")
          ||
          Context.Childs.Any(c => c.ParentID == parent.ID 
                                  && c.Type == "SomeType")
       )
       select parent;

In Linq to SQL Count(<some condition>) is translated into:

SELECT COUNT(*) WHERE <some condition>

query which requires iterating over all rows in the database to find the count.

In Linq to SQL Any(<some condition>) is translated to a

EXISTS (.. <some condition>)

subquery which allows short circuiting the result once the first match is found.

The exact SQL mapping can be found in this SO answer: query result what should i use Count() or Any()