I've been recently looking into my web app performance and found some LINQ queries that I'm not sure if changing them would improve performance.
Basically the current code looks like:
var result = _carsRepository.GetAll()
.Where(x => x.Name == input.Name)
.FirstOrDefault();
if (result != null)
{
throw new Exception("test");
}
I'm thinking of changing it to:
var result = _carsRepository.GetAll()
.Where(x => x.Name == input.Name)
.Any();
if (result)
{
throw new Exception("test");
}
In my understanding the first query would return an actual entity, which I don't need because I only want to know whether the record with the same name already exists in the database. The second query returns just a bool.
I'd be thankful for any comments.
EDIT: I could be running the query on EF db context, so please ignore that. The current repository is a generic Abp.Domian.Repository. GetAll() returns IQueryable
I'm not sure what GetAll()
does. If it moves all items from your database to your local memory, then I wouldn't bother: try to improve that statement. Why fetch all items if you only need the first one.
If GetAll()
returns an IQueryable<...>
, then there is a slight difference:
FirstOrDefault()
will change the Expression in the query, such that the SQL statement will be Select top 1 ... from
.
After changing the expression it will ask the Provider
of the IQqueryable
to execute the Expression
, the complete result of the SQL statement will b transferred to local memory, which in this case will be one item.
Any()
will almost do the same, except that the SQL will be: Select top 1 1 from ...
It is easy to see that a Select top 1 1
will at utmost transfer one integer, while Select top 1
will transfer all selected columns.
Hence, if you only want to check if there are any elements, Any()
is more efficient then FirstOrDefault
There could be a slight difference because of
.FirstOrDefault()
- Reads all the columns
.Any()
- Just check if there are entries
Difference will be mostly based on data size and SQL structure, indexes and all. Recommend to benchmark them by testing