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How to improve the performance of Entity Framework Code?

In the project, I need to call an external API based on time. So, for one day, I may need to call the API 24 times, one call for one hour period. The API result is a XML file which has 6 fields. I will need to insert these data into a table. Averagely, for each hour, it has about 20,000 rows data.
The table has these 6 columns:
col1, col2, col3, col4, col5, col6
When all 6 columns are the same, we consider the rows are the same, and we should not insert duplications.
I'm using C# and Entity Framework for this:
foreach (XmlNode node in nodes)
{
try
{
count++;
CallData data = new CallData();
...
// get all data and set in 'data'
// check whether in database already
var q = ctx.CallDatas.Where(x => x.col1 == data.col1
&& x.col2 == data.col2
&& x.col3 == data.col3
&& x.col4 == data.col4
&& x.col5 == data.col5
&& x.col6 == data.col6
).Any();
if (q)
{
// exists in database, skip
// log info
}
else
{
string key = $"{data.col1}|{data.col2}|{data.col3}|{data.col4}|{data.col5}|{data.col6}";
// check whether in current chunk already
if (dic.ContainsKey(key))
{
// in current chunk, skip
// log info
}
else
{
// insert
ctx.CallDatas.Add(data);
// update dic
dic.Add(key, true);
}
}
}
catch (Exception ex)
{
// log error
}
}
Logger.InfoFormat("Saving changes ...");
if (ctx.ChangeTracker.HasChanges())
{
await ctx.SaveChangesAsync();
}
Logger.InfoFormat("Saving changes ... Done.");
The code works fine. However, we will need to use this code to run for past several months. The issue is: the code runs slow since for each row it will need to check whether it exists already.
Is there any suggestions to improve the performance?
Thanks

You don't show the code on when the context is created or the life-cycle. I'm inclined to point you to your indexes on the table. If these aren't primary keys then you might see the performance issue there. If you are doing full table scans, it will be progressively slower. With that said, there are two separate ways to handle the
The EF Native way: You can explicitly create a new connection on each interaction (avoiding change tracking for all entries reducing progressive slowdown). Also, your save is async but your *Any statement is sync. Using async for that as well might help take some pressure off the current thread if it's waiting.
// Start your context scope closer to the data call, as if the look is long
// running you could be building up tracked changes in the cache, this prevents
// that situation.
using (YourEntity ctx = new YourEntity())
{
CallData data = new CallData();
if (await ctx.CallDatas.Where(x => x.col1 == data.col1
&& x.col2 == data.col2
&& x.col3 == data.col3
&& x.col4 == data.col4
&& x.col5 == data.col5
&& x.col6 == data.col6
).AnyAsync()
)
{
// exists in database, skip
// log info
}
else
{
string key = $"{data.col1}|{data.col2}|{data.col3}|{data.col4}|{data.col5}|{data.col6}";
// check whether in current chunk already
if (dic.ContainsKey(key))
{
// in current chunk, skip
// log info
}
else
{
// insert
ctx.CallDatas.Add(data);
await ctx.SaveChangesAsync();
// update dic
dic.Add(key, true);
}
}
}
Optional Way: Look into inserting the data using a bulk operation via store procedure. 20k rows is trivial, and you can still use entity framework for that as well. See https://stackoverflow.com/a/9837927/1558178
I have created my own version of this (customized for my specific needs) and have found that it works well and give more control for bulk inserts.
I have used this ideology to insert 100k records at a time. I have my logic in the stored procedure for checking for duplicates which gives me better control as well as reducing the over the wire call to 0 reads and 1 write. This should just take a second or two to execute assuming your stored procedure is optimized.

Different approach:
Save all rows with duplicates - should be very efficient
When you use data from the table use DISTINCT for all fields.

For raw, bulk operations like this I would consider avoiding EF entities and context tracking and merely execute SQL through the context:
var sql = $"IF NOT EXISTS(SELECT 1 FROM CallDates WHERE Col1={data.Col1} AND Col2={data.Col2} AND Col3={data.Col3} AND Col4={data.Col4} AND Col5={data.Col5} AND Col6={data.Col6}) INSERT INTO CallDates(Col1,Col2,Col3,Col4,Col5,Col6) VALUES ({data.Col1},{data.Col2},{data.Col3},{data.Col4},{data.Col5},{data.Col6})";
context.Database.ExeculeSqlCommand(sql);
This does without the extra checks and logging, just effectively raw SQL with duplicate detection.

C# EF / LINQ hack fix hitting perfomance? Other way of fixing?

I've been learning C# / LINQ / ASP.NET / MVC 3 / EF for a few months now comming from Java / Icefaces / Ibatis base (Real world uses .NET D;). I really enjoy LINQ / Entity Framework from the .NET Framework but I'm having a few issues understand what's really happening behind the scenes.
Here's my problem:
I'm using a AJAX / JSON fed jQuery datatable (that I highly recommend to anyone in need of a free web datatable system by the way). I have a method in my MVC3 application that returns a JSON result of the data needed by the table, doing the sorting and all. Everything is working nicely and smoothly. However, I'm having a concern with the "dirty" hack I had to do to make this work.
Here's the complete code:
//inEntities is the Entity Framework Database Context
//It includes the following entities:
// Poincon
// Horaire
// HoraireDetail
//Poincon, Horaire and HoraireDetail are "decorated" using the Metadata technic which
//adds properties methods and such to the Entity (Like getEmploye which you will see in
//the following snippet)
//
//The Entity Employe is not a database data and therefor not handled by the EF.
//Instead, it is a simple object with properties that applies Lazy Loading to get an
//Employe Name based off of his Employe ID in the Active Directory. An employe object
//can be constructed with his Employe ID which will expose the possibility of getting
//the Employe Name from the AD if needed.
[HttpPost]
public JsonResult List(FormCollection form)
{
String sEcho;
int iDisplayStart;
int iDisplayLength;
String sSearch;
int iSortingCols;
Dictionary<String, String> sorting;
try
{
sEcho = form["sEcho"];
iDisplayStart = int.Parse(form["iDisplayStart"]);
iDisplayLength = int.Parse(form["iDisplayLength"]);
sSearch = form["sSearch"];
iSortingCols = int.Parse(form["iSortingCols"]);
sorting = new Dictionary<string,string>();
for (int i = 0; i < iSortingCols; i++)
sorting.Add(form["mDataProp_" + form["iSortCol_" + i]].ToUpper(), form["sSortDir_" + i].ToUpper());
}
catch
{
HttpContext.Response.StatusCode = 500;
return null;
}
var qPoincon = inEntities.Poincons.AsEnumerable();
var lPoincon = qPoincon.Select(o => new
{
o.id,
emp = o.getEmploye(),
o.poinconStart,
o.poinconEnd,
o.commentaire,
o.codeExceptions
}).AsEnumerable();
//Search
lPoincon = lPoincon.Where(p => (p.emp.empNoStr.Contains(sSearch) || p.emp.empNom.Contains(sSearch) || (p.commentaire != null && p.commentaire.Contains(sSearch))));
//Keep count
int iTotalDisplayRecords = lPoincon.Count();
//Sorting
foreach(KeyValuePair<String,String> col in sorting)
{
switch (col.Key)
{
case "EMPNO":
if (col.Value == "ASC")
lPoincon = lPoincon.OrderBy(h => h.emp.empNo);
else
lPoincon = lPoincon.OrderByDescending(h => h.emp.empNo);
break;
case "POINCONSTART":
if (col.Value == "ASC")
lPoincon = lPoincon.OrderBy(h => h.poinconStart);
else
lPoincon = lPoincon.OrderByDescending(h => h.poinconStart);
break;
case "POINCONEND":
if (col.Value == "ASC")
lPoincon = lPoincon.OrderBy(h => h.poinconEnd);
else
lPoincon = lPoincon.OrderByDescending(h => h.poinconEnd);
break;
case "COMMENTAIRE":
if (col.Value == "ASC")
lPoincon = lPoincon.OrderBy(h => h.commentaire);
else
lPoincon = lPoincon.OrderByDescending(h => h.commentaire);
break;
}
}
//Paging
lPoincon = lPoincon.Skip(iDisplayStart).Take(iDisplayLength);
//Building Response
var jdt = new
{
iTotalDisplayRecords = iTotalDisplayRecords,
iTotalRecords = inEntities.Poincons.Count(),
sEcho = sEcho,
aaData = lPoincon
};
return Json(jdt);
}
As you can see, when I'm grabbing the entire list of "Poincons" from the EF and turning it into a Enumerable. From my current understanding, turning the LINQ query into a Enumerable "kills" the link to the EF, or in other words, will generate the SQL required to get that list at that point instead of keeping the LINQ data until the end and execute a percise query that will return only the data you require. After turning this LINQ Query into a Enumerable, I'm heavily filtering the LINQ (since there is paging, sorting, searching in the datatable). This leads me to thinkg that what my code is currently doing is "Grab all the "Poincons" from the database and put it into the web server's memory as a Enumerable, do your work with the Enumerable then serialize the result as a JSON string and send it to the client.
If I'm correct, the performance hit is quite heavy when you hit the couple thousand of entries (which will happen quite fast once in production... everytime an employe comes to work, it will add 1 entry. 100 employes, ~300 work days a year, you get the idea).
The reason for this hack is that the EF does not know what "getEmploye" method of "Poincon" is, therefor throwing an exception at runtime similar to this:
LINQ to Entities ne reconnaît pas la méthode « PortailNorclair.Models.Employe getEmploye() », et cette dernière ne peut pas être traduite en expression de magasin.
Approximated traduction (If anyone can let me know in a comment how to configure IIS / ASP.NET to display errors in english while keeping the globalization in a foreign language, I would be really grateful. French information about error messages is sometimes lacking):
LINQ to Entity does not recognize the method " PortailNorclair.Models.Employe getEmploye()" and the following could not be translated to a SQL expression.
The "getEmploye" method instances and returns a Employe object with the employe id found in the Poincon object. That Employe object has properties that "lazy loads" information like the employe name from the Active Directory.
So the question is: How can I avoid the performance hit from using .AsEnumerable() on the non-filtered list of objects?
Thanks a lot!

The "getEmploye" method instances and returns a Employe object with
the employe id found in the Poincon object. That Employe object has
properties that "lazy loads" information like the employe name from
the Active Directory.
You should be storing the Employee Name in the database, so you can then order, sort, skip and take in your Linq Query without having to load every employee object.
If empNoStr, empNom, and empNo were all in the database, you could retrieve just the records you want, and call getEmploye() (loading whatever else you need from active directory, or wherever) for each of those.

There are some classes on which your program performs its main work.
There are other classes which represent to database rows.
If you keep them separated, you can also separate actions you intend to occur in the database from actions you intend to perform locally. This makes it trivial to avoid loading the full table, when specific rows are required.
I see you're also doing Paging locally, while the database can do that and save your webserver some memory.

Multiple SELECT in NHibernate native SQL

I create a complex search query in native SQL. It's basically something like this:
SELECT ID FROM t_Product WHERE Name LIKE #criteria
SELECT publisher, count(*) as number FROM t_Product GROUP BY publisher
It has 2 SELECT statements and I want it to be sent to DB server in one round trip.
But I can't figure out how to achieve this in Nhibernate.
I considered following options but none seems to work
Use CreateMultiQuery, but this only accept HQL, not native SQL
Use CreateSQLQuery, but call to List() only return result for the first SELECT statement
Moving to a stored procedure is not an option since the whole SQL is very dynamic.
We still use Nhibernate 1.2 thus new features in later version couldn't be used either.
Advice are welcome.

Not possible using NH version 1.2
Futures was released in version 2.1 which allows you to do exactly this.
e.g.
var blogs = s.CreateCriteria<Invoice>()
.SetMaxResults(30)
.Future<Invoice>();
var countOfInvoices = s.CreateCriteria<Invoice>()
.SetProjection(Projections.Count(Projections.Id()))
.FutureValue<int>();
So you are going to either upgrade, fall back to ADO.NET and use multiple recordsets or live with what you have! Sorry!

This is really going to be scenario-specific, but if you're stuck with NH Version 1.2, and eliminating the round-trip is your goal, you could consider rewriting this as a single query using a sub-select.
Something along the lines of:
SELECT publisher, count(*) as number,
(SELECT ID FROM t_Product WHERE Name LIKE #criteria) As theId
FROM t_Product GROUP BY publisher
Would work if your subquery only returned a single value.

I don't think that it is possible, because both queries are SELECTs.
You may try a semicolon after the first query, and two line feeds between them, this is required for some databases. I successfully run query-scripts like this. If it runs, use a debugger to see what you get back ...
If this doesn't work, you need separate round trips or switch to HQL / Criteria.

You can use MultiQuery "Hack" like this:
The procudure:
CREATE PROCEDURE [dbo].[proc_Name]
AS BEGIN
SELECT * FROM t_Question where ...
SELECT * FROM t_Question where ........
END
The NHibernate Query Code:
public void ProcdureMultiTableQuery()
{
var session = Session;
var procSQLQuery = session.CreateSQLQuery("exec [proc_Name] ?,?");// prcodure returns two table
procSQLQuery.SetParameter(0, userId);
procSQLQuery.SetParameter(1, page);
procSQLQuery.AddEntity(typeof(Question));
var multiResults = session.CreateMultiQuery()
.Add(procSQLQuery)
// More table your procedure returns,more empty SQL query you should add
.Add(session.CreateSQLQuery(" ").AddEntity(typeof(Question))) // the second table returns Question Model
.List();
if (multiResults == null || multiResults.Count == 0)
{
return;
}
if (multiResults.Count != 2)
{
return;
}
var questions1 = ConvertObjectsToArray<Question>((System.Collections.IList)multiResults[0]);
var questions2 = ConvertObjectsToArray<Question>((System.Collections.IList)multiResults[1]);
}
static T[] ConvertObjectsToArray<T>(System.Collections.IList objects)
{
if (objects == null || objects.Count == 0)
{
return null;
}
var array = new T[objects.Count];
for (int i = 0; i < array.Length; i++)
{
array[i] = (T)objects[i];
}
return array;
}

Bulk inserts and duplicate records with LINQ to SQL

Is there a "best practice" way of handling bulk inserts (via LINQ) but discard records that may already be in the table? Or I am going to have to either do a bulk insert into an import table then delete duplicates, or insert one record at a time?
08/26/2010 - EDIT #1:
I am looking at the Intersect and Except methods right now. I am gathering up data from separate sources, converting into a List, want to "compare" to the target DB then INSERT just the NEW records.
List<DTO.GatherACH> allACHes = new List<DTO.GatherACH>();
State.IState myState = null;
State.Factory factory = State.Factory.Instance;
foreach (DTO.Rule rule in Helpers.Config.Rules)
{
myState = factory.CreateState(rule.StateName);
List<DTO.GatherACH> stateACHes = myState.GatherACH();
allACHes.AddRange(stateACHes);
}
List<Model.ACH> newRecords = new List<Model.ACH>(); // Create a disconnected "record set"...
foreach (DTO.GatherACH record in allACHes)
{
var storeInfo = dbZach.StoreInfoes.Where(a => a.StoreCode == record.StoreCode && (a.TypeID == 2 || a.TypeID == 4)).FirstOrDefault();
Model.ACH insertACH = new Model.ACH
{
StoreInfoID = storeInfo.ID,
SourceDatabaseID = (byte)sourceDB.ID,
LoanID = (long)record.LoanID,
PaymentID = (long)record.PaymentID,
LastName = record.LastName,
FirstName = record.FirstName,
MICR = record.MICR,
Amount = (decimal)record.Amount,
CheckDate = record.CheckDate
};
newRecords.Add(insertACH);
}
The above code builds the newRecords list. Now, I am trying to get the records from this List that are not in the DB by comparing on the 3 field Unique Index:
AchExceptComparer myComparer = new AchExceptComparer();
var validRecords = dbZach.ACHes.Intersect(newRecords, myComparer).ToList();
The comparer looks like:
class AchExceptComparer : IEqualityComparer<Model.ACH>
{
public bool Equals(Model.ACH x, Model.ACH y)
{
return (x.LoanID == y.LoanID && x.PaymentID == y.PaymentID && x.SourceDatabaseID == y.SourceDatabaseID);
}
public int GetHashCode(Model.ACH obj)
{
return base.GetHashCode();
}
}
However, I am getting this error:
LINQ to Entities does not recognize the method 'System.Linq.IQueryable1[MisterMoney.LARS.ZACH.Model.ACH] Intersect[ACH](System.Linq.IQueryable1[MisterMoney.LARS.ZACH.Model.ACH], System.Collections.Generic.IEnumerable1[MisterMoney.LARS.ZACH.Model.ACH], System.Collections.Generic.IEqualityComparer1[MisterMoney.LARS.ZACH.Model.ACH])' method, and this method cannot be translated into a store expression.
Any ideas? And yes, this is completely inline with the original question. :)

You can't do bulk inserts with LINQ to SQL (I presume you were referring to LINQ to SQL when you said "LINQ"). However, based on what you're describing, I'd recommend checking out the new MERGE operator of SQL Server 2008.
Inserting, Updating, and Deleting Data by Using MERGE
Another example here.

I recommend you just write the SQL yourself to do the inserting, I find it is a lot faster and you can get it to work exactly how you want it to. When I did something similar to this (just a one-off program) I just used a Dictionary to hold the ID's I had inserted already, to avoid duplicates.
I find LINQ to SQL is good for one record or a small set that does its entire lifespan in the LINQ to SQL.
Or you can try to use SQL Server 2008's Bulk Insert .

One thing to watch out for is if you queue more than 2000 or so records without calling SubmitChanges() - TSQL has a limit on the number of statements per execution, so you cannot simply queue up every record and then call SubmitChanges() as this will throw an SqlException, you need to periodically clear the queue to avoid this.

Linq update query - Is there no pretty way?

I want to update my database using a LINQ2SQL query.
However this seems for some reason to be a very ugly task compared to the otherwise lovely LINQ code.
The query needs to update two tables.
tbl_subscription
(
id int,
sub_name nvarchar(100),
sub_desc nvarchar(500),
and so on.
)
tbl_subscription2tags
(
sub_id (FK to tbl_subscription)
tag_id (FK to a table called tbl_subscription_tags)
)
Now down to my update function a send a tbl_subscription entity with the tags and everything.
I can't find a pretty way to update my database..
I can only find ugly examples where I suddenly have to map all attributes..
There most be a smart way to perform this. Please help.
C# Example if possible.
I have tried this with no effect:
public void UpdateSubscription(tbl_subscription subscription)
{
db.tbl_subscriptions.Attach(subscription);
db.Refresh(System.Data.Linq.RefreshMode.OverwriteCurrentValues, subscription);
db.SubmitChanges(System.Data.Linq.ConflictMode.FailOnFirstConflict);
}
Source for this code is here:
http://skyeyefive.spaces.live.com/blog/cns!6B6EB6E6694659F2!516.entry

Why don't just make the changes to the objects and perform a SubmitChanges to the DataContext?
using(MyDataContext dc = new MyDataContext("ConnectionString"))
{
foreach(var foo in dc.foo2)
{
foo.prop1 = 1;
}
dc.SubmitChanges();
}
Otherwise you need to tell us more about the lifecycle of the object you want to manipulate
edit: forgot to wrap in brackets for using

Unless I'm misunderstanding your situation, I think that citronas is right.
The best and easiest way that I've found to update database items through LINQ to SQL is the following:
Obtain the item you want to change from the data context
Change whatever values you want to update
Call the SubmitChanges() method of the data context.
Sample Code
The sample code below assumes that I have a data context named DBDataContext that connects to a database that has a Products table with ID and Price parameters. Also, a productID variable contains the ID of the record you want to update.
using (var db = new DBDataContext())
{
// Step 1 - get the item from the data context
var product = db.Products.Where(p => p.ID == productID).SingleOrDefault();
if (product == null) //Error checking
{
throw new ArgumentException();
}
// Step 2 - change whatever values you want to update
product.Price = 100;
// Step 3 - submit the changes
db.SubmitChanges();
}

I found out that you can use "Attach" as seen in my question to update a table, but apparently not the sub tables. So I just used a few Attach and it worked without having to run through parameters!