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  • Should I create a unique clustered index, or non-unique clustered index on this SQL 2005 table?

    - by Bremer
    I have a table storing millions of rows. It looks something like this: Table_Docs ID, Bigint (Identity col) OutputFileID, int Sequence, int …(many other fields) We find ourselves in a situation where the developer who designed it made the OutputFileID the clustered index. It is not unique. There can be thousands of records with this ID. It has no benefit to any processes using this table, so we plan to remove it. The question, is what to change it to… I have two candidates, the ID identity column is a natural choice. However, we have a process which does a lot of update commands on this table, and it uses the Sequence to do so. The Sequence is non-unique. Most records only contain one, but about 20% can have two or more records with the same Sequence. The INSERT app is a VB6 piece of crud throwing thousands insert commands at the table. The Inserted values are never in any particular order. So the Sequence of one insert may be 12345, and the next could be 12245. I know that this could cause SQL to move a lot of data to keep the clustered index in order. However, the Sequence of the inserts are generally close to being in order. All inserts would take place at the end of the clustered table. Eg: I have 5 million records with Sequence spanning 1 to 5 million. The INSERT app will be inserting sequence’s at the end of that range at any given time. Reordering of the data should be minimal (tens of thousands of records at most). Now, the UPDATE app is our .NET star. It does all UPDATES on the Sequence column. “Update Table_Docs Set Feild1=This, Field2=That…WHERE Sequence =12345” – hundreds of thousands of these a day. The UPDATES are completely and totally, random, touching all points of the table. All other processes are simply doing SELECT’s on this (Web pages). Regular indexes cover those. So my question is, what’s better….a unique clustered index on the ID column, benefiting the INSERT app, or a non-unique clustered index on the Sequence, benefiting the UPDATE app?

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  • What does DataContext.GetTable<TEntry> do?

    - by Bryan
    Consider I have a DataContext db, and there is an Entity class User. So when System.Data.Linq.Table<User> table = db.GetTable<User>(); is called for the first time, does it pull the data from the database immediately, does it use deferred execution, or were the data already loaded from database when db was initialized?

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  • Does Table.InsertOnSubmit create a copy of the original table?

    - by Bryan
    Using InsertOnSubmit seems to have some memory overhead. I have a System.Data.Linq.Table<User> table. When I do table.InsertOnSubmit(user) and then int count = table.Count(), the memory usage of my application increases by roughly the size of the User table, but the count is the number of items before user was inserted. So I'm guess an enumeration after InsertOnSubmit will create a copy of the table. Is that true?

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  • Repository Pattern: SaveOrUpdate() in Entity Framework and L2S

    - by JMSA
    These web articles uses separate Save() and Update() methods in the repository pattern. I am using repository pattern. How can I write a SaveOrUpdate() method in Entity Framework with the help of ObjectContext and in Linq-To-SQL with the help of DataContext? That is, how can I write a single method that shall do both save and update job?

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  • A few problems with Delphi involving Mail Merge, SQL + Databases.

    - by Daniel
    My first problem is with mail merge. I have created a a Data File and a table, yet I am not able to fill my table with information from my Data File. The << just seems to be inserted after wherever the cursor is on the page, which is not where the table is. All that is entered into the actual table is a '59'. Therefore I think I either need to to change the code or be able to move the cursor. Here is the code I am currently using: wrdDoc.Tables.Add(wrdSelection.Range, ADOTable1.FieldCount, 3); wrdDoc.Tables.Item(1).Columns.Item(1).SetWidth(51,wdAdjustNone); wrdDoc.Tables.Item(1).Columns.Item(2).SetWidth(20,wdAdjustNone); wrdDoc.Tables.Item(1).Columns.Item(3).SetWidth(100,wdAdjustNone); // Set the shading on the first row to light gray wrdDoc.Tables.Item(1).Rows.Item(1).Cells .Shading.BackgroundPatternColorIndex := wdGray25; // BOLD the first row wrdDoc.Tables.Item(1).Rows.Item(1).Range.Bold := True; // Center the text in Cell (1,1) wrdDoc.Tables.Item(1).Cell(1,1).Range.Paragraphs.Alignment := wdAlignParagraphCenter; // Fill each row of the table with data wrdDoc.Tables.Item(1).Cell(1, 1).Range.InsertAfter('Time'); wrdDoc.Tables.Item(1).Cell(1, 2).Range.InsertAfter(''); wrdDoc.Tables.Item(1).Cell(1, 3).Range.InsertAfter('Teacher'); For Count := 1 to (ADOTable1.FieldCount - 1) do begin wrdDoc.Tables.Item(1).Cell((Count + 1), 1).Range.InsertAfter(wrdSelection.Range,'Time' + IntToStr(Count)); wrdDoc.Tables.Item(1).Cell((Count + 1), 2).Range.InsertAfter(wrdSelection.Range,'THonorific' + IntToStr(Count)); wrdDoc.Tables.Item(1).Cell((Count + 1), 3).Range.InsertAfter(wrdSelection.Range,'TSurname' + IntToStr(Count)); end; My second problem is that I do not know what the correct SQL syntax is for editing the name of a column in the database (I am using Delphi 7 and Microsoft Jet Engine if that makes a difference). The third problem is that when I add a new column to my database manually (which I need to do) I get a 'violation' error in one of my units when I activate an ADOTable. This only happens on one unit and it happens when I add a column with any name anywhere in the table. I know that is vague but I can't seem to narrow down the problem any further than that. If you could help with me with any of those it would be great. Thanks.

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  • Looping over ILookup, accessing values

    - by Jono
    I've got a ILookup< string, List<CustomObject> > from some linq I've done. I'd like to now iterate over the results: foreach(IGrouping<string, List<CustomObject>> groupItem in lookupTable) { groupItem.Key; //You can access the key, but not the list of CustomObject } I know I must be misrepresenting a IGrouping as a KeyValuePair, but now I'm not sure how to access it properly.

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  • c# Lambda Expression built with LinqKit does not compile

    - by Frank Michael Kraft
    This lambda does not compile, but I do not understand why. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Linq.Expressions; using LinqKit; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { var barModel = new BarModel(); string id = "some"; Console.WriteLine(barModel.subFor(id).ToString()); // output: m => (True AndAlso (m.key == value(ConsoleApplication2.Bar`1+<>c__DisplayClass0[ConsoleApplication2.Model]).id)) Console.ReadKey(); var subworkitems = barModel.list.Where(barModel.subFor(id).Compile()); // Exception {"variable 'm' of type 'ConsoleApplication2.Model' referenced from scope '', but it is not defined"} Console.WriteLine(subworkitems.ToString()); Console.ReadKey(); } } class Bar<TModel> { public Bar(Expression<Func<TModel, string>> foreignKeyExpression) { _foreignKeyExpression = foreignKeyExpression; } private Expression<Func<TModel, string>> _foreignKeyExpression { get; set; } public Expression<Func<TModel, bool>> subFor(string id) { var ex = forTargetId(id); return ex; } public Expression<Func<TModel, bool>> forTargetId(String id) { var fc = _foreignKeyExpression; Expression<Func<TModel, bool>> predicate = m => true; var result = predicate.And(m => fc.Invoke(m) == id).Expand(); return result; } } class Model { public string key; public string value; } class BarModel : Bar<Model> { public List<Model> list; public BarModel() : base(m => m.key) { list = new List<Model>(); } } }

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  • Cannot convert lamda expression

    - by Kirsty White
    If I try: Groups = students.Remove(f => f.StudentID.Equals(studentID)); I get an error on this line: f => f.StudentID.Equals(studentID) I am having difficulty from my previous posts here linq deleted users still associated with groups and here Delete method in WCF So I thought maybe I could delete the students contained within groups but I get an error Cannot convert lamda expression to type Student because it is not a delegate type.

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  • Most suitable collection for multithreading requests?

    - by Raj Aththanayake
    I have ~10,000 records would like to keep in a collection in memory and execute LINQ queries against it. This collection should be available for all the users in the application domain and can access concurrently. I’m looking for a .NET collection that supports multithreading can query asynchronously and efficiently without any threading issues. Any suggestions on deciding a collection for this?

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  • Cast IEnumerable<Inherited> To IEnumerable<Base>

    - by david2342
    I'm trying to cast an IEnumerable of an inherited type to IEnumerable of base class. Have tried following: var test = resultFromDb.Cast<BookedResource>(); return test.ToList(); But getting error: You cannot convert these types. Linq to Entities only supports conversion primitive EDM-types. The classes involved look like this: public partial class HistoryBookedResource : BookedResource { } public partial class HistoryBookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } public partial class BookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } [MetadataType(typeof(BookedResourceMetaData))] public partial class BookedResource { } public class BookedResourceMetaData { [Required(ErrorMessage = "Resource id is Required")] [Range(0, int.MaxValue, ErrorMessage = "Resource id is must be an number")] public object ResourceId { get; set; } [Required(ErrorMessage = "Date is Required")] public object DateFrom { get; set; } [Required(ErrorMessage = "Time From is Required")] public object TimeFrom { get; set; } [Required(ErrorMessage = "Time to is Required")] public object TimeTo { get; set; } } The problem I'm trying to solve is to get records from table HistoryBookedResource and have the result in an IEnumerable<BookedResource> using Entity Framework and LINQ. UPDATE: When using the following the cast seams to work but when trying to loop with a foreach the data is lost. resultFromDb.ToList() as IEnumerable<BookedResource>; UPDATE 2: Im using entity frameworks generated model, model (edmx) is created from database, edmx include classes that reprecent the database tables. In database i have a history table for old BookedResource and it can happen that the user want to look at these and to get the old data from the database entity framework uses classes with the same name as the tables to receive data from db. So i receive the data from table HistoryBookedResource in HistoryBookedResource class. Because entity framework generate the partial classes with the properties i dont know if i can make them virtual and override. Any suggestions will be greatly appreciated.

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  • group object with equal collections

    - by Jeroen
    Hi, Suppose 2 classes, Person and Pet. Each person has a collection of 1 or more pets. How do i group the Person in to a collection where they share the same pets. Example: Person 1: Cat, Dog, Spider Person 2: Cat, Spider, Snake Person 3: Dog Person 4: Spider, Cat, Dog Person 5: Dog What i want as a result is this: Group 1: Person 1, Person 4 Group 2: Person 3, Person 5 Group 3: Person 2 How do i achieve this using LINQ?

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  • Foreign Keys Duplicated in DataGridView

    - by John Doe
    I created a Windows Forms Application to which I added a DataGridView and LINQ to SQL Classes from one of my databases. I can successfully bind one of my database's tables to my DataGridView: var dataSource = from c in _db.NetworkedEquipments select c; dataGridView1.DataSource = dataSource; However, the foreign keys get duplicated, that is, the columns appear twice. How can I prevent this?

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  • Adding a clustered index to a SQL table: what dangers exist for a live production system?

    - by MoSlo
    Right, keep in mind i need to describe this by abstracting all possible confidential info: I've been put in charge of a 10-year old transactional system of which the majority business logic is implemented at database level (triggers, stored procedures etc). Win2000 server, MSSQL 2000 Enterprise. No immediate plans for replacing/updating the system are being considered :( The core process is a program that executes transactions - specifically, it executes a stored procedure with various parameters, lets call it sp_ProcessTrans. The program executes the stored procedure at asynchronous intervals. By itself, things work fine. But there are 30 instances of this program on remotely located workstations, all of them asynchronously executing sp_ProcessTrans and then retrieving data from the SQL server (execution is pretty regular - ranging 0 to 60 times a minute, depending on what items the program instance is responsible for) . Performance of the system has dropped considerably with 10 yrs of data growth: the reason is the deadlocks and specifically deadlock wait times. The deadlock is on the Employee table. I have discovered: In sp_ProcessTrans' execution, it selects from an Employee table 7 times (dont ask) The select is done on a field that is NOT the primary key No index exists on this field. Thus a table scan is performed. 7 times. per transaction So the reason for deadlocks is clear. I created a non-unique ordered clustered index on the field (field looks good, almost unique, NUM(7), very rarely changes). Immediate improvement in the test environment. The problem is that i cannot simulate the deadlocks in a test environment (I'd need 30 workstations; i'd need to simulate 'realistic' activity on those stations, so visualization is out). I need to know if i must schedule downtime. Creating an index shouldn't be a risky operation for MSSQL, but is there any danger (data corruption in transactions/select statements/extra wait time etc) to create this field index on the production database while the transactions are still taking place? (although i can select a time when transactions are fairly quiet through the 30 stations) Are there any hidden dangers i'm not seeing (not looking forward to needing to restore the DB if something goes wrong, restoring would take a lot of time with 10yrs of data).

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  • Alternatives of Datatable

    - by mavera
    In my web application, I have a dynamic query that returns huge data to datatable, and this query is often recalled with different parameters. So database is exhausted. I want to get all record with no parameters to an object, and perform queries (may be with linq) on this object. So database will not be exthausted. Which objects can be used instead of datatable?

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  • Foreach loop problem for Iqueyable object

    - by Vikas
    Hi, Can we use foreach loop for Iqueryable object? I'd like to do something as follow: query = Iqueryable<Myclass> = objDataContext.Myclass; // objDataContext is an object of LINQ datacontext class int[] arr1 = new int[] { 3, 4, 5 }; foreach (int i in arr1) { query = query.Where(q => (q.f_id1 == i || q.f_id2 == i || q.f_id3 == i)); } It gives me wrong output as each time value if i is changed.

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  • How to convert a 2-d array into a dictionary object

    - by Nikron
    Hi, I have an array of type string that looks like this: "test1|True,test2|False,test3|False,test4|True". This is essentially a 2d array like so [test1][True] [test2][False] [test3][False] [test4][True]. I want to convert this into a dictionary<string,bool> using linq, something like: Dictionary<string, bool> myResults = results.Split(",".ToCharArray).ToDictionary() any ideas?

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  • How to get an array of members of an array

    - by Mystere Man
    Suppose I have a class public class Foo { public Bar { get; set; } } Then I have another class public class Gloop { public List<Foo> Foos { get; set; } } What's the easiest way to get a List of Foo.Bars? I'm using C# 4.0 and can use Linq if that is the best choice. My first thought was something like

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