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  • Why do updates inside of a SQL transaction still need disk IO?

    - by usr
    In SQL Profiler you can see that very simple updates to a table by primary key take about 10-30ms each. On about every 10th update the write column shows 1, on all other updates it shows 0. This must mean that about every 10th update statement still requires disk IO. I wonder why that is. Would it not be more efficient queue up all IO until the transaction commits?

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  • Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

    - by Kaleb Brasee
    I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

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  • JTA Transaction: What happens if an exception happens but rollback is not called on the transaction?

    - by kellyfj
    We have some third party code wherein they do the following 1) Create a User Transaction e.g. txn = (UserTransaction)ctx.lookup( "UserTransaction" ); txn.begin( ); 2) Do some work persisting to the database (via JPA) to a MySQL database 3) txn.commit() They have Exception blocks but NONE of them call txn.rollback. Good coding practice says they NEED to call rollback if an exception occurs but my question is If the txn is not commited, and an exception occurs what is the negative effect of them NOT calling rollback?

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  • Atomic operations on several transactionless external systems

    - by simendsjo
    Say you have an application connecting 3 different external systems. You need to update something in all 3. In case of a failure, you need to roll back the operations. This is not a hard thing to implement, but say operation 3 fails, and when rolling back, the rollback for operation 1 fails! Now the first external system is in an invalid state... I'm thinking a possible solution is to shut down the application and forcing a manual fix of the external system, but then again... It might already have used this information (and perhaps that's why it failed), or we might not have sufficient access. Or it might not even be a good way to rollback the action! Are there some good ways of handling such cases? EDIT: Some application details.. It's a multi user web application. Most of the work is done with scheduled jobs (through Quartz.Net), so most operations is run in it's own thread. Some user actions should trigger jobs that update several systems though. The external systems are somewhat unstable. I Was thinking of changing the application to use the Command and Unit Of Work pattern

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  • Row insertion order entity framework

    - by Wouter
    I'm using a transaction to insert multiple rows in multiple tables. For these rows I would like to add these rows in order. Upon calling SaveChanges all the rows are inserted out of order. When not using a transaction and saving changes after each insertion does keep order, but I really need a transaction for all entries.

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  • Insert takes too long, code optimization needed

    - by Pentium10
    I have some code I use to transfer a table1 values to another table2, they are sitting in different database. It's slow when I have 100.000 records. It takes forever to finish, 10+ minutes. (Windows Mobile smartphone) What can I do? cmd.CommandText = "insert into " + TableName + " select * from sync2." + TableName+""; cmd.ExecuteNonQuery(); EDIT The problem is not resolved. I am still after answers.

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  • SQLAlchemy autocommiting?

    - by muckabout
    I have an issue with SQLAlchemy apparently committing. A rough sketch of my code: trans = self.conn.begin() try: assert not self.conn.execute(my_obj.__table__.select(my_obj.id == id)).first() self.conn.execute(my_obj.__table__.insert().values(id=id)) assert not self.conn.execute(my_obj.__table__.select(my_obj.id == id)).first() except: trans.rollback() raise I don't commit, and the second assert always fails! In other words, it seems the data is getting inserted into the database even though the code is within a transaction! Is this assessment accurate?

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  • Translate HTML files to another language

    - by Saif Bechan
    I have a website with Dutch text which I want to translate to English. Is there a fast way of doing this with keeping the HTML tags(<strong>,<span>) in tact. I know I can just copy the parsed TEXT into a translator but this will remove the formatting. I also know that at the end I have to go trough the text manually to fix some minor spelling and grammar.

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  • Unit Testing the Use of TransactionScope

    - by Randolpho
    The preamble: I have designed a strongly interfaced and fully mockable data layer class that expects the business layer to create a TransactionScope when multiple calls should be included in a single transaction. The problem: I would like to unit test that my business layer makes use of a TransactionScope object when I expect it to. Unfortunately, the standard pattern for using TransactionScope is a follows: using(var scope = new TransactionScope()) { // transactional methods datalayer.InsertFoo(); datalayer.InsertBar(); scope.Complete(); } While this is a really great pattern in terms of usability for the programmer, testing that it's done seems... unpossible to me. I cannot detect that a transient object has been instantiated, let alone mock it to determine that a method was called on it. Yet my goal for coverage implies that I must. The Question: How can I go about building unit tests that ensure TransactionScope is used appropriately according to the standard pattern? Final Thoughts: I've considered a solution that would certainly provide the coverage I need, but have rejected it as overly complex and not conforming to the standard TransactionScope pattern. It involves adding a CreateTransactionScope method on my data layer object that returns an instance of TransactionScope. But because TransactionScope contains constructor logic and non-virtual methods and is therefore difficult if not impossible to mock, CreateTransactionScope would return an instance of DataLayerTransactionScope which would be a mockable facade into TransactionScope. While this might do the job it's complex and I would prefer to use the standard pattern. Is there a better way?

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  • Can I create a transaction using ADO NET Entity Data Model?

    - by Junior Mayhé
    Hi is it possible on the following try-catch to execute a set of statements as a transaction using ADO NET Entity Data Model? [ValidateInput(false)] [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(Customer c) { try { c.Created = DateTime.Now; c.Active = true; c.FullName = Request.Form["FirstName"]; db.AddToCustomer(c); db.SaveChanges(); Log log = new Log();//another entity model object log.Created = DateTime.Now; log.Message = string.Format(@"A new customer was created with customerID {0}", c.CustomerID); db.AddToLog(log); db.SaveChanges(); return RedirectToAction("CreateSuccess", "Customer"); } catch { return View(); } } Any thoughts would be very appreciated.

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  • How do i set Savepoints for Linq to SQL and use "NO" ExecuteCommand ?

    - by nik
    TransactionScope TransactionABC = new TransactionScope(); try { context.Connection.Open(); { context.ExecuteCommand("insert into test (test) values (1)") context.SubmitChanges(); context.ExecuteCommand("savepoint test"); context.ExecuteCommand("insert into test (test) values (2)") context.SubmitChanges(); context.ExecuteCommand("rollback to test"); } TransactionABC.Complete(); TransactionABC.Dispose(); } catch (Exception ec) { MessageBox.Show(" ", ec.Message); } finally { context.Connection.Close(); } It works, but only with ExecuteCommand. I want to use a function, because i can't see what happens in the savepoint !

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  • How to handle dynamic site localizations?

    - by James Simpson
    I've got a website that is currently all in english. It is an online game, so it has a bunch of different pages with static text, as well as a lot of content in a database. I am trying to expand more globally and am gearing up to release some localizations of the site. However, I'm not sure about the best way to go about setting this up so that it'll be the easiest for me to manage and the easiest for users to use as well. Should I be storing the translated texts in a database, or should this be done in a completely different way? If it matters at all, the site is written in PHP and uses MySQL.

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  • Access DB Transaction on insert or updating

    - by Raju Gujarati
    I am going to implement the database access layer of the Window application using C#. The database (.accdb) is located to the project files. When it comes to two notebooks (clients) connecting to one access database through switches, it throws DBConcurrency Exception Error. My target is to check the timestamp of the sql executed first and then run the sql . Would you please provide me some guidelines to achieve this ? The below is my code protected void btnTransaction_Click(object sender, EventArgs e) { string custID = txtID.Text; string CompName = txtCompany.Text; string contact = txtContact.Text; string city = txtCity.Text; string connString = ConfigurationManager.ConnectionStrings["CustomersDatabase"].ConnectionString; OleDbConnection connection = new OleDbConnection(connString); connection.Open(); OleDbCommand command = new OleDbCommand(); command.Connection = connection; OleDbTransaction transaction = connection.BeginTransaction(); command.Transaction = transaction; try { command.CommandText = "INSERT INTO Customers(CustomerID, CompanyName, ContactName, City, Country) VALUES(@CustomerID, @CompanyName, @ContactName, @City, @Country)"; command.CommandType = CommandType.Text; command.Parameters.AddWithValue("@CustomerID", custID); command.Parameters.AddWithValue("@CompanyName", CompName); command.Parameters.AddWithValue("@ContactName", contact); command.Parameters.AddWithValue("@City", city); command.ExecuteNonQuery(); command.CommandText = "UPDATE Customers SET ContactName = @ContactName2 WHERE CustomerID = @CustomerID2"; command.CommandType = CommandType.Text; command.Parameters.AddWithValue("@CustomerID2", custIDUpdate); command.Parameters.AddWithValue("@ContactName2", contactUpdate); command.ExecuteNonQuery(); adapter.Fill(table); GridView1.DataSource = table; GridView1.DataBind(); transaction.Commit(); lblMessage.Text = "Transaction successfully completed"; } catch (Exception ex) { transaction.Rollback(); lblMessage.Text = "Transaction is not completed"; } finally { connection.Close(); } }

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  • Is there any difference in which order I createCriteria and beginTransaction using Hibernate?

    - by user2519543
    Just wondering is there any difference when I beginTransaction [org.hibernate] before or after creating Criteria/Query etc.? example 1: ... Transaction tx= session.beginTransaction(); Criteria c = session.createCriteria(class); result = c.uniqueResult(); tx.commit(); ... example 2: ... Criteria c = session.createCriteria(class); Transaction tx= session.beginTransaction(); result = c.uniqueResult(); tx.commit(); ... Thanks.

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  • Exit and rollback everything in script on error

    - by Jan W.
    Hey guys ! I'm in a bit of a pickle here. I have a TSQL script that does a lot of database structure adjustments but it's not really safe to just let it go through when something fails. to make things clear: using MS SQL 2005 it's NOT a stored procedure, just a script file (.sql) what I have is something in the following order BEGIN TRANSACTION ALTER Stuff GO CREATE New Stuff GO DROP Old Stuff GO IF @@ERROR != 0 BEGIN PRINT 'Errors Found ... Rolling back' ROLLBACK TRANSACTION RETURN END ELSE PRINT 'No Errors ... Committing changes' COMMIT TRANSACTION just to illustrate what I'm working with ... can't go into specifics now, the problem ... When I introduce an error (to test if things get rolled back), I get a statement that the ROLLBACK TRANSACTION could not find a corresponding BEGIN TRANSACTION. This leads me to believe that something when REALLY wrong and the transaction was already killed. what I also noticed is that the script didn't fully quit on error and thus DID try to execute every statement after the error occured. (I noticed this when new tables showed up when I wasn't expecting them because it should have rollbacked) any help in this department is welcome if more speficics are needed, ask! greetz

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  • Can a Snapshot transaction fail and only partially commit in a TransactionScope?

    - by Travis Brooks
    Greetings I stumbled onto a problem today that seems sort of impossible to me, but its happening...I'm calling some database code in c# that looks something like this: using(var tran = MyDataLayer.Transaction()) { MyDataLayer.ExecSproc(new SprocTheFirst(arg1, arg2)); MyDataLayer.CallSomethingThatEventuallyDoesLinqToSql(arg1, argEtc); tran.Commit(); } I've simplified this a bit for posting, but whats going on is MyDataLayer.Transaction() makes a TransactionScope with the IsolationLevel set to Snapshot and TransactionScopeOption set to Required. This code gets called hundreds of times a day, and almost always works perfectly. However after reviewing some data I discovered there are a handful of records created by "SprocTheFirst" but no corresponding data from "CallSomethingThatEventuallyDoesLinqToSql". The only way that records should exist in the tables I'm looking at is from SprocTheFirst, and its only ever called in this one function, so if its called and succeeded then I would expect CallSomethingThatEventuallyDoesLinqToSql would get called and succeed because its all in the same TransactionScope. Its theoretically possible that some other dev mucked around in the DB, but I don't think they have. We also log all exceptions, and I can find nothing unusual happening around the time that the records from SprocTheFirst were created. So, is it possible that a transaction, or more properly a declarative TransactionScope, with Snapshot isolation level can fail somehow and only partially commit?

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  • Which isolation level should I use for the following insert-if-not-present transaction?

    - by Steve Guidi
    I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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  • Is it necessary to write ROLLBACK if queries fail?

    - by Donator
    I write mysql_query("SET AUTOCOMMIT=0"); mysql_query("START TRANSACTION"); before I write all queries. Then check if all of them are true and then write: mysql_query("COMMIT"); But if one of query fails, I just pass COMMIT query. So do I really need ROLLBACK function if one of the queries fail? Because without ROLLBACK it also works. Thanks.

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  • What happens if a message is rolled back in MQ?

    - by Manglu
    Hi, I receive a message from a WebSPhere MQ queue. I try to process and if i receive some exceptions i want to rollback the message to the MQ Queue. I have no problems in doing the same. What happens to the message? Does it go to the bottom of the queue? If i try and pull a message from the queue would i receive the same message that i rolledback? What is the behaviour likely to be? I want to know this behaviour typically in a high volume Queue scenario? Appreciate any inputs. Thanks, Manglu

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  • Forcing a method to be non-transactional in JPA (Eclipselink)

    - by rhinds
    Hi, I am developing an application using Eclipselink and as part of the app I need to be able to manipulate some of the objects which involves changing data without it being persisted to the database (i merging/changing objects for some batch generation processes). I am reluctant to change the data in the Entity objects, as there is a risk that even though i have not marked the methods as @Transactional, this method could in the future be inadvertantly called from within a transactional method and these changes could be persisted. So my question is, is there anyway to get around this? Such as force a method to always be non-transactional regardless; terminate any transactionality as soon as the method is started; etc. I know there is a .detach() method that can detach the objects from the Entity Manager, however, there are many objects and this seems like a potentially error prone fail-safe on my code.

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  • NHibernateUnitOfWork + ASP.Net MVC

    - by Felipe
    Hi Guys, hows it going? I'm in my first time with DDD, so I'm begginer! So, let's take it's very simple :D I developed an application using asp.net mvc 2 , ddd and nhibernate. I have a domain model in a class library, my repositories in another class library, and an asp.net mvc 2 application. My Repository base class, I have a construct that I inject and dependency (my unique ISessionFactory object started in global.asax), the code is: public class Repository<T> : IRepository<T> where T : Entidade { protected ISessionFactory SessionFactory { get; private set; } protected ISession Session { get { return SessionFactory.GetCurrentSession(); } } protected Repository(ISessionFactory sessionFactory) { SessionFactory = sessionFactory; } public void Save(T entity) { Session.SaveOrUpdate(entity); } public void Delete(T entity) { Session.Delete(entity); } public T Get(long key) { return Session.Get<T>(key); } public IList<T> FindAll() { return Session.CreateCriteria(typeof(T)).SetCacheable(true).List<T>(); } } And After I have the spefic repositories, like this: public class DocumentRepository : Repository<Domain.Document>, IDocumentRepository { // constructor public DocumentRepository (ISessionFactory sessionFactory) : base(sessionFactory) { } public IList<Domain.Document> GetByType(int idType) { var result = Session.CreateQuery("from Document d where d.Type.Id = :IdType") .SetParameter("IdType", idType) .List<Domain.Document>(); return result; } } there is not control of transaction in this code, and it's working fine, but, I would like to make something to control this repositories in my controller of asp.net mvc, something simple, like this: using (var tx = /* what can I put here ? */) { try { _repositoryA.Save(objA); _repositoryB.Save(objB); _repositotyC.Delete(objC); /* ... others tasks ... */ tx.Commit(); } catch { tx.RollBack(); } } I've heared about NHibernateUnitOfWork, but i don't know :(, How Can I configure NHibernateUnitOfWork to work with my repositories ? Should I change the my simple repository ? Sugestions are welcome! So, thanks if somebody read to here! If can help me, I appretiate! PS: Sorry for my english! bye =D

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  • Why are these two sql statements deadlocking? (Deadlock graph + details included).

    - by Pure.Krome
    Hi folks, I've got the following deadlock graph that describes two sql statements that are deadlocking each other. I'm just not sure how to analyse this and then fix up my sql code to prevent this from happening. Main deadlock graph Click here for a bigger image. Left side, details Click here for a bigger image. Right side, details Click here for a bigger image. What is the code doing? I'm reading in a number of files (eg. lets say 3, for this example). Each file contains different data BUT the same type of data. I then insert data into LogEntries table and then (if required) I insert or delete something from the ConnectedClients table. Here's my sql code. using (TransactionScope transactionScope = new TransactionScope()) { _logEntryRepository.InsertOrUpdate(logEntry); // Now, if this log entry was a NewConnection or an LostConnection, then we need to make sure we update the ConnectedClients. if (logEntry.EventType == EventType.NewConnection) { _connectedClientRepository.Insert(new ConnectedClient { LogEntryId = logEntry.LogEntryId }); } // A (PB) BanKick does _NOT_ register a lost connection .. so we need to make sure we handle those scenario's as a LostConnection. if (logEntry.EventType == EventType.LostConnection || logEntry.EventType == EventType.BanKick) { _connectedClientRepository.Delete(logEntry.ClientName, logEntry.ClientIpAndPort); } _unitOfWork.Commit(); transactionScope.Complete(); } Now each file has it's own UnitOfWork instance (which means it has it's own database connection, transaction and repository context). So i'm assuming this means there's 3 different connections to the db all happening at the same time. Finally, this is using Entity Framework as the repository, but please don't let that stop you from having a think about this problem. Using a profiling tool, the Isolation Level is Serializable. I've also tried ReadCommited and ReadUncommited, but they both error :- ReadCommited: same as above. Deadlock. ReadUncommited: different error. EF exception that says it expected some result back, but got nothing. I'm guessing this is the LogEntryId Identity (scope_identity) value that is expected but not retrieve because of the dirty read. Please help! PS. It's Sql Server 2008, btw.

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  • GAE update different fields of the same entity

    - by bach
    Hi, UserA and UserB are changing objectA.filedA objectA.filedB respectively and at the same time. Because they are not changing the same field one might think that there are no overlaps. Is that true? or the implementation of pm.makePersistnace() actually override the whole object... good to know...

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  • Store LAST_INSERT_ID() in a transaction

    - by Oden
    Hi, I use codeigniter's database abstarction, and im doing a transaction with it. My problem is, that i have several inserts into several tables, but i need the insert id from the first insert query. Is there any way to store the last insert id for more than one following insert?

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  • Can you modify SQL DB schema in a transaction to know if all changes were applied?

    - by Chris F
    As part of my (new) database version control methodology, I'm writing a "change script" and want the change script to insert a new row into the SchemaChangeLog table if the script is executed successfully, or to reverse changes if any single change in the script fails. Is it possible to do schema changes in a transaction and only if it gets committed to then do the INSERT? For example (psuedo-code, I'm not too good with SQL): SET XACT_ABORT ON BEGIN TRANSACTION PRINT 'Add Col2 to Table1' IF NOT EXIST (SELECT * FROM sys.columns WHERE NAME='Col2' AND object_id=OBJECT_ID('Table1')) BEGIN ALTER TABLE [dbo].[Table1] ADD Col2 int NULL END -- maybe COMMIT here? INSERT INTO SchemaChangeLog VALUES(...) COMMIT TRANSACTION

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