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Search found 813 results on 33 pages for 'concurrency'.

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• Does DB2 have an "insert or update" statement?

  - by Mikael Eriksson

  From my code (Java) I want to ensure that a row exists in the database (DB2) after my code is executed. My code now does a select and if no result is returned it does an insert. I really don't like this code since it exposes me to concurrency issuses when running in a multi-threaded environment. What I would like to do is to put this logic in DB2…

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• Is it really wrong to version documents using CouchDB's default behaviour?

  - by Tomas Sedovic

  This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is strongly discouraged for programmer's use: "You cannot rely on document revisions for…

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• Why better isolation level means better performance in SQL Server

  - by Oleg Zhylin

  When measuring performance on my query I came up with a dependency between isolation level and elapsed time that was surprising to me READUNCOMMITTED - 409024 READCOMMITTED - 368021 REPEATABLEREAD - 358019 SERIALIZABLE - 348019 Left column is table hint, and the right column is elapsed time in microseconds…

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• Clojure lots of threads

  - by Timothy Baldridge

  I just got done watching Rick Hickey's "Clojure Concurrency" talk, and I have a few questions about threads. Let's say I have a situation with lots of Agents, let's say 10,000 of them running one machine. I'd rather not have 10,000 CPU threads running at once, but I don't want threads to be blocked by the…

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• the MVCC effect on migration from oracle to db2

  - by Ryan Fernandes

  I have a simple (actually simplified :) ) scenario that is possibly the cause for the headache I've been having for the last few days... My current application (that serves 100's of users) currently uses Oracle as the database. I have no stored procs (I wish actually). Now, I've been asked if the product…

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• What parallel programming model do you recommend today to take advantage of the manycore processors

  - by Doctor J

  If you were writing a new application from scratch today, and wanted it to scale to all the cores you could throw at it tomorrow, what parallel programming model/system/language/library would you choose? Why? I am particularly interested in answers along these axes: Programmer productivity / ease of use…

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• net c# lock statement in data access layer

  - by Pedro Rivera

  I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ …

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• basic unique ModelForm field for Google App Engine

  - by Alexander Vasiljev

  I do not care about concurrency issues. It is relatively easy to build unique form field: from django import forms class UniqueUserEmailField(forms.CharField): def clean(self, value): self.check_uniqueness(super(UniqueUserEmailField, self).clean(value)) def check_uniqueness(self,…

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• performance of parameterized queries for different db's

  - by tuinstoel

  A lot of people know that it is important to use parameterized queries to prevent sql injection attacks. Parameterized queries are also much faster in sqlite and oracle when doing online transaction processing because the query optimizer doesn't have to reparse every parameterized sql statement…

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• Can we view objects in the JVM memory?

  - by Sebastien Lorber

  Hey, At work we found that on some instances (particulary the slow ones) we have a different behaviour, acquired at the reboot. We guess a cache is not initialized correctly, or maybe a concurrency problem... Anyway it's not reproductible in any other env than production. We actually don't…

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• how to initialize spring bean from database

  - by wavelet

  hi,i use spring security and my config is in database: <sec:http auto-config="true" entry-point-ref="casProcessingFilterEntryPoint"> <sec:remember-me /> <sec:session-management> <sec:concurrency-control max-sessions="1" …

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• Advice about a good Java book?

  - by camac1

  Hi people, I am new to Java but have experience programming in C/C++/C#. I wanted to learn Java SE 6 first before moving to Java EE 6. After making some research online for appropriate Java SE 6 books, I found that these are appropriate for me to get an excellent idea of Java SE 6: …

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• Injecting EntityManager Vs. EntityManagerFactory

  - by SB

  A long question, please bear with me. We are using Spring+JPA for a web application. My team is debating over injecting EntityManagerFactory in the GenericDAO(a DAO based on Generics something on the lines provided by APPFUSE, we do not use JpaDaosupport for some reason) over…

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• What is the preferred sql server column definition to use for a LINQ to SQL Version property?

  - by Mike Two

  We are using the IsVersion property on the ColumnAttribute on a property in a LINQ to SQL class for optimistic concurrency checks. What should the column definition be in the database? Currently we are using version_number int NOT NULL IDENTITY (1, 1) Do we need Identity?…

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• What do you read?

  - by sixtyfootersdude

  I have almost finished reading all the articles on Joel on software. I am a new developer and hoping to get something interesting to read. Here is what is currently on my list: Java Concurrency in Practice by Brian Goetz sed & awk by Dougherty & Robbins…

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• Why hasn't functional programming taken over yet?

  - by pankrax

  I've read some texts about declarative/functional programming (languages), tried out Haskell as well as written one myself. From what I've seen, functional programming has several advantages over the classical imperative style: Stateless programs; No side effects…

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• Write a network simulator for fun

  - by Jono

  I want to write my own network simulator, for fun and for personal challenge. I hope to learn both new programming techniques, and a little bit more about networking. Previous object-oriented attempts ended very quickly, but I've recently downloaded and played with…

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• unable to catch org.hibernate.StaleObjectStateException while deleting record that doesn't exists in database

  - by JAB

  My application has a delete user option. Now in order to check concurrency condition I tried the following use case opened application in chrome and firefox browser. deleted user in firefox now trying to delete the same user in chrome browser I get exception…

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• What is the optimal number of threads for performing IO operations in java?

  - by marc

  In Goetz's "Java Concurrency in Practice", in a footnote on page 101, he writes "For computational problems like this that do not I/O and access no shared data, Ncpu or Ncpu+1 threads yield optimal throughput; more threads do not help, and may in fact degrade…

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• Is it really wrong to version documents using CouchDB's behaviour?

  - by Tomas Sedovic

  This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is…

  Read the article

• How can this be done with (N)Hibernate?

  - by Vilx-

  I'm creating a windows forms application with NHibernate. It's an MDI application, so there is no limit to how many forms the user can have open at the same time (probably many). For most forms I want to have an "OK" and a "Cancel" button. Both close the…

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• Can we view objets in the JVM memory?

  - by Sebastien Lorber

  Hey, At work we found that on some instances (particulary the slow ones) we have a different behaviour, acquired at the reboot. We guess a cache is not initialized correctly, or maybe a concurrency problem... Anyway it's not reproductible in any other…

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• Threading Problems in ActionScript 2.0?

  - by yar

  Is it possible to have concurrency problems (thread competition) in an onEnterFrame method in ActionScript 2.0? I have written this cheesy code as a guard: if (!busy) { // I suspect some threading problems: is that even possible in flash busy =…

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• Emulating a transaction-safe SEQUENCE in MySQL

  - by Michael Pliskin

  We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance…

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• When is porting data from MySQL to CouchDB NOT advisable? Seeking cautionary tales

  - by dan

  I've dabbled in CouchDB and I have pretty good MySQL experience. I've also created one production application that uses both. I like MySQL but I've run into scaling/concurrency issues with MySQL that CouchDB advertises itself as a general…

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