transaction-isolation

I have a tasks thread running in two separate instances of tomcat. The Task threads concurrently reads (using select) TASKS table on certain where condition and then does some processing. Issue is ,sometimes both the threads pick the same task , because of which the task is executed twice. My question is how do i make both thread not to read the same set of data from the TASKS table I think you need have some variable (column) where you keep last modified date of rows. Your threads can read same set of data with same modified date limitation. Edit: I did not see "not to read" In this case you

I have a bunch of utility procedures that just check for some conditions in the database and return a flag result. These procedures are run with READ UNCOMMITTED isolation level, equivalent to WITH NOLOCK. I also have more complex procedures that are run with SERIALIZABLE isolation level. They also happen to have these same kind of checks in them. So I decided to call these check procedures from within those complex procedures instead of replicating the check code. Basically it looks like this: CREATE PROCEDURE [dbo].[CheckSomething] AS SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED BEGIN

I have a function, that does multiple queries on the same dataset and I want to ensure all the queries would see exactly the same data. In terms of SQL, this means REPEATABLE READ isolation level for the databases that support it. I don't mind having higher level or even a complete lockdown if the database isn't capable. As far as I see, this isn't the case. I.e. if I run something like this code in one Python shell: with transaction.atomic(): for t in range(0, 60): print("{0}: {1}".format(t, MyModel.objects.count())) time.sleep(1) As soon as I do MyModel.objects.create(...) in another, the

Closed . This question needs to be more focused. It is not currently accepting answers. Learn more . Want to improve this question? Update the question so it focuses on one problem only by editing this post . Closed 8 months ago . I would like to know different isolation levels with respect to commit, and would also like to know about row-level and table-level lock. ANSI/ISO SQL defines four isolation levels: serializable repeatable read read committed read uncommitted According to Oracle's Database Development Guide, chapter 6.6.1: Transaction Interaction and Isolation Level , you can request

Following statement: INSERT INTO dbo.Changes([Content], [Date], [UserId], [CompanyId]) VALUES (@1, @2, @3, @4); SELECT @@identity; gives me this SQL error 3960: Snapshot isolation transaction aborted due to update conflict. You cannot use snapshot isolation to access table 'dbo.Companies' directly or indirectly in database 'myDatabase' to update, delete, or insert the row that has been modified or deleted by another transaction. Retry the transaction or change the isolation level for the update/delete statement. As far as I understood, from the error message, I should not update, delete, or

I have an application that uses hibernate version 3.6.4, and c3p0 version 0.9.1.2 for connection pooling. My underlying RDBMS is MySql version 5.0.67. My installation of MySql indicates that the default transaction isolation level is "REPEATABLE-READ" (4): mysql> select @@GLOBAL.tx_isolation, @@tx_isolation; +-----------------------+-----------------+ | @@GLOBAL.tx_isolation | @@tx_isolation | +-----------------------+-----------------+ | REPEATABLE-READ | REPEATABLE-READ | +-----------------------+-----------------+ I have not changed or configured the transaction isolation level within