Stack Overflow
Stack Overflow

Questions tagged [read-uncommitted]

49 questions
8
votes
2 answers

In MySQL Why does setting a variable from a select acquire a lock when using read uncommitted?

We have a table in MySQL using InnoDB, and we are using a transaction isolation level of read uncommitted. Why does setting @x as shown acquire a lock? mysql> set @x = (select userID from users limit 1); Query OK, 0 rows affected (0.02…
Yoseph
  • 730
  • 1
  • 7
  • 8
7
votes
1 answer

"SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED" not taking? Or am I looking in the wrong way?

We have a problem with some database code that apparently executes with the wrong isolation level. In this particular part of the code, it is supposed to execute with "READ UNCOMMITTED" to minimize locks. Inconsistent data is OK at this…
Lasse V. Karlsen
  • 380,855
  • 102
  • 628
  • 825
6
votes
4 answers

Read Committed vs Read Uncommited if both transaction do not rollback

I am trying to understand read committed and read uncommitted isolation levels. I know that theoreticay read uncommitted allows dirty reads and read committed doesn't, but I still can't really understand. Considering Figure above, if none of the…
user1264
  • 61
  • 1
  • 4
5
votes
4 answers

High volume site using ADO.NET TransactionScope vs ExecuteCommand on NOLOCK, READ UNCOMMITTED directly?

Just read this interesting article by Omar on his blog Linq to SQL solve Transaction deadlock and Query timeout problem using uncommitted reads and at the end Javed Hasan started arguing with him about his solution to the nolock situation on a…
Ray
  • 12,101
  • 27
  • 95
  • 137
5
votes
3 answers

EF6 with TransactionScope - IsolationLevel.ReadUncommitted but got ReadCommitted first

There is a performance and lock issue when using EF for a update-from-query case on MSSQL 2008. So I put ReadUncommitted transaction isolationlevel, hoping to resolve it, like this, Before using (MyEntities db = new MyEntities()) { // large…
nwpie
  • 665
  • 11
  • 24
5
votes
1 answer

How to set isolation level in @Transactional "READ_UNCOMMITTED". I am using EclipseLink 2.5.1-RC1

I have a requirement to start new Transaction within an ongoing Transaction so that an exception in 2nd transaction will rollback only new transaction not the old one. This I am doing by setting propagation attribute in 2nd transaction like…
Noor Khan
  • 255
  • 2
  • 3
  • 8
4
votes
2 answers

Reading uncommitted changes (dirty read) from SQLite database

I wrote an application (using Qt in C++) which inserts data into a SQLite database. Another application reads data from the same database, but I noticed that it is not possible to read uncommitted data (dirty read). I would like instead to be able…
Luca Carlon
  • 9,546
  • 13
  • 59
  • 91
4
votes
1 answer

Oracle SQL: NOLOCK in join statment

I can not use NOLOCK after table names in join statements. Is it even a valid scenario to try to read uncommitted data over JOINs
Naren Karanam
  • 61
  • 1
  • 3
  • 10
4
votes
1 answer

How to use WITH(NOLOCK) in LINQ to SQL?

we can use SQL just like this: SELECT * FROM student WITH(NOLOCK); How can I achieve this with LINQ to SQL without the use of a TransactionScope?
ligaoren
  • 1,043
  • 1
  • 9
  • 10
4
votes
1 answer

SQL Server Read Uncommitted is blocking transactions

I have a work queue in SQL, managed by some services that read out entries to process with READPAST queries. I recently added a UI to check on queue status that uses READ UNCOMMITTED NHibernate queries in C#. It's not at all critical that they give…
Michael
  • 8,362
  • 6
  • 61
  • 88
3
votes
1 answer

How set transaction isolation level to ReadUncommitted in SQLite?

According to the answer on this post it states: Did you know that ReadUncommitted will revert to Serialized isolation unless you've enabled the shared cache and both connections are from the same thread? Working in C#, I then went ahead and…
Elan
  • 6,084
  • 12
  • 64
  • 84
3
votes
1 answer

How does MySQL InnoDB implement Read Uncommitted isolation level

Oracle doesn't allow dirty reads, so Read Uncommitted is not even allowed to be set from JDBC. PostgreSQL also falls back to Read Committed, when choosing Read Uncommitted. SQL Server defines a Read Uncommitted isolation level, because its…
Vlad Mihalcea
  • 142,745
  • 71
  • 566
  • 911
3
votes
1 answer

Can't see rows inserted by a running transaction when isolation level is READ_UNCOMMITTED

I have applications that insert rows into table A concurrently. Each application inserts rows in batch mode (using a JDBC prepared statement) using a single transaction per batch (to avoid rebuilding index after each INSERT). The rows present in…
manash
  • 6,985
  • 12
  • 65
  • 125
2
votes
1 answer

A recognition error occurred when nolock is used in hibernate query

I have simple hibernate query with nolock used in query. I am getting error - A recognition error occurred and hibernate error is Exception thrown: 'NHibernate.Hql.Ast.ANTLR.QuerySyntaxException' in NHibernate.dll. it works without nolock. I don't…
SSD
  • 1,041
  • 3
  • 19
  • 39
1
vote
2 answers

How can we set the Read Uncommitted isolation level with JPA and Hibernate?

In he famous book "Java persistence with Hibernate" we can read the following: "A persistence context is a cache of persistent entity instances.... Automatic dirty checking is one of the benefits of this caching. Another benefit is repeatable read…
Alex Mi
  • 1,409
  • 2
  • 21
  • 35
1
2 3 4