isolation-level

问题 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 | +-----------------

问题 I am reading a manual about innodb transactions but still, there is lots of unclear stuff to me. For instance, I don't quite understand to the following behaviour: -- client 1 -- client 2 mysql> create table simple (col int) engine=innodb; mysql> insert into simple values(1); Query OK, 1 row affected (0.00 sec) mysql> insert into simple values(2); Query OK, 1 row affected (0.00 sec) mysql> select @@tx_isolation; +-----------------+ | @@tx_isolation | +-----------------+ | REPEATABLE-READ | +-

问题 I am reading a manual about innodb transactions but still, there is lots of unclear stuff to me. For instance, I don't quite understand to the following behaviour: -- client 1 -- client 2 mysql> create table simple (col int) engine=innodb; mysql> insert into simple values(1); Query OK, 1 row affected (0.00 sec) mysql> insert into simple values(2); Query OK, 1 row affected (0.00 sec) mysql> select @@tx_isolation; +-----------------+ | @@tx_isolation | +-----------------+ | REPEATABLE-READ | +-

问题 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. I would like instead to be able to read data even if it is not committed yet. Reading the SQLite documentation I found the pragma read_uncommitted which, from what I understand, should be what I need. Problem is that, even if I set that to true, I cannot get uncommitted data. I tried to run my

问题 I want to know that what is the best way to arrive at the isolation level of the transaction? This is a good link of the available ISOLATION levels. Blockquote It will be nice if someone can explain the various isolation levels of a transaction 回答1: Update: Clarified and corrected explanation. Isolation levels just indicate how much of your transaction is affected by other concurrent transactions. The higher the isolation level, the less affected it is. The effort will be made manifest in cpu

问题 I cannot figure out how to specify default transaction isolation level in Grails application . Please help and point where my mistake is. Following are the details. Grails: 1.3.7 Database: Sql Server 2008. DataSource.groovy: dataSource { ... driverClassName = "net.sourceforge.jtds.jdbc.Driver" dialect = org.hibernate.dialect.SQLServerDialect defaultTransactionIsolation = java.sql.Connection.TRANSACTION_READ_UNCOMMITTED } hibernate { ... connection.isolation = java.sql.Connection.TRANSACTION

问题 I've always considered that there were no isolation within a single transaction. For example if I have 2 methods M1 and M2, M1 update X in database and M2 select X or a set containing X. If both method belongs to the same transaction and M2 is executed after M1: Does M2 always seen M1 update whatever the type of operation, the RDBMS or the isolation level is ? If no, can someone explain in details the different possible behavior according to associated criteria 回答1: In the situation described

问题 I have read about how REPEATABLE READ causes locks held by SELECT statements to be held to the end of the transaction. Is the same true for exclusive locks taken by UPDATE statements? Consequentially, is it the case that when I UPDATE a row in a transaction, subsequent SELECTs will return the value left by the UPDATE? So I understand that if I SELECT a row in transaction 1, then transaction 2 cannot UPDATE it until transaction 1 completes. However, if I UPDATE The row in transaction 1, will

问题 Is it possible to set the database isolation level (ie Serializable, repeatable-read etc) for a given EJB 3 method call? I understand that this is not covered by the EJB Spec, so details of how to do it on either a JBoss or Glassfish specific manner would be great. I'm starting to get the impression it's not possible and that you can only set it per Connection Pool which is clearly by no means an ideal solution. 回答1: This is indeed not covered by the spec and but can be configured through

问题 I'm using the following format for commiting changes to my db using linq. Begin Transaction (Scope Serialized, Required) Check Business Rule 1...N MyDataContext.SubmitChanges() Save Changes Done In Previous Query To Log File End Transaction Scope But in the SQL Server profiler I see the following line in the Connection:Start. set transaction isolation level read committed I went through this (http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/93a45026-0425-4d49-a4ac