Question

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_READ_UNCOMMITTED
}

Then I’m navigating through the application and execute the following query at the same time:

SELECT session_id, host_name, program_name, login_name, status, transaction_isolation_level
FROM sys.dm_exec_sessions
WHERE host_name IS NOT NULL AND login_name = 'cm'
ORDER BY host_name, program_name

that returns:

session_id  host_name   program_name    login_name  status  transaction_isolation_level
61          ANDREYK-WS  jTDS            cm          running 2

2 means READ_COMMITTED. I expect to see 1, i.e. READ_UNCOMMITTED.

If I explicitly specify:
@Transactional(isolation=Isolation.READ_UNCOMMITTED)

The query above returns 1 as expected.
However I do not want to attribute all the services in my application.
What am I missing?

Answer 1

This needs to be set under the properties attribute of the datasource configuration i.e.

dataSource {
  ...
  driverClassName = "net.sourceforge.jtds.jdbc.Driver".
  dialect = org.hibernate.dialect.SQLServerDialect
  properties {
    defaultTransactionIsolation = java.sql.Connection.TRANSACTION_READ_UNCOMMITTED.
  }
}