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Posted to ojb-user@db.apache.org by "Ferrer, Eric" <er...@transcore.com> on 2007/02/23 02:21:06 UTC
SQL Hints
Is it possible to hint to OJB on persisted calls to use the WITH (NO
LOCK) attributes on tables?
When ever we are in a multiple transaction and selecting data from large
tables we sometimes slow things down and for performance reasons
sometimes have to create views.
Thanks
-Eric
Re: SQL Hints
Posted by Armin Waibel <ar...@apache.org>.
Hi Eric,
Ferrer, Eric wrote:
> Is it possible to hint to OJB on persisted calls to use the WITH (NO
> LOCK) attributes on tables?
The "WITH (NOLOCK)" clause is a proprietary sql extension for mssql, so
same problem as with "native limit" support. If using "WITH (NOLOCK)"
dirty reads can occur - what about data consistency?
Isn't it possible to change the transaction level of the current used
connection
http://msdn2.microsoft.com/en-gb/library/ms378149.aspx
AFAIK is TRANSACTION_READ_UNCOMMITTED the same as "WITH (NOLOCK)".
Something like this:
PersistenceBroker broker = lookup PB instance (no tx running!!)
// get the current connection
Connection con = broker.serviceConnectionManager().getConnection();
int iso = con.getTransactionIsolation();
try
{
con.setTransactionIsolation(Connection.TRANSACTION_READ_UNCOMMITTED);
...
// perform the query or other work
broker.getCollectionByQuery(...);
...
}
finally
{
// rollback to default tx-isolation
con.setTransactionIsolation(iso);
broker.close();
}
regards,
Armin
>
>
>
> When ever we are in a multiple transaction and selecting data from large
> tables we sometimes slow things down and for performance reasons
> sometimes have to create views.
>
>
>
> Thanks
>
> -Eric
>
>
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