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Postings from March 2008
On 14.03.2008 11:48, Martin Evans wrote: > Alexander Foken wrote: >> On 14.03.2008 09:46, Martin Evans wrote: >>> Alexander Foken wrote: >>>> There is one annoyance with SQL server: You can't have more than >>>> one "active" statement, i.e. a statement that is executing but not >>>> yet finished, per connection. This is a limitation of the SQL >>>> server protocol, not a DBI limitation. Other databases, like Oracle >>>> and the free PostgreSQL, can handle at least a sufficiently large >>>> number of parallel active statements. For the MS SQL Server, you >>>> have to use several distinct connections if you need parallel >>>> active statements. >>> >>> That is no longer true Alexander: >>> >>> MARS. Multiple Active Result Sets (MARS), enables your applications >>> to have more than one pending request per connection, and, in >>> particular to have more than one default result set open per >>> connection. The MARS feature removes the restriction present in >>> earlier versions of SQL Server in which an open default result set >>> blocks the driver from sending requests to the server until the >>> entire result set is consumed. >> Glad to see that this particular restriction is gone. I once had to >> port one of my projects from Oracle to SQL Server 8, when that was >> the most recent version. SQL Server 8 did not have that feature or it >> was so well hidden that I did not found it in days of research. That >> project is also used with newer SQL Server versions, SQL Server 2003 >> is the latest version used in a production environment I know of. For >> all SQL Server versions, the project uses the multi-connection hack. >> Switching to a single connection with multiple parallel statements >> would be a great improvement. >> >> Is it possible to use that feature with DBD::ODBC? What are the >> minimum required versions of DBI, DBD::ODBC, SQL Server? Where and >> how is MARS enabled? >> >> Alexander > > I believe this came in around SQL Server 2005. You can set it in some > registry setting! or in the connection string with > "MARS_Connection=Yes". You can find detailed info about MARS on the MS > web site including some things to watch out for when using MARS and > transactions. You will need a 2005 ODBC Driver and the best one to use > is the new "SQL Native Client" (mine is version 2005.90.1399.00). > > As you can set it in the connection string you can use it from > DBD::ODBC using something like: > > set DBI_DSN=dbi:ODBC:DSN=mydsn;MARS_Connection=Yes > > If you do this and run the 20SQLServer test you'll find the multiple > active statement tests fail because they check you cannot use MAS and > you can now. > > Martin Thanks a lot, I'll see if my ex-collegues can get it working with DBD::ODBC 1.13 + my Unicode patch. They won't run the DBD::ODBC build tests, they will just check if the application works with the multi-connection hack disabled. Alexander -- Alexander Foken mailto:alexander@foken.de http://www.foken.de/alexander/Thread Previous | Thread Next