How to cancel a long-running Database operation?

Question

Currently working with Oracle, but will also need a solution for MS SQL.

I have a GUI that allows users to generate SQL that will be executed on the database. This

Answer 1

If you're using ADO.NET and SQL data provider, take a look at SqlCommand.Cancel method. That does what you're looking for. However, it tries to cancel and the cancellation may take time. Basically, it's up to SQL Server to decide when to grant your cancellation request. When the query is cancelled, you should get a SqlException that indicates that the operation was cancelled by user. Apparently, you don't want to treat this exception as exception and handle it specially such as if SqlException is due to user cancelling the operation, just swallow it.

Answer 2

If you're using an SQLCommand, you could try calling it's Cancel method.

Answer 3

I dont think it is possible. Here is a link to a discussion on Oracle's website about this topic: http://forums.oracle.com/forums/thread.jspa?threadID=400492&start=15&tstart=0

Answer 4

You could have the background worker fire off the actual database call on a different thread, and then periodically check to see if either the database call has finished, or cancel has been pressed, at which point you could kill off the database thread. This wouldn't actually help the database load any (as your query has been sent and is still processing) but it does release your local resources related to it.

Answer 5

I have tried both Cancel and Close with ADO 2.8 and SQLOLEDB or SQL Server native client. With Cancel, the recordset stops fetching data, but in the backround the reading from the server continues and consumes memory from the application. In a 32 bit application it can happen that you get an "out of memory" message some minutes later. When I close the recordset (or the connection, with or without Cancel before), ADO 2.8 waits until all records are fetched.

I don't know if ADO.NET does it better, but I think it's a good idea to monitor memory and network access after Cancel/Close to be sure that ADO really stops reading data.