Corey Roth [MVP]

SharePoint 2010 has a number of new features centered around working with large lists.  SP2010 can support up to 50 million items in a list now, but you don’t obviously want to return all of those in a single query.  To aid with this, SP2010 introduces list throttling settings (configured at the web application level), that allow you to specify how many items a user can query before the throttle kicks in and aborts the query.  At the time of writing, these limits are set to 5,000 for normal users and 20,000 for super users.  Remember you can change these settings if you so choose.  I’ll be curious to see what numbers people actually end up running with.  This applies to anything that queries the list whether its through the SharePoint UI or from your own custom code.  If the user submits a query that is too large, the SharePoint UI will tell the user that the query is too big and they need to filter it.

Of course, some people don’t care about throttles and they may want to override it at times.  If the code has the appropriate permissions, you can call RequestThrottleOverride on the SPQuery object and execute large unsafe queries.  If you have existing code that does large queries in your current SharePoint environment that, throttling is definitely something you will want to be aware of.