My organisation recently applied an update to TFS 2015 (14.102.25423.0 according to the 'About' page of the web interface) that resulted in the 'My Work' tab in Visual Studio 2015 taking up to one minute to populate. I played around with the queries and managed to narrow the problem down to population of the 'Incoming Requests' section of that tab. Under the hood, this is executing the following WIQL query.
SELECT [System.Id], [System.Links.LinkType], [System.Title], [System.State], [System.Reason], [System.AssignedTo]
WHERE (Source.[System.TeamProject] = @project and Source.[System.WorkItemType] in group 'Microsoft.CodeReviewRequestCategory' and Source.[System.AssignedTo] <> @me and Source.[Microsoft.VSTS.Common.StateCode] <> '1')
and ([System.Links.LinkType] = 'System.LinkTypes.Hierarchy-Forward')
and (Target.[System.WorkItemType] in group 'Microsoft.CodeReviewResponseCategory' and (Target.[System.AssignedTo] = @me or Target.[Microsoft.VSTS.Common.ReviewedBy] = @me) and Target.[Microsoft.VSTS.Common.StateCode] <> '2')
ORDER BY [System.CreatedDate] desc, [System.Id] mode(MustContain)
Answering my own question here... My organisation ended up escalating this through Microsoft and eventually found that there was an issue with out of date statistics causing bad query plan generation. The query that was used to retrieve code review details was taking more than 60 seconds each time it was run.
The queries below will most likely make a significant different to performance if you encounter the same problem.
use <collection db name>; UPDATE STATISTICS [dbo].[tbl_WorkItemCoreLatest] WITH FULLSCAN use <collection db name>; UPDATE STATISTICS [dbo].[tbl_WorkItemCustomLatest] WITH FULLSCAN
For reference, there's a duplicate of my original post on Microsoft Connect here: https://connect.microsoft.com/VisualStudio/Feedback/Details/3107261. The comments from Microsoft in this post indicate a number of people were seeing similar behaviour.