Aaron Bertrand blogs on an estimation failure with DATEADD and SYSDATETIME/SYSUTCDATETIME:

Essentially, the problem is that a poor estimate can be made not simply when SYSDATETIME() (or SYSUTCDATETIME()) appears, as Erland originally reported, but when any datetime2expression is involved in the predicate (and perhaps only when DATEADD() is also used). And it can go both ways – if we swap >= for <=, the estimate becomes the whole table, so it seems that the optimizer is looking at the SYSDATETIME() value as a constant, and completely ignoring any operations like DATEADD() that are performed against it.

Paul shared that the workaround is simply to use a datetime equivalent when calculating the date, before converting it to the proper data type. In this case, we can swap outSYSUTCDATETIME() and change it to GETUTCDATE()

I suppose switching to GETUTCDATE isn’t too much of a loss, but it looks like (according to Paul White in the second linked Connect item) this appears to have been fixed in SQL Server 2014.

Related Posts

Refreshing Views After DDL Changes

Eduardo Pivaral shows how you can refresh the metadata for a view in SQL Server after one of its underlying tables or functions changes: So we proceed to execute an alter view over the first view: ALTER VIEW dbo.[vi_invoices_received_by]ASSELECT ConfirmedReceivedBy as [Received by], COUNT(InvoiceID) as [# of Invoices], CustomerIDFROM Sales.InvoicesGROUP BY ConfirmedReceivedBy, CustomerID;GO So we […]

Read More

Finding Gaps in Dates

Jason Brimhall shows how you can find gaps in your data: This method is the much maligned recursive CTE method. In my testing it runs consistently faster with a lower memory grant but does cause a bit more IO to be performed. Some trade-off to be considered there. Both queries are returning the desired data-set […]

Read More


April 2016
« Mar May »