SQL Server Standard 2008 R2
I have a rather complex MERGE command with when matched, not matched target, and not matched source. It runs just fine on a data set of 360K rows, but does not complete on a 500K data set. sp_who2 indicates millions of pagelatch_sh waits. Yet if on that same data set, I break the Merge up and run each part individually (insert, update, delete) they each run very quickly.
Has anyone seen this before?