Earlier this week I experimented, once again, with using temporary hash tables to speed up intermediate processing. Temp tables can be very useful for creating “optimizer fences” that serve to simplify queries to the point where the optimizer will consistently (more or less) come up with a good plan if not a great one. Temp heaps seem well suited to this purpose, when used simply as low-overhead FIFO structures.
Update (3/28/17): As a simple workaround, I added a string split UDF that does the same thing (only much more slowly). If I need to compile the DB project, I replace the intrinsic function with the UDF in the two places it is called. Otherwise I switch back to the intrinsic. It’s annoying, but what else is a person to do? (I noticed this comment on Connect: “Some fixes have been added to SSDT regarding STRING_SPLIT. If you continue to experience the issue, please try out the next SSDT release.” I will indeed check it out.) [The fix is supposed to be in a “preview” release, which I have not installed. I will test it when the production release comes out.]
I happened to use the new (SQL Server 2016) STRING_SPLIT function in a table-valued function that I wrote the other day. When I went to sync the database to my SSDT database project, however, the project would no longer compile.
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