Non-indexed temporary tables in warehouse stored procs

The definitive work on this by Paul White explains in tremendous detail some surprising facts about the caching of temporary tables and their statistics.

I’m going to summarise some of these points and outline some general recommendations I like my team to follow.  This goes a little beyond Paul’s advice, possibly because he thought this corollary too obvious to mention, or because he wanted to retain applicability to OLTP workloads with a high volume of concurrent transactions.

Continue reading

Advertisements

XML datatype instance has too many levels of nested nodes. Maximum allowed depth is 128 levels. Gah!

Yeah, that’s pretty annoying! You’re in a rush to troubleshoot the performance of a stored proc that’s gone rogue, and the tool you are using (something like the SQL statement pictured above) is crashing with this XML error with sys.dm_exec_text_query_plan. You don’t have time to fix the tool properly, so you hack it apart and finally get the query plan text displayed graphically, address the issue and hastily move on to the next burning issue.

Continue reading