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Forwarded Records Without User Table Heaps

Erik Darling unravels a conundrum:

When people think about Heaps and the problems they can cause, they don’t often think of temp tables and table variables as Heaps.

Of course, without a clustered index, any table is a Heap.

This isn’t an argument for or against indexing temp tables, but while working with a client we came across something strange!

sp_BlitzFirst was reporting hundreds of thousands of Forwarded Records, but there were no Heaps in user databases.

When we dug in closer to what queries were doing, we found lots of places where temp tables had an insert/update pattern.

Click through for a demonstration and an explanation of why this can be trouble.