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Filtered Indexes and Functions

Eitan Blumin looks at filtered indexes:

In fact, absolutely no functions of any kind can be used within the WHERE clause of a filtered index. Not even schema-bound user-defined scalar functions.

Unfortunately, as stated in the Microsoft Docs page about Filtered Indexes, the WHERE clause of a filtered index can only support simple comparison operators.

Well, it’s not entirely true, as you CAN actually use some functions, but on two conditions:

Read the whole thing. Eitan lays out one limitation of filtered indexes and provides a couple of potential workarounds.