Fixing Issues Related To Filtered Indexes

Kevin Chant looks at a few problems that can pop up when using filtered indexes:

In a past post here I did an overview of different index types. I said in that post that I think filtered indexes could be more popular. In this post I will cover fixing some of the problems caused when you first introduce rowstore filtered indexes to a SQL Server database.

Some of you have probably been there already. You’ve put in your first filtered index on a database only to find an issue has happened. I’ve witnessed these issues at a few places. This will hopefully reduce the pain.

I’ve definitely experienced the third issue (which also pops up when using parameterized queries, so the optimizer doesn’t know that it can use the filtered index), but never the first two.

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Forced Parameterization and Filtered Indexes

Aaron Bertrand walks us through a case where filtered indexes become unhelpful: Again, focusing on the areas highlighted in orange: the statement has a parameter @0 (previously it had @1) but, more importantly, the clustered index is scanned now instead of the filtered index. This has impacts throughout the plan, including how many rows are […]

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When Indexes Collide

Andy Mallon gives us a case where it makes sense to have a non-clustered index which shares the same columns as your clustered index columns: First off, let’s remember the difference between clustered & nonclustered indexes The clustered index is organized by the key columns. It also includes every other column as part of the row structure […]

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