Indexes On Disk

Kendra Little has a great diagram showing which indexes are disk-based and which are memory-resident:

I was looking through some terms in SQL Server documentation the other day, thinking about what it’s like to learn about SQL Server’s indexes when you’re new to the field. I jotted down a note: B-tree = Rowstore = Disk Based

And then I realized that’s not quite right.

Not all disk based indexes are traditional clustered and nonclustered indexes. Columnstore indexes are also disk based. Updatable Columnstore indexes use special rowstore B-trees behind the scenes. And Books Online says “rowstore” also refers to Memory-Optimized tables.

If you’re new to indexing, this picture will save you some learning time.

Related Posts

Making Non-SARGable Queries SARGable with an Index

Denis Gobo violates Betteridge’s Law of Headlines: This question came up the other day from a co-worker, he said he couldn’t change a query but was there a way of making the same query produce a better plan by doing something else perhaps (magic?) He said his query had a WHERE clause that looked like […]

Read More

A Sizing Problem with Heaps

Slava Murygin shows an example where adding a clustered index to an existing table can reduce its size: Tables were very narrow with just a few columns and my expectations for data growth were very modest. However, after just a little while I was very surprised when my database showed huge unexpected growth and size […]

Read More

Categories

July 2016
MTWTFSS
« Jun Aug »
 123
45678910
11121314151617
18192021222324
25262728293031