Columnstore Indexes

There’s a widespread misconception that SQL Server’s columnstore indexes are like an index on every column. I debunk that myth in the first 30 minutes of my Fundamentals of Columnstore class, where I explain that a better way to think of them is that your table is broken up into groups of rows (1M rows…

Lock Escalation Sucks on Columnstore Indexes.

Last Updated June 29, 2021

If you’ve got a regular rowstore table and you need to modify thousands of rows, you can use the fast ordered delete technique to delete rows in batches without hitting the lock escalation threshold. That’s great for rowstore indexes, but…columnstore indexes are different. To demo this technique, I’m going to use the setup from my…

Learn Fundamentals of Columnstore for $1.

Last Updated July 3, 2021

Last week, I gave you a 1-week, $1 deadline, and 777 of you took me up on it. That’s awesome! I love having fun with stuff like this. Let’s do it again! You’ve got 1 week to learn the Fundamentals of Columnstore for $1, and sales close Saturday. Here’s the abstract: Your report queries are…

Free Columnstore Training Class on Tuesday

Last Updated April 1, 2021

Your report queries are too slow. You’ve tried throwing some hardware at it: your production SQL Server has 12 CPU cores or more, 128GB RAM, and SQL Server 2016 or newer. It’s still not enough to handle your growing data. It’s already up over 250GB, and they’re not letting you purge old data. Will columnstore…

Want to use columnstore indexes? Take the ColumnScore test.

Last Updated September 27, 2020

When columnstore indexes first came out in SQL Server 2012, they didn’t get a lot of adoption. Adding a columnstore index made your entire table read-only. I often talk about how indexing is a tradeoff between fast reads and slow writes, but not a lot of folks can make their writes quite that slow. Thankfully, Microsoft…

Announcing a New Class: Fundamentals of Columnstore

Last Updated September 26, 2020

Your report queries are too slow. Will columnstore indexes help? You’ve tried throwing some hardware at it: your production SQL Server has 12 CPU cores or more, 128GB RAM, and SQL Server 2016 or newer. It’s still not enough to handle your growing data. It’s already up over 250GB, and they’re not letting you purge…

When a Columnstore Index Makes Your Query Fail

Last Updated June 8, 2020

If you wanna count the number of rows in a table, I’ve usually said, “It doesn’t matter what you put inside the COUNT() – it can be COUNT(*), COUNT(Id), COUNT(1), or COUNT(‘Chocula’), or even COUNT(1/0) – it all works the same.” And that was true right up until I added a columnstore index. Start with…

How to Make SELECT COUNT(*) Queries Crazy Fast

Last Updated December 22, 2019

Columnstore Indexes, Execution Plans

When you run a SELECT COUNT(*), the speed of the results depends a lot on the structure & settings of the database. Let’s do an exploration of the Votes table in the Stack Overflow database, specifically the 2018-06 ~300GB version where the Votes table has 150,784,380 rows taking up ~5.3GB of space. I’m going to measure…

Research Paper Week: Query Execution in Column-Oriented Database Systems

Last Updated August 20, 2019

This week, I’m sharing some of my favorite papers that I’ve read. Sometimes they’re about future technologies that haven’t shipped yet – and may never ship! Sometimes, like this one, they’re not from Microsoft at all, but from someone else in the industry who’s explaining a problem that we face in SQL Server. SQL Server…

New System Stored Procedures in SQL Server 2017

Last Updated October 3, 2017

Columnstore Indexes, SQL Server 2017

Got a few new stored procs for columnstore indexes: sp_add_columnstore_column_dictionary – input params for @table_id, @column_id sp_is_columnstore_column_dictionary_enabled – as above, plus output param for @is_enabled bit sp_remove_columnstore_column_dictionary – input params for @table_id, @column_id And a couple for snapshot views (which appear to be related to the new snapshot messages in sys.messages) sp_refresh_single_snapshot_view – input param for @view_name…

Why Columnstore Indexes May Still Do Key Lookups

Last Updated June 25, 2021

Columnstore Indexes, Execution Plans, Indexing, SQL Server

I was a bit surprised that key lookups were a possibility with ColumnStore indexes, since “keys” aren’t really their strong point, but since we’re now able to have both clustered ColumnStore indexes alongside row store nonclustered indexes AND nonclustered ColumnStore indexes on tables with row store clustered indexes, this kind of stuff should get a…

ColumnStore Indexes: Rowgroup Elimination and Parameter Sniffing In Stored Procedures

Last Updated May 26, 2020

Columnstore Indexes, Development, Execution Plans, Indexing, Parameter Sniffing, SQL Server, SQL Server 2017

Yazoo Over on his blog, fellow Query Plan aficionado Joe Obbish has a Great Post, Brent® about query patterns that qualify for Rowgroup Elimination. This is really important to performance! It allows scans to skip over stuff it doesn’t need, like skipping over the dialog in, uh… movies with really good fight scenes. Car chases?…

ColumnStore Indexes And Recursive CTEs

Last Updated July 26, 2017

Columnstore Indexes, Indexing, SQL Server

Alone Together When I think about SQL Server features, I often picture a high school cafeteria. AGs are making fun of Mirroring, index rebuilds are walking around taking everyone’s lunch, dta is making a glue sandwich, and no one knows who Service Broker is even though they’ve been going to school together since Kindergarten. At…

Clustered Index key columns in Nonclustered Indexes

Last Updated March 12, 2018

Columnstore Indexes, Indexing, SQL Server

Clustered indexes are fundamental And I’m not just saying that because Kendra is my spiritual adviser! They are not ~a copy~ of the table, they are the table, ordered by the column(s) you choose as the key. It could be one. It could be a few. It could be a GUID! But that’s for another…

How to Add Nonclustered Indexes to Clustered Columnstore Indexes

Last Updated February 13, 2017