Conor vs. more SARGable predicates

I got another question in the mail this week from another reader:   Hi Conor Thanks for an interesting blog. Maybe you have the answer to this question: Why I SQL Server having performance problems with these types of expressions: —————————————————————————————— DECLARE TABLE dbo.Archive( LastName varchar(50), Reference INT, SocialSecurityNumer VARCHAR(10) ) —————– DECLARE dbo.MySearch @Reference…


Conor vs. Join Search Space

I received a question this week from a reader about how SQL Server determines the join order if there are more than 6 joins in a query. There are a lot of details about how SQL Server’s optimizer works here, and some of them are beyond the level of detail that I can/will share publicly….


Conor vs. Row Growth in Read Committed Snapshot Isolation

At PASS last week, I was asked about fragmentation caused by RCSI when a row is first converted to use RCSI. I talked to some people in the team and found that one of my colleagues had already written a nice blog entry about it. Basically, the overhead is taken once and you can…


Conor vs. PASS (Slide Decks)

I had a great time at PASS last week and got to talk to a lot of wonderful customers- thank you! As promised, here are the decks: Update Talk Performance Troubleshooting Talk Happy Querying! Conor


Conor vs. PASS

It’s one of the most exciting weeks of the year to be a SQL Server junkie – PASS is this week in Seattle! I’m giving a talk on the many details of Update queries.  It will cover the various operators and how they work, why the plan shapes look the way they do, where things…


Conor vs. PASS (November in Seattle)

A note to let you know that I will be at PASS this year and plan to give two talks (one in collaboration with a colleague of mine on the QP). One will be a 500 level talk on how Update queries work – lots and lots of gory details.  The other will be a…


Conor vs. Optional Parameters Redux – LIKE %

A question from a reader (thank you, Price, for sending it in).  This is a follow up to my prior post on Optional parameters The question is whether using col LIKE @p where @p is ‘%’ in the case of no parameter is an acceptable workaround to the problems listed in the original post…


Conor vs. Updates – Talk (for those of you in Austin)

I am giving a talk tomorrow (Tuesday) night at the Austin PASS group on how Update Queries are processed/optimized in SQL Server.  The talk will be at the Microsoft office in Austin (which recently moved). More details can be found at the CACTUS web page.  (I don’t know if they have my talk announcement up…


Conor vs. Misbehaving Parameterized Queries + OPTIMIZE FOR hints

In my previous post, I debugged a customer problem for you, including the various guesses I had to make and why they matter. The specific problem was likely related to parameter sensitivity, an issue in query optimization where the optimizer will try to generate a plan that is optimal for one parameter value but perhaps…


Conor vs. Finding a Misbehaving Query

(well, one case of it – the topic is too large for a blog post, so I will focus) I will paraphrase a question I received over the weekend from a SQL Server user: “My server is doing fine.  all of a sudden CPU use goes to 100% and stays there.  If I do dbcc…