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. Sinergija 2011

As a professional announcement, I will not be speaking at PASS this year (nor will I be at the conference).  Instead, I will be in Belgrade, Serbia the following week to speak at the Sinergija 11 conference.  I’ll be doing a talk on the new ColumnStore index and I believe I’ll also be doing a…


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. Left Outer Join Reordering

A question from two of the MVPs: Are these two queries conceptually the same? select,, from A left join C on = left join B on =;   select,, from A left join B on = left join C on =;…


Conor vs. SQLBits X Slide Decks

Thanks for all who attended SQLBits last weekend and for those of you who attended my talks. I had three talks this time at SQLBits, including the technical keynote on Saturday.  I’ve attached these decks for your reference here: Making DW Easy ppt deck SQL Server 2012 ColumnStore Keynote ppt deck Distributed Query Deep Dive…


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…


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. FOREIGN KEY join elimination

I received a question from a friend in Brazil related to foreign keys and join elimination in SQL Server.  Yes, SQL Server can detect that some joins are not needed to return results to the user and skip them.  What is this evil magic, you ask?  Well, let’s walk through it before we get out…


Conor vs. “Does Join Order Matter?”

I got this question/claim again this week, so I’ll write a blog post on it while I wait for my build to complete: It usually goes something like “When I rewrite my query, SQL Server gives me a different plan.  Therefore, I should rewrite all my queries until I find the best plan for each…


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