We All Have It
You know those tables, right? The ones where developers went and got lazy or didn’t know any better and decided every string column was going to be gigantic.
They may have read, of course, that SQL …
Category: Execution Plans
SQL Server Performance Mysteries: Why Does Production Get A Bad Plan That Development Doesn’t?
Statistical Legacy
A client question that I get quite a bit is around why queries in production get a bad query plan that queries in dev, QA, or staging don’t get is typically answered by looking at statistics.
Primarily, it’s …
CPU & RAM Don’t Lie: Query Metrics I Care About For Tuning
Discarded
There are metrics that I care and don’t care about when I’m looking for queries to tune.
Metrics I don’t care about:
- Logical Reads
- Costs
If a query does “a lot” of reads or has a high “cost”, I …
Getting Parameter Values From A SQL Server Query Plan For Performance Tuning
Property Management
I’m a really big fan of using operator properties for a lot of things, at least visually. Where things sort of fall down for that is copying and pasting things out.
For some stuff, you still need …
Understand Your Plan: Operator Properties
Dragging The Line
There’s a lot of stuff flying around in a query plan. Data and what not.
Sure, you can hover over operators and arrows and see some stuff, but if you really wanna see stuff — I mean …
Understand Your Plan: Query Plan Warnings
Good And Bad
The good news is that SQL Server’s query plans will attempt to warn you about problems. The bad news is that most of the warnings only show up in Actual Execution Plans. The worse news is that …
Understand Your Plan: Missing Index Requests
Just A Friend
Missing index requests aren’t perfect, and that’s okay. But you need to know where they’re not okay so you can start creating better ones.
Let’s start with some basics:
- They really only care about the where clause
Understand Your Plan: Costs (And Why You Shouldn’t Bother With Them)
Goodfor
Costs are okay for figuring out why SQL Server’s cost-based optimizer:
- Chose a particular query plan
- Chose a particular operator
Costs are not okay for figuring out:
- Which queries are the slowest
- Which queries you should tune first
- Which
Understand Your Plan: Estimates And Actuals
But Really
Remember way back when maps were on paper? Some maps were so fancy they called themselves an atlas, even though you bought them at a gas station.
They were neat, and they were mostly right. If there was …
Understand Your Plan: Computing Scalars
Blank Slate
This is awful. It really is. It’s so awful. These operators skated by undetected for years. Acting so innocent with their 0% cost.
Subprime operators, or something.
In this post, I’m going to show you how compute scalars …