Starting Query Tuning

Tim Radney has in introduction on how he tunes a SQL Server instance:

Typically the common compliant when someone’s stating they need to tune a SQL Server is that it’s running slow. What does slow mean? Is it a certain report, a specific application, or everything? Did it just start happening, or has it been getting worse over time? I start by asking the usual triage questions of what the memory, CPU, and disk utilization is compared to when things are normal, did the problem just start happening, and what recently changed. Unless the client is capturing a baseline, they don’t have metrics to compare against to know if current stats are abnormal.

Tuning is about method and tools (in that order).  I like the way Tim does both.

Related Posts

When Adding Indexes Hurts Performance

Jeffry Schwartz takes us through an odd case: Recently, a customer requested that we tune a query that took 13 seconds to return 11 rows.  SQL Server 2017 suggested an index to improve performance, so we added it in a development environment.  The improvement made the query run 647 seconds, almost 50 TIMES longer than the original!  This naturally caused […]

Read More

Power Query and the Benefits of Immutability

Chris Webb explains why immutable expressions can be faster to run multiple times than mutable processes: Instead of taking the value #”Sorted Rows”[Column2]{0} and storing it in the variable Column2 then adding Column2 four times, I’m  adding the expression #”Sorted Rows”[Column2]{0} together four times. The query returns the same number as the previous query. However […]

Read More

Categories

January 2016
MTWTFSS
« Dec Feb »
 123
45678910
11121314151617
18192021222324
25262728293031