Which Filegroup is that Partition Using? How Many Rows Does It Have?
Category:
tsql-programming
Table Partitioning in SQL Server has a bit of a learning curve. It’s tricky to just figure out how much data you have and where the data is stored.
What is that Garbage in my Execution Plan? (Dear SQL DBA Episode 27)
Category:
query-performance
Today I was working on some code samples for a user question, and I hit a weird roadblock.
There was a bunch of garbage in my execution plan that I couldn’t explain. And by ‘garbage’, I mean a nested loop to a whole branch of code that I hadn’t asked SQL Server to run – and a warning about an implicit conversion possibly causing problems with the quality of my execution plan.
How to Find Queries Using an Index (and Queries Using Index Hints)
Category:
query-performance
Sometimes you know a query is out there, but it’s hard to find the exact query.
SQL Server stores query execution plans in cache, but it can be difficult to query the XML it stores. And there’s always a chance that the query plan won’t be there, due to memory pressure, recompile hints, or the plan cache being cleared by setting changes or other administrative actions.
Why You Should Switch in Staging Tables Instead of Renaming Them (Dear SQL DBA Episode 26)
Category:
query-performance
, sql-server
Over the years, I’ve come across a pattern fairly frequently: an application in an OLTP database periodically creates new tables, loads some data into them and fixes it up, then does a switcheroo and replaces old tables with the new tables.
This can cause major problems with blocking if anyone else is querying the table.
Bug: Incorrect modification_counter for Column Stats on Tables with a Clustered Columnstore Index
Category:
query-performance
I don’t find bugs in SQL Server all that often. I find bugs in my own code all the time.
In this case I double checked, and I think it’s a real SQL Server bug.
How to Query Histogram Target XML in Extended Events
Category:
query-performance
When I was recently testing tempdb file usage, I used an Extended Events session that used SQL Server’s histogram target to track sqlserver.file_read events in the tempdb database for a specific session.
Administering COTS databases (ISVs / Third Party Vendors)
Category:
database-administration
, sql-server
I recently received a question from a vendor about databases created by software vendors.