Tag Archives: Query

by

Starting now, is the wrong date for insert…

This is part 2 of my log-shipping journey, if you missed part 1, you can find it here.

I collected all of the file names I need, but you will notice I left the dates off. When my files are moved from one domain to another, their created dates are being changed. I needed the real dates for the correct restore order and to match the backups to the logs. If I were a Dark Knight Powershell master, I am sure I would have figured out how to do it. Every time I started to get close, I would would have a production issue or another distraction that needed my time. In the end I landed in my happy place, so we are fixing the dates in the database!

How do I get the right date for a file when the created date is being changed after it has moved? I was super lucky that the date is being stored in the filename too! (Huge thank you to Ola for his awesome database maintenance solution.)

An example of my filename is this:

Batcentral$Alfred_Batman_LOG_20210610_224501.trn

This is how I dissect the filename to get the date and time from it:

  UPDATE [DBAStuff].[dbo].[LogshippingFile]
  SET CreatedDate = CAST(Substring(FileName, (LEN(FileName)-18),8)  +' '+ (Substring(FileName, (LEN(FileName)-9),2)+ ':' + Substring(FileName, (LEN(FileName)-7),2) + ':' + Substring(FileName, (LEN(FileName)-5),2)) AS DATETIME)
  WHERE CreatedDate IS NULL

My filenames are different lengths which means the the dates won’t always be in the same place, instead I go to the end of the string and count backwards because my dates are always consistent. Then I add all the parts back together to get my datetime and update it into my table.

Are we done yet? Nope, there is more.

The song for this post is Toad the Wet Sprockets’ Starting Now

by

Sometimes I get so high, so low, where did all my good plans go?

Greetings! Today I was playing with query store and noticed that I had some failing forced plans. How do you find failing forced plans? I asked this question over and over and finally found an answer.

I started on my main database and ran this query to look at query store:

SELECT *
FROM sys.query_store_plan
WHERE is_forced_plan = 1 and force_failure_count > 0

I had over 20 of them that were failing! Next, I had to figure out how to unforce the failing plans. Some of them were so old, they wouldn’t come up when I tried to look for them using the plan id in the GUI. I did more digging and found this:

EXEC sp_query_store_unforce_plan @query_id = Enter your queryid, @plan_id = Enter your planid

It was incredibly satisfying to watch each of the rows in the first query disappear as I ran them through the second query. This is now on my list of things to check so I can have a clean and healthy query store.

This post’s song is High Low by The Unlikely Candidates

by

I’m Going Under and This Time DBCC Can’t Save Me…

Over the weekend I was troubleshooting an issue and found that part of it was being caused by corruption on one of my databases.  I have seen DBCC CheckDB fix corruption a few times and thought, “No problem, I’ve got this.”

I ran:


ALTER DATABASE CorruptDB SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
BEGIN TRANSACTION;
DBCC CHECKDB ('CorruptDB', REPAIR_REBUILD);
ALTER DATABASE CorruptDB SET MULTI_USER;
COMMIT

I waited for it to finish because the rule is, “Let it finish”.

There were still errors. So I ran it again.

The same errors appeared saying that some errors were waiting on others to be fixed first.  But nothing had fixed and my heart sank.  I had a moment of panic as I furiously googled.  I saw post after post telling me to restore the backup…Did I mention the small problem that the corruption had prevented the backups from completing for this database but didn’t throw an error? My backups were over two weeks old and a roll back was not an option.

I found a post by Paul Randal from 2006 talking about when DBCC CheckDB won’t solve the issue.  He mentioned that sometimes it is just an index or statistic that is corrupted.  This gave me hope and I started tracing my error.  I found it was on a Change Data Capture table that is being used in our replication.  I began pondering an idea.  I removed replication and ran the DBCC CheckDB.  It was clean! No corruption! I breathed and took a backup. Then I added replication back on and ran the DBCC CheckDB again.  It was clean again! Everything was healthy and fine!

Thank you to everyone for your past posts that save my sanity and thank you for DBCC CheckDB!!!

 

The song for this post is Someone You Loved by Lewis Capaldi

by

If I need to rearrange my fragmentation, I will for you….

Oh my goodness, I have been buried and learning tons about Indexing.  Something super cool that I learned was how to know if you need to adjust your fillfactors on your indexes.  My whole DBA career I have usually set it 85 and forgotten it. I learned that I can check my CommandLog and see how often that index is being rebuilt.   I am currently using Ola and when my indexes are rebuilt for maintenance (rebuilt nightly in this case), it is all logged to a table named CommandLog in the master database.  If an index is rebuilt everyday, adjust the fillfactor  down (75) so that it will rebuild less often.  If it nearly never rebuilds, adjust the fillfactor up (90) so it gets rebuilt once in a while and to avoid wasting space in an index. Here is the query I am using to see how often an index has rebuilt in the last 10 days.


SELECT Command, COUNT(StartTime) AS Rebuilt
FROM master.[dbo].[CommandLog]
WHERE CommandType LIKE '%Index%' AND StartTime > GETDATE()-10
GROUP BY Command
ORDER BY Rebuilt DESC

When I see ones that have a rebuilt number of 10, 9 or 8, I know those are rebuilding nearly everyday.  I will adjust their fillfactors down so that I don’t rebuild as often.  My sweet spot right now is once a week, but that doesn’t work for every index (or environment).  This is where the art part comes into the DBA world and I have to think about what is best for the system.  If I have already adjusted something down to 75 and it is still rebuilding frequently, I will adjust that number down more (65, then 55), and back up if it is too low.  I also evaluate how much that index is used and how important it is to keep healthy. If it is hardly ever used, do I want to waste fillfactor space?

Indexing is absolutely an art, but now I have a new brush for my kit by being able to query the CommandLog.

This post’s song is Particles by Nothing But Thieves

by

Lay your weary head to rest and run your query more…

Just coming from a wonderful week at PASS Summit. I sat in two separate sessions where this trick came up and watched as people furiously wrote it down.  Did you know that you can set a query to run multiple times in one command?  All you have to do is add “Go” and the number of times you want it to run.  For example:

SELECT GETDATE()
GO 5

Will return something like this:

go5results

Super cool, right?  It was mentioned in both Brent Ozar’s and Argenis Fernandez’s presentations and I didn’t want to forget. Now you can easily run your queries more and create load on your test system without having to click run over and over again.

Today’s post features Lyrics from Panic! At the Disco’s Cover of Carry On My Wayward Son

by

If Crazy = Genius, I’m rebuilding one partition at a time!

We have had an index job that has been failing for a while.  This is one of those things you really don’t want to clean up because no one is complaining, but you know you should.  I had heard that I could rebuild one partition at a time, but where to start?  Today, I worked my way through it, so here it is so that you can do it too.

First you need to find the biggest indexes, there is a good chance those are the ones that live on partitions. I am removing Primary Keys.


SELECT i.[name] AS IndexName
,SUM(ps.[used_page_count]) * 8 AS IndexSizeKB
FROM sys.dm_db_partition_stats AS ps
INNER JOIN sys.indexes AS i ON ps.[object_id] = i.[object_id]
AND ps.[index_id] = i.[index_id]
WHERE i.name NOT LIKE 'PK%'
GROUP BY i.[name]
ORDER BY IndexSizeKB DESC

The top ones are most likely the ones you want to focus on.  Next, we need to track down the partition function.


SELECT * FROM sys.partition_functions

Next we are going to figure out which partition we want to rebuild.


SELECT sprv.value AS [Value], sprv.boundary_id AS [ID]
FROM sys.partition_functions AS spf
INNER JOIN sys.partition_range_values sprv ON sprv.function_id = spf.function_id
WHERE (spf.name = N'NameOfFunctionFromPartitionFunctions')
ORDER BY [ID] ASC

Pick the number of the partition you want to rebuild.

Next use your index name from earlier.  You will also need the table name and the partition number.


ALTER INDEX [IndexName]
ON [dbo].[TableName]
REBUILD PARTITION = 3

This will rebuild just the partition that you requested.

by

What you gonna do? Memory, I’m coming for you!

Today I needed to quickly check 68 SQL Server Instances Min and Max memory settings. I didn’t have time to go through each one and I know I will need to do this again in the future. Thank goodness I have my Central Management Server configured with all those servers. I was able to connect to my main CMS server, and run this simple query that will tell me all my servers min and max memory setting:

SELECT ServerName, [Max], [Min]
FROM
(SELECT @@ServerName AS ServerName, LEFT(name,3) AS Memory, value
FROM sys.configurations
WHERE name like '%server memory%') AS SourceTable
PIVOT
(
MAX(Value)
FOR Memory IN ([Max], [Min])
) AS PivotTable;

Then, I also used this code from my last post but added a server name to it so I could see what memory was available on each server. 

SELECT @@Servername,physical_memory_kb * 9.5367431640625E-7
FROM sys.dm_os_sys_info