SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Very large table - performance issues


Very large table - performance issues

Author
Message
nivek-224024
nivek-224024
SSC-Enthusiastic
SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)SSC-Enthusiastic (111 reputation)

Group: General Forum Members
Points: 111 Visits: 1287
With 2.6 billion rows, be mindful of those INT datatypes. You have probably already considered that, just throwing it out there.
Eric M Russell
Eric M Russell
SSChampion
SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)

Group: General Forum Members
Points: 12094 Visits: 10634
nivek-224024 (5/21/2013)
With 2.6 billion rows, be mindful of those INT datatypes. You have probably already considered that, just throwing it out there.


Your comment is referring to the maximum 2,147,483,647 value for Int datatype?


"The universe is complicated and for the most part beyond your control, but your life is only as complicated as you choose it to be."
Eric M Russell
Eric M Russell
SSChampion
SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)SSChampion (12K reputation)

Group: General Forum Members
Points: 12094 Visits: 10634
Abu Dina (5/21/2013)
We have a tall table that contains 2.6 billion rows

Table structure:



The application which uses this table has been running slow for the last couple of days and it seems to have happened following the addition of about 400 million rows last weekend.

I think it's because of the index fragmentation although I'm not sure how to check if this the case without affecting the application?

So my first question is, how do I check to see if the indexes are fragmented and whether the stats need updating on such a large table?


I notice that your clustered index is on IX_dType. Why was that column chosen to cluster the table. Especially for tables with a large number of rows, you typically want to cluster on a column with unique sequential values. There could very well be fragmentation.


"The universe is complicated and for the most part beyond your control, but your life is only as complicated as you choose it to be."
Bhaskar.Shetty
Bhaskar.Shetty
SSC Eights!
SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)

Group: General Forum Members
Points: 854 Visits: 509
Try running below query, will return you tables list with last statistic updated date and rows updated later on, these tables requires a statistics update with FullScan

SELECT OBJECT_NAME(id),name,STATS_DATE(id, indid),rowmodctr
FROM sys.sysindexes
WHERE STATS_DATE(id, indid)<=DATEADD(DAY,-1,GETDATE())
AND rowmodctr>0
AND id IN (SELECT object_id FROM sys.tables)


GilaMonster
GilaMonster
SSC Guru
SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)

Group: General Forum Members
Points: 86600 Visits: 45246
I would disagree there, stats that are more than a day old and have a single row change absolutely do not need updating. That's almost as bad as blanket updating everything.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


Bhaskar.Shetty
Bhaskar.Shetty
SSC Eights!
SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)SSC Eights! (854 reputation)

Group: General Forum Members
Points: 854 Visits: 509
GilaMonster (5/22/2013)
I would disagree there, stats that are more than a day old and have a single row change absolutely do not need updating. That's almost as bad as blanket updating everything.



It also shows the Rows being inserted / updated / deleted after the last statistics updated, which can give good idea which table need a statistics update, instead of blanket updating everything.
GilaMonster
GilaMonster
SSC Guru
SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)

Group: General Forum Members
Points: 86600 Visits: 45246
Bhaskar.Shetty (5/22/2013)
GilaMonster (5/22/2013)
I would disagree there, stats that are more than a day old and have a single row change absolutely do not need updating. That's almost as bad as blanket updating everything.



It also shows the Rows being inserted / updated / deleted after the last statistics updated, which can give good idea which table need a statistics update, instead of blanket updating everything.


Yes, however your post made no mention of making an educated decision based on the number of rows changed. It said "these tables require a statistics update with full scan", which is not necessarily true and is likely to mislead someone new to SQL that doesn't have the background to understand the nuances of statistics maintenance.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


lnardozi 61862
lnardozi 61862
SSC-Enthusiastic
SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)SSC-Enthusiastic (166 reputation)

Group: General Forum Members
Points: 166 Visits: 615
Have any of the queries changed? Is there maybe an unindexed column in a where clause now? Maybe one index needs a covering column added?
John_P
John_P
Grasshopper
Grasshopper (21 reputation)Grasshopper (21 reputation)Grasshopper (21 reputation)Grasshopper (21 reputation)Grasshopper (21 reputation)Grasshopper (21 reputation)Grasshopper (21 reputation)Grasshopper (21 reputation)

Group: General Forum Members
Points: 21 Visits: 63
I have no idea (maybe someone else here does) but your last 400 million rows would put your DID into negative numbers - assuming it is not an unsigned int. Could that be causing a problem?
GilaMonster
GilaMonster
SSC Guru
SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)SSC Guru (86K reputation)

Group: General Forum Members
Points: 86600 Visits: 45246
John_P (5/22/2013)
I have no idea (maybe someone else here does) but your last 400 million rows would put your DID into negative numbers - assuming it is not an unsigned int. Could that be causing a problem?


If an identity hits maxint, it doesn't loop round and start at negative numbers, instead any further inserts fail with an out of bounds error.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass


Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search