SQL 2012 :: Remove Auto Generated Statistics After Adding Index
Nov 21, 2014
We have implemented a very small reporting database which has a main table that started off small and has now grown to around half a million rows. Initially, there were no indexes on the table apart from a clustered index, but as the data has grown, performance has dropped and so we have added a number of indexes. This has resolved the performance issues.
Before creating the indexes SQL Server had auto created a number of statistic objects (_WA_Sys_000... etc). After creating the indexes, new statistic objects where created for the new indexes. In some cases, there are duplicate statistics (auto and index) for the same columns.Should I go through and drop the duplicate auto statistics? Will having duplicates cause issues at all?
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Dec 29, 2014
My question: Is it okay to drop all the auto generated column statistics? (for the following scenario)
- I am cleaning up unnecessary objects (tables, unused indexes, overlapping statistics etc) from databases and found out there are more than 1400 auto generated column statistics on one database (lets call it A).
- Database A was used to be our reporting database but from last several years we are using database B for reporting. DB A has all the historical data while DB B only has valid records.
- We are updating all the column statistics with full scan nightly on database A and it is talking almost 2.5 hours to do that. Now I want to drop all the "unnecessary" statistics those were created when DB A was reporting database and they are no longer in use. There is no way to know the creation date of the column statistics that I know of. Statistics "last update date" is of no use because of our nightly job. So I was thinking of dropping all the auto generated column statistics and let the sql server create as it needs from now.
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Apr 23, 2015
I have a sql query:
SELECT
'5' AS 'value/@version',
'database' AS 'value/@type',
'master' AS 'value/name',
LTRIM(RTRIM(( [Server Name] ))) AS 'value/server',
'True' AS 'value/integratedSecurity',
15 AS 'value/connectionTimeout',
4096 AS 'value/packetSize',
'False' AS 'value/encrypted',
'True' AS 'value/selected',
LTRIM(RTRIM(( [Server Name] ))) AS 'value/cserver'
FROM dbo.RedGateServerList
FOR XML PATH(''), ELEMENTS
I need to add some header information to the beginning of the query:
<?xml version="1.0" encoding="utf-16" standalone="yes"?><!--
SQL Multi Script 1
SQL Multi Script
Version:1.1.0.34--><multiScriptApplication version="2" type="multiScriptApplication"><databaseLists type="List_databaseList" version="1">
Everything I have tried ends up as a failure, usually compile issues. My goal here is to be able to automare a configuration file for multiscript so I can keep my server list up to date.
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Jul 20, 2005
Hello group.I have an issue, which has bothered me for a while now:I'm wondering why the column statistics, which SQL Server wants me tocreate, if I turn off auto-created statistics, are so important to theoptimizer?Example: from Northwind (with auto create stats off), I do the following:SELECT * FROM Customers WHERE Country = 'Sweden'My query plan show a clustered index scan, which is expected - no indexexists for Country. BUT, the query plan also shows, that the optimizer ismissing a statistic on Country, which tells me, that the optimizer wouldbenefit from knowing this.I cannot see why? (and I've been trying for a while now).If I create the missing statistics, nothing happens in the query plan (andwhy should it?). I could understand it, if the optimizer suggested an indexon Country - this would make sense, but if creating the missing index, queryanalyzer creates the statistics with an empty index, which seems to me to beless than usable.I've been thinking long and hard about this, but haven't been able to reacha conclusion :) It has some relevance to my work, because allowing theoptimizer to create missing statistics limits my options for designingindexes (e.g. covering) for some rather wide tables, so I'm thinking why notturn it off altogether. But I would like to know the consequences - hopesomebody has already delved into this, and knows a good explanation.RgdsJesper
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Feb 3, 2015
At one of your client sides we have configured Always on with synchronous mode.Also we have schedule rebuild index and update statistics job which runs in night every alternate day. the issue is there are more then 100 sleeping queries which is blocking update statistics job.
I have to stop update statistics job manually once i come to office manually.
Once I have killed blocking sleeping query but then other sleeping query blocked it and so on.
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Feb 7, 2007
Hello,
I've a problem with auto-generated key. In my parent table, some lines have been deleted. I would like to add new lines with the same content in order to restore my database, but I cannot decide on the id value which is an auto-generated key. Is there a solution to set an auto-generated key with a specific value ?
Thank you in advance,
regards,
mathmax
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Mar 13, 2008
Hi,
I want to remove default animated gif report is being generated, how can i achieve it when i upload the rdl to share point, Need to remove actions and print option avialble when i upload my rdl to share point.
Regards,
Navin
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Apr 5, 2006
Hi all,
I'm using SQL 7, there is a setting on DB properties called "Auto update statistics", what kind of statistics does this refers to and how can this stats be accessed?
Thanks for your help!
Gustavo
Thanks,
GS
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Jun 20, 2007
I have Auto Create Statistics and Auto Update Statistics ON in one of my databases.
How do I know what time the Auto Update Statistics Kicks on ?
I dont see it in the log.
Is there a way for me to find out when was the last time Auto Update Statistics kicked on?
TIA
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Feb 3, 2008
Hello everyone,i have a web form to take user details.as soon as the submit button is clicked the form is submitting and the new row is being added into the sqldatabase.its fine ..but in the newly added row, i want the user id(primary key and auto generating) to display in different manner.in mytable column(userid),instead of userid auto displaying 1,2,3,4 ...i want it to display in this way.these are all primary keys of rows added.todaydate-username-1 eg(2.2.2008-jack-1)todaydate-usernaem-2 eg(2.2.2008-zak-2)todaydate-usernaem-3 eg(2.3.2008-leme-2)any idea how to achieve this.?thanks.jack.
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Oct 22, 2006
I downloaded the AdventureWorks OLTP Schema and am trying to use some of the design concepts that are used in this example but I don€™t quite understand some things.
First there is a column named rowguid, at the moment I assume that this is a GUID. If this is wrong most likely my next question will make no sense.
Second if that is indeed a guid all the tables have another id; example would be Employee table would have employeeid and rowguid, why do this? My best guess is that you would use the guid to easily insert (linked/sync) data into multiple tables without needing to retrieve the id from the table that was first input into. My scenario would be inserting an employee; to insert an employee you need to create a row in the employee, contact and address tables and for ease you would use the guid to link these rows. But if this is the case wouldn€™t there be sync issues that would arise?
If my guess is totally off please correct me also if anyone can direct me to some good resources that cover database design.
The schema can be downloaded at http://www.microsoft.com/downloads/details.aspx?familyid=0F6E0BCF-A1B5-4760-8D79-67970F93D5FF&displaylang=en#filelist
Thanks for any help.
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Sep 1, 2000
Hi everyone,
I know that statistics called _WA_... are created on tables when auto create statistics is set on a database. Is this an indication that queries against the table would perform better if indexes were created on the columns in question? (The tables I'm interested in optimising are used equally for transactional querying and reporting)
Thanks for any replies!
Les
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Dec 7, 2007
Hi all,
We are using SQL Server 2005. The auto update statistics and auto create statistics for a database is set to ON. This database has a very heavy work load. When I checked the individual statitics , still the last updated statistics is in a old date value (few months ago).
Is it necessary to manually update the statistics for the same database? Or can we rely upon "auto update statistics" itself ?
Usually in what frequency the manual UPDATE STATISTICS should be run on production system which has heavy transactions ?
Thanks & Regards,
Hariarul
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Aug 31, 2014
can i create Custom Auto-Generated Sequences with SQL Server like DD-0001,DD-0002,DD-0003...... to DD-000........
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Jan 9, 2007
Hey there :)I'm using Ruby on Rails to create a migration of a legacy database onan MS SQL Server. I'd like to name my constraints myself, such as'pk_authors', but in the cases where a table has an auto incrementedIDENTITY(1,1) id field, Rails takes over and adds the primary keyitself when creating the table.This is fine, except then the constraint gets a name like'PK__authors_384934' which is not very intuitive or easily remembered;)I'd like to just throw in an 'ALTER TABLE authors...' statement justafter that table has been created, but I'm not sure how to go aboutrenaming the auto generated constraint since the name it gets ispartially random. Is there any way to indirectly refer to theconstraint like 'RENAME PRIMARY KEY CONSTRAINT ON authors TOpk_authors' or something like that, so that I can rename theconstraint?Thanks in advance,Daniel Buus :)
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Feb 7, 2007
hi guys,
just a question regarding database design
i have a table with an auto-generated primary key but the problem is this:
say i have 4 records,so logically they'll be numbered 1 to 4.so the problem is whenever i delete all records and add new ones,the numbering will start from 5 and not 1 again.
how do i remedy this?
thanx
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Jan 5, 1999
Hi,
How do I quick remove all the documentation generated in the
catalog by sp_primary and sp_foreignkey.
The documentation is misleading and does not correspond with the current primary and foreign keys. I do not wish to drop and create the
tables.
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Sep 12, 2007
Ok, let's say that I do a following inline INSERT statement.....
INSERT INTO Car ( carMake, carModel ) VALUES ( 'Honda', 'S2000' )
When I do this, a carId int value will automatically be generated because it is the Car table's PK and is an int identity. How do I obtain this value so I can immediately use it in let's say, the following example.
INSERT INTO Person ( carId ) VALUES ( @carId ) ..... where @carId is the value I need
Maybe you would say I should do something like.....
SELECT carId FROM Car WHERE carMake = 'Honda' AND carModel = 'S2000'
However, let's assume that the carMake and the carModel fields are NOT unique. I'm sure there's an easy way to extract the new identity value (maybe even in the same query) as the INSERT, but I just don't know how.
Thanks.
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Oct 20, 2007
Over the past week and a half we started experiencing a sporadic slowdown in our production x64 SQL 2005 Ent. Edition server. Users started complaining of slowness then they started getting timeouts. In looking at sp_who2 and perfmon we saw the following during the slow/frozen periods:
* Dramatic increase in Perfmon Active Transactions
* CPU higher than norm, but not dramatically so
* sp_who2 shows a number of spids in SUSPENDED state (and not running waits)
* no blocking indicated from sp_who2
* active connections slowly increasing
* no disk queuing (or at most some spikes to 1)
After a couple of minutes of this we would then see the following:
* no more spids in SUSPENDED state
* Logins per second spikes dramatically
* Active transactions spikes down to "normal levels"
* CPU goes high then levels out at moderately higher than normal
* active connections slowly decreases back towards normal levels
* large spike in lock wait time
We turned on the Async Auto Update Statistics option (after testing in our staging environment) on the primary database about a week before we saw this problem. By turning it off we can visually see the problem go away by watching the above metrics. So my question is, What metrics can I use to see the "blocking" or resouce locking that is causing these problems?
Anyone?
Thx
Ron
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Feb 16, 2014
Since upgrading from SQL Server Management Studio 2008 R2, I've noticed that it no longer autosaves queries that have not been manually saved first. If a file has been manually saved the autorecover files end up in the following directory:
%appdata%MicrosoftSQL Server Management Studio11.0AutoRecoverDatSolution1
However, I have ended up in the situation where I have unsaved queries when my computer has crashed and have not been able to recover them.
I have also found references to .sql files stored in temp files in the following directory, but the files here seem to be very haphazardly caught:
%userprofile%AppDataLocalTemp
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Jun 6, 2000
What are some ways to analyze index coverage and usage? I have a 18 GB database, half is data, other half is indexes and I want to cut down that number as much as I can without affecting performance. Thanks
Peter Karhatsu
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Feb 14, 2001
I have been monitoring some indexes on a table with a lot of inserts, no updates and no deletes. I was wanting to determine when to update the statistics on the index. Does anyone know what would be a good target range for the density when you run the dbcc show_statistics?
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Jun 9, 2000
I was wondering how often you should reindex. By looking at dbcc showcontig and statistics I see that I am heavily fragmented and scan density is between 10-30% on my important indexes. I'm thinking of scheduling this to be done nightly. nay help is much appreciated.
Pete Karhatsu
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Jan 13, 1999
At managing index SQL Server 6.5, there is distribution button. I have a database on production server, one of the table has 20 indexes. When I press the Distribution button, it reveals that most of the indexes have very poor selection of index, from 30% to 99%. There are 6 of them are very good. Based on this statistics, do you think I should remove these indexes? As the book says, if the statistics is higher than 5%, the optimizer will not use index but do a table scan. Removing those index should not affect the performance, is that right?
Your suggestion is very appreciated.
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Sep 5, 2007
Hi
I have a question regarding updating statistics for a primary key.
Background: An update statistics with fullscan is sometimes taking 30 minutes - the table is 80 million rows, with only 4 columns. The table is truncated, and then 80 million rows inserted all in one go.
Now why the update stats is taking that long is another question (I have no idea - any thoughts?), but my question is; Since you can't disable the "not automatically recompute statistics" option for a primary key, and you would think it would be imperitive for the stats to be kept up to date for a PK for inserts.... does this mean the stats would be kept up to date? and an update stat with fullscan isn't required?
Hope someone can help
Thanks
James
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Dec 26, 1999
Anybody had experience dropping the system generated index?
I tried to drop some auto-generated index which usually have name like _WA_Sys_[column name}_07F6335A. Then I follow the table.index name rule. It always show no such index exists in the database. But I can query these indexes in sysindexes and verify they are there. What went wrong?
Help appreciated very much.
wilson
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Nov 28, 2006
I ran the DBCC SHOW_STATISTICS command for all of my indexes; I was told that high density numbers are bad, low numbers good. I have some questions about my results, though; I'm not sure how to interpret them.
Of 48 indexes, 14 have a density of 0. Does this mean that the indexes are not selective enough? Does it mean they're garbage and I should toss them?
6 have a density of NULL. They are all primary keys. I suppose this just means that they're never used because these tables are rarely queried. Would this assumption be correct?
13 have a density of 1. I have no idea what this means.
The others have densities ranging from 0.01210491 to 0.5841165. I was told that the lower this number is, the more selective and thus more useful an index is. I think 0.5841165 is too high a number. Would this be correct?
Thanks in advance.
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Feb 26, 2008
Is it neccessary to schedule a update statistics on index in sql server 2005 on daily basis
Is it neccessary to schedule a rebuild index on index in sql server 2005 on daily basis
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Nov 26, 2007
Hi
I'm trying to add columns to an existing table using ADOX. I'm using C++/CLI. My code is as follow
Table->default->Append("new_column", ADOX:: DataTypeEnum::adWChar, 255);
Table->default["prev_instance_id"]->Properties["Jet OLEDB:Compressed UNICODE Strings"]->default = true;
The first line of code works fine but when I try to set the value of the property I get the following excpetion:
An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in MyDll.dll
Additional information: Multiple-step OLE DB operation generated errors. Check each OLE DB status value, if available. No work was done.
Any idea?
Marco
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Sep 7, 2004
Hello!
Is there any way to determine index usage statistics for a given table?
For examle, I have a table, with three indices. I need to know how many times each index was used. Is it possible?
And second part of question: I need to know, which user overloads my base with their giantic queries. Is there any way to determine, how many system resources each of user's sessions uses?
MS SQL Server 2000 Enterprise Edition.
Thank you!
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Jul 30, 2007
We have a 20 GB database and reorganize indexes and update statistics maintainance takes about 4 hours and the log files grows out of control what is a serious problem since it can not be truncated (database mirroring).
Ivan
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Dec 12, 2006
Hi ..
Please advice whether i have to do update statistics along with Index rebuild (online /off line)
Thanks in advance
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Jan 15, 1999
I have an index that shows distribution statistics of 98.20%, which is very poor. I set show query plan and show statis I/O on. This table has 1113675 rows of data.
*************
select orderID, custId, intertcsi from tblorders
where intertcsi = '2815'
STEP 1
The type of query is SELECT
FROM TABLE
tblorders
Nested iteration
Index : indxInterTCSI
orderID custId intertcsi
----------- ----------- ---------
1015245 1011313 2815
2556392 2556392 2815
....
Table: tblOrders scan count 1, logical reads: 104, physical reads: 58, read ahead reads: 0
***************
Then I use the same select statement to force a table scan:
select orderID, custId, intertcsi from tblorders (index=0)
where intertcsi = '2815'
STEP 1
The type of query is SELECT
FROM TABLE
tblorders
Nested iteration
Table Scan
orderID custId intertcsi
----------- ----------- ---------
60472 61084 2815
102184 102333 2815
...
Table: tblOrders scan count 1, logical reads: 110795, physical reads: 6891, read ahead reads: 103980
When the index is not provided, the logical reads and physical reads increased dramatically. Does this tell me that I should keep that index though it is a poor selection? Is that because a huge table like this make the optimizer use the index. The query without using index takes longer time to run.
Any idea or comment would be very appreciated.
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