SQL 2012 :: Update Stats Full Scan And Memory
Apr 9, 2014
I noticed today a session that was executing a FULL SCAN update as follows:
UPDATE STATISTICS [XXXX].[XXXX].[XXXX] [_WA_Sys_00000009_318D45CA] WITH FULLSCAN
When I checked the sys.dm_exec_query_memory_grants DMV for the session I could see the following values:
requested_memory_kb granted_memory_kb used_memory_kb max_used_memory_kb
145,705,216 145,705,216 139,977,336 139,980,408
When I checked the Properties of the Statistic I can see it is on a varchar(3) field when there are only 3 different values in there - all char(1)
The total size of the data in the table according to the Disk Usage By Top Table Report is 199,680,712KB
So my question is this...
For the UPDATE STATS on this one column with FULL SCAN, does SQL Server read the entire table into the Buffer Pool. If so then if the table had 199,680,712KB of data then why did the session request 145,705,216KB.
Or does SQL Server just read the column and ClusteredIndex Key into the Buffer Pool?
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Jul 22, 2014
I am using Ola Hallengrens scripts for index and stats maintenance but I am wondering what most people to in terms of the maintenance schedules. At present we do an index rebuild reorg weekly, but do people also do update stats nightly?
I suppose there is an element of "it depends" here in that the data may be fairly static so the update stats may not be required, or if heavily updated then perhaps rebuilding indexes may be required more frequently.
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Mar 24, 2015
We have a file import job. This job typically imports millions of records into a SQL2008 DB. After the load the DB performance goes down the drain. Thus far, their solution has been to rebuild indexes on effected tables. I'd like to come up with a better solution. My guess is that after the load, the statistics are shot until the next stats update.
What is the best way to handle this scenario? There must be some way to keep the stats current during a big data load.
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Mar 18, 2015
I have a job that runs nightly, rebuild index. job runs fine every night but every few weeks it fails.
USE msdb
GO
EXECUTE dbo.IndexOptimize
@Databases = 'USER_DATABASES',
@FragmentationLow = NULL,
@FragmentationMedium = 'INDEX_REORGANIZE,INDEX_REBUILD_ONLINE,INDEX_REBUILD_OFFLINE',
@FragmentationHigh = 'INDEX_REBUILD_ONLINE,INDEX_REBUILD_OFFLINE',
@FragmentationLevel1 = 5,
@FragmentationLevel2 = 30,
@SortInTempdb = 'Y',
@UpdateStatistics = 'ALL',
@OnlyModifiedStatistics = 'Y'
This calls the Sp that does the Reindex. It fails at the update statistics with a very generic message. like " Command: UPDATE STATISTICS [xxxx_DB].[dbo].[xxxx_xxx] [_WA_Sys_00000007_49C3F6B7] [SQ... The step failed."
I suspect it has more error but this is all it is showing me when I right click on the job history. therefore, I updated the job step in the advance tab with log to a txt file. Am I on the right track or there is another way to see error some where else.
I looked at the logs but they didn't show any thing.
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Jul 20, 2005
Hi all. Anyone know if sql server collects stats on how many fulltable scans a table gets and if so how do I get at those stats? Tryingto track down poorly indexed tables / processes and I am guessing thatsql server does have this data secreted away somewhere much like mydb2 and informix databases do.
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Sep 19, 2015
I've been having some trouble getting a single-column "varchar(5)" field to reliably use a table seek instead of a table scan. The production table in this case contains 25 million rows. As impressive as it is to scan 25 million rows in 35 seconds, the query should run much faster.
Here's a partial table description:
CREATE TABLE [dbo].[Summaries_MO]
(
[SummaryId] [int] IDENTITY(1,1) NOT NULL,
[zipcode] [char](5) COLLATE Latin1_General_100_BIN2 NOT NULL,
[Golf] [bit] NULL,
[Homeowner] [bit] NULL,
[Code] .....
Typically, this table is accessed with a query that includes:
SELECT ...
FROM SummaryTable
WHERE ixZIP IN (SELECT ZipCode FROM @ZipCodesForMO)
This query insists on using a table scan. I've tried WITH (FORCESEEK) for example, but that just makes the query fail.
As I've investigated this issue I also tried:
SELECT * FROM Summaries WHERE ZipCode IN ('xxxxx', 'xxxxx', 'xxxxx')
When I run this query with 64 or fewer (actual, valid) ZIP codes, the query uses a table seek.But when I give it 65 or more ZIP codes it uses a table scan.
To summarize, the production query always uses a table scan, and when I specify 65 or more ZIP codes the query also uses a table scan. I'm wondering if the data type of the indexed column (Latin1_General_100_BIN2) is somehow the problem. I'll likely try converting the ZIP codes to an integer to see what happens.
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Aug 11, 2004
Is it true that Update Statistics perform record commits if a query is outstanding?
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Aug 8, 2007
Has anyone noticed a performance improvement during trading hours when they replaced sp_updatestats with UPDATE STATISTICS FULLSCAN in their nightly maintenance?
Or is it negligible?
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Apr 17, 2006
SQL Server 2000 on Win2k
I'm fairly new to SQL Server and I'm just wondering if it's possible to Update Statistice for all indexes somehow? I'm looking at the Update Statistics command and it doesn't seem to be possible.
The situation we have is a reporting DB that basically has all it's tables truncated and remade every night by some DTS jobs that import from another datasource and change the data and build some denormalzed tables etc.
Some of the large Insert operations go from taking 8 mins to taking several hours sometimes and updating the stats seems to fix the problem for a while. So I'd like to make sure the optimizer has all the latest stats for all tables.
Any other advice would be appreciated.
Cheers.
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Mar 10, 2003
Does anyone know how to tell how long it took for an auto update statistics to run? I looked under DBCC Show_Statistics and it shows the time the stats were last updated, but not how long it took to update them. Thanks.
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Mar 12, 2015
I am having the following errors with the script below
Msg 102, Level 15, State 1, Line 44
Incorrect syntax near '?'.
Msg 319, Level 15, State 1, Line 47
Incorrect syntax near the keyword 'with'. If this statement is a common table expression, an xmlnamespaces clause or a change tracking context clause, the previous statement must be terminated with a semicolon. it also does not seem to loop around each db
DECLARE @commandNVARCHAR(MAX)
CREATE TABLE #worktable
(
[Database]SYSNAME
,SchemaNameSYSNAME
,ObjectNameSYSNAME
,StatsNameSYSNAME
,ColNameSYSNAME
[code]....
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Nov 6, 2007
Recently we moved few of our databases from SQL 2000 to SQL 2005 (SP 2) using backup and restore. After the restore I did Reindex and update stats on the databases. Since then we have observed performance issues on SQL 2005 databases but this performance problem vanishes the moment we run (sp_updatestats). Is this a problem with SQL 2005 that we have to run sp_updatestats 2 times a days or 3 times a day. In SQL 2000 we ran it only Once a week and still we never had any performance issues. Is there any config change we need to do to fix this problem in SQL 2005?
Thanks !
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Sep 26, 2005
(Assuming SQL Server 2000, auto create statistics on, auto updatestatistics on.)DoesDBCC DBREINDEX(<tablename>)update statistics? If yes, are the statistics equivalent to thosethat would be produced by:UPDATE STATISTICS <tablename> WITH FULLSCAN
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Mar 10, 2003
Recently a production server suffered a critical blocking period and I wanted to know if I could solicit some input. It seems that a stored procedure was in the middle of recompiling while and auto update statistics started. This caused blocking for like an hour on the
single object (stored procedure) that was originally called. The table that the update occurred on and that the
stored procedure is reading form is quite large. It is 2 mil rows and about 140 columns wide. Some info from
sysprocesses is below. The table alone takes up almost 4GB of space, when looking at sp_spaceused. I have some
questions.
1. Can the update statistics for a '_WA%' stats cause
blocking on a table?
2. Does an update stats on an index survive a restart of
SQL server? We tried restarting, but the blocking did not
end.
3. If the stored procedure is running under a compile, can
the server automatically start an update stats and cause
the stored procedure to wait?
4. Can the server automatically start an update stats on
more than one column stats at a time, causing one to be
blocked by the other?
5. We had never seen this issue before going to SQL2K
clustering. Is this something specific to SQL2K and not
SQL7 ?
Thanks for your input.
John Lee
This is the lock info for the blocking processes.
spid dbid ObjId IndId Type Resource Mode Status name
------ ------ ----------- ------ ---- ---------------- -------- ------ -------------------------
142 7 2 1 KEY (6f00035ef42b) S GRANT sysindexes
142 7 2 1 KEY (6f00035ef42b) S GRANT sysindexes
142 7 421576540 0 TAB Sch-S GRANT tJob
142 7 1141579105 0 TAB Sch-S GRANT tPatient_info
142 7 1141579105 0 TAB [UPD-STATS] Sch-M GRANT tPatient_info
142 7 1659921035 0 TAB [COMPILE] X GRANT iDBGetPatInfoRecord
142 7 1659921035 0 TAB Sch-S GRANT iDBGetPatInfoRecord
These are the processes that are being blocked:
spid
------
137
140
Below this is a snapshot of all the SQL processes on the server being blocked.
Save the report and send to the whole database group.
spid kpid blocked waittype waittime lastwaittype waitresource
------ ------ ------- -------- ----------- -------------------------------- -----------------------------
140 4292 142 0x0005 68609 LCK_M_X TAB: 7:1659921035 [[COMPILE]]
137 2576 140 0x0005 64671 LCK_M_X TAB: 7:1659921035 [[COMPILE]]
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Jul 22, 2004
Microsoft states that dbcc DBREINDEX automatically updates statistics but INDEXDEFRAG does not. If this is the case, does MS mean that only the affected statistics are updated or all statistics? Also, is it a good idea to run 'Update Statistics' after doing INDEXDEFRAG?
Clive
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Feb 17, 2012
How do i update the stats of tables when we insert data into it. I believe Auto stats update happens only when 500+ 20% of the rows are changed for a table. Once we insert say some 1000 records in to a particular table the query time takes too long (more than 1 min). The same query executes faster once i manually update the stats.
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Sep 28, 2015
We are planning to standardize our newly deployed sql server, As a part of it we have configured 2 maintenance plans 1) Update Statistics which runs daily and 2) Index Reorganize which runs on weekly.
Apart from above, any other things to be in place for better maintenance of the sql server.
Also, how to Index Rebuild activity for clustered indexes requires any downtime.
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Mar 21, 2014
I am doing sp tuning. It has several lines. SO I divided into several small queries and executed individually and check the execution plans. In one small query, I found table scan is happening. That query is basically retrieving all columns from a table but the table doesn't have any pk or Indexes. So is it better to create non-clustered index to remove table sca.
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Jan 29, 2006
How can I improve performance of my search if I am looking in a table with more than ten million rows with a "like query"?
Does putting an index mean only telling the computer to start in a particular order?
if I index all the coloums does my search get faster ?
how can I decide on an indexing strategy?
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Oct 17, 2014
I have this t-sql code which will get some table stats on one database at a time, I was wondering how I would get it to loop through all databases so it will pull the stats from all tables in all databases. Here is my code:
Select object_schema_name(UStat.object_id)
+ '.' + object_name(UStat.object_id) As [Object Name]
,Case
When Sum(User_Updates + User_Seeks + User_Scans + User_Lookups) = 0 Then Null
Else Cast(Sum(User_Seeks + User_Scans + User_Lookups) As Decimal)
/ Cast(Sum(User_Updates
[code]....
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Mar 28, 2014
I have a table with clustered index on that. I have only 5 columns in that table. Execution plan is showing that Index scan occurred. What are the cause of the Index scan how can we change that to index seek?
I am giving that kind of similar query below
SELECT @ProductID= ProductID FROM Product WITH (NOLOCK) WHERE SalesID= '@salesId' and Product = 'Clothes '
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Mar 4, 2015
I wanted to demonstrate something about CXPACKET wait type. For the purpose of this demo I've created a query in AdventureWorks database that uses a parallel query plan, an extended events session that captured the wait statistics for a single session and a query that shows the extended event's data. I ran it and it worked fine. Then I dropped and recreated the event session (to clear the data), in a new window I wrote a transaction that updated the table fallowed by waitfor statement so the first query will be blocked for few seconds and ran the whole thing again. The select statement was blocked as expected (ran for 9 seconds instead on 1 second as it ran without the blocking), but the wait stats that I got were almost identical to the those that I got without blocking the query.
--Query that uses parallel query plan
With MyCTE as (
select top 50 * from Sales.SalesOrderHeader)
select top 10000 * from Sales.SalesOrderHeader, MyCTE
order by newid()
[code]....
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Jun 26, 2015
We face slow performance issue for like taking long time for same query execution after We apply index rebuild and reorganize index. But, after execution of query or procedure for 2 -3 times, performance will be faster. I have following questions
1 do we need to update stats after we rebuild an reorganize index.
2. is it will be slow for 1-2 times for every query and stored procedure execution after we rebuild and reorganize index?
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Aug 14, 2001
In an ASP, I have a dynamically created SQL statement that amounts to "SELECT * FROM Server1.myDB.dbo.myTable WHERE Col1 = 1" (Col1 is the table's primary key). It returns the data immediately when executed.
However, when the same record is updated with "UPDATE Server1.myDB.dbo.myTable SET Comments = 'blah blah blah' WHERE Col1 = 1", the page times out before the query can complete.
I watched the program in Profiler, and I saw on the update that sp_cursorfetch was being executed as an RPC once per each row in the table. In a table of 78000 records, the timeout occurs well before the last record is fetched, and the update bombs.
I can run the same statements in Query Analyzer from a linked server and have the same results. The execution plan shows that a Remote Query is occurring on the select that returns 1 row, and a Remote Scan is taking place on the update scanning 78000 rows (I guess this is where all the sp_cursorfetch calls are happening...?).
How can I prevent the Remote Scan? How can I prevent the execution of the RPC sp_cursorfetch for each row in the remote table?
Thank you!
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Jun 15, 2015
We have recently migrated quite a databases around 20 from SQL 2000 and 2005 to SQL server 2008R2.
I am using Ola's script for index maintenance for those with compatibility level above 80 as i heard it supports that way.
Hence separated in 2 way job where for those with compatibility level 80, we are running job with below query on each database with 80 as compared
USE ABC
GO
EXEC sp_MSforeachtable @command1="print '?' DBCC DBREINDEX ('?', ' ', 80)"
GO
EXEC sp_updatestats
GO
I am not sure if this is the only way in for those databases, because we are seeing the database getting because of that somewhere using above query.( seems log file filling very rapidly).
But above is not the case with those databases , with compatibility 90 and above.
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Nov 24, 2001
I am running a 9GB SQL Server Database on Compaq ML 530 Prolent with 3 GB of board memory. Max Server Size has been specified as 2.7 Gb, but SQL server is only able to use 1.72 Gb and beyond that even after putting more load the memory usage does not increase, infact the performance starts to degrade.
Any Clues.
Service Pack has been installed.
Thanks in Advance
Manish Wadhwa
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Feb 10, 2015
So I started a new job recently and have noticed a few strange configurations. Typically I would never mess with min memory per query option and index create memory option configuration because i just haven't seen any need to. My typical thought is that if it isn't broke... They have been modified on every single server in my environment.
From Books Online:
• This option is an advanced option and should be changed only by an experienced database administrator or certified SQL Server technician.
• The index create memory option is self-configuring and usually works without requiring adjustment. However, if you experience difficulties creating indexes, consider increasing the value of this option from its run value.
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Aug 9, 2007
I would like to know what happens when a very large reference data set for a lookup transform with full caching enabled is getting loaded during package execution and the computer memory runs out or is very low.
Does SSIS
a) give an out of memory error of some sort
b) resort to a no caching or partial caching mode
c) maintain the full caching mode but will switch to using the paging file(virtual memory).
I think it will resort to using the page file in which case the benefits of in memory lookups are lost and performance would suffer. If I cannot upgrade the memory or shrink the reference set somehow, i should switch that lookup task to use partial caching or no caching with an indexed lookup table. Would this make sense?
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Oct 4, 2007
Hey,
what is the difference between Table Scan und Index Scan?
I find no difitions in the internet
Finchen
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Sep 21, 2007
Hi,
I want to know wht is a
TABLE SCAN
INDEX SCAN
INDEX SEEKand When they are used, Wht is the difference between all these.????
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Sep 20, 2006
Hi,
This is on Sybase but I'm guessing that the same situation would happen on SQL Server. (Please confirm if you know).
I'm looking at these new databases and I'm seeing code similar to this all over the place:
if not exists (select 1 from dbo.t1 where f1 = @p1)
begin
select @errno = @errno | 1
end
There's a unique clustered in dex on t1.f1.
The execution plan shows this for this statement:
FROM TABLE
dbo.t1
EXISTS TABLE : nested iteration.
Table Scan.
Forward scan.
Positioning at start of table.
It's not using my index!!!!!
It seems to be the case with EXISTS statements. Can anybody confirm?
I also hinted to use the index but it still didn't use it.
If the existence check really doesn't use the index, what's a good code alternative to this check?
I did this and it's working great but I wonder if there's a better alternative. I don't really like doing the SET ROWCOUNT 1 and then SET ROWCOUNT 0 thing. SELECT TOP 1 won't work on Sybase, :-(.
SET ROWCOUNT 1
SELECT @cnt = (SELECT 1 FROM dbo.t1 (index ix01)
WHERE f1 = @p1
)
SET ROWCOUNT 0
Appreciate your help.
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Mar 8, 2007
i am using visual web developer 2005 and SQL Express 2005 with VB as the code behindi am using the following code to update the database table Dim update As New SqlDataSource() update.ConnectionString = ConfigurationManager.ConnectionStrings("DatabaseConnectionString").ToString() update.UpdateCommandType = SqlDataSourceCommandType.Text update.UpdateCommand = "UPDATE orderdetail SET fromdesignstatus = 2 ,progresspercentage = 15 , fromdesignlink = '" + designlink + "' WHERE order_id =" + ordersid.ToString() update.Update() update.Dispose() update = Nothing i am using update.Dispose() and update = nothing to release the memoryis it really necessary to use both the commandsif not , in my case which one is enough and what is the reasonplease help me
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Mar 20, 2008
Hi,
I just ended a case with microsoft because I had an issue with Analysis services. The thing is, one of the solutions given by microsoft was to install cumulative update 5 for SQL Server 2005 SP2. Now SQL Server is using all the memory on the server which has windows 2003 server R2 Enterprise SP2 (8GB of Ram) /3GB and /PAE enabled. The weird thing is non of the sql server processes displayed in Task manager shows more than 200MB of memory. But, the server only has 500MB of memory available and 7GB of PF Usage. How did I find out that SQL Server was using the memory, well I shut down the service and 6.8 GB of memory available and the PF Usage went down to just 1.8GB. Turned on again and then the same situation.
well it seems SQL Server is reserving memory or something.
Any clues?
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