Checking For Dirty Reads/writes

Apr 17, 2008

Problem Statement........

Lets say user A accesses a record and is making an update to a column... next user B accesses the same record and makes an update to the same column and saves the data... how can user A check to see if an update has been made to prevent overwriting the data..

Is there a query statement that user A can write to check for this?

I understand locking can be used to prevent this but is there an alternative to locking.

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Dirty Reads

Aug 1, 2001

If I'm doing a dirty reads and a someone updates a record when I'm trying to read it is it possible to read both the old and new records thereby retrieving two records?

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Can REPLICATION On SQL Server 2000 Allow Dirty Reads

Dec 1, 2005

All my queries are being blocked while the tables are being replicatedand it is causing some 2 minute blocking. Is there a way for theReplication to allow dirty reads because I really don't care aboutthat, I would rather have dirty reads than 2 minute waits.Thanks.

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Reads / Writes Per Second.

Oct 30, 2006

How can You find the reads and writes per second of your hard drives in sql. I am reading my SQL book and it says that your average disk should have 125 or less i/o's. And it gave the forumal but as mentioned I don't know how to find the reads and writes.

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COUNT Of READS And WRITES On A 6.5 Db.

Jul 21, 2000

Is there a way to get a total count of all SELECT, UPDATE, DELETE and INSERT statements to a SQL Server 6.5 database during a 12 hour period? I'm thinking maybe someone knows of a software that reads the log or monitors the server... I've been looking at the performance monitor and, although it has good information, it doesn't capture DML's.

FYI - it's for capacity planning.

TIA,
Mike

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Track Reads And Writes

Mar 5, 2008

GUys,

Is there any way track tables which have most no of reads and writes from a database of 400 tables.

Thanks

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SQL Server 2008 :: Disk Reads And Writes

Nov 5, 2015

How can I measure the disk reads and writes to see if I need to add aditional disks to the server?

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Reads And Writes To A Sql Server Database Per Table

Aug 1, 2006

Is it possible to find the reads/writes to a sql server table ?

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SQL Server 2008 :: High Volume Reads And Writes?

Jul 6, 2015

We are in the process of moving existing clustered SQL server databases to AWS. There is one major database that has intensive reads and writes transactions. I'm wondering what is the best design to optimize the performance for both R/W since we have constant issues historically with the current environment when massive updates are happening. Reads shall have higher priority over writes.

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SQL Server Admin 2014 :: Indexes With More Writes Than Reads

Jul 17, 2015

I have inherited a database that is over-indexed, i.e. there are sometimes 10-20 indexes on a table. The performance is at times not great due to blocking from long running queries. I want to clean up the indexes as a starting point.

Through a query I found some time ago on the SQLCat blog I have discovered a large number of indexes in the database that have a huge disparity between reads and writes. The range of difference is sometimes almost 2 million more writes than reads. Should I just drop the indexes that have say, more than 100,000 more writes than reads and then see what the Missing Index DMVs tell me after a few days of running without those indexes?

In some cases there are a few hundred thousand reads but maybe a million writes on the index. Thus, there are a fair number of reads happening, just not in comparison to the number of writes. In some cases there are almost no reads and a million or more writes. I am obviously dropping those indexes. I just am not sure what to do about the indexes that do have a fair number of reads.

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What Is The Best Way To Achieve Best Latency For Reads And Writes To SQL Server 2005?

Oct 18, 2007

I am looking into various options to improve latency of our application (we figured the latency is mainly because data persistence - writes and reads from DB). I am looking into In-Memory databases also. But, before making that decision (of using in memory databases), I would like to see if there is a way to configure SQL Server 2005 to get as close performance as in-memory databases?

My question:
1. Is there a way that I can configure SQL Server 2005 to use a CACHE that gets loaded as needed basis, so that future database reads/writes will happen to the cache as opposed to disk (db writes)?
2. Is SQL Server 2005 recoverable in such configurations?
3. Are there any ideas/resources where I can get more details? (Such as sample configurations with bench mark numbers, rpevious experiences..etc)

Thanks
Murthy

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Dirty Read

Jun 10, 1999

Can someone tell me what a dirty read is?

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Down And Dirty Database Infrastructure

Mar 29, 2006

Does any have a link, or know of an MS book(s) that details theunderlying database structure, tables, processes? Something thatexplains in detail how/why this stuff is configured and works, likeDDL, TDS, varchar, int, index, tables, normalization, DML, PrimaryKey/Foreign key.

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Keeping Dirty Data

Jan 24, 2008

This may be more of a data design question and not an ssis question, but figured folks here could have a good idea.....the organization I'm in has the business need of collecting data from outside organizations and tracking what data is bad and what data is good. When I say bad data I mean everything from things outside of range to absolute *** - characters in integer columns, integers in character columns, special characters, etc. The data comes in in the form of flat file so it's a free for all until it hits ssis & the db engine.

Eventually of course they work to get the data corrected at the source & resubmitted but in the meantime, they have the legitimate need of not only pushing the data into the database (dirty or not), but keeping all the bad stuff. I can't in good conscience make everything a varchar to catch everything - that would go against the database gods. IMO - I still must make an integer be an integer , characters are characters, etc. But what do I do with the junk? Any thoughts?

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Dirty Read With DataSource Control

Nov 19, 2007

Hi all,
Can anyone tell me how I can do a "Dirty Read" on a SqlDataSource Control? I'm affraid that the record locks are causing problems on the live system.
It is connected to an infromix db using odbc. Thanks.

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BULK INSERT && DIRTY BUFFERS

Aug 26, 2005

Hi all

Using SQL 2000 MSDE

I'm bulk inserting about 3.200.000 records into a table

unfortunately all memory dissapears and never returns the dirty buffers count goes up to 48000 approx.

any ideas on how to rectify this ..... ?

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SQL Server 2005 SP2 'dirty' Install Results In SSIS Failure

Feb 28, 2007

Hi all,

Hope this helps someone. My experience is that an interrupted install of SP2 screws things royally, despite signifying success.

My initial attempt at installing SQL Server 2005 SP2 (64-bit) on our dev server resulted in massive corruption of at least one SSIS solution. Without the option to uninstall the SP2, the prospect of a complete reinstall/recovery totally ruined my day.

When I loaded the SSIS solution, all packages returned the following connection based errors "connection manager will not acquire a connection because the package OffLineMode property is TRUE". OffLineMode property was in fact set to the default "False" for all packages. Individual tasks were broken also. I did not search all packages, but FTP and File System tasks were all corrupted. Nor could I successfully create these tasks in a new packages, even within a new solution.

During the install I recived the following error:
Error Log:
Product : Database Services (MSSQLSERVER)
Product Version (Previous): 2153
Product Version (Final) :
Status : Failure
Log File : C:Program FilesMicrosoft SQL Server90Setup BootstrapLOGHotfixSQL9_Hotfix_KB921896_sqlrun_sql.msp.log
Error Number : 29506
Error Description : MSP Error: 29506 SQL Server Setup failed to modify security permissions on file D:Program FilesMicrosoft SQL ServerMSSQL.1MSSQLData for user xxxxx. To proceed, verify that the account and domain running SQL Server Setup exist, that the account running SQL Server Setup has administrator privileges, and that exists on the destination drive.

The SP2 install continued and with the exception of database Services, all other components were installed successfully.

A very helpful person had posted this solution:

The problem is that there exists a file in this Data directory that the user running SP1 does not have permissions to modify. The workaround is to figure out which file this is (typically a user created DB or some backup program files) and to temporarily assign permission to that file(s). You can revert back to the intended permissions after running SP1.

Sure enough, there was a data and a log file with permission restricted to a single user. Granting permission to the account doing the install worked.

I ran the SP2 again and the database Services component "succeeded". In fact, as outlined, my SSIS packages were unusable.

I re-ran the SP2 install. No components were selected for update, so I manually rechecked each component and executed. This time the install completed successfully for all components, and much to my relief, SSIS functionality was restored.

Pretty scrappy install package IMHO. There are obviously dependencies between the different components being updated, but if these dependencies, and therefore integrity of the update, are broken, the installer nevertheless reports success.

Cheers, Jeremy

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Do Indexes Help Writes?

Sep 26, 2005

I have an application that is insertting thousands of records houlry. The server's hard drives are staying maxxed out. My boss says there is an index problem. I say it is a drive subsystem issue.

Any help would be appreciated to understand this performance problem.

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Writes Are Not Commited Right Away

Mar 25, 2008

Hi!

First of all I want to tell you that I'm not a dba or tuning expert but I've ran a trace on a database with perfomance problems and I've found a strange thing.

The user creates orders for their service people in the organisation. I can see in the trace that inserts are done but they don't produce any writes rightaway. However after 10-15 minutes all the writes are done, what could make the actual write be delayed so much. The application is developed using .net.

/Magnus

Jesus saves. But Gretzky slaps in the rebound.

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Got An Expensive Server, SQL Is Very Slow On Writes

Feb 2, 2004

Hi,

i am experiencing SQl write performance problems on a very shiny server. Got data files on a Raid 1+0, log files on a separate drive, all SCSI, Win2003 server, 6G RAM, 2 Xeon processors. I've created a small benchmarking program and run it on my desktop pc and this 'big' server. Here are the results:

Desktop: SQL server inserts: 78 Seconds, Direct writes to the harddisk(Just write a string to the file 10000 times): 13 seconds

SQLServer: SQL server inserts: 422 Seconds, Direct writes to the harddisk: 16 seconds

So, for some reason, my 'shiny' machine is 6 times slower on writes than my desktop. When i tried comparing the select performance, my shiny server is 10 times faster than my desktop.

Initially i had Raid5 on my server and it had poorer direct write performance but now, direct writes seem to be ok, so, i recon this is a problem related to SQL server.

What can i do to improve the insert performance?

Thanks in advance

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Too Many Writes At Once Causing Time Outs?

Feb 18, 2004

Hi everyone! I'm new to this forum and I suspect I'll be using this forum frequently. Good stuff.

Allow this question may appear to be Web-related, I think the problem is with what I'm doing with the database. Please read.

I'm trying to implement a page tracking solution using ASP and SQL 2000. It basically writes a new record to a table every time a user visits a page on the site. It appeared to work fine at first, then I've increasingly been getting time out errors on my pages -- all pointing to the include file that fires the database write.

Here's the code that's referenced on every page:

Set Conn = Server.CreateObject("ADODB.Connection")
Conn.Open "dsn=x;uid=y;pwd=z;"

Set objRecordset1= Server.CreateObject("ADODB.Recordset")
objRecordset1.Open "SELECT * FROM table",Conn,1,2
objRecordset1.AddNew
objRecordset1.Fi elds("PAGE") = Left(request.servervariables("SCRIPT_NAME"),100)
objReco rdset1.Fields("QUERY_STRING") = Left(request.servervariables("QUERY_STRING"),100)
objRec ordset1.Fields("DATE") = Date()
objRecordset1.Fields("TIME") = Time()
objRecordset1.Fields("PLATFORM") = Left(request.servervariables("HTTP_USER_AGENT"),100)
obj Recordset1.Fields("REFERRER") = Left(request.servervariables("HTTP_REFERER"),100)
objRec ordset1.Fields("USER_IP") = Left(request.servervariables("REMOTE_ADDR"),20)
If Request.Cookies("TEST")("ID")<>"" Then
objRecordset1.Fields("VISITOR_ID") = Request.Cookies("TEST")("ID")
End If
objRecordset1.Update

Conn.Close
Set Conn=Nothing
%>

After taking out the reference to the above code everything speeds back up. So, I know the performance hit and time out issues have to do with the code above.

Is it the simultaneous write to the table, the constant opening and closing of the recordset, the cursor type, the lock type � or combination of things?

HELP!! Thanks!

David

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How To Make Sure No Other Table Writes Happen Between 2 SQL Statements ?

Nov 25, 2007

Ok, here is my situation.....
When someone navigates to a user's profile page on my site, I present them with a slideshow of the user's photos using the AJAX slideshow extender. I obtain the querystring value in the URL (to determine which user's page I'm on) and feed that into a webservice via a context value where an array of photos is created for the slideshow. Now, in order to create the array's size, I do a COUNT of all of that specific user's photos. Then, I run another SQL statement to obtain the path of those photos in the file system. However, during the time of that first SQL query's execution (the COUNT statement) to the time of the second SQL query (getting the paths of the photos), the owner of that profile may upload or delete a photo from his profile. I understand this would be a very rare occurrence since SQL statements 1 and 2 will be executed within milliseconds of each other, but it is still possible I suppose. When this happens, when I try to populate the array, either the array will be too small or too large. I'm using SqlDataReader for this as it seems to be less memory and resource intensive than datasets, but I could be wrong since I'm a relative beginner and newbie. This is what I have in my vb file for the webservice.....Public Function GetSlides(ByVal contextKey As String) As AjaxControlToolkit.Slide()     Dim dbConnection As New SqlConnection("string for the data source, etc.")     Try          dbConnection.Open()          Dim memberId = CInt(contextKey)          Dim photoCountLookupCmd As New SqlCommand _               ("SELECT COUNT(*) FROM Photo WHERE memberId = " & memberId, dbConnection)          Dim thisReader As SqlDataReader = photoCountLookupCmd.ExecuteReader()          Dim photoCount As Integer          While (thisReader.Read())               photoCount = thisReader.GetInt32(0)          End While          thisReader.Close()          Dim MySlides(photoCount - 1) As AjaxControlToolkit.Slide          Dim photoLookupCmd As New SqlCommand _               ("SELECT fullPath FROM Photo WHERE memberId = " & memberId, dbConnection)          thisReader = photoLookupCmd.ExecuteReader()
          Dim i As Integer          For i = 0 To 2               thisReader.Read()               Dim photoUrl As String = thisReader.GetString(0)               MySlides(i) = New AjaxControlToolkit.Slide(photoUrl, "", "")          Next i          thisReader.Close()          Return MySlides     Catch ex As SqlException     Finally          dbConnection.Close()
     End Try
End FunctionI'm trying to use the most efficient method to interact with the database since I don't have unlimited hardware and there may be moderate traffic on the site. Is SqlDataReader the way to go or do I use something else? If I do use SqlDataReader, can someone show me how I can run those 2 SQL statements in best practice? Would I have to somehow lock writing to that table when I start the first SQL statement, then release the lock after I execute the second SQL statement? What's the best practice in this kind of scenario.
Thanks in advance.

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After Upgrading To SQL 7.0 Database Writes/saves Are Slow...

Apr 18, 2002

I upgraded from 6.5 to 7.0 SP3. Now when I save (write) an invoice it takes about 10-12 seconds, at 6.5 it was 1-3 seconds. SQL Server and my Materials App are the only thing running on this box. This is the only area that has gotten slower everything else works great. I have 3 users saving invoices and about 15 people total using the system at one time. It's a compaq DL580 loaded with memory, database is 2,195MB in size. Same 6.5 client to access system as before. Should I rebuild/reindex the database? Is there something from the old 6.5 version I need to remove?? Thanks in advance!!!

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Large Binary Writes Slower Than Expected

Jul 23, 2005

Hello, we are investigating the use of SQL Server as a backend to ourscientific imaging application. We have found that when we write alarge image (60 Megabytes) the performance is quite a bit slower thanwriting 60 single megabyte images. The tests were performed runningSQL Server 2000 on Windows 2003 Enterprise on a single machine toeliminate the network's contribution. Perhaps there is a configurationoption that will allow us to tune SQL Server to better handle largewrites?TIA

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How To Avoid That My Application Writes To Windows' EventLog?

Oct 25, 2006

Hi everyone,

Every time that my application throws an .DTSX file I don't know who or what is writing on eventviewer.application if failed or successful.
Execute method implements a customized class which implements IDTEVENTS but I promise that in any place of my code I'm writing that information.

app.execute(nothing,... MYEVENTS)

Public Class MYEVENTS
Implements IDTEVENTS

..
..
..
..

All the methods are declared although empty but OnQueryCancel which is customized.

How to disable this behaviour?

I'm concerned for that because of we could launch (when it's gonna in live) 300 or 400 packages on-daily basis!!!

Thanks in advance and regards,

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Looking For A Good Example Of A Script Task In The Dataflow That Writes To A File

Jul 4, 2006

I need to write back to a legacy system in the form of flat file --the first row would be a header and the remaining rows would be the actuals rows of data--each field would have a column delimiter of , and a row delimter of CRLF.

The source is a SQL Server 2005 table.

Im looking for a good example of a script task in the dataflow section that writes to a file.

Can anyone show me the code how to do this or point me to a link.

thanks in advance

Dave

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My Error Handler Writes Duplicate Messages To Email!

Aug 22, 2007

I am using an error handler that was provided to me from another source. However, I notice that there's something in the code that writes the error message twice. I tried to discover what it was, but could not seem to pinpoint it. Here's an example of what my email messages look like:

Is activity file current?
The Script returned a failure result.
The extracts in D:myFolder are not current! Data NOT loaded.
Is activity file current?
The Script returned a failure result.
The extracts in D:myFolder are not current! Data NOT loaded.

Obviously, I just want my email to read:

Is activity file current?
The Script returned a failure result.
The extracts in D:myFolder are not current! Data NOT loaded.

Somewhere, errorMessages is being written to more than once. Need help finding the error.

Thanks!

Here is the code from my Event Handlers:

OnError event:

Public Sub Main()

Dim messages As Collections.ArrayList

Try

messages = CType(Dts.Variables("errorMessages").Value, Collections.ArrayList)

Catch ex As Exception

messages = New Collections.ArrayList()

End Try

messages.Add(Dts.Variables("SourceName").Value.ToString())

messages.Add(Dts.Variables("ErrorDescription").Value.ToString())

messages.Add(Dts.Variables("scriptError").Value.ToString())

Dts.Variables("errorMessages").Value = messages

Dts.TaskResult = Dts.Results.Success

End Sub

On PostExecute:

Public Sub Main()

Dim errorDesc As String

Dim messages As Collections.ArrayList

Try

messages = CType(Dts.Variables("errorMessages").Value, Collections.ArrayList)

Catch ex As Exception

Return

End Try

For Each errorDesc In messages

Dts.Variables("emailText").Value = Dts.Variables("emailText").Value.ToString + errorDesc + vbCrLf

Next

Dts.TaskResult = Dts.Results.Success

End Sub

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Deploy To Production Server / SSIS Writes Out Garbage Data

Apr 2, 2015

I built a SSIS(writing out to a flat file ) in 32 bit machine and it woks fine . But however when I deploy to the produciton server(64 bit) the SSIS writes out garbage data . After some research I found out that the problem with the 32 bit OS and 64 bit OS problem.What is my next step. Am I out of luck that now I will have to redesing the SSIS in 64 bit?

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Many Reads

Mar 25, 2008

Hi!
I was assigned to solve performance problems for an application. I fired up Sql Server profiler and started a trace. Downloaded Sql Server Trace Analyzer. It's a trial version so it's very limited. What I found is that one stored procedure generates almost 400 000 reads everytime it's used and it's used everytime the user wants to see his orders. I've tried to translate the t-sql to english from swedish, it looks something like this:

select top 100
o.orderid,
o.name,
o.latestdeldate,
os.name as OrderStatus,
os.orderstatusID,
p.placeID,
p.name as place,
p.address,
p.city,
a.name as worktype,
noOfActions=(select count(*) from actions a where a.order_orderid=o.orderid),
noOfServiceObjects = (select count(*) from Serviceobject s, Actions a where s.Place_PlaceID = o.Place_PlaceID and a.order_orderid = o.orderid and a.Serviceobject_serviceobjectid = s.serviceobjectid),
...
...
...

It has 8 select count(*) in the select statement then in the where statement it has 2 more select count(*).

I know it's very difficult for you to come up with a solution but do you know a better way than to use select count(*) everywhere? The count is used for to show different status flags on the website.

/Magnus

Jesus saves. But Gretzky slaps in the rebound.

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SQL Server Admin 2014 :: Backing Up To Mount Point - Perfmon Shows Zero Writes

Apr 20, 2015

Im backing up to a network directory thats actually a mount point on a different server.My backup was slower than usual so i opened up perfmon to have a look.

When selecting the mount point from the Logical Disks section in perfmon i can see that writes/sec & write bytes/sec both show zero for a long period of time, even though the backup percent complete is increasing.Then all of a sudden the writes to the network share jump massively.

Is there some caching mechanism for backups in sql where during a backup data is only flushed to the disk periodically during backup?

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Reads, Clustering, Etc

May 1, 2008

server: QAT on clustering server ----> 23 seconds
----------------------------------------------------
SS 2000 developer edition SP4
win NT 5.2 (3790) SP4
MeM 7935 MB
processors 4
root directory C:program files...
use a fixed memeroy size 640 MB

reserve physical memory for sql server
minimum query memory 1024 kb

use all available processors
minimum query plan threshold for considering 5

PROFILER READS = 5234

server: MILLER ----> 3 seconds
----------------------------------------------------
SS 2000 developer edition no service pack
win NT 5.2 (3790) SP4
MeM 2047 MB
processors 4
root directory f:MSSQL$INAQAT

dynamically configure sql server memory

use all available processors
minimum query plan threshold for considering 5
PROFILER READS = 598

----------------------------------------------------
Making story short. I got an application that hits only 1 database called RECORDS. I'm getting different duration when running an application. 23 and 3 seconds.
Same database, same objects and same application.
SERVER QAT is our staging server, means lots of databases
SERVER MILLER is just a server i just assembled, means just one database (RECORDS).

Not sure if it's because it's a clustering server that is causing the issue nor the reads. If its the reads, what is causing it? Do you think is the how the memory is configured?. Will the experts pls stand up?

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SQL Server Admin 2014 :: How Data Writes In Multiple Secondary Files If There Is No Filegroup Created

Nov 12, 2014

I read , When sql server Database having multiple data files within single filegroup then sql server writes data in multiple proportional file algorithm where the amount of data written to a file is proportionate to the amount of free space in that file, compared to other files in the filegroup.

so if there is no filegroups created and multiple secondary files are attached in databse , is there same way data stored and writes data in multiple files by the same algorithm or any different way.

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