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• DataView Vs DataTable.Select()

  - by Aseem Gautam

  Considering the code below: Dataview someView = new DataView(sometable) someView.RowFilter = someFilter; if(someView.count > 0) { …. } Quite a number of articles which say Datatable.Select() is better than using DataViews, but these are prior to VS2008. Solved: The Mystery of DataView's Poor Performance with Large Recordsets Array of DataRecord vs. DataView: A Dramatic Difference in Performance So in a situation where I just want a subset of datarows based on some filter criteria(single query) and what is better DataView or DataTable.Select()?

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• MsSql Server high Resource Waits and Head Blocker

  - by MartinHN

  Hi I have a MS SQL Server 2008 Standard installation running a database for a webshop. The current size of the database is 2.5 GB. Running on Windows 2008 Standard. Dual Intel Xeon X5355 @ 2.00 GHz. 4 GB RAM. When I open the Activity Monitor, I see that I have a Wait Time (ms/sec) of 5000 in the "Other" category. In the Processes list, all connections from the webshop, the Head Blocker value is 1. I see every day that when I try to access the website, it can take 20-30 secs before it even starts to "work". I know that it is not network latency. (I have a 301 redirect from the same server that is executed instantly). When the first request has been served, it seems as if it's not a sleep anymore and every subsequent request is served instantly with the speed of light. The problem was worse two weeks ago, until I changed every query to include WITH (NOLOCK). But I still experience the problem, and the Wait times in the Activity Monitor is about the same. The largest table (Images) has 32764 rows (448576 KB). Some tables exceed 300000 rows, thought they're much smaller in size than the Images table. I have the default clustered index for every primary key column, only. Any ideas?

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• No performance gain with -setfetchbatchsize on NSfetchedresultscontroller

  - by Snej

  Hi: I tried to gain performance by setting -setfetchbatchsize to 20 on NSFetchedResultsController with about 2k core data entries. But I can't recognize any changes in retrieval time by using -setfetchbatchsize. It is as slow as before on the iPhone... Any experiences?

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• Should we denormalize database to improve performance?

  - by Groo

  We have a requirement to store 500 measurements per second, coming from several devices. Each measurement consists of a timestamp, a quantity type, and several vector values. Right now there is 8 vector values per measurement, and we may consider this number to be constant for needs of our prototype project. We are using HNibernate. Tests are done in SQLite (disk file db, not in-memory), but production will probably be MsSQL. Our Measurement entity class is the one that holds a single measurement, and looks like this: public class Measurement { public virtual Guid Id { get; private set; } public virtual Device Device { get; private set; } public virtual Timestamp Timestamp { get; private set; } public virtual IList<VectorValue> Vectors { get; private set; } } Vector values are stored in a separate table, so that each of them references its parent measurement through a foreign key. We have done a couple of things to ensure that generated SQL is (reasonably) efficient: we are using Guid.Comb for generating IDs, we are flushing around 500 items in a single transaction, ADO.Net batch size is set to 100 (I think SQLIte does not support batch updates? But it might be useful later). The problem Right now we can insert 150-200 measurements per second (which is not fast enough, although this is SQLite we are talking about). Looking at the generated SQL, we can see that in a single transaction we insert (as expected): 1 timestamp 1 measurement 8 vector values which means that we are actually doing 10x more single table inserts: 1500-2000 per second. If we placed everything (all 8 vector values and the timestamp) into the measurement table (adding 9 dedicated columns), it seems that we could increase our insert speed up to 10 times. Switching to SQL server will improve performance, but we would like to know if there might be a way to avoid unnecessary performance costs related to the way database is organized right now. [Edit] With in-memory SQLite I get around 350 items/sec (3500 single table inserts), which I believe is about as good as it gets with NHibernate (taking this post for reference: http://ayende.com/Blog/archive/2009/08/22/nhibernate-perf-tricks.aspx). But I might as well switch to SQL server and stop assuming things, right? I will update my post as soon as I test it.

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• Java - Collections.sort() performance

  - by msr

  Hello, Im using Collections.sort() to sort a LinkedList whose elements implements Comparable interface, so they are sorted in a natural order. In the javadoc documentation its said this method uses mergesort algorithm wich has n*log(n) performance. My question is if there is a more efficient algorithm to sort my LinkedList? The size of that list could be very high and sort will be also very frequent. Thanks!

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• Large Y-axis tickInterval in high charts does not work

  - by ckovacs

  I have a chart at this JSFiddle to demonstrate a problem where our charts are not respecting the y-axis tick interval for large values: http://jsfiddle.net/z2cDu/1/ var plots = {"usBytePlots":[[1362009600000,143663192997],[1362096000000,110184848742],[1362182400000,97694974247],[1362268800000,90764690805],[1362355200000,112436517747],[1362441600000,113563368701],[1362528000000,139579327454],[1362614400000,118406594506],[1362700800000,125366899935],[1362787200000,134189435596],[1362873600000,132873135854],[1362960000000,121002328604],[1363046400000,123138222001],[1363132800000,115667785553],[1363219200000,103746172138],[1363305600000,108602633473],[1363392000000,89133998142],[1363478400000,92170701458],[1363564800000,86696922873],[1363651200000,80980159054],[1363737600000,97604615694],[1363824000000,108011666339],[1363910400000,124419138381],[1363996800000,121704988344],[1364083200000,124337959109],[1364169600000,137495512348],[1364256000000,136017103319],[1364342400000,60867510427]],"dsBytePlots":[[1362009600000,1734982247336],[1362096000000,1471928923201],[1362182400000,1453869593201],[1362268800000,1411787942581],[1362355200000,1460252447519],[1362441600000,1595590020177],[1362528000000,1658007074783],[1362614400000,1411941908699],[1362700800000,1447659369450],[1362787200000,1643008799861],[1362873600000,1792357973023],[1362960000000,1575173242169],[1363046400000,1565139003978],[1363132800000,1549211975554],[1363219200000,1438411448469],[1363305600000,1380445413578],[1363392000000,1298319283929],[1363478400000,1194578344720],[1363564800000,1211409679299],[1363651200000,1142416351471],[1363737600000,1223822672626],[1363824000000,1267692136487],[1363910400000,1384335759541],[1363996800000,1577205919828],[1364083200000,1675715948928],[1364169600000,1517593781592],[1364256000000,1562183018457],[1364342400000,681007264598]],"aggregatedTotalBytes":43476367948896,"aggregatedUsBytes":3150320403841,"aggregatedDsBytes":40326047545055,"maxTotalBytes":328186292129,"maxTotalBitsPerSecond":30387619.641574074} ; $('#container').highcharts({ yAxis: { tickInterval: 53687091200 // 500 gigabytes. Maximum y-axis value is approx 1.8TB }, series : [ { color: 'rgba(80, 180, 77, 0.7)', type: 'areaspline', name : 'Downstream', data : plots.dsBytePlots, total: plots.aggregatedDsBytes }, { color: 'rgba(33, 143, 197, 0.7)', type: 'areaspline', name : 'Upstream', data : plots.usBytePlots, total: plots.aggregatedUsBytes }] }); In this example we are charting bandwidth utilization in bytes. The chart has a maximum value of about 1.8TB. We set the y-axis tick interval to exactly 500GB but the rendered y-axis ticks don't make any sense for the given interval.

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• Need some help understanding the MATLAB `cat` command in high dimensions

  - by Runner

  The commands a = magic(3); b = pascal(3); c = cat(4,a,b); produce a 3-by-3-by-1-by-2 array. Why is the result 3-3-1-2 when the dimension is 4?

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• Performance tuning of a Hibernate+Spring+MySQL project operation that stores images uploaded by user

  - by Umar

  Hi I am working on a web project that is Spring+Hibernate+MySQL based. I am stuck at a point where I have to store images uploaded by a user into the database. Although I have written some code that works well for now, but I believe that things will mess up when the project would go live. Here's my domain class that carries the image bytes: @Entity public class Picture implements java.io.Serializable{ long id; byte[] data; ... // getters and setters } And here's my controller that saves the file on submit: public class PictureUploadFormController extends AbstractBaseFormController{ ... protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception{ MutlipartFile file; // getting MultipartFile from the command object ... // beginning hibernate transaction ... Picture p=new Picture(); p.setData(file.getBytes()); pictureDAO.makePersistent(p); // this method simply calls getSession().saveOrUpdate(p) // committing hiernate transaction ... } ... } Obviously a bad piece of code. Is there anyway I could use InputStream or Blob to save the data, instead of first loading all the bytes from the user into the memory and then pushing them into the database? I did some research on hibernate's support for Blob, and found this in Hibernate In Action book: java.sql.Blob and java.sql.Clob are the most efficient way to handle large objects in Java. Unfortunately, an instance of Blob or Clob is only useable until the JDBC transaction completes. So if your persistent class defines a property of java.sql.Clob or java.sql.Blob (not a good idea anyway), you’ll be restricted in how instances of the class may be used. In particular, you won’t be able to use instances of that class as detached objects. Furthermore, many JDBC drivers don’t feature working support for java.sql.Blob and java.sql.Clob. Therefore, it makes more sense to map large objects using the binary or text mapping type, assuming retrieval of the entire large object into memory isn’t a performance killer. Note you can find up-to-date design patterns and tips for large object usage on the Hibernate website, with tricks for particular platforms. Now apparently the Blob cannot be used, as it is not a good idea anyway, what else could be used to improve the performance? I couldn't find any up-to-date design pattern or any useful information on Hibernate website. So any help/recommendations from stackoverflowers will be much appreciated. Thanks

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• memory usage in C# (.NET) app is very high, until I call System.GC.Collect()

  - by Chris Gray

  I've written an app that spins a few threads each of which read several MB of memory. Each thread then connects to the Internet and uploads the data. this occurs thousands of times and each upload takes some time I'm seeing a situation where (verified with windbg/sos and !dumpheap) that the Byte[] are not getting collected automatically, causing 100/150MB of memory to be reported in task manager if I call System.GC.Collect() i'm seeing a huge drop in memory, a drop of over 100MB I dont like calling System.GC.Collect() and my PC has tons of free memory. however if anyone looks at TaskManager they're going to be concerned, thinking my app is leaking horribly. tips?

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• Caching Mysql database for better performance

  - by kobey

  Hi, I'm using Amazon cloud and I've performance issue since the HDD is not located on my machine. My database is small (~500MB) and I can afford to keep it all in my RAM. I do not want to keep queries in my RAM, i need all the tables there. How can i do it? Thanks, Koby P.S. I'm using ubuntu server...

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• Index on column with only 2 distinct values

  - by Will

  I am wondering about the performance of this index: I have an "Invalid" varchar(1) column that has 2 values: NULL or 'Y' I have an index on (invalid), as well as (invalid, last_validated) Last_validated is a datetime (this is used for a unrelated SELECT query) I am flagging a small amount of items (1-5%) of rows in the table with this as 'to be deleted'. This is so when i DELETE FROM items WHERE invalid='Y' it does not perform a full table scan for the invalid items. A problem seems to be, the actual DELETE is quite slow now, possibly because all the indexes are being removed as they are deleted. Would a bitmap index provide better performance for this? or perhaps no index at all?

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• Are bit operations quick?

  - by flashnik

  I'm dealing with a problem which needs to work with a lot of data. Currently its' values are represented as unsigned int. I know that real values do not exceed some limit, say 1000. That means that I can use unsigned short to store it. One profit is that it'll use less space. Do I have to pay for it by loosing in performance? Another assumption. I decided to store data as short but all calling functions use int, so I need to convert between these datatypes when storing/extracting values. Wiil the performance lost be dramatic? Third assumption. Due to great wish to econom memory I decided to use not short but just 10 bits packed into array of unsigned int. What will happen in this case comparing with previous ones?

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• Lack of ImageList in MenuStrip and performance issues

  - by Ivan

  MenuStrip doesn't support using ImageList images. What are performance issues of this? Are there chances of using too much GDI resources and slow-downs? How many items should be considered acceptable, after which one should implement custom control that draws images from ImageList?

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• CSS font-size causing the last line to be too high

  - by tster

  OK, I have a list (<ul>) then inside each <li> element I have an <a...> Here are all the applicable CSS items to the <a> tag .search_area li a { font-size:11px; } sResCntr li { list-style-type:none; } body { font-family:Arial; } Everything looked great, until I put that font-size:11px in there. The problem is that the hyperlinks wrap to multiple lines within the list (which is fine). But when I decrease the font-size, the last line of the hyperlink always has a larger gap between it and the line above it than the other lines. All the other lines look good, but the last line looks like it is 1.5 spaced or something. I have adjusted the line-height property, but always the last line is larger than the rest. If you need a demo to look at to see what I mean, I can arrange it when I get home.

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• beneficial in terms of performance

  - by Usama Khalil

  Hi, is it better to declare Webservice class object instances as static as the .asmx webservice classes have only static methods. what i want is that i declare and instantiate webservice asmx class as static in aspx Page Behind Class. and on every event call on that page i could perform operation against webservice methods. is it beneficial in terms of performance? Thanks Usama

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• linq: SQL performance on high loaded web applications

  - by Alex

  I started working with linq to SQL several weeks ago. I got really tired of working with SQL server directly through the SQL queries (sqldatareader, sqlcommand and all this good stuff).  After hearing about linq to SQL and mvc I quickly moved all my projects to these technologies. I expected linq to SQL work slower but it suprisongly turned out to be pretty fast, primarily because I always forgot to close my connections when using datareaders. Now I don't have to worry about it. But there's one problem that really bothers me. There's one page that's requested thousands of times a day. The system gets data in the beginning, works with it and updates it. Primarily the updates are ++ @ -- (increase and decrease values). I used to do it like this UPDATE table SET value=value+1 WHERE ID=@I'd It worked with no problems obviously. But with linq to SQL the data is taken in the beginning, moved to the class, changed and then saved. Stats.registeredusers++; Db.submitchanges(); Let's say there were 100 000 users. Linq will say "let it be 100 001" instead of "let it be increased by 1". But if there value of users has already been increased (that happens in my site all the time) then linq will be like oops, this value is already 100 001. Whatever I'll throw an exception" You can change this behavior so that it won't throw an exception but it still will not set the value to 100 002. Like I said, it happened with me all the time. The stas value was increased twice a second on average. I simply had to rewrite this chunk of code with classic ado net. So my question is how can you solve the problem with linq

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• WinForms notifyicon high dpi

  - by Dubila

  in my c# application (2.0 framework) I'm using notifyicon. I set the icon to an ico file that contains 16X16 and 32X32 icons. when I change the DPI to 150% in win7 the icon looks the 16X16 icon. it looks with very low resolution.

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• OpenGL: Textured Primitives + High Framerate

  - by James D

  Short version: What's the best practice going forward for efficiently rendering large numbers of independent texture-mapped, lighted 2D/3D primitives (circles, rects, etc.) in OpenGL? For example: a typical particle system using billboarded quads/triangles, point sprites, or whatever other technique, with blending. Because after reading this thread on the messiness of OpenGL versioning/deprecation I'm starting to have my doubts. My specific question is not the ABCs of displaying primitives in OpenGL, but rather how to do so efficiently in post-deprecation (or pre-deprecation) OpenGL, in a way that's going to be compatible with a wide range of commodity hardware and in a way that's not going to break or itself get deprecated, five years down the line. Thanks!

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• Is there some performance issue between leaving empty ListProperties or using dynamic (expando) prop

  - by indiehacker

  Is there a datastore performance difference between adding dynamic properties of the expando class when they are needed for an entity or the simpler (for me) framework of just setting up all possible properties I might need from the start even though most instances will just be left empty. In my specific case I would be having 5-8 empty ReferenceList properties as 'overhead' that will be empty when I skip using expando class.

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• High performance querying - Suggestions please

  - by Alex Takitani

  Supposing that I have millions of user profiles, with hundreds of fields (name, gender, preferred pet and so on...). You want to make searches on profiles. Ex.:All profiles that has age between x and y, loves butterflies, hates chocolate.... With database would you choose? Suppose that You have a Facebook like load. Speed is a must. Open Source preferred. I've read a lot about Cassandra, HBase, Mongo, Mysql... I just can't decide.....

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• High performance querying - Sugestions please

  - by Alex Takitani

  Supposing that I have millions of user profiles, with hundreds of fields (name, gender, preferred pet and so on...). With database would You choose? Suppose that You have a Facebook like load. Speed is a must. Open Source preferred. I've read a lot about Cassandra, HBase, Mongo, Mysql... I just can't decide.....

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• LINQ entity query performance

  - by Abdel Olakara

  Hi all, I have a silly question. I would like to know if there is performance deference in these two quries: var cObject = from cust in entities.Customer where cust.id == cid select cust; and var cObject = entities.Customer.First( c=> c.id == cid); My query return only one record as I am querying with the primary key. But do they make any difference?

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• Array performance question

  - by Konrad

  I am very familiar with STL vector (and other container) performance guarantees, however I can't seem to find anything concrete about plain arrays. Are pointer arithmetic and [] methods constant or linear time?

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• CEIL is one too high for exact integer divisions

  - by Synetech

  This morning I lost a bunch of files, but because the volume they were one was both internally and externally defragmented, all of the information necessary for a 100% recovery is available; I just need to fill in the FAT where required. I wrote a program to do this and tested it on a copy of the FAT that I dumped to a file and it works perfectly except that for a few of the files (17 out of 526), the FAT chain is one single cluster too long, and thus cross-linked with the next file. Fortunately I know exactly what the problem is. I used ceil in my EOF calculation because even a single byte over will require a whole extra cluster: //Cluster is the starting cluster of the file //Size is the size (in bytes) of the file //BPC is the number of bytes per cluster //NumClust is the number of clusters in the file //EOF is the last cluster of the file’s FAT chain DWORD NumClust = ceil( (float)(Size / BPC) ) DWORD EOF = Cluster + NumClust; This algorithm works fine for everything except files whose size happens to be exactly a multiple of the cluster size, in which case they end up being one cluster too much. I thought about it for a while but am at a loss as to a way to do this. It seems like it should be simple but somehow it is surprisingly tricky. What formula would work for files of any size?

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• Choking experienced while using the TCP/IP Adapter for BizTalk Server 2006

  - by Burhan

  I am using the TCP/IP Adapter for BizTalk Server 2006 which was obtained from codeplex: http://www.codeplex.com/BTSTCPIP Once the application was deployed in production, we started to experience choking in the performance of the application. The more the requests, the more the performance degradation. Sometimes, it happens that the receive ports become non-responsive and we have to forcefully restart the host instances to temporarily let the services respond again but we experience the same problems again and again. I would like to ask if any of you have used the same adapter and have you ever experienced the similar issues? If yes, how can we overcome theses issues. Thanks.

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