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  • Insert rownumber repeatedly in records in t-sql.

    - by jeff
    Hi, I want to insert a row number in a records like counting rows in a specific number of range. example output: RowNumber ID Name 1 20 a 2 21 b 3 22 c 1 23 d 2 24 e 3 25 f 1 26 g 2 27 h 3 28 i 1 29 j 2 30 k I rather to try using the rownumber() over (partition by order by column name) but my real records are not containing columns that will count into 1-3 rownumber. I already try to loop each of record to insert a row count 1-3 but this loop affects the performance of the query. The query will use for the RDL report, that is why as much as possible the performance of the query must be good. any suggestions are welcome. Thanks

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  • Windows and system processes

    - by jemper
    Note: I've asked this question in a similiar format on superuser but it seems like it may fit here on SO better. It definitely also is about programming as it concerns parts of the Win32 API, Windows in general and process management. So there are these processes that can't be terminated with taskkill - system processes in general. But there also is, for example my Anti Virus program that makes itself "unterminateable". How can I access and mainly terminate system processes under windows? (kill.exe by Microsoft doesn't work) How do processes like anti-virus programs protect themselves? How can you turn them off again, then?

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  • Is it too early to start designing for Task Parallel Library?

    - by Joe Erickson
    I have been following the development of the .NET Task Parallel Library (TPL) with great interest since Microsoft first announced it. There is no doubt in my mind that we will eventually take advantage of TPL. What I am questioning is whether it makes sense to start taking advantage of TPL when Visual Studio 2010 and .NET 4.0 are released, or whether it makes sense to wait a while longer. Why Start Now? The .NET 4.0 Task Parallel Library appears to be well designed and some relatively simple tests demonstrate that it works well on today's multi-core CPUs. I have been very interested in the potential advantages of using multiple lightweight threads to speed up our software since buying my first quad processor Dell Poweredge 6400 about seven years ago. Experiments at that time indicated that it was not worth the effort, which I attributed largely to the overhead of moving data between each CPU's cache (there was no shared cache back then) and RAM. Competitive advantage - some of our customers can never get enough performance and there is no doubt that we can build a faster product using TPL today. It sounds fun. Yes, I realize that some developers would rather poke themselves in the eye with a sharp stick, but we really enjoy maximizing performance. Why Wait? Are today's Intel Nehalem CPUs representative of where we are going as multi-core support matures? You can purchase a Nehalem CPU with 4 cores which share a single level 3 cache today, and most likely a 6 core CPU sharing a single level 3 cache by the time Visual Studio 2010 / .NET 4.0 are released. Obviously, the number of cores will go up over time, but what about the architecture? As the number of cores goes up, will they still share a cache? One issue with Nehalem is the fact that, even though there is a very fast interconnect between the cores, they have non-uniform memory access (NUMA) which can lead to lower performance and less predictable results. Will future multi-core architectures be able to do away with NUMA? Similarly, will the .NET Task Parallel Library change as it matures, requiring modifications to code to fully take advantage of it? Limitations Our core engine is 100% C# and has to run without full trust, so we are limited to using .NET APIs.

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  • SQL Query to delete oldest rows over a certain row count?

    - by Casey
    I have a table that contains log entries for a program I'm writing. I'm looking for ideas on an SQL query (I'm using SQL Server Express 2005) that will keep the newest X number of records, and delete the rest. I have a datetime column that is a timestamp for the log entry. I figure something like the following would work, but I'm not sure of the performance with the IN clause for larger numbers of records. Performance isn't critical, but I might as well do the best I can the first time. DELETE FROM MyTable WHERE PrimaryKey NOT IN (SELECT TOP 10,000 PrimaryKey FROM MyTable ORDER BY TimeStamp DESC)

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  • Weaknesses of Hibernate

    - by Sinuhe
    I would like to know which are the weak points of Hibernate 3. This is not pretended to be a thread against Hibernate. I think it will be a very useful knowledge for decide if Hibernate is the best option for a project or for estimating its time. A weakness can be: A bug Where JDBC or PLSQL are better Performance issues ... Also, can be useful to know some solutions for that problems, better ORM or techniques, or it will be corrected in Hibernate 4. For example, AFAIK, Hibernate will have a very bad performance updating 10000 rows comparing to JDBC in this query: update A set state=3 where state=2

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  • What are the Hot and Cold observables?

    - by Sergey Aldoukhov
    I watched the video and I know the general principles - hot happens even when nobody is subscribed, cold happens "on demand". Also, Publish() converts cold to hot and Defer() converts hot to cold. But still, I feel I am missing the details. Here are some questions I'd like to have answered: Can you give a comprehensive definition for these terms? Does it ever make sense to call Publish on hot observable or Defer on cold? Is there differences between hot and cold definitions for IObservable and IEnumerable? What are the general principles you should take into account when programming for cold or hot? Any other tips on hot/cold observables?

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  • image processing toolbox in matlab

    - by yasuhiro89
    I've got a specific question and a related more general one... Why does imextendedmax() not give for example 9 in A(3,3) as a max? Generally... what is the best way for finding multiple maxes/peaks? The nice thing about imextended max is it allows a threshold where presumably everything under that threshold is not counted whereas imregionalmax and findpeaks are more general, less effective. A=round(rand(5)*10) A = 1 5 4 8 3 5 1 8 8 3 9 3 9 1 2 9 7 3 5 9 6 3 5 6 8 B=imextendedmax(A,8) B = 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

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  • Best way to encrypt certain fiels in SQL Server 2008?

    - by Josh
    I'm writing a .net web app that will read and write information to a SQL 2008 backend database. Some of this information will be highly confidential in nature so I want to encrypt certain data elements. I dont want to use TDE or any full-database encryption for performance reasons. My main concern is protecting this sensitive data as a last resort against a SQL injection or even a database server compromise. My question is what is the best way to do this to preserve performance? Is it faster to use the SQL2008 encryption functions such as EncryptByKey, or would it be faster to encrypt and decrypt the data in the .NET web app itself using a symmetric key stored in the secure web.config and store the encrypted values in the DB?

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  • fastest in-memory cache for XslCompiledTransform

    - by rudnev
    I have a set of xslt stylesheet files. I need to produce the fastest performance of XslConpiledTransform, so i want to make in-memory representation of these stylesheets. I can load them to in-memory collection as IXpathNavigable on application start, and then load each IXPAthNavigable into singleton XslCompiledTransform on each request. But this works only for styleshhets without xsl:import or xsl:include. (Xsl:import is only for files). also i can load into cache many instances of XSLCompiledTransform for each template. Is it reasonable? Are there other ways? What is the best? what are another tips for improving performance MS Xslt processor?

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  • ASMX Still slow after 'Generate serialization assembly'

    - by Buzzer
    This question is related to: http://stackoverflow.com/questions/784918/asmx-web-service-slow-first-request. I inherited a proxy to a legacy ASMX Service. Basically as the post above states, the first call performance is literally 10 times slower than the subsequent calls. I went ahead and turned on ‘Generate serialization assembly' on the project that contains the proxy. The 'serializers' assembly is actually generated. However, I haven't seen any performance increase at all. Do I need to do anything else other than make sure the 'serializers' assembly is in the client's bin directory? Do I have to 'link' the proxy to the 'serializers' assembly during proxy generation (wsdl.exe)? I guess I'm stuck at this point. J Saunders where u at? :)

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  • What are some best practises and "rules of thumb" for creating database indexes?

    - by Ash
    I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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  • Avoid implicit conversion from date to timestamp for selects with Oracle using Hibernate

    - by sapporo
    I'm using Hibernate 3.2.7.GA criteria queries to select rows from an Oracle Enterprise Edition 10.2.0.4.0 database, filtering by a timestamp field. The field in question is of type java.util.Date in Java, and DATE in Oracle. It turns out that the field gets mapped to java.sql.Timestamp, and Oracle converts all rows to TIMESTAMP before comparing to the passed in value, bypassing the index and thereby ruining performance. One solution would be to use Hibernate's sqlRestriction() along with Oracle's TO_DATE function. That would fix performance, but requires rewriting the application code (lots of queries). So is there a more elegant solution? Since Hibernate already does type mapping, could it be configured to do the right thing? Update: The problem occurs in a variety of configurations, but here's one specific example: Oracle Enterprise Edition 10.2.0.4.0 Oracle JDBC Driver 11.1.0.7.0 Hibernate 3.2.7.GA Hibernate's Oracle10gDialect Java 1.6.0_16

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  • What's wrong with my logic here?

    - by stu
    In java they say don't concatenate Strings, instead you should make a stringbuffer and keep adding to that and then when you're all done, use toString() to get a String object out of it. Here's what I don't get. They say do this for performance reasons, because concatenating strings makes lots of temporary objects. But if the goal was performance, then you'd use a language like C/C++ or assembly. The argument for using java is that it is a lot cheaper to buy a faster processor than it is to pay a senior programmer to write fast efficient code. So on the one hand, you're supposed let the hardware take care of the inefficiencies, but on the other hand, you're supposed to use stringbuffers to make java more efficient. While I see that you can do both, use java and stringbuffers, my question is where is the flaw in the logic that you either use a faster chip or you spent extra time writing more efficient software.

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  • How to set that compiler flag?

    - by mystify
    Shark told me this: This instruction is the start of a loop that is not aligned to a 16-byte address boundary. For optimal performance, you should align the start of a hot loop using a compiler directive. With gcc 3.3 or later, use the -falign-loops=16 compiler flag. for (int i=0; i < 4; i++) { // line with the info //...code } How would I set that flag, and does it really improve performance?

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  • Can output from OutputDebugString be viewed in VisualStudio's output window

    - by wageoghe
    I am using C# and VS2010. When I use OutputDebugString to write debug information, should it show up in the output window? I can see the output from OutputDebugString in DebugView, but I thought I would see it in Visual Studio's Output window. I have looked under Tools-Options-Debugging-General and the output is NOT being redirected to the Immediate window. I have also looked under Tools-Options-Debugging-Output Window and all General Output Settings are set to "On". Finally, I have used the drop-down list in the Output window to specify that Debug messages should appear. If I change Tools-Options-Debugging-General to redirect the output to the Immediate window, the OutputDebugString messages do not appear in the immediate window. Here is my entire test program: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; using System.Diagnostics; namespace OutputDebugString { class Program { [DllImport("kernel32.dll", CharSet = CharSet.Auto)] public static extern void OutputDebugString(string message); static void Main(string[] args) { Console.WriteLine("Main - Enter - Console.WriteLine"); Debug.WriteLine("Main - Enter - Debug.WriteLine"); OutputDebugString("Main - Enter - OutputDebugString"); OutputDebugString("Main - Exit - OutputDebugString"); Debug.WriteLine("Main - Exit - Debug.WriteLine"); Console.WriteLine("Main - Exit - Console.WriteLine"); } } } If I run within the debugger, the Debug.WriteLine output does show up in the output window, but the OutputDebugString output does not. If I run from a console window, both Debug.WriteLine and OutputDebugString show up in DebugView. Why doesn't the OutputDebugString output ever show up in the output window? Ultimately, my intent is not to write a lot of debug output with OutputDebugString, rather I will use System.Diagnostics or NLog or something similar. I am just trying to find out, if I configure a logging platform to write to OutputDebugString, will the output be visible from within the debugger. Edit: I went back to my original program (not the simple test above) which uses TraceSources and TraceListeners configured via the app.config file. If I configure the trace sources to write to the System.Diagnostics.DefaultTraceListener (which is documented as writing to OutputDebugString), then the trace source output DOES go to the debug window. However, lines that write directly with OutputDebugString (such as in my simple example) DO NOT go to the debug window. Also, if I use a different TraceListener that writes to OutputDebugString (I got one from Ukadc.Diagnostics at codeplex), that output DOES NOT go to the debug window. Note that I have seen these questions but they did not provide a working solution: here and here

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  • Use XSLT to arrange a list of items in a table

    - by Mark Sp
    I have a linear list of items which I wish to arrange in a table using XSLT. I wish to specify the number of columns as a parameter. For example, if I have a list of 12 items, I can select a 2x6, 3x4, 4x3 or 6x2 table. I cannot see a general way to do this. I have seen this article: http://www.nedcomp.nl/support/origdocs/xml4/extracted/xpath_hdi_1_4llx.aspx It tells you how to generate a table with a specific number of columns, but does not allow a general case. (Ideally there would be a loop for the xsl:value-of lines). Thanks Mark

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  • Managing EntityConnection lifetime

    - by kervin
    There have been many question on managing EntityContext lifetime, e.g. http://stackoverflow.com/questions/813457/instantiating-a-context-in-linq-to-entities I've come to the conclusion that the entity context should be considered a unit-of-work and therefore not reused. Great. But while doing some research for speeding up my database access, I ran into this blog post... Improving Entity Framework Performance The post argues that EFs poor performance compared to other frameworks is often due to the EntityConnection object being created each time a new EntityContext object is needed. To test this I manually created a static EntityConnection in Global.asax.cs Application_Start(). I then converted all my context using statements to using( MyObjContext currContext = new MyObjeContext(globalStaticEFConnection) { .... } This seems to have sped things up a bit without any errors so far as far as I can tell. But is this safe? Does using a applicationwide static EntityConnection introduce race conditions? Best regards, Kervin

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  • filter to reverse lines of a text file

    - by Greg Hewgill
    I'm writing a small shell script that needs to reverse the lines of a text file. Is there a standard filter command to do this sort of thing? My specific application is that I'm getting a list of Git commit identifiers, and I want to process them in reverse order: git log --pretty=oneline work...master | grep -v DEBUG: | cut -d' ' -f1 | reverse The best I've come up with is to implement reverse like this: ... | cat -b | sort -rn | cut -f2- This uses cat to number every line, then sort to sort them in descending numeric order (which ends up reversing the whole file), then cut to remove the unneeded line number. The above works for my application, but may fail in the general case because cat -b only numbers nonblank lines. Is there a better, more general way to do this?

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  • Virtual Function Implementation

    - by Gokul
    Hi, I have kept hearing this statement. Switch..Case is Evil for code maintenance, but it provides better performance(since compiler can inline stuffs etc..). Virtual functions are very good for code maintenance, but they incur a performance penalty of two pointer indirections. Say i have a base class with 2 subclasses(X and Y) and one virtual function, so there will be two virtual tables. The object has a pointer, based on which it will choose a virtual table. So for the compiler, it is more like switch( object's function ptr ) { case 0x....: X->call(); break; case 0x....: Y->call(); }; So why should virtual function cost more, if it can get implemented this way, as the compiler can do the same in-lining and other stuff here. Or explain me, why is it decided not to implement the virtual function execution in this way? Thanks, Gokul.

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