Search Results

Search found 7722 results on 309 pages for 'pitfalls to avoid'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 65/309 | < Previous Page | 61 62 63 64 65 66 67 68 69 70 71 72  | Next Page >

  • How can I specify processor affinity?

    - by BenAlabaster
    I have an application that's having some trouble handling multi-processor systems. It's not an app that I have a particular affection for modifying and would like to avoid it if possible. However, I'm not above modifying the code if I have to. The application is written in VBA (and hence my inclination to avoid touching it). We've noticed that the application seems to run pretty smoothly if we set the processor affinity to a single processor using task manager, only manifesting instability when processor affinity isn't set. I know that I can specify the processor affinity of a task using .NET and as such, there lies a possibility of me writing a shell application that could be used to run legacy applications with a specified processor affinity, does anyone have any experience with this and can throw out some ideas as to headaches I'm likely to run into with this approach? The other question is: Is it in fact possible to modify the core VBA product to handle its own processor affinity? I've never had to handle this with any of my applications natively so this (at this point in time) is completely outside my realm of expertise. Thanks in advance

    Read the article

  • Inheritance of TCollectionItem

    - by JamesB
    I'm planning to have collection of items stored in a TCollection. Each item will derive from TBaseItem which in turn derives from TCollectionItem, With this in mind the Collection will return TBaseItem when an item is requested. Now each TBaseItem will have a Calculate function, in the the TBaseItem this will just return an internal variable, but in each of the derivations of TBaseItem the Calculate function requires a different set of parameters. The Collection will have a Calculate All function which iterates through the collection items and calls each Calculate function, obviously it would need to pass the correct parameters to each function I can think of three ways of doing this: Create a virtual/abstract method for each calculate function in the base class and override it in the derrived class, This would mean no type casting was required when using the object but it would also mean I have to create lots of virtual methods and have a large if...else statement detecting the type and calling the correct "calculate" method, it also means that calling the calculate method is prone to error as you would have to know when writing the code which one to call for which type with the correct parameters to avoid an Error/EAbstractError. Create a record structure with all the possible parameters in and use this as the parameter for the "calculate" function. This has the added benefit of passing this to the "calculate all" function as it can contain all the parameters required and avoid a potentially very long parameter list. Just type casting the TBaseItem to access the correct calculate method. This would tidy up the TBaseItem quite alot compared to the first method. What would be the best way to handle this collection?

    Read the article

  • Scalability 101: How can I design a scalable web application using PHP?

    - by Legend
    I am building a web-application and have a couple of quick questions. From what I learnt, one should not worry about scalability when initially building the app and should only start worrying when the traffic increases. However, this being my first web-application, I am not quite sure if I should take an approach where I design things in an ad-hoc manner and later "fix" them. I have been reading stories about how people start off with an app that gets millions of users in a week or two. Not that I will face the same situation but I can't help but wonder, how do these people do it? Currently, I bought a shared hosting account on Lunarpages and that got me started in building and testing the application. However, I am interested in learning how to build the same application in a scalable-manner using the cloud, for instance, Amazon's EC2. From my understanding, I can see a couple of components: There is a load balancer that first receives requests and then decides where to route each request This request is then handled by a server replica that then processes the request and updates (if required) the database and sends back the response to the client If a similar request comes in, then a caching mechanism like memcached kicks into picture and returns objects from the cache A blackbox that handles database replication Specifically, I am trying to do the following: Setting up a load balancer (my homework revealed that HAProxy is one such load balancer) Setting up replication so that databases can be synchronized Using memcached Configuring Apache to work with multiple web servers Partitioning application to use Amazon EC2 and Amazon S3 (my application is something that will need great deal of storage) Finally, how can I avoid burning myself when using Amazon services? Because this is just a learning phase, I can probably do with 2-3 servers with a simple load balancer and replication but until I want to avoid paying loads of money accidentally. I am able to find resources on individual topics but am unable to find something that starts off from the big picture. Can someone please help me get started?

    Read the article

  • How to model in J2EE / JEE?

    - by Harry
    Let's say, I have decided to go with J(2)EE stack for my enterprise application. Now, for domain modelling (or: for designing the M of MVC), which APIs can I safely assume and use, and which I should stay away from... say, via a layer of abstraction? For example, Should I go ahead and litter my Model with calls to Hibernate/JPA API? Or, should I build an abstraction... a persistence layer of my own to avoid hard-coding against these two specific persistence APIs? Why I ask this: Few years ago, there was this Kodo API which got superseded by Hibernate. If one had designed a persistence layer and coded the rest of the model against this layer (instead of littering the Model with calls to specific vendor API), it would have allowed one to (relatively) easily switch from Kodo to Hibernate to xyz. Is it recommended to make aggressive use of the *QL provided by your persistence vendor in your domain model? I'm not aware of any real-world issues (like performance, scalability, portability, etc) arising out of a heavy use of an HQL-like language. Why I ask this: I would like to avoid, as much as possible, writing custom code when the same could be accomplished via query language that is more portable than SQL. Sorry, but I'm a complete newbie to this area. Where could I find more info on this topic? Many thanks in advance. /HS

    Read the article

  • Animate screen while loading textures

    - by Omega
    My RPG-like game has random battles. When the player enters a random battle, it is necessary for my game to load the textures used within that battle (animated monsters, animations, etc). The textures are quite a lot, and rather big (the battles are very graphical intensive). Such process consumes significant time. And while it is loading, the whole screen freezes. The game's map freezes, and the wait time is significant - I personally find it annoying. I can't afford to preload the textures because, after doing some math, I realized: If I preload all the textures at the beginning of the game, the application will definitely crash. If I preload the textures that are used in a specific map when the player enters the map, the application is very likely to crash as well. I can only afford to load the textures when I need them, and dispose of them as soon as the battle ends. I'd prefer to not use a "loading screen" image because it affects my game's design and concept. I want to avoid this approach. If I could do some kind of animation while loading the textures, it would be great, which leads to my question: is that possible? What kind of animation, you ask? Well, how about... you remember when Final Fantasy used to distort the screen while apparently loading the textures? Something like that. But well, distorting is quite a time-consuming process as well, so maybe just a cool frame-by-frame animation or something. While writing this, I realized that I could make small pauses between textures (there are multiple textures), and during such pauses, I update the screen to represent the animation's state. However, this is very unlikely to happen, because each texture is 2048x2048, so the animation would be refreshed at a rather laggy (and annoying) rate. I'd prefer to avoid this as well.

    Read the article

  • java.net.BindException How can I clear the sockets or what ever is causing it?

    - by user2266067
    I need some help with, I guess a simple networking related problem I'm having. It will also help me better understand how all this works by knowing what isn't being .close()'ed. I'm sure this is pretty simple, but for me its all very new. This is the client program. I can most likely append the server then, if I can figure this out. Thanks public class Server { public static void main(String[] args) { start(); } static int start = 0; public static void start() { try { ServerSocket serverSocket = new ServerSocket(4567); Socket socket = serverSocket.accept(); //1) Take and echo input (In this case a message) BufferedReader bf = new BufferedReader(new InputStreamReader(socket.getInputStream())); String message = bf.readLine(); System.out.println("Message recieved from Client:" + message); //2) Response of client message PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true); printWriter.println("Server echoing back the message ' " + message + " ' from Client"); } catch (IOException e) { System.out.println("e " + e); System.exit(-1); } start++; clearUp(); if (start < 5) { System.out.println("Closing binds and Restarting" + start); start(); } } public void clearUp(){ //How would I clear the stuff that is left bound so I can restart via start() and avoid the java.net.BindException: Address already in use: JVM_Bind ? } } How would I clear the stuff that is left bound so I can restart via start() and avoid java.net.BindException: Address already in use: JVM_Bind ?

    Read the article

  • std::vector elements initializing

    - by Chameleon
    std::vector<int> v1(1000); std::vector<std::vector<int>> v2(1000); std::vector<std::vector<int>::const_iterator> v3(1000); How elements of these 3 vectors initialized? About int, I test it and I saw that all elements become 0. Is this standard? I believed that primitives remain undefined. I create a vector with 300000000 elements, give non-zero values, delete it and recreate it, to avoid OS memory clear for data safety. Elements of recreated vector were 0 too. What about iterator? Is there a initial value (0) for default constructor or initial value remains undefined? When I check this, iterators point to 0, but this can be OS When I create a special object to track constructors, I saw that for first object, vector run the default constructor and for all others it run the copy constructor. Is this standard? Is there a way to completely avoid initialization of elements? Or I must create my own vector? (Oh my God, I always say NOT ANOTHER VECTOR IMPLEMENTATION) I ask because I use ultra huge sparse matrices with parallel processing, so I cannot use push_back() and of course I don't want useless initialization, when later I will change the value.

    Read the article

  • ASP.Net MVC: Change Routes dynamically

    - by Frank
    Hi, usually, when I look at a ASP.Net MVC application, the Route table gets configured at startup and is not touched ever after. I have a couple of questions on that but they are closely related to each other: Is it possible to change the route table at runtime? How would/should I avoid threading issues? Is there maybe a better way to provide a dynamic URL? I know that IDs etc. can appear in the URL but can't see how this could be applicable in what I want to achieve. How can I avoid that, even though I have the default controller/action route defined, that default route doesn't work for a specific combination, e.g. the "Post" action on the "Comments" controller is not available through the default route? Background: Comment Spammers usually grab the posting URL from the website and then don't bother to go through the website anymore to do their automated spamming. If I regularly modify my post URL to some random one, spammers would have to go back to the site and find the correct post URL to try spamming. If that URL changes constantly I'd think that that could make the spammers' work more tedious, which should usually mean that they give up on the affected URL.

    Read the article

  • GNU Makefile: multiple outputs from single rule + preventing intermediate files from being deleted

    - by makesaurus
    This is sort of a continuation of question from link text. The problem is that there is a rule generating multiple outputs from a single input, and the command is time-consuming so we would prefer to avoid recomputation. Now there is an additional twist, that we want to keep files from being deleted as intermediate files, and rules involve wildcards to allow for parameters. The solution suggested was that we set up the following rule: file-a.out: program file.in ./program file.in file-a.out file-b.out file-c.out file-b.out: file-a.out @ file-c.out: file-b.out @ Then, calling make file-c.out creates both and we avoid issues with running make in parallel with -j switch. All fine so far. The problem is the following. Because the above solution sets up a chain in the DAG, make considers it differently; the files file-a.out and file-b.out are treated as intermediate files, and they by default get deleted as unnecessary as soon as file-c.out is ready. A way of avoiding that was mentioned somewhere here, and consists of adding file-a.out and file-b.out as dependencies of a target .SECONDARY, which keeps them from being deleted. Unfortunately, this does not solve my case because my rules use wildcard patters; specifically, my rules look more like this: file-a-%.out: program file.in ./program $* file.in file-a-$*.out file-b-$*.out file-c-$*.out file-b-%.out: file-a-%.out @ file-c-%.out: file-b-%.out @ so that one can pass a parameter that gets included in the file name, for example by running make file-c-12.out The solution that make documentation suggests is to add these as implicit rules to the list of dependencies of .PRECIOUS, thus keeping these files from being deleted. The solution with .PRECIOUS works, but it also prevents these files from being deleted when a rule fails and files are incomplete. Is there any other way to make this work?

    Read the article

  • Refactoring a complicated if-condition

    - by kumar kasimala
    Hi all, Can anyone suggest best way to avoid most if conditions? I have below code, I want avoid most of cases if conditions, how to do it ? any solution is great help; if (adjustment.adjustmentAccount.isIncrease) { if (adjustment.increaseVATLine) { if (adjustment.vatItem.isSalesType) { entry2.setDebit(adjustment.total); entry2.setCredit(0d); } else { entry2.setCredit(adjustment.total); entry2.setDebit(0d); } } else { if (adjustment.vatItem.isSalesType) { entry2.setCredit(adjustment.total); entry2.setDebit(0d); } else { entry2.setDebit(adjustment.total); entry2.setCredit(0d); } } } else { if (adjustment.increaseVATLine) { if (adjustment.vatItem.isSalesType) { entry2.setCredit(adjustment.total); entry2.setDebit(0d); } else { entry2.setDebit(adjustment.total); entry2.setCredit(0d); } } else { if (adjustment.vatItem.isSalesType) { entry2.setDebit(adjustment.total); entry2.setCredit(0d); } else { entry2.setCredit(adjustment.total); entry2.setDebit(0d); } } }

    Read the article

  • mod_rewrite: no access to real files and directories

    - by tshabalala
    Hello. I use mod_rewrite/.htaccess for pretty URLs. I forward all the requests to my index.php, like this: RewriteRule ^/?([a-zA-Z0-9/-]+)/?$ /index.php [NC,L] The index.php then handles the requests. I'm also using this condition/rule to eliminate trailing slashes (or rather rewrite them to the URL without a trailing slash, with a 301 redirect; I'm doing this to avoid duplicate content and because I like no trailing slashes better): RewriteCond %{HTTP_HOST} !^\.localhost$ [NC] RewriteRule ^(.+)/$ http://%{HTTP_HOST}/$1 [R=301,L] This works well, except that I now get an infinite loop when trying to access a (real) directory (the rewrite rule removes the trailing slash, the server adds it again, ...). I solved this by setting the DirectorySlash directive to Off: DirectorySlash Off I don't know how good this solution is, I don't feel too confident about it tbh. Anyway, what I'd like to do is completely ignore "real" files and directories, since I don't need them and I only use pretty URLs with "virtual" files/directories anyway. This would allow me to avoid the DirectorySlash workaround/hack too. Is this possible? Thanks!

    Read the article

  • why it makes ie6 or ie8 compatible mode crash

    - by hylin
    Anybody can tell me why those code can make ie6 or ie8 compatible mode crash? PS:I know,there is so many ways to avoid this satuation, but I just want to know why. To avoid: Change class="wrapper"--class="wrapper2" or other != "wrapper" $('wrapper').style.overflow='visible'; -- setTimeout(function(){$('wrapper').style.overflow='visible';},10); Or remove any style , js operation... <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <style>.wrapper{width:975px;margin:60px auto 0}</style> </head> <body id="wrapper" style="overflow:hidden;"> <div id="overlay" style="position:absolute;"></div> <div class="wrapper"> <input type="text" id="input1"/> <a id="btn" href="javascript:;">test</a> </div> <script type="text/javascript"> $('btn').onclick = function(){ $('overlay').style.display='none'; $('wrapper').style.overflow='visible'; $("input1").focus(); } function $(s){ return document.getElementById(s); } </script> </body> </html>

    Read the article

  • MySQL Datefields: duplicate or calculate?

    - by Konerak
    We are using a table with a structure imposed upon us more than 10 years ago. We are allowed to add columns, but urged not to change existing columns. Certain columns are meant to represent dates, but are put in different format. Amongst others: * CHAR(6): YYMMDD * CHAR(6): DDMMYY * CHAR(8): YYYYMMDD * CHAR(8): DDMMYYYY * DATE * DATETIME Since we now would like to do some more complex queries, using advanced date functions, my manager proposed to d*uplicate those problem columns* to a proper FORMATTED_OLDCOLUMNNAME column using a DATE or DATETIME format. Is this the way to go? Couldn't we just use the STR_TO_DATE function each time we accessed the columns? To avoid every query having to copy-paste the function, I could still work with a view or a stored procedure, but duplicating data to avoid recalculation sounds wrong. Solutions I see (I guess I prefer 2.2.1) 1. Physically duplicate columns 1.1 In the same table 1.1.1 Added by each script that does a modification (INSERT/UPDATE/REPLACE/...) 1.1.2 Maintained by a trigger on each modification 1.2 In a separate table 1.2.1 Added by each script that does a modification (INSERT/UPDATE/REPLACE/...) 1.2.2 Maintained by a trigger on each modification 2. On-demand transformation 2.1 Each query has to perform the transformation 2.1.1 Using copy-paste in the source code 2.1.2 Using a library 2.1.3 Using a STORED PROCEDURE 2.2 A view performs the transformation 2.2.1 A separate table replacing the entire table 2.2.2 A separate table just adding the date-fields for the primary keys Am I right to say it's better to recalculate than to store? And would a view be a good solution?

    Read the article

  • make java plugin use the browser certificates

    - by Shalom938
    We have a java applet that communicates with a spring application running on tomcat and using spring's http invoker. We want to secure the applet using ssl with client authentication, we have a jsp page for login, after successful login the applet loads. The jsp page is secured with ssl, when the applet loads the http invoker inside the applet is doing a second handshake apparently not related to the browser handshake, OK, I don't mind that, but I want the java plugin to use browser certificates and client certificates but its not, I have to load the client certificate to the java plugin also using the java ControlPanel, and if my server's certificate is self signed then I have to load the server certificate also to the java ControlPanel and to the nrowser. Another thing is when the applet starts loading the java plugin pops a dialog asking for the client keystore password, I would like to avoid that. So to conclude: I would like the java plugin to use the browser's trusted certificates and client certificates, and to avoid the keystore password dialog that pops up. I have googled for it for two days and can't find any clue of how to accomplish that. I will appreciate any help. I'm using jdk 1.6.0 u23 and firefox 3.6.13.

    Read the article

  • What is the proper way to wait a script loaded completely before another

    - by FatDogMark
    I am making a website that is divided by several sections <div id='section-1' class='section'>web content</div> <div id='section-2' class='section'>web content</div> I have like ten sections on my webpage ,each sections height is set to the user window height when document is ready by javascript $('.section').height($(window).height()); Some effects like slideshows on my webpage require the calculated height of the section in order to work properly. Therefore I always use something like this at document ready as a solution. setTimeout(startslideshow,1000); setTimeout(startanimations,1000); ...etc To make sure the section height is the user window height before the slideshow's code start because the sections cannot change to user window height instantly once the webpage loaded will generate serious problems in my slideshow code,like wrong calculated positions. Therefore there will be a situation that's after the page loaded, there will be about a second everything is messed up,before everything can works properly, how could I avoid that being seen by the user? I tried to $(document).hide(),or $('html,body').hide(), then fade in after a second,but I get other weird problems, especially on ipad,my fixed position top navigation bar will always become 'not fixed' while user is scrolling. As I am a self-learner, I afraid my method is not typical. I want to know what is the common ways of real web programmers usually do when they have to divide his webpage into different sections and set its height to window height , then make sure the other effects that's depends on the section height works properly and avoid to wait the height change for a second?

    Read the article

  • safe structures embedded systems

    - by user405633
    I have a packet from a server which is parsed in an embedded system. I need to parse it in a very efficient way, avoiding memory issues, like overlapping, corrupting my memory and others variables. The packet has this structure "String A:String B:String C". As example, here the packet received is compounded of three parts separated using a separator ":", all these parts must be accesibles from an structure. Which is the most efficient and safe way to do this. A.- Creating an structure with attributes (partA, PartB PartC) sized with a criteria based on avoid exceed this sized from the source of the packet, and attaching also an index with the length of each part in a way to avoid extracting garbage, this part length indicator could be less or equal to 300 (ie: part B). typedef struct parsedPacket_struct { char partA[2];int len_partA; char partB[300];int len_partB; char partC[2];int len_partC; }parsedPacket; The problem here is that I am wasting memory, because each structure should copy the packet content to each the structure, is there a way to only save the base address of each part and still using the len_partX.

    Read the article

  • Built in background-scheduling system in .NET?

    - by Lasse V. Karlsen
    I ask though I doubt there is any such system. Basically I need to schedule tasks to execute at some point in the future (usually no more than a few seconds or possibly minutes from now), and have some way of cancelling that request unless too late. Ie. code that would look like this: var x = Scheduler.Schedule(() => SomethingSomething(), TimeSpan.FromSeconds(5)); ... x.Dispose(); // cancels the request Is there any such system in .NET? Is there anything in TPL that can help me? I need to run such future-actions from various instances in a system here, and would rather avoid each such class instance to have its own thread and deal with this. Also note that I don't want this (or similar, for instance through Tasks): new Thread(new ThreadStart(() => { Thread.Sleep(5000); SomethingSomething(); })).Start(); There will potentially be a few such tasks to execute, they don't need to be executed in any particular order, except for close to their deadline, and it isn't vital that they have anything like a realtime performance concept. I just want to avoid spinning up a separate thread for each such action.

    Read the article

  • NHibernate / ORM - Child Update over Web Service

    - by tyndall
    What is the correct way to UPDATE a child object with NHibernate but not have to "awake" the parent object. Lets say you would like to try to avoid this because the parent object is large or expensive to initiate. Lets assume classes are called Author(parent) and Book(child). (still, trying to avoid instantiating Author) Book comes back over a web service as XML. It gets deserialized back into a CLR object. Book has an AuthorId property which allows this to happen. But it also has a Author property. Problem, comes when you try to SaveOrUpdate() Book and the author_id in the database gets wiped out because the Author was null when the object gets deserialized. This seems like this would be a common problem. What is the workaround? Also, if you instantiate the Author and it has a Books property. The book you are trying to update is already one of these books (List<Book>). We have also run into the "a different object with the same identifier value was already associated with the session" problems. What is the standard process to update a child over a web service?

    Read the article

  • task_current redundant field

    - by user341940
    Hi, I'm writing a kernel module that reads from a /proc file. When someone writes into the /proc file the reader will read it, but if it reads again while there is no "new" write, it should be blocked. In order to remember if we already read, i need to keep a map of the latest buffer that process read. To avoid that, I was told that there might be some redundant field inside the current- (task_struct struct) that i can use to my benefits in order to save some states on the current process. How can I find such fields ? and how can i avoid them being overwritten ? I read somewhere that i can use the offset field inside the struct in order to save my information there and i need to block lseek operations so that field will stay untouched. How can I do so ? and where is that offset field, i can't find it inside the task_Struct. Thanks and I need to save for each process some information in order to map it against other information. I can write a ma

    Read the article

  • Beware Sneaky Reads with Unique Indexes

    - by Paul White NZ
    A few days ago, Sandra Mueller (twitter | blog) asked a question using twitter’s #sqlhelp hash tag: “Might SQL Server retrieve (out-of-row) LOB data from a table, even if the column isn’t referenced in the query?” Leaving aside trivial cases (like selecting a computed column that does reference the LOB data), one might be tempted to say that no, SQL Server does not read data you haven’t asked for.  In general, that’s quite correct; however there are cases where SQL Server might sneakily retrieve a LOB column… Example Table Here’s a T-SQL script to create that table and populate it with 1,000 rows: CREATE TABLE dbo.LOBtest ( pk INTEGER IDENTITY NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( some_value, lob_data ) SELECT TOP (1000) N.n, @Data FROM Numbers N WHERE N.n <= 1000; Test 1: A Simple Update Let’s run a query to subtract one from every value in the some_value column: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; As you might expect, modifying this integer column in 1,000 rows doesn’t take very long, or use many resources.  The STATITICS IO and TIME output shows a total of 9 logical reads, and 25ms elapsed time.  The query plan is also very simple: Looking at the Clustered Index Scan, we can see that SQL Server only retrieves the pk and some_value columns during the scan: The pk column is needed by the Clustered Index Update operator to uniquely identify the row that is being changed.  The some_value column is used by the Compute Scalar to calculate the new value.  (In case you are wondering what the Top operator is for, it is used to enforce SET ROWCOUNT). Test 2: Simple Update with an Index Now let’s create a nonclustered index keyed on the some_value column, with lob_data as an included column: CREATE NONCLUSTERED INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); This is not a useful index for our simple update query; imagine that someone else created it for a different purpose.  Let’s run our update query again: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; We find that it now requires 4,014 logical reads and the elapsed query time has increased to around 100ms.  The extra logical reads (4 per row) are an expected consequence of maintaining the nonclustered index. The query plan is very similar to before (click to enlarge): The Clustered Index Update operator picks up the extra work of maintaining the nonclustered index. The new Compute Scalar operators detect whether the value in the some_value column has actually been changed by the update.  SQL Server may be able to skip maintaining the nonclustered index if the value hasn’t changed (see my previous post on non-updating updates for details).  Our simple query does change the value of some_data in every row, so this optimization doesn’t add any value in this specific case. The output list of columns from the Clustered Index Scan hasn’t changed from the one shown previously: SQL Server still just reads the pk and some_data columns.  Cool. Overall then, adding the nonclustered index hasn’t had any startling effects, and the LOB column data still isn’t being read from the table.  Let’s see what happens if we make the nonclustered index unique. Test 3: Simple Update with a Unique Index Here’s the script to create a new unique index, and drop the old one: CREATE UNIQUE NONCLUSTERED INDEX [UQ dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); GO DROP INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest; Remember that SQL Server only enforces uniqueness on index keys (the some_data column).  The lob_data column is simply stored at the leaf-level of the non-clustered index.  With that in mind, we might expect this change to make very little difference.  Let’s see: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; Whoa!  Now look at the elapsed time and logical reads: Scan count 1, logical reads 2016, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   CPU time = 172 ms, elapsed time = 16172 ms. Even with all the data and index pages in memory, the query took over 16 seconds to update just 1,000 rows, performing over 52,000 LOB logical reads (nearly 16,000 of those using read-ahead). Why on earth is SQL Server reading LOB data in a query that only updates a single integer column? The Query Plan The query plan for test 3 looks a bit more complex than before: In fact, the bottom level is exactly the same as we saw with the non-unique index.  The top level has heaps of new stuff though, which I’ll come to in a moment. You might be expecting to find that the Clustered Index Scan is now reading the lob_data column (for some reason).  After all, we need to explain where all the LOB logical reads are coming from.  Sadly, when we look at the properties of the Clustered Index Scan, we see exactly the same as before: SQL Server is still only reading the pk and some_value columns – so what’s doing the LOB reads? Updates that Sneakily Read Data We have to go as far as the Clustered Index Update operator before we see LOB data in the output list: [Expr1020] is a bit flag added by an earlier Compute Scalar.  It is set true if the some_value column has not been changed (part of the non-updating updates optimization I mentioned earlier). The Clustered Index Update operator adds two new columns: the lob_data column, and some_value_OLD.  The some_value_OLD column, as the name suggests, is the pre-update value of the some_value column.  At this point, the clustered index has already been updated with the new value, but we haven’t touched the nonclustered index yet. An interesting observation here is that the Clustered Index Update operator can read a column into the data flow as part of its update operation.  SQL Server could have read the LOB data as part of the initial Clustered Index Scan, but that would mean carrying the data through all the operations that occur prior to the Clustered Index Update.  The server knows it will have to go back to the clustered index row to update it, so it delays reading the LOB data until then.  Sneaky! Why the LOB Data Is Needed This is all very interesting (I hope), but why is SQL Server reading the LOB data?  For that matter, why does it need to pass the pre-update value of the some_value column out of the Clustered Index Update? The answer relates to the top row of the query plan for test 3.  I’ll reproduce it here for convenience: Notice that this is a wide (per-index) update plan.  SQL Server used a narrow (per-row) update plan in test 2, where the Clustered Index Update took care of maintaining the nonclustered index too.  I’ll talk more about this difference shortly. The Split/Sort/Collapse combination is an optimization, which aims to make per-index update plans more efficient.  It does this by breaking each update into a delete/insert pair, reordering the operations, removing any redundant operations, and finally applying the net effect of all the changes to the nonclustered index. Imagine we had a unique index which currently holds three rows with the values 1, 2, and 3.  If we run a query that adds 1 to each row value, we would end up with values 2, 3, and 4.  The net effect of all the changes is the same as if we simply deleted the value 1, and added a new value 4. By applying net changes, SQL Server can also avoid false unique-key violations.  If we tried to immediately update the value 1 to a 2, it would conflict with the existing value 2 (which would soon be updated to 3 of course) and the query would fail.  You might argue that SQL Server could avoid the uniqueness violation by starting with the highest value (3) and working down.  That’s fine, but it’s not possible to generalize this logic to work with every possible update query. SQL Server has to use a wide update plan if it sees any risk of false uniqueness violations.  It’s worth noting that the logic SQL Server uses to detect whether these violations are possible has definite limits.  As a result, you will often receive a wide update plan, even when you can see that no violations are possible. Another benefit of this optimization is that it includes a sort on the index key as part of its work.  Processing the index changes in index key order promotes sequential I/O against the nonclustered index. A side-effect of all this is that the net changes might include one or more inserts.  In order to insert a new row in the index, SQL Server obviously needs all the columns – the key column and the included LOB column.  This is the reason SQL Server reads the LOB data as part of the Clustered Index Update. In addition, the some_value_OLD column is required by the Split operator (it turns updates into delete/insert pairs).  In order to generate the correct index key delete operation, it needs the old key value. The irony is that in this case the Split/Sort/Collapse optimization is anything but.  Reading all that LOB data is extremely expensive, so it is sad that the current version of SQL Server has no way to avoid it. Finally, for completeness, I should mention that the Filter operator is there to filter out the non-updating updates. Beating the Set-Based Update with a Cursor One situation where SQL Server can see that false unique-key violations aren’t possible is where it can guarantee that only one row is being updated.  Armed with this knowledge, we can write a cursor (or the WHILE-loop equivalent) that updates one row at a time, and so avoids reading the LOB data: SET NOCOUNT ON; SET STATISTICS XML, IO, TIME OFF;   DECLARE @PK INTEGER, @StartTime DATETIME; SET @StartTime = GETUTCDATE();   DECLARE curUpdate CURSOR LOCAL FORWARD_ONLY KEYSET SCROLL_LOCKS FOR SELECT L.pk FROM LOBtest L ORDER BY L.pk ASC;   OPEN curUpdate;   WHILE (1 = 1) BEGIN FETCH NEXT FROM curUpdate INTO @PK;   IF @@FETCH_STATUS = -1 BREAK; IF @@FETCH_STATUS = -2 CONTINUE;   UPDATE dbo.LOBtest SET some_value = some_value - 1 WHERE CURRENT OF curUpdate; END;   CLOSE curUpdate; DEALLOCATE curUpdate;   SELECT DATEDIFF(MILLISECOND, @StartTime, GETUTCDATE()); That completes the update in 1280 milliseconds (remember test 3 took over 16 seconds!) I used the WHERE CURRENT OF syntax there and a KEYSET cursor, just for the fun of it.  One could just as well use a WHERE clause that specified the primary key value instead. Clustered Indexes A clustered index is the ultimate index with included columns: all non-key columns are included columns in a clustered index.  Let’s re-create the test table and data with an updatable primary key, and without any non-clustered indexes: IF OBJECT_ID(N'dbo.LOBtest', N'U') IS NOT NULL DROP TABLE dbo.LOBtest; GO CREATE TABLE dbo.LOBtest ( pk INTEGER NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( pk, some_value, lob_data ) SELECT TOP (1000) N.n, N.n, @Data FROM Numbers N WHERE N.n <= 1000; Now here’s a query to modify the cluster keys: UPDATE dbo.LOBtest SET pk = pk + 1; The query plan is: As you can see, the Split/Sort/Collapse optimization is present, and we also gain an Eager Table Spool, for Halloween protection.  In addition, SQL Server now has no choice but to read the LOB data in the Clustered Index Scan: The performance is not great, as you might expect (even though there is no non-clustered index to maintain): Table 'LOBtest'. Scan count 1, logical reads 2011, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   Table 'Worktable'. Scan count 1, logical reads 2040, physical reads 0, read-ahead reads 0, lob logical reads 34000, lob physical reads 0, lob read-ahead reads 8000.   SQL Server Execution Times: CPU time = 483 ms, elapsed time = 17884 ms. Notice how the LOB data is read twice: once from the Clustered Index Scan, and again from the work table in tempdb used by the Eager Spool. If you try the same test with a non-unique clustered index (rather than a primary key), you’ll get a much more efficient plan that just passes the cluster key (including uniqueifier) around (no LOB data or other non-key columns): A unique non-clustered index (on a heap) works well too: Both those queries complete in a few tens of milliseconds, with no LOB reads, and just a few thousand logical reads.  (In fact the heap is rather more efficient). There are lots more fun combinations to try that I don’t have space for here. Final Thoughts The behaviour shown in this post is not limited to LOB data by any means.  If the conditions are met, any unique index that has included columns can produce similar behaviour – something to bear in mind when adding large INCLUDE columns to achieve covering queries, perhaps. Paul White Email: [email protected] Twitter: @PaulWhiteNZ

    Read the article

  • Stored Procedures with SSRS? Hmm… not so much

    - by Rob Farley
    Little Bobby Tables’ mother says you should always sanitise your data input. Except that I think she’s wrong. The SQL Injection aspect is for another post, where I’ll show you why I think SQL Injection is the same kind of attack as many other attacks, such as the old buffer overflow, but here I want to have a bit of a whinge about the way that some people sanitise data input, and even have a whinge about people who insist on using stored procedures for SSRS reports. Let me say that again, in case you missed it the first time: I want to have a whinge about people who insist on using stored procedures for SSRS reports. Let’s look at the data input sanitisation aspect – except that I’m going to call it ‘parameter validation’. I’m talking about code that looks like this: create procedure dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) as begin     /* First check that @eomdate is a valid date */     if isdate(@eomdate) != 1     begin         select 'Please enter a valid date' as ErrorMessage;         return;     end     /* Then check that time has passed since @eomdate */     if datediff(day,@eomdate,sysdatetime()) < 5     begin         select 'Sorry - EOM is not complete yet' as ErrorMessage;         return;     end         /* If those checks have succeeded, return the data */     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales     from Sales.SalesOrderHeader     where OrderDate >= dateadd(month,-1,@eomdate)         and OrderDate < @eomdate     group by SalesPersonID     order by SalesPersonID; end Notice that the code checks that a date has been entered. Seriously??!! This must only be to check for NULL values being passed in, because anything else would have to be a valid datetime to avoid an error. The other check is maybe fair enough, but I still don’t like it. The two problems I have with this stored procedure are the result sets and the small fact that the stored procedure even exists in the first place. But let’s consider the first one of these problems for starters. I’ll get to the second one in a moment. If you read Jes Borland (@grrl_geek)’s recent post about returning multiple result sets in Reporting Services, you’ll be aware that Reporting Services doesn’t support multiple results sets from a single query. And when it says ‘single query’, it includes ‘stored procedure call’. It’ll only handle the first result set that comes back. But that’s okay – we have RETURN statements, so our stored procedure will only ever return a single result set.  Sometimes that result set might contain a single field called ErrorMessage, but it’s still only one result set. Except that it’s not okay, because Reporting Services needs to know what fields to expect. Your report needs to hook into your fields, so SSRS needs to have a way to get that information. For stored procs, it uses an option called FMTONLY. When Reporting Services tries to figure out what fields are going to be returned by a query (or stored procedure call), it doesn’t want to have to run the whole thing. That could take ages. (Maybe it’s seen some of the stored procedures I’ve had to deal with over the years!) So it turns on FMTONLY before it makes the call (and turns it off again afterwards). FMTONLY is designed to be able to figure out the shape of the output, without actually running the contents. It’s very useful, you might think. set fmtonly on exec dbo.GetMonthSummaryPerSalesPerson '20030401'; set fmtonly off Without the FMTONLY lines, this stored procedure returns a result set that has three columns and fourteen rows. But with FMTONLY turned on, those rows don’t come back. But what I do get back hurts Reporting Services. It doesn’t run the stored procedure at all. It just looks for anything that could be returned and pushes out a result set in that shape. Despite the fact that I’ve made sure that the logic will only ever return a single result set, the FMTONLY option kills me by returning three of them. It would have been much better to push these checks down into the query itself. alter procedure dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) as begin     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales     from Sales.SalesOrderHeader     where     /* Make sure that @eomdate is valid */         isdate(@eomdate) = 1     /* And that it's sufficiently past */     and datediff(day,@eomdate,sysdatetime()) >= 5     /* And now use it in the filter as appropriate */     and OrderDate >= dateadd(month,-1,@eomdate)     and OrderDate < @eomdate     group by SalesPersonID     order by SalesPersonID; end Now if we run it with FMTONLY turned on, we get the single result set back. But let’s consider the execution plan when we pass in an invalid date. First let’s look at one that returns data. I’ve got a semi-useful index in place on OrderDate, which includes the SalesPersonID and TotalDue fields. It does the job, despite a hefty Sort operation. …compared to one that uses a future date: You might notice that the estimated costs are similar – the Index Seek is still 28%, the Sort is still 71%. But the size of that arrow coming out of the Index Seek is a whole bunch smaller. The coolest thing here is what’s going on with that Index Seek. Let’s look at some of the properties of it. Glance down it with me… Estimated CPU cost of 0.0005728, 387 estimated rows, estimated subtree cost of 0.0044385, ForceSeek false, Number of Executions 0. That’s right – it doesn’t run. So much for reading plans right-to-left... The key is the Filter on the left of it. It has a Startup Expression Predicate in it, which means that it doesn’t call anything further down the plan (to the right) if the predicate evaluates to false. Using this method, we can make sure that our stored procedure contains a single query, and therefore avoid any problems with multiple result sets. If we wanted, we could always use UNION ALL to make sure that we can return an appropriate error message. alter procedure dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) as begin     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales, /*Placeholder: */ '' as ErrorMessage     from Sales.SalesOrderHeader     where     /* Make sure that @eomdate is valid */         isdate(@eomdate) = 1     /* And that it's sufficiently past */     and datediff(day,@eomdate,sysdatetime()) >= 5     /* And now use it in the filter as appropriate */     and OrderDate >= dateadd(month,-1,@eomdate)     and OrderDate < @eomdate     group by SalesPersonID     /* Now include the error messages */     union all     select 0, 0, 0, 'Please enter a valid date' as ErrorMessage     where isdate(@eomdate) != 1     union all     select 0, 0, 0, 'Sorry - EOM is not complete yet' as ErrorMessage     where datediff(day,@eomdate,sysdatetime()) < 5     order by SalesPersonID; end But still I don’t like it, because it’s now a stored procedure with a single query. And I don’t like stored procedures that should be functions. That’s right – I think this should be a function, and SSRS should call the function. And I apologise to those of you who are now planning a bonfire for me. Guy Fawkes’ night has already passed this year, so I think you miss out. (And I’m not going to remind you about when the PASS Summit is in 2012.) create function dbo.GetMonthSummaryPerSalesPerson(@eomdate datetime) returns table as return (     select SalesPersonID, count(*) as NumSales, sum(TotalDue) as TotalSales, '' as ErrorMessage     from Sales.SalesOrderHeader     where     /* Make sure that @eomdate is valid */         isdate(@eomdate) = 1     /* And that it's sufficiently past */     and datediff(day,@eomdate,sysdatetime()) >= 5     /* And now use it in the filter as appropriate */     and OrderDate >= dateadd(month,-1,@eomdate)     and OrderDate < @eomdate     group by SalesPersonID     union all     select 0, 0, 0, 'Please enter a valid date' as ErrorMessage     where isdate(@eomdate) != 1     union all     select 0, 0, 0, 'Sorry - EOM is not complete yet' as ErrorMessage     where datediff(day,@eomdate,sysdatetime()) < 5 ); We’ve had to lose the ORDER BY – but that’s fine, as that’s a client thing anyway. We can have our reports leverage this stored query still, but we’re recognising that it’s a query, not a procedure. A procedure is designed to DO stuff, not just return data. We even get entries in sys.columns that confirm what the shape of the result set actually is, which makes sense, because a table-valued function is the right mechanism to return data. And we get so much more flexibility with this. If you haven’t seen the simplification stuff that I’ve preached on before, jump over to http://bit.ly/SimpleRob and watch the video of when I broke a microphone and nearly fell off the stage in Wales. You’ll see the impact of being able to have a simplifiable query. You can also read the procedural functions post I wrote recently, if you didn’t follow the link from a few paragraphs ago. So if we want the list of SalesPeople that made any kind of sales in a given month, we can do something like: select SalesPersonID from dbo.GetMonthSummaryPerSalesPerson(@eomonth) order by SalesPersonID; This doesn’t need to look up the TotalDue field, which makes a simpler plan. select * from dbo.GetMonthSummaryPerSalesPerson(@eomonth) where SalesPersonID is not null order by SalesPersonID; This one can avoid having to do the work on the rows that don’t have a SalesPersonID value, pushing the predicate into the Index Seek rather than filtering the results that come back to the report. If we had joins involved, we might see some of those being simplified out. We also get the ability to include query hints in individual reports. We shift from having a single-use stored procedure to having a reusable stored query – and isn’t that one of the main points of modularisation? Stored procedures in Reporting Services are just a bit limited for my liking. They’re useful in plenty of ways, but if you insist on using stored procedures all the time rather that queries that use functions – that’s rubbish. @rob_farley

    Read the article

  • R Package Installation with Oracle R Enterprise

    - by Sherry LaMonica-Oracle
    Normal 0 false false false EN-US X-NONE X-NONE Programming languages give developers the opportunity to write reusable functions and to bundle those functions into logical deployable entities. In R, these are called packages. R has thousands of such packages provided by an almost equally large group of third-party contributors. To allow others to benefit from these packages, users can share packages on the CRAN system for use by the vast R development community worldwide. R's package system along with the CRAN framework provides a process for authoring, documenting and distributing packages to millions of users. In this post, we'll illustrate the various ways in which such R packages can be installed for use with R and together with Oracle R Enterprise. In the following, the same instructions apply when using either open source R or Oracle R Distribution. In this post, we cover the following package installation scenarios for: R command line Linux shell command line Use with Oracle R Enterprise Installation on Exadata or RAC Installing all packages in a CRAN Task View Troubleshooting common errors 1. R Package Installation BasicsR package installation basics are outlined in Chapter 6 of the R Installation and Administration Guide. There are two ways to install packages from the command line: from the R command line and from the shell command line. For this first example on Oracle Linux using Oracle R Distribution, we’ll install the arules package as root so that packages will be installed in the default R system-wide location where all users can access it, /usr/lib64/R/library.Within R, using the install.packages function always attempts to install the latest version of the requested package available on CRAN:R> install.packages("arules")If the arules package depends upon other packages that are not already installed locally, the R installer automatically downloads and installs those required packages. This is a huge benefit that frees users from the task of identifying and resolving those dependencies.You can also install R from the shell command line. This is useful for some packages when an internet connection is not available or for installing packages not uploaded to CRAN. To install packages this way, first locate the package on CRAN and then download the package source to your local machine. For example:$ wget http://cran.r-project.org/src/contrib/arules_1.1-2.tar.gz Then, install the package using the command R CMD INSTALL:$ R CMD INSTALL arules_1.1-2.tar.gzA major difference between installing R packages using the R package installer at the R command line and shell command line is that package dependencies must be resolved manually at the shell command line. Package dependencies are listed in the Depends section of the package’s CRAN site. If dependencies are not identified and installed prior to the package’s installation, you will see an error similar to:ERROR: dependency ‘xxx’ is not available for package ‘yyy’As a best practice and to save time, always refer to the package’s CRAN site to understand the package dependencies prior to attempting an installation. If you don’t run R as root, you won’t have permission to write packages into the default system-wide location and you will be prompted to create a personal library accessible by your userid. You can accept the personal library path chosen by R, or specify the library location by passing parameters to the install.packages function. For example, to create an R package repository in your home directory: R> install.packages("arules", lib="/home/username/Rpackages")or$ R CMD INSTALL arules_1.1-2.tar.gz --library=/home/username/RpackagesRefer to the install.packages help file in R or execute R CMD INSTALL --help at the shell command line for a full list of command line options.To set the library location and avoid having to specify this at every package install, simply create the R startup environment file .Renviron in your home area if it does not already exist, and add the following piece of code to it:R_LIBS_USER = "/home/username/Rpackages" 2. Setting the RepositoryEach time you install an R package from the R command line, you are asked which CRAN mirror, or server, R should use. To set the repository and avoid having to specify this during every package installation, create the R startup command file .Rprofile in your home directory and add the following R code to it:cat("Setting Seattle repository")r = getOption("repos") r["CRAN"] = "http://cran.fhcrc.org/"options(repos = r)rm(r) This code snippet sets the R package repository to the Seattle CRAN mirror at the start of each R session. 3. Installing R Packages for use with Oracle R EnterpriseEmbedded R execution with Oracle R Enterprise allows the use of CRAN or other third-party R packages in user-defined R functions executed on the Oracle Database server. The steps for installing and configuring packages for use with Oracle R Enterprise are the same as for open source R. The database-side R engine just needs to know where to find the R packages.The Oracle R Enterprise installation is performed by user oracle, which typically does not have write permission to the default site-wide library, /usr/lib64/R/library. On Linux and UNIX platforms, the Oracle R Enterprise Server installation provides the ORE script, which is executed from the operating system shell to install R packages and to start R. The ORE script is a wrapper for the default R script, a shell wrapper for the R executable. It can be used to start R, run batch scripts, and build or install R packages. Unlike the default R script, the ORE script installs packages to a location writable by user oracle and accessible by all ORE users - $ORACLE_HOME/R/library.To install a package on the database server so that it can be used by any R user and for use in embedded R execution, an Oracle DBA would typically download the package source from CRAN using wget. If the package depends on any packages that are not in the R distribution in use, download the sources for those packages, also.  For a single Oracle Database instance, replace the R script with ORE to install the packages in the same location as the Oracle R Enterprise packages. $ wget http://cran.r-project.org/src/contrib/arules_1.1-2.tar.gz$ ORE CMD INSTALL arules_1.1-2.tar.gzBehind the scenes, the ORE script performs the equivalent of setting R_LIBS_USER to the value of $ORACLE_HOME/R/library, and all R packages installed with the ORE script are installed to this location. For installing a package on multiple database servers, such as those in an Oracle Real Application Clusters (Oracle RAC) or a multinode Oracle Exadata Database Machine environment, use the ORE script in conjunction with the Exadata Distributed Command Line Interface (DCLI) utility.$ dcli -g nodes -l oracle ORE CMD INSTALL arules_1.1-1.tar.gz The DCLI -g flag designates a file containing a list of nodes to install on, and the -l flag specifies the user id to use when executing the commands. For more information on using DCLI with Oracle R Enterprise, see Chapter 5 in the Oracle R Enterprise Installation Guide.If you are using an Oracle R Enterprise client, install the package the same as any R package, bearing in mind that you must install the same version of the package on both the client and server machines to avoid incompatibilities. 4. CRAN Task ViewsCRAN also maintains a set of Task Views that identify packages associated with a particular task or methodology. Task Views are helpful in guiding users through the huge set of available R packages. They are actively maintained by volunteers who include detailed annotations for routines and packages. If you find one of the task views is a perfect match, you can install every package in that view using the ctv package - an R package for automating package installation. To use the ctv package to install a task view, first, install and load the ctv package.R> install.packages("ctv")R> library(ctv)Then query the names of the available task views and install the view you choose.R> available.views() R> install.views("TimeSeries") 5. Using and Managing R packages To use a package, start up R and load packages one at a time with the library command.Load the arules package in your R session. R> library(arules)Verify the version of arules installed.R> packageVersion("arules")[1] '1.1.2'Verify the version of arules installed on the database server using embedded R execution.R> ore.doEval(function() packageVersion("arules"))View the help file for the apropos function in the arules packageR> ?aproposOver time, your package repository will contain more and more packages, especially if you are using the system-wide repository where others are adding additional packages. It’s good to know the entire set of R packages accessible in your environment. To list all available packages in your local R session, use the installed.packages command:R> myLocalPackages <- row.names(installed.packages())R> myLocalPackagesTo access the list of available packages on the ORE database server from the ORE client, use the following embedded R syntax: R> myServerPackages <- ore.doEval(function() row.names(installed.packages()) R> myServerPackages 6. Troubleshooting Common ProblemsInstalling Older Versions of R packagesIf you immediately upgrade to the latest version of R, you will have no problem installing the most recent versions of R packages. However, if your version of R is older, some of the more recent package releases will not work and install.packages will generate a message such as: Warning message: In install.packages("arules") : package ‘arules’ is not availableThis is when you have to go to the Old sources link on the CRAN page for the arules package and determine which version is compatible with your version of R.Begin by determining what version of R you are using:$ R --versionOracle Distribution of R version 3.0.1 (--) -- "Good Sport" Copyright (C) The R Foundation for Statistical Computing Platform: x86_64-unknown-linux-gnu (64-bit)Given that R-3.0.1 was released May 16, 2013, any version of the arules package released after this date may work. Scanning the arules archive, we might try installing version 0.1.1-1, released in January of 2014:$ wget http://cran.r-project.org/src/contrib/Archive/arules/arules_1.1-1.tar.gz$ R CMD INSTALL arules_1.1-1.tar.gzFor use with ORE:$ ORE CMD INSTALL arules_1.1-1.tar.gzThe "package not available" error can also be thrown if the package you’re trying to install lives elsewhere, either another R package site, or it’s been removed from CRAN. A quick Google search usually leads to more information on the package’s location and status.Oracle R Enterprise is not in the R library pathOn Linux hosts, after installing the ORE server components, starting R, and attempting to load the ORE packages, you may receive the error:R> library(ORE)Error in library(ORE) : there is no package called ‘ORE’If you know the ORE packages have been installed and you receive this error, this is the result of not starting R with the ORE script. To resolve this problem, exit R and restart using the ORE script. After restarting R and ">running the command to load the ORE packages, you should not receive any errors.$ ORER> library(ORE)On Windows servers, the solution is to make the location of the ORE packages visible to R by adding them to the R library paths. To accomplish this, exit R, then add the following lines to the .Rprofile file. On Windows, the .Rprofile file is located in R\etc directory C:\Program Files\R\R-<version>\etc. Add the following lines:.libPaths("<path to $ORACLE_HOME>/R/library")The above line will tell R to include the R directory in the Oracle home as part of its search path. When you start R, the path above will be included, and future R package installations will also be saved to $ORACLE_HOME/R/library. This path should be writable by the user oracle, or the userid for the DBA tasked with installing R packages.Binary package compiled with different version of RBy default, R will install pre-compiled versions of packages if they are found. If the version of R under which the package was compiled does not match your installed version of R you will get an error message:Warning message: package ‘xxx’ was built under R version 3.0.0The solution is to download the package source and build it for your version of R.$ wget http://cran.r-project.org/src/contrib/Archive/arules/arules_1.1-1.tar.gz$ R CMD INSTALL arules_1.1-1.tar.gzFor use with ORE:$ ORE CMD INSTALL arules_1.1-1.tar.gzUnable to execute files in /tmp directoryBy default, R uses the /tmp directory to install packages. On security conscious machines, the /tmp directory is often marked as "noexec" in the /etc/fstab file. This means that no file under /tmp can ever be executed, and users who attempt to install R package will receive an error:ERROR: 'configure' exists but is not executable -- see the 'R Installation and Administration Manual’The solution is to set the TMP and TMPDIR environment variables to a location which R will use as the compilation directory. For example:$ mkdir <some path>/tmp$ export TMPDIR= <some path>/tmp$ export TMP= <some path>/tmpThis error typically appears on Linux client machines and not database servers, as Oracle Database writes to the value of the TMP environment variable for several tasks, including holding temporary files during database installation. 7. Creating your own R packageCreating your own package and submitting to CRAN is for advanced users, but it is not difficult. The procedure to follow, along with details of R's package system, is detailed in the Writing R Extensions manual.

    Read the article

  • Recommend a basic 3D graphics card for HP ProLiant DL360 G5?

    - by arathorn
    We've got an HP ProLiant DL360 G5 running Windows Server 2008 R2 that needs a graphics card with 3D acceleration (the integrated ATI ES1000 graphics don't have this). This is an unfortunate requirement that we can't avoid, as it is required by S/W installed on the server that is beyond our control. Looks like the PCI-Express slots in the box are x8 (1 full and 1 low profile). We just need a basic card, as long as it has the 3D acceleration. Any recommendations?

    Read the article

  • Postifx disable local delivery

    - by Simon
    Hi there, is there any form to prevent local delivery on a postfix server? Ideally, I want to avoid local delivery to some domains, because this postfix server is a google apps backup one. Thanks in advance, Simon.

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 61 62 63 64 65 66 67 68 69 70 71 72  | Next Page >