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• Azure Mobile Services with persistent authentication

  - by akshay2000

  I am trying to implement authentication with Windows Azure Mobile Services in my Windows Phone app. I have followed the official tutorials and the authentication works fine. The issue is that, whenever the app is closed and started again, the user has to enter username and password. Since the services only use authentication tokens, the 'Remember me' option on log in page is not likely to work. The official documentation for Windows Azure shows possibility of Single Sign On with the Microsoft account using the Live SDK. The Live SDK provides authentication token in form of string. However, even this token expires in about 24 hours. Moreover, this is restricted to the Microsoft Account only. What are my possibilities if I want to cache the user's identity and enable automatic log in? I have already gone through the article here. User will still have to log in again once the token expires. I have seen apps which require user to sign in only once!

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• problem adding object to hashtable

  - by daemonkid

  I am trying to call a class method dynamically depending on a condition. This is how I am doing it I have three classes implement a single interface interface IReadFile { string DoStuff(); } The three classes A,B,C implement the interface above. I am trying to add them to a hashtable with the code below _HashT.Add("a", new classA()); _HashT.Add("b", new classB()); _HashT.Add("c", new classC()); This compiles fine, but gives a runtime error.{Object reference not set to an instance of an object.} I was planning to return the correct class to the interface type depending on a parameter that matches the key value. say if I send in a. ClassA is returned to the interface type and the method is called. IReadFile Obj = (IReadFile )_HashT["a"].GetType(); obj.DoStuff(); How do I correct the part above where the objects need to be added to the hashtable? Or do I need to use a different approach? All the classes are in the same assembly and namespace. Thanks for your time.

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• Bind to a property of a parent element in wpf

  - by msfanboy

  Hello all, I want to bind the Height property of the RichTextBox to the Height Property of the GridViews Row. How can I do that? I do not know how to get the Rows Height as I can not access the Row in xaml what I would like to do. <my:RadGridView Height="524" ItemsSource="{Binding Lessons}" AutoGenerateColumns="False" Name="dataGrid1" VerticalAlignment="Top" SelectionMode="Single" CanUserSortColumns="False" IsFilteringAllowed="False"> <my:RadGridView.Columns> <my:GridViewDataColumn Name="ContentColumn" Width="0.3*" Header="Content"> <my:GridViewDataColumn.CellTemplate> <DataTemplate> <RichTextBox Height="{Binding ElementName=MyRowNameToBindTo,Path=Height}"> <FlowDocument> <Paragraph> <Run Text="{Binding Content}"/> </Paragraph> </FlowDocument> </RichTextBox> </DataTemplate> </my:GridViewDataColumn.CellTemplate> ...

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• ZeroMQ REQ/REP on ipc:// and concurrency

  - by Metiu

  I implemented a JSON-RPC server using a REQ/REP 0MQ ipc:// socket and I'm experiencing strange behavior which I suspect is due to the fact that the ipc:// underlying unix socket is not a real socket, but rather a single pipe. From the documentation, one has to enforce strict zmq_send()/zmq_recv() alternation, otherwise the out-of-order zmq_send() will return an error. However, I expected the enforcement to be per-client, not per-socket. Of course with a Unix socket there is just one pipeline from multiple clients to the server, so the server won't know who it is talking with. Two clients could zmq_send() simultaneously and the server would see this as an alternation violation. The sequence could be: ClientA: zmq_send() ClientB: zmq_send() : will it block until the other send/receive completes? will it return -1? (I suspect it will with ipc:// due to inherent low-level problems, but with TCP it could distinguish the two clients) ClientA: zmq_recv() ClientB: zmq_recv() so what about tcp:// sockets? Will it work concurrently? Should I use some other locking mechanism to work around this?

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• Database design - table relationship question

  - by iama

  I am designing schema for a simple quiz application. It has 2 tables - "Question" and "Answer Choices". Question table has 'question ID', 'question text' and 'answer id' columns. "Answer Choices" table has 'question ID', 'answer ID' and 'answer text' columns. With this simple schema it is obvious that a question can have multiple answer choices & hence the need for the answer choices table. However, a question can have only one correct answer and hence the need for the 'answer ID' in the question table. However, this 'answer ID' column in the question table provides a illusion as though there can be multiple questions for a single answer which is not correct. The other alternative to eliminate this illusion is to have another table just for correct answer that will have just 2 columns namely the question ID and the answer ID with a 1-1 relationship between the two tables. However, I think this is redundant. Any recommendation on how best to design this thereby enforcing the rules that a question can have multiple answer choices but only one correct answer? Many Thanks.

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• Implementing a c/c++ style union as a column in MySQL

  - by user81338

  Friends, I have a strange need and cannot think my way through the problem. The great and mighty Google is of little help due to keyword recycling (as you'll see). Can you help? What I want to do is store data of multiple types in a single column in MySQL. This is the database equivalent to a C union (and if you search for MySQL and Union, you obviously get a whole bunch of stuff on the UNION keyword in SQL). [Contrived and simplified case follows] So, let us say that we have people - who have names - and STORMTROOPERS - who have TK numbers. You cannot have BOTH a NAME and a TK number. You're either BOB SMITH -or- TK409. In C I could express this as a union, like so: union { char * name; int tkNo; } EmperialPersonnelRecord; This makes it so that I am either storing a pointer to a char array or an ID in the type EmperialPersonnelRecord, but not both. I am looking for a MySQL equivalent on a column. My column would store either an int, double, or varchar(255) (or whatever combination). But would only take up the space of the largest element. Is this possible? (of course anything is possible given enough time, money and will - I mean is it possible if I am poor, lazy and on a deadline... aka "out of the box")

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• Java: which configuration framework to use?

  - by Laimoncijus

  Hi, I need to decide which configuration framework to use. At the moment I am thinking between using properties files and XML files. My configuration needs to have some primitive grouping, e.g. in XML format would be something like: <configuration> <group name="abc"> <param1>value1</param1> <param2>value2</param2> </group> <group name="def"> <param3>value3</param3> <param4>value4</param4> </group> </configuration> or a properties file (something similar to log4j.properties): group.abc.param1 = value1 group.abc.param2 = value2 group.def.param3 = value3 group.def.param4 = value4 I need bi-directional (read and write) configuration library/framework. Nice feature would be - that I could read out somehow different configuration groups as different objects, so I could later pass them to different places, e.g. - reading everything what belongs to group "abc" as one object and "def" as another. If that is not possible I can always split single configuration object into smaller ones myself in the application initialization part of course. Which framework would best fit for me?

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• How to avoid hard-coded credentials in Sharepoint webpart?

  - by Bryan

  I am building a Sharepoint web part that will be used by all users, but can only be modified by admins. The web part connects to a web service which needs credentials. I hard coded credentials in the web part's code. query.Credentials = new System.Net.NetworkCredential("username", "password", "domain"); query is an instance of the web service class This may not be a good approach. In regard with security, the source code of the web apart is available to people who are not allowed to see the credentials. In normal ASP.net applications, credentials can be written into web.config and encrypted. A web part doesn't have a .config file associated. There is a application-level .config file for the whole sharepoint site, but I don't want to modify it for a single webpart. I wonder if there is a webpart-specific way to solve the credential problem? Say we provide a WebBrowsable property of that web part so that privileged users can modify credentials. If this is desirable, how should I make the property displayed in a password ("*") rather than in plain text? Thanks.

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• JSF2.0: variable list of custom component

  - by rattaman

  Hello Is there any way of using JSF2.0 in connection with variable lists of components? For example, lets say I have list o people that I would like to edit. They are presented on the page as list of components PersonEditor, which allow changing person data. Each editor is associated with single Person element. In order for this to work I need to perform following steps: On initial request: Get list of people For each person create PersonEditor and associate it with Person object. Fill editor's data. On user action: When user changes values and presses Save, data is processed by backing bean. I can either fill editor with data from list of people or bind it to the backing bean, but not at the same time, so I am stuck. I tried people.xhtml <ui:render value="#{bean.people}" var="person"> <example:personEditor person="#{person}"/> </ui:render> where personEditor.xhtml: a) proper association with person object, but no connection to backing bean <h:form> <h:outputText value="#{cc.attr.person.name}"/> <h:commandButton name="Save" actionListener="editorBean.save"> <f:ajax execute="@form" render="@form"/> </h:commandButton> </h:form> b) no association with person object, but there is connection to backing bean - there is no way to pass that person to the backing bean <h:form> <h:outputText value="#{editorBean.name}"/> <h:commandButton name="Save" actionListener="editorBean.save"> <f:ajax execute="@form" render="@form"/> </h:commandButton> </h:form> If I had each editor on separate page, I could pass the person id as url parameter (either using f:param or f:attribute) and initialize it accordingly. Is there any solution to this problem?

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• HTTP POST with URL query parameters -- good idea or not?

  - by Steven Huwig

  I'm designing an API to go over HTTP and I am wondering if using the HTTP POST command, but with URL query parameters only and no request body, is a good way to go. Considerations: "Good Web design" requires non-idempotent actions to be sent via POST. This is a non-idempotent action. It is easier to develop and debug this app when the request parameters are present in the URL. The API is not intended for widespread use. It seems like making a POST request with no body will take a bit more work, e.g. a Content-Length: 0 header must be explicitly added. It also seems to me that a POST with no body is a bit counter to most developer's and HTTP frameworks' expectations. Are there any more pitfalls or advantages to sending parameters on a POST request via the URL query rather than the request body? Edit: The reason this is under consideration is that the operations are not idempotent and have side effects other than retrieval. See the HTTP spec: In particular, the convention has been established that the GET and HEAD methods SHOULD NOT have the significance of taking an action other than retrieval. These methods ought to be considered "safe". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is made aware of the fact that a possibly unsafe action is being requested. ... Methods can also have the property of "idempotence" in that (aside from error or expiration issues) the side-effects of N 0 identical requests is the same as for a single request. The methods GET, HEAD, PUT and DELETE share this property. Also, the methods OPTIONS and TRACE SHOULD NOT have side effects, and so are inherently idempotent.

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• Summarising grouped records in a dataframe in R

  - by monch1962

  Hello all, I have a data frame in R that looks like this: > TimeOffset, Source, Length > 0 1 1500 > 0.1 1 1000 > 0.2 1 50 > 0.4 2 25 > 0.6 2 3 > 1.1 1 1500 > 1.4 1 18 > 1.6 2 2500 > 1.9 2 18 > 2.1 1 37 > ... and I want to convert it to > TimeOffset, Source, Length > 0.2 1 2550 > 0.6 2 28 > 1.4 1 1518 > 1.9 2 2518 > ... Trying to put this into English, I want to group consecutive records with the same 'Source' together, then printing out a single record per group showing the highest time offset in that group, the source, and the sum of the lengths in that group. The TimeOffset values will always increase. I suspect this is possible in R, but I really don't know where to start. In a pinch I could export the data frame out and do it in e.g. Python, but I'd prefer to stay within R if possible. Thanks in advance for any assistance you can provide

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• Codeigniter return config file as array with autoload enabled

  - by Fverswijver

  So I'm using CodeIgniter to build a website and I've made it so that all my specific settings are stored in a config file that's automatically loaded. I've also built a page that loads the settings file, makes a nice little table and allows me to edit everything from that page, afterwards it saves the entire page again (I know I could've done the same with a database but I want to try it this way). My problem is that I can't seem to use this bit when autoloading of my config file is enabled, but when I disable autoloading I can't seem to manually load it, it never finds my variables. So what I'm doing here is just taking all values from the config file and putting them in a single array so I can pass this array onto my settings administration page (edit/show all settings). $this->config->load('site_settings', TRUE); $data['settings'] = $this->config->item('site_settings'); ... $this->load->view('template', $data); config/site_settings.php <?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); $config['header_img'] = './img/header/'; $config['copyright_text'] = 'Copyright Instituto Kabu'; $config['copyright_font'] = './system/fonts/motoroil.ttf'; $config['copyright_font_color'] = 'ffffff'; $config['copyright_font_size'] = '32';

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• Mysql Performance Question - Essentially about normalizing efficiency

  - by freqmode

  Hi there. Just a quick question about database performance. I'll outline my site purpose below as background. I'm creating a dictionary site that saves the words users define to a database. What I'm wondering is whether or not to create a words table for each user or to keep one massive words table. This site will be used for entire schools so the single words table would be massive! The database structure is as follows: A user table with: User_ID PRIMARY KEY Username First Last Password Email Country Research Standings SendInfo Donated JoinedOn LastLogin Logins Correct Attempts Admin Active And one word table with: User_ID PRIMARY KEY Word Vocab Spell Defined DefinedAttempted Spelled SpelledAttempted Sentenced SentencedAttempted So what I'm asking is , performance-wise, should I create a new table for each user when they join the site - each user could have hundreds or thousands of words over time? Or is it better to have one massive table with thousands and thousands of records and filter by User_ID. I don't think I'll perform many table joins. My gut feeling is to create a new table for each user, but I thought I'd ask for expert advice! Thanks in advance.

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• loading files through one file to hide locations

  - by Phil Jackson

  Hello all. Im currently doing a project in which my client does not want to location ( ie folder names and locations ) to be displayed. so I have done something like this: <link href="./?0000=css&0001=0001&0002=css" rel="stylesheet" type="text/css" /> <link href="./?0000=css&0001=0002&0002=css" rel="stylesheet" type="text/css" /> <script src="./?0000=js&0001=0000&0002=script" type="text/javascript"></script> </head> <body> <div id="wrapper"> <div id="header"> <div id="left_header"> <img src="./?0000=jpg&0001=0001&0002=pic" width="277" height="167" alt="" /> </div> <div id="right_header"> <div id="top-banner"></div> <ul id="navigation"> <li><a href="#" title="#" id="nav-home">Home</a></li> <li><a href="#" title="#">Signup</a></li> all works but my question being is or will this cause any complications i.e. speed of the site as all requests are being made to one single file and then loading in the appropriate data. Regards, Phil

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• C Program Stalls or Infinite Loops inside and else statement?

  - by Bobby S

  I have this weird thing happening in my C program which has never happened to me before. I am calling a void function with a single parameter, the function is very similar to this so you can get the jist: ... printf("Before Call"); Dumb_Function(a); printf("After Call"); ... ... void Dumb_Function(int a){ if(a == null) { } else{ int i; for(i=0; i<a; i++) { do stuff } printf("test"); } } This will output Before Call test and NOT "After Call" How is this possible? Why does my function not return? Did my program counter get lost? I can not modify it to a non void function. When running the cursor will blink and I am able to type, I press CTRL+C to terminate. Any ideas?

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• Can not open ports in iptables on CentOS 5??

  - by abszero

  I am trying to open up ports in CentOS's firewall and am having a terrible go at it. I have followed the "HowTo" here: http://wiki.centos.org/HowTos/Network/IPTables as well as a few other places on the Net but I still can't get the bloody thing to work. Basically I wanted to get two things working: VNC and Apache over the internal network. The problem is that the firewall is blocking all attempts to connect to these services. Now if I issue service iptables stop and then try to access the server via VNC or hit the webserver everything works as expected. However the moment I turn iptables back on all of my access is blocked. Below is a truncated version of my iptables file as it appears in vi -A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 5801 -j ACCEPT -A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 5901 -j ACCEPT -A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 6001 -j ACCEPT -A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 5900 -j ACCEPT -A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT Really I would just be happy if I could get port 80 opened up for Apache since I can do most stuff via putty but if I could figure out VNC as well that would be cool. As far as VNC goes there is just a single/user desktop that I am trying to connect to via: [ipaddress]:1 Any help would be greatly appreciated!

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• PDFBox: Problem with converting pdf page into image

  - by user552910

  My mission is pretty simple: converting every single page of a pdf file into images. I tried using icepdf open source version to generate the images but they don't generate the image with the correct font. So I start using PDFBox instead. The code is the following: PDDocument document = PDDocument.load(new File("testing.pdf")); List<PDPage> pages = document.getDocumentCatalog().getAllPages(); for (int i = 0; i < pages.size(); i++) { PDPage singlePage = pages.get(i); BufferedImage buffImage = convertToImage(singlePage, 8, 12); ImageIO.write(buffImage, "png", new File(PdfUtil.DATA_OUTPUT_DIR+(count++)+".png")); } The font looks good, but the pictures within the pdf file look fainted out (See the attachment). I look into the source code but I still have no clue how to fix it. Do you guys have any idea what's going on? Please help. Thanks!!

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• Pump Messages During Long Operations + C#

  - by Newbie

  Hi I have a web service that is doing huge computation and is taking more than a minute. I have generated the proxy file of the web service and then from my client end I am using the dll(of course I generated the proxy dll). My client side code is TimeSeries3D t = new TimeSeries3D(); int portfolioId = 4387919; string[] str = new string[2]; str[0] = "MKT_CAP"; DateRange dr = new DateRange(); dr.mStartDate = DateTime.Today; dr.mEndDate = DateTime.Today; Service1 sc = new Service1(); t = sc.GetAttributesForPortfolio(portfolioId, true, str, dr); But since it is taking to much time for the server to compute, after 1 minute I am receiving an error message The CLR has been unable to transition from COM context 0x33caf30 to COM context 0x33cb0a0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Kindly guide me what to do? Thanks

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• Why might my PHP log file not entirely be text?

  - by Fletcher Moore

  I'm trying to debug a plugin-bloated Wordpress installation; so I've added a very simple homebrew logger that records all the callbacks, which are basically listed in a single, ultimately 250+ row multidimensional array in Wordpress (I can't use print_r() because I need to catch them right before they are called). My logger line is $logger->log("\t" . $callback . "\n"); The logger produces a dandy text file in normal situations, but at two points during this particular task it is adding something which causes my log file to no longer be encoded properly. Gedit (I'm on Ubuntu) won't open the file, claiming to not understand the encoding. In vim, the culprit corrupt callback (which I could not find in the debugger, looking at the array) is about in the middle and printed as ^@lambda_546 and at the end of file there's this cute guy ^M. The ^M and ^@ are blue in my vim, which has no color theme set for .txt files. I don't know what it means. I tried adding an is_string($callback) condition, but I get the same results. Any ideas?

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• Refactor link to show/hide a table row

  - by abatishchev

  I have a table with row which cab be hidden by user. It's implemented this way: Markup: <table> <tr> <td> <table style="margin-left: auto; text-align: right;"> <tr> <td class="stats-hide"> <a href="#" onclick="hideStats();">Hide</a> </td> <td class="stats-show" style="display: none;"> <a href="#" onclick="showStats();">Show</a> </td> </tr> </table> </td> </tr> <tr class="stats-hide"> <td> <!-- data --> </td> </tr> </table> And jQuery code: <script type="text/javascript" language="javascript"> function hideStats() { hideControls(true, $('.stats-hide')); hideControls(false, $('.stats-show')); } function showStats() { hideControls(false, $('.stats-hide')); hideControls(true, $('.stats-show')); } function hideControls(value, arr) { $(arr).each(function () { if (value) { $(this).hide(); } else { $(this).show(); } }); } </script> How to implement the same behavior with one, single link and one, probably, CSS class? My idea - store somewhere a boolean variable and toggle controls visibility relatively to this variable. Are there more?

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• pyPDF - Retrieve page numbers from document

  - by SquidneyPoitier

  At the moment I'm looking into doing some PDF merging with pyPdf, but sometimes the inputs are not in the right order, so I'm looking into scraping each page for its page number to determine the order it should go in (e.g. if someone split up a book into 20 10-page PDFs and I want to put them back together). I have two questions - 1.) I know that sometimes the page number is stored in the document data somewhere, as I've seen PDFs that render on Adobe as something like [1243] (10 of 150), but I've read documents of this sort into pyPDF and I can't find any information indicating the page number - where is this stored? 2.) If avenue #1 isn't available, I think I could iterate through the objects on a given page to try to find a page number - likely it would be its own object that has a single number in it. However, I can't seem to find any clear way to determine the contents of objects. If I run: pdf.getPage(0).getContents() This usually either returns: {'/Filter': '/FlateDecode'} or it returns a list of IndirectObject(num, num) objects. I don't really know what to do with either of these and there's no real documentation on it as far as I can tell. Is anyone familiar with this kind of thing that could point me in the right direction?

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• (Oracle) How get total number of results when using a pagination query?

  - by BestPractices

  I am using Oracle 10g and the following paradigm to get a page of 15 results as a time (so that when the user is looking at page 2 of a search result, they see records 16-30). select * from ( select rownum rnum, a.* from (my_query) a where rownum <= 30 ) where rnum > 15; Right now I'm having to run a separate SQL statement to do a "select count" on "my_query" in order to get the total number of results for my_query (so that I can show it to the user and use it to figure out total number of pages, etc). Is there any way to get the total number of results without doing this via a second query, i.e. by getting it from above query? I've tried adding "max(rownum)", but it doesn't seem to work (I get an error [ORA-01747] that seems to indicate it doesnt like me having the keyword rownum in the group by). My rationale for wanting to get this from the original query rather than doing it in a separate SQL statement is that "my_query" is an expensive query so I'd rather not run it twice (once to get the count, and once to get the page of data) if I dont have to; but whatever solution I can come up with to get the number of results from within a single query (and at the same time get the page of data I need) should not add much if any additional overhead, if possible. Please advise. Here is exactly what I'm trying to do for which I receive an ORA-01747 error because I believe it doesnt like me having ROWNUM in the group by. Note, If there is another solution that doesnt use max(ROWNUM), but something else, that is perfectly fine too. This solution was my first thought as to what might work. SELECT * FROM (SELECT r.*, ROWNUM RNUM, max(ROWNUM) FROM (SELECT t0.ABC_SEQ_ID AS c0, t0.FIRST_NAME, t0.LAST_NAME, t1.SCORE FROM ABC t0, XYZ t1 WHERE (t0.XYZ_ID = 751) AND t0.XYZ_ID = t1.XYZ_ID ORDER BY t0.RANK ASC) r WHERE ROWNUM <= 30 GROUP BY r.*, ROWNUM) WHERE RNUM > 15

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• Which is faster for large "for" loop: function call or inline coding?

  - by zaplec

  Hi, I have programmed an embedded software (using C of course) and now I'm considering ways to improve the running time of the system. The most important single module in my system is one very large nested for loop module. That module consists of two nested for loops that loops max 122500 times. That's not very much yet, but the problem is that inside that nested for loop I have a function call to a function that is in another source file. That specific function consists mostly of two another nested for loops which loops always 22500 times. So now I have to make a function call 122500 times. I have made that function that is to be called a lot lighter and shorter (yet still works as it should) and now I started to think that would it be faster to rip off that function call and write that process directly inside those first two for loops? The processor in that system is ARM7TDMI and its frequency is 55MHz. The system itself isn't very time critical so it doesn't have to be real time capable. However the faster it can process its duties the better. Also would it be also faster to use while loops instead of fors? And any piece of advice about how to improve the running time is appreciated. -zaplec

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• How to exclude rows where matching join is in an SQL tree

  - by Greg K

  Sorry for the poor title, I couldn't think how to concisely describe this problem. I have a set of items that should have a 1-to-1 relationship with an attribute. I have a query to return those rows where the data is wrong and this relationship has been broken (1-to-many). I'm gathering these rows to fix them and restore this 1-to-1 relationship. This is a theoretical simplification of my actual problem but I'll post example table schema here as it was requested. item table: +------------+------------+-----------+ | item_id | name | attr_id | +------------+------------+-----------+ | 1 | BMW 320d | 20 | | 1 | BMW 320d | 21 | | 2 | BMW 335i | 23 | | 2 | BMW 335i | 34 | +------------+------------+-----------+ attribute table: +---------+-----------------+------------+ | attr_id | value | parent_id | +---------+-----------------+------------+ | 20 | SE | 21 | | 21 | M Sport | 0 | | 23 | AC | 24 | | 24 | Climate control | 0 | .... | 34 | Leather seats | 0 | +---------+-----------------+------------+ A simple query to return items with more than one attribute. SELECT item_id, COUNT(DISTINCT(attr_id)) AS attributes FROM item GROUP BY item_id HAVING attributes > 1 This gets me a result set like so: +-----------+------------+ | item_id | attributes | +-----------+------------+ | 1 | 2 | | 2 | 2 | | 3 | 2 | -- etc. -- However, there's an exception. The attribute table can hold a tree structure, via parent links in the table. For certain rows, parent_id can hold the ID of another attribute. There's only one level to this tree. Example: +---------+-----------------+------------+ | attr_id | value | parent_id | +---------+-----------------+------------+ | 20 | SE | 21 | | 21 | M Sport | 0 | .... I do not want to retrieve items in my original query where, for a pair of associated attributes, they related like attributes 20 & 21. I do want to retrieve items where: the attributes have no parent for two or more attributes they are not related (e.g. attributes 23 & 34) Example result desired, just the item ID: +------------+ | item_id | +------------+ | 2 | +------------+ How can I join against attributes from items and exclude these rows? Do I use a temporary table or can I achieve this from a single query? Thanks.

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• Efficient way to store order in mySQL for list of items

  - by ninumedia

  I want to code cleaner and more efficiently and I wanted to know any other suggestions for the following problem: I have a mySQL database that holds data about a set of photograph names. Oh, say 100 photograph names Table 1: (photos) has the following fields: photo_id, photo_name Ex data: 1 | sunshine.jpg 2 | cloudy.jpg 3 | rainy.jpg 4 | hazy.jpg ... Table 2: (categories) has the following fields: category_id, category_name, category_order Ex data: 1 | Summer Shots | 1,2,4 2 | Winter Shots | 2,3 3 | All Seasons | 1,2,3,4 ... Is it efficient to store the order of the photos in this manner per entry via comma delimited values? It's one approach I have seen used before but I wanted to know if something else is faster in run time. Using this way I don't think it is possible to do a direct INNER JOIN on the category table and photo table to get a single matched list of all the photographs per category. Ex: Summer shots - sunshine.jpg, cloudy.jpg, hazy.jpg because it was matched against 1,2,4 The iteration through all the categories and then the photos will have a O(n^2) and there has to be a better/faster way. Please educate me :)

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