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• phppgadmin : How does it kick users out of postgres, so it can db_drop?

  - by egarcia

  I've got one Posgresql database (I'm the owner) and I'd like to drop it and re-create it from a dump. Problem is, there're a couple applications (two websites, rails and perl) that access the db regularly. So I get a "database is being accessed by other users" error. I've read that one possibility is getting the pids of the processes involved and killing them individually. I'd like to do something cleaner, if possible. Phppgadmin seems to do what I want: I am able to drop schemas using its web interface, even when the websites are on, without getting errors. So I'm investigating how its code works. However, I'm no PHP expert. I'm trying to understand the phppgadmin code in order to see how it does it. I found out a line (257 in Schemas.php) where it says: $data->dropSchema(...) $data is a global variable and I could not find where it is defined. Any pointers would be greatly appreciated.

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• If attacker has original data and encrypted data, can they determine the passphrase?

  - by Brad Cupit

  If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require storage in the database. I'm leaning towards the the one-way-hash-stored-in-the-db, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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• When developing a Microsoft Office Add-In (for Word), is it possible to store hidden metadata inform

  - by leftend

  I am trying to store metadata (basically a unique id) along with each cell of a table in a Word document. Currently, for the add-in I'm developing, I am querying the database, and building a table inside the Word document using the data that is retrieved. I want to be able to save any of the user's edits to the document, and persist it back to the database. My initial thought was to store a unique id along with each cell in the table so that I would be able to tell which records to update. I would also like to store some sort of "isChanged" flag within each cell so that I could tell which cells were changed. I found that I could add the needed information into the "ID" property of the cell - however, that information was not retained if the user saved the document, closed it, and re-opened it. I then tried storing the data by adding a data to the "Fields" collection - but that did not work and threw a runtime error. Here is the code that I tried: object t1 = Word.WdFieldType.wdFieldEmpty; object val = "myValue: " + counter; object preserveFormatting = true; tbl.Cell(i, j).Range.Fields.Add(tbl.Cell(i, j).Range, ref t1, ref val, ref preserveFormatting); This compiles fine, but throws this runtime error "This command is not available". So, is this possible at all? Or am I headed in the wrong direction? Thanks in advance.

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• problem with mysql character set & GWT

  - by Ehsan Khodarahmi

  Hi I've a SmartGWT application which interacts with a mysql database using rpc services. Suppose it as a simple form with a textbox & two save & load buttons. My database & tables & all fields collation is utf8_persian_ci. All java source files & module html & xml files have saved with utf8 character set. & also I've a meta tag in module html file which contains my form : <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> my application works correctly in eclipse develpment mode & also in my local tomcat server. Then i put it on remote server (I compress it using jar.exe into a war file with -cvf flag & then upload it using my server's plesk control panel). In this mode, when I load data from a mysql table (load a record from any table), data will load into my form with no problem, but when I want to save some data (in persian language), mysql just writes some ? (question sign) in characteristic table fields. Any idea ?

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• What do these .NET auto-generated table adapter commands do? e.g. UPDATE/INSERT followed by a SELECT

  - by RickL

  I'm working with a legacy application which I'm trying to change so that it can work with SQL CE, whilst it was originally written against SQL Server. The problem I am getting now is that when I try to do dataAdapter.Update, SQL CE complains that it is not expecting the SELECT keyword in the command text. I believe this is because SQL CE does not support batch SELECT statements. The auto-generated table adapter command looks like this... this._adapter.InsertCommand.CommandText = @"INSERT INTO [Table] ([Field1], [Field2]) VALUES (@Value1, @Value2); SELECT Field1, Field2 FROM Table WHERE (Field1 = @Value1)"; What is it doing? It looks like it is inserting new records from the datatable into the database, and then reading that record back from the database into the datatable? What's the point of that? Can I just go through the code and remove all these SELECT statements? Or is there an easier way to solve my problem of wanting to use these data adapters with SQL CE? I cannot regenerate these table adapters, as the people who knew how to have long since left.

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• PHP not obeying my defined ETags

  - by Sam Bisbee

  What I'm doing I'm pulling an image from the database and sending it to the browser with all the proper headers - the image displays fine. I also send an ETag header, using the SHA1 of the image's content as the tag. The images are getting called semi regularly, so caching is a bit of an issue (won't kill the site, but nice to have). The Problem $_SERVER['HTTP_IF_NONE_MATCH'] is not available to me. As far as I can tell, this is because of PHP's "disobey the cache controls" life style. I can't mess with the session cache limiter, because I don't have access. But, even if I did have access, I wouldn't want to touch it: 99% of the site is under WordPress. The Environment PHP 4 (don't ask) Apache 2.2 WordPress The images live in the database (largeblog), which I can't change. Any guidance, tip/tricks, etc. would be helpful. I don't have much room to change the environmental/structural stuff. Cheers.

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• partial entity loading and management in silverlight / wcf ria

  - by Dan Wray

  I have a Silverlight 4 app which pulls entities down from a database using WCF RIA services. These data objects are fairly simple, just a few fields but one of those fields contains binary data of an arbitrarily size. The application needs access to this data basically asap after a user has logged in, to display in a list, enable selection etc. My problem is because of the size of this data, the load times are not acceptable and can approach the default timeout of the RIA service. I'd like to somehow partially load the objects into my local data context so that I have the IDs, names etc but not the binary data. I could then at a later point (ie when it's actually needed) populate the binary fields of those objects I need to display. Any suggestions on how to accomplish this would be welcome. Another approach which has occurred to me whilst writing this question (how often does that happen?!) is that I could move the binary data into a seperate database table joined to the original record 1:1 which would allow me to make use of RIA's lazy loading on that binary data. again.. comments welcome! Thanks.

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• Communication between EJB3 Instances (JEE inter-bean communication) possible?

  - by Hank

  I'm designing a part of a JEE6 application, consisting of EJB3 beans. Part of the requirements are multiple parallel (say a few hundred) long running (over days) database hunts. Individual hunts have different search parameters (start time, end time, query filter). Parameters may get changed over time. Currently I'm thinking of the following: SearchController (Stateless Session Bean) formulates a set of search parameters, sends it off to a SearchListener via JMS SearchListener (Message Driven Bean) receives search parameters, instantiates a SearchWorker with the parameters SearchWorker (SLSB) hunts repeatedly through the database; when it finds something, the result is sent off via JMS, and the search continues; when the given 'end-time' has reached, it ends What I'm wondering now: Is there a problem, with EJB3 instances running for days? (Other than that I need to be able to deal with container restarts...) How do I know how many and which EJB instances of SearchWorker are currently running? Is it possible to communicate with them individually (similar to sending a System V signal to a unix process), e.g. to send new parameters, to end an instance, etc..

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• Search book by title, and author

  - by Swoosh

  I got a table with columns: author firstname, author lastname, and booktitle Multiple users are inserting in the database, through an import, and I'd like to avoid duplicates. So I'm trying to do something like this: I have a record in the db: First Name: "Isaac" Last Name: "Assimov" Title: "I, Robot" If the user tries to add it again, it would be basically a non-split-text (would not be split up into author firstname, author lastname, and booktitle) So it would basically look like this: "Isaac Asimov - I Robot" or "Asimov, Isaac - I Robot" or "I Robot by Isaac Asimov" You see where I am getting at? (I cannot force the user to split up all the books into into author firstname, author lastname, and booktitle, and I don't even like the idea to force the user, because it's not too user-friendly) What is the best way (in SQL) to compare all this possible bookdata scenarios to what I have in the database, not to add the same book twice. I was thinking about a possibility of suggesting the user: "is THIS the book you are trying to add?" (imagine a list instead of the THIS word, just like on stackoverflow - ask question - Related Questions. I was thinking about soundex and maybe even the like operators, but so far i didn't get the results i was hoping.

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• Computing complex math equations in python

  - by dassouki

  Are there any libraries or techniques that simplify computing equations ? Take the following two examples: F = B * { [ a * b * sumOf (A / B ''' for all i ''' ) ] / [ sumOf(c * d * j) ] } where: F = cost from i to j B, a, b, c, d, j are all vectors in the format [ [zone_i, zone_j, cost_of_i_to_j], [..]] This should produce a vector F [ [1,2, F_1_2], ..., [i,j, F_i_j] ] T_ij = [ P_i * A_i * F_i_j] / [ SumOf [ Aj * F_i_j ] // j = 1 to j = n ] where: n is the number of zones T = vector [ [1, 2, A_1_2, P_1_2], ..., [i, j, A_i_j, P_i_j] ] F = vector [1, 2, F_1_2], ..., [i, j, F_i_j] so P_i would be the sum of all P_i_j for all j and Aj would be sum of all P_j for all i I'm not sure what I'm looking for, but perhaps a parser for these equations or methods to deal with multiple multiplications and products between vectors? To calculate some of the factors, for example A_j, this is what i use from collections import defaultdict A_j_dict = defaultdict(float) for A_item in TG: A_j_dict[A_item[1]] += A_item[3] Although this works fine, I really feel that it is a brute force / hacking method and unmaintainable in the case we want to add more variables or parameters. Are there any math equation parsers you'd recommend? Side Note: These equations are used to model travel. Currently I use excel to solve a lot of these equations; and I find that process to be daunting. I'd rather move to python where it pulls the data directly from our database (postgres) and outputs the results into the database. All that is figured out. I'm just struggling with evaluating the equations themselves. Thanks :)

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• Using WCF to expose underlying process

  - by Steven

  I think I must be a little dull because I'm having so much difficulty with this. I use WCF for pretty much everything in-house, it's the most appropriate technology. I have a new Silverlight 3 app that is connecting to the WCF service and that's working fine. Where the problem begins is: Because of the expense in creating the objects within this service and the high correlation of individual objects being shared between clients I want to have a console application that basically gathers/calculates/caches all the data for the service 24/7 and the service basically connects to the console app (or whatever it is) and gets the pre-processed data. eg, think of it in terms of a stock reporting app (which it is). Person A has a portfolio of x, y z Person B has a portfolio of x, q, z, r The service needs to provide updated metrics on how their portfolio is performing. So instead of every 1 second processing person A, then person B, the app independently gathers the stock price and persons position information into memory and the service just queries the in memory result. Thanks for your help, I really am feeling dumb right now.

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• JMX - MBean automated registration on application deployment

  - by Gadi

  Hi All, I need some direction with JMX and J2EE. I am aware (after few weeks of research) that the JMX specification is missing as far as deployment is concerned. There are few vendor specific implementations for what I am looking for but none are cross vendor. I would like to automate the deployment of MBeans and registration with the Server. I need the server to load and register my MBeand when the application is deployed and remove when the application is un-deployed. I develop with: NetBean 6.7.1, GlassFish 2.1, J2EE5, EJB3 More specific, I need a way to manage timer service runs. My application need to run different archiving agents and batch reporting. I was hoping the JMX will give me remote access to create and manage the timer services and enable the user to create his own schedule. If the JMX is auto registered on application deployment the user can immediately connect and manage the schedule. On the other hand, how can an EJB connect/access an MBean? Many thanks in advance. Gadi.

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• How do I pass a lot of parameters to views in Dango?

  - by Mark

  I'm very new to Django and I'm trying to build an application to present my data in tables and charts. Till now my learning process went very smooth, but now I'm a bit stuck. My pageview retrieves large amounts of data from a database and puts it in the context. The template then generates different html-tables. So far so good. Now I want to add different charts to the template. I manage to do this by defining <img src=".../> tags. The Matplotlib chart is generate in my chartview an returned via: response=HttpResponse(content_type='image/png') canvas.print_png(response) return response Now I have different questions: the data is retrieved twice from the database. Once in the pageview to render the tables, and again in the chartview for making the charts. What is the best way to pass the data, already in the context of the page to the chartview? I need a lot of charts, each with different datasets. I could make a chartview for each chart, but probably there is a better way. How do I pass the different dataset names to the chartview? Some charts have 20 datasets, so I don't think that passing these dataset parameters via the url (like: <imgm src="chart/dataset1/dataset2/.../dataset20/chart.png />) is the right way. Any advice?

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• How can I print a web page on a server?

  - by Gavin Schultz

  Suppose I develop a web page using the cool Google visualization API, and it does everything the user wants. They can the parameters, look at the graphs, and print the page to get a reasonable-looking report. All good. Now suppose I want to do the same thing server-side. For example, say we need a set of report generated at a specific time of day, printed to a PDF and emailed to a manager. It's not a user-initiated action, so we don't have a user's browser or their printer. We have a URL that would render the report if we had a browser, and that's it. Is there a good way to do this server-side? Is this just foolish? Has anyone done anything like that before? Do any of the major browsers have APIs that might provide such functionality? Keep in mind too that it's not just static HTML; probably javascript will be running first to shift the DOM around. I know we could implement a whole different reporting engine on the server side to do this, but that will (a) generate reports that look a bit different, and (b) require me to build/maintain two sets of functionality. Instead, I'd be happy if I could just render the page / pages I want in an invisible server-side browser and print it to a PDF (let's mostly ignore that step - I know any number of PDF printer drivers that could do this). I don't really want to do it ugly either - i.e. by starting a browser process and then sending keystrokes directly to the window either - that's just bound to fall apart with a slight nudge. The only related question I found had an answer like that. Any advice appreciated!

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• How much should the AppDelegate do?

  - by Rudiger

  I'm designing quite a large App and on startup it will create sessions with a few different servers. As they are creating a session which is used across all parts of the app its something I thought would be best in App Delegate. But the problem is I need the session progress to be represented on the screen. I plan to have a UIToolBar at the bottom of the main menu which I don't want to cover with the progress bar but cover the UIView above it.So the way I see it I could do it a few different ways. 1) Have the App Delegate establish the sessions and report the progress to the main menu class so it can represent it in the progress bar (will I have any issues doing this if the sessions are created in a separate thread?), 2) have the App delegate display the main menu (UIView with a bunch of buttons and UIToolBar) and have it track and display the progress (I have never displayed anything in the App Delegate but assume you can do this but its not recommended) or 3) have the App Delegate just push the main menu and have the mainMenu class create the sessions and display the progress bar. 4) I think the other way to do it is to create the sessions in a delegate class and have the delegate set to mainMenu rather than self (AppDelegate), although I've never used anything other then self so not sure if this will work or if I will be able to close the thread (through calling super maybe?) as its running in the AppDelegate rather than the delegate of the class. As I've kinda said before the sessions are being created in a class in a separate thread so it wont lock the UI and I think the best way is the first but am I going to have issues having it running in a separate thread, reporting back to the app delegate and then sending that message to the mainMenu view? I hope that all makes sense, let me know if you need any further clarification. Any information is appreciated Cheers,

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• Hadoop Map/Reduce - simple use example to do the following...

  - by alexeypro

  I have MySQL database, where I store the following BLOB (which contains JSON object) and ID (for this JSON object). JSON object contains a lot of different information. Say, "city:Los Angeles" and "state:California". There are about 500k of such records for now, but they are growing. And each JSON object is quite big. My goal is to do searches (real-time) in MySQL database. Say, I want to search for all JSON objects which have "state" to "California" and "city" to "San Francisco". I want to utilize Hadoop for the task. My idea is that there will be "job", which takes chunks of, say, 100 records (rows) from MySQL, verifies them according to the given search criteria, returns those (ID's) which qualify. Pros/cons? I understand that one might think that I should utilize simple SQL power for that, but the thing is that JSON object structure is pretty "heavy", if I put it as SQL schemas, there will be at least 3-5 tables joins, which (I tried, really) creates quite a headache, and building all the right indexes eats RAM faster than I one can think. ;-) And even then, every SQL query has to be analyzed to be utilizing the indexes, otherwise with full scan it literally is a pain. And with such structure we have the only way "up" is just with vertical scaling. But I am not sure it's the best option for me, as I see how JSON objects will grow (the data structure), and I see that the number of them will grow too. :-) Help? Can somebody point me to simple examples of how this can be done? Does it make sense at all? Am I missing something important? Thank you.

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• Setting nested object to null when selected option has empty value

  - by Javi

  Hello, I have a Class which models a User and another which models his country. Something like this: public class User{ private Country country; //other attributes and getter/setters } public class Country{ private Integer id; private String name; //other attributes and getter/setters } I have a Spring form where I have a combobox so the user can select his country or can select the undefined option to indicate he doen't want to provide this information. So I have something like this: <form:select path="country"> <form:option value="">-Select one-</form:option> <form:options items="${countries}" itemLabel="name" itemValue="id"/> </form:select> In my controller I get the autopopulated object with the user information and I want to have country set to null when the "-Select one-" option has been selected. So I have set a initBinder with a custom editor like this: @InitBinder protected void initBinder(WebDataBinder binder) throws ServletException { binder.registerCustomEditor(Country.class, "country", new CustomCountryEditor()); } and my editor do something like this: public class CustomCountryEditor(){ @Override public String getAsText() { //I return the Id of the country } @Override public void setAsText(String str) { //I search in the database for a country with id = new Integer(str) //and set country to that value //or I set country to null in case str == null } } When I submit the form it works because when I have country set to null when I have selected "-Select one-" option or the instance of the country selected. The problem is that when I load the form I have a method like the following one to load the user information. @ModelAttribute("user") public User getUser(){ //loads user from database } The object I get from getUser() has country set to a specific country (not a null value), but in the combobox is not selected any option. I've debugged the application and the CustomCountryEditor works good when setting and getting the text, thoughgetAsText method is called for every item in the list "countries" not only for the "country" field. Any idea? Is there a better way to set null the country object when I select no country option in the combobox? Thanks

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• How do you read a file line by line in your language of choice?

  - by Jon Ericson

  I got inspired to try out Haskell again based on a recent answer. My big block is that reading a file line by line (a task made simple in languages such as Perl) seems complicated in a functional language. How do you read a file line by line in your favorite language? So that we are comparing apples to other types of apples, please write a program that numbers the lines of the input file. So if your input is: Line the first. Next line. End of communication. The output would look like: 1 Line the first. 2 Next line. 3 End of communication. I will post my Haskell program as an example. Ken commented that this question does not specify how errors should be handled. I'm not overly concerned about it because: Most answers did the obvious thing and read from stdin and wrote to stdout. The nice thing is that it puts the onus on the user to redirect those streams the way they want. So if stdin is redirected from a non-existent file, the shell will take care of reporting the error, for instance. The question is more aimed at how a language does IO than how it handles exceptions. But if necessary error handling is missing in an answer, feel free to either edit the code to fix it or make a note in the comments.

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• Programatically create web application & sub site

  - by Tejas

  I am using the following code to programatically create a web application & sub site, try { SPWebApplicationBuilder webAppBuilder = new SPWebApplicationBuilder(SPFarm.Local); SPWebApplication newApplication; int myPort = 3333; webAppBuilder.Port = myPort; //Port No. webAppBuilder.RootDirectory = new System.IO.DirectoryInfo("C:\\Inetpub\\wwwroot\\wss\\VirtualDirectories\\" + myPort); webAppBuilder.CreateNewDatabase = true; // Create new database webAppBuilder.DatabaseName = "WSS_Content_372772890a5a4a04abb460cd9ea3bd22"; // Database name webAppBuilder.DatabaseServer = webAppBuilder.DefaultZoneUri.Host; // DatabaseServer Host name/computer name webAppBuilder.UseNTLMExclusively = true; // Use NTLM authentication newApplication = webAppBuilder.Create(); // Create new web application newApplication.Provision(); // Provision it into web farm using (var mySiteCollection = newApplication.Sites.Add("/", "Site 3", "Site 3 Decscription", 1033, "STS#1", "In-Wai-Svr2\\Administrator", "Administrator", "[email protected]")) { using (var rootWeb = mySiteCollection.RootWeb) { // Code customizing root site goes here using (var subSite = rootWeb.Webs.Add("Site3.1", "Site 3.1", "Site 3.1 Description", 1033, "STS#1", true, false)) { // Code customizing sub site goes here } } } } catch(Exception ex) { ; } It works fine i.e. it creates the web application on the specified port with sub site but this sub site will not be shown under Sites menu of Quick launch bar also it will not be shown as a separate tab on the Home Page. Is it possible to do it programatically?

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• How to port an Ajax CMS based on metadata in Asp.Net MVC?

  - by Maushu

  I'm maintaining a CMS where I have this feeling it was made in the age of dinosaurs (Asp.net 1.0?) and decided to upgrade it with Asp.Net MVC and jQuery. But I have some problems regarding the design/specifications of the CMS which I cannot change. The CMS The CMS uses JavaScript. Alot. As in "I don't load pages, I request new pages using Ajax and render the information using javascript" alot. Not to mention the animations, the weird horizontal apresentation of structures... anyways, besides the first page (that is the login page) every other "page" is just data requested from a WebService that comes with the website. Would MVC have any problems with this design? The Database The database is in a SQL Server 2k8 and, like the CMS, this part is also... interesting. Basically, the user can create data structures using metadata (and saved on the Structure table). These structures are saved on tables that are created (and regenerated when changed) at runtime using said metadata. I don't know how I would implement this part in MVC. The question is, can and should I convert this project to MVC? Any tips regarding the metadata and overuse of ajax?

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• How to change default locale in BIRT

  - by zlajo

  Hi everybody, I am working with the BIRT reporting engine and my current task is to implement internationalization for reports. We are using the webviewer to generate and download pdf reports. There is a parameter (__locale) which allows me to specify the locale that should be used to generate a report. So far everything works fine. There is an additional requirement I have not been able to implement, though. Additionally to the locale which is set by the http parameter there should also be the possibility to specify some kind of fallback locale. Take the following example: There are two property-files common_en_US.properties and common_en_GB.properties. The first locale to be used should be en_GB (__locale=en_GB). Everything works fine if the common_en_GB.properties file exist. But I would also like to tell BIRT to use common_en_US.properties if the en_GB-file cannot be found, which does not work as expected. I tried to solve this by manually setting the Java default locale before executing BIRT because I thought that BIRT would use the Java mechanism to resolve localized strings. Unfortunately this attempt does not work. Is there a different way to do what I would like to do? Is it possible to do something like that at all? Thanks a lot! Johannes

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• Why isn't this simple PHP/MySQL code working?

  - by Sammy

  I am very new to php/mysql and this is causing me to loose hairs, I am trying to build a multi level site navigation. In this part of my script I am readying the sub and parent categories coming from a form for insertion into the database: // get child categories $catFields = $_POST['categories']; if (is_array($catFields)) { $categories = $categories; for ($i=0; $i<count($catFields); $i++) { $categories = $categories . $catFields[$i]"; } } // get parent category $select = mysql_query ("SELECT parent FROM categories WHERE id = $categories"); while ($return = mysql_fetch_assoc($select)) { $parentId = $return['parent']; } The first part of my script works fine, it grabs all the categories that the user has chosen to assign a post by checking the checkboxes in a form and readies it for insertion into the database. But the second part does not work and I can't understand why. I am trying to match a category with a parent that is stored in it's own table, but it returns nothing even though the categories all have parents. Can anyone tell me why this is? p.s. The $categories variable contains the sub category id.

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• What is optimal hardware configuration for heavy load LAMP application

  - by Piotr Kochanski

  I need to run Linux-Apache-PHP-MySQL application (Moodle e-learning platform) for a large number of concurrent users - I am aiming 5000 users. By concurrent I mean that 5000 people should be able to work with the application at the same time. "Work" means not only do database reads but writes as well. The application is not very typical, since it is doing a lot of inserts/updates on the database, so caching techniques are not helping to much. We are using InnoDB storage engine. In addition application is not written with performance in mind. For instance one Apache thread usually occupies about 30-50 MB of RAM. I would be greatful for information what hardware is needed to build scalable configuration that is able to handle this kind of load. We are using right now two HP DLG 380 with two 4 core processors which are able to handle much lower load (typically 300-500 concurrent users). Is it reasonable to invest in this kind of boxes and build cluster using them or is it better to go with some more high-end hardware? I am particularly curious how many and how powerful servers are needed (number of processors/cores, size of RAM) what network equipment should be used (what kind of switches, network cards) any other hardware, like particular disc storage solutions, etc, that are needed Another thing is how to put together everything, that is what is the most optimal architecture. Clustering with MySQL is rather hard (people are complaining about MySQL Cluster, even here on Stackoverflow).

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• Collecting high-volume video viewing data

  - by DanK

  I want to add tracking to our Flash-based media player so that we can provide analytics that show what sections of videos are being watched (at the moment, we just register a view when a video starts playing) For example, if a viewer watches the first 30 seconds of a video and then clicks away to something else, we want the data to reflect that. Likewise, if someone watches the first 10 seconds, then scrubs the timeline to the last minute of the video and watches that, we want to register viewing on the parts watched and not the middle section. My first thought was to collect up the viewing data in the player and send it all to the server at the end of a viewing session. Unfortunately, Flash does not seem to have an event that you can hook into when a viewer clicks away from the page the movie is on (probably a good thing - it would be open to abuse) So, it looks like we're going to have to make regular requests to the server as the video is playing. This is obviously going to lead to a high volume of requests when there are large numbers of simultaneous viewers. The simple approach of dumping all these 'heartbeat' events from clients to a database feels like it will quickly become unmanageable so I'm wondering whether I should be taking an approach where viewing sessions are cached in memory and flushed to database when they become inactive (based on a timeout). That way, the data could be stored as time spans rather than individual heartbeats. So, to the question - what is the best way to approach dealing with this kind of high-volume viewing data? Are there any good existing architectures/patterns? Thanks, Dan.

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• Mysql InnoDB performance optimization and indexing

  - by Davide C

  Hello everybody, I have 2 databases and I need to link information between two big tables (more than 3M entries each, continuously growing). The 1st database has a table 'pages' that stores various information about web pages, and includes the URL of each one. The column 'URL' is a varchar(512) and has no index. The 2nd database has a table 'urlHops' defined as: CREATE TABLE urlHops ( dest varchar(512) NOT NULL, src varchar(512) DEFAULT NULL, timestamp timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, KEY dest_key (dest), KEY src_key (src) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 Now, I need basically to issue (efficiently) queries like this: select p.id,p.URL from db1.pages p, db2.urlHops u where u.src=p.URL and u.dest=? At first, I thought to add an index on pages(URL). But it's a very long column, and I already issue a lot of INSERTs and UPDATEs on the same table (way more than the number of SELECTs I would do using this index). Other possible solutions I thought are: -adding a column to pages, storing the md5 hash of the URL and indexing it; this way I could do queries using the md5 of the URL, with the advantage of an index on a smaller column. -adding another table that contains only page id and page URL, indexing both columns. But this is maybe a waste of space, having only the advantage of not slowing down the inserts and updates I execute on 'pages'. I don't want to slow down the inserts and updates, but at the same time I would be able to do the queries on the URL efficiently. Any advice? My primary concern is performance; if needed, wasting some disk space is not a problem. Thank you, regards Davide

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