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• While porting a windows application to web, is it better to stick to conventional web technologies o

  - by Kabeer

  Hello. The web based application I am working on currently is a port from a windows application. This application is very data intensive. There are scores of modules and each of these modules have number of forms (data entry screens) and reports whereas the forms have many many fields and likewise the reports. I have been trying to identify the most suitable architecture for the presentation tier. There are many functions that are not very easily portable, for example printing (this too is very complex). For most of the others, I am planning to us "Ext JS" library which looks like capable of handling about 70% of complexity out of the box while for the remaining I would be custom coding or extending Ext JS. Having said that (sorry for being so descriptive), I wonder, if this is an Intranet application, why not port the entire application to SilverLight? While I am good at .Net, I'm somewhat alien to SilverLight. Considering I know my target audience and that the software will be used per seat license, would it be better to ride on SilverLight or is it better to stick to conventional web (XHTML, JS, CSS, etc)? Further, I have to support multiple devices in future and considering that SilverLight plug-ins for many devices are yet not out, would it be a risk?

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• Javascript/CSS rollover menus are patented and subject to licensing?

  - by Scott B

  Very interesting finding that a client brought to my attention today regarding javascript style rollover menus. They got a call from their legal dept that they need to change the manner in which their rollover menu is activated (at the risk of having to pay license to continue using the navigation technique). Its no April fools joke, apparently this is really happening. Apparently a company named Webvention LLC has obtained enforcement rights to a patent, U.S. Patent No. 5,251,294 - "Accessing, assembling, and using bodies of Information." A menu link, that when rolled over, expands to show a list of categorized, related links. Dropdown menus and slide-out menus are examples of this patented navigational methodology. A key component of this patent is that the dropdown/slide-out action must be initiated by a rollover or mouseover event. If the dropdown/slide-out action is initiated by any other event, such as a mouse-click event, then this behavior is not in violation of the patent. Anyone ever heard of this or know of the validity of its claims? Website is here: http://www.webventionllc.com/

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• How to improve the use of Delphi Frames

  - by Brian Frost

  I've used frames in Delphi for years, and they are one of the most powerful features of the VCL, but standard use of them seems to have some risk such as: It's easy to accidentally move or edit the frame sub-components on a frame's host form without realising that you are 'tweaking' with the frame - I know this does not affect the original frame code, but it's generally not what you would want. When working with the frame you are still exposed to its sub-components for visual editing, even when that frame is years old and should not be touched. So I got to thinking.... Is there a way of 'grouping' components such that their positions are 'locked'? This would be useful for finished forms as well as frames. Often other developers return code to me where only the form bounds have changed and even they did not intend any change. Is there any way of turning a frame and its components into a single Delphi component? If so, the frame internals would be completely hidden and its useability would increase further. I'm interested in any thoughts... Brian.

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• Junit: splitting integration test and Unit tests.

  - by jeff porter

  Hello all, I've inherited a load of Junit test, but these tests (apart from most not working) are a mixture of actual unit test and integration tests (requiring external systems, db etc). So I'm trying to think of a way to actually separate them out, so that I can run the unit test nice and quickly and the integration tests after that. The options are.. 1: Split them into separate directories. 2: Move to Junit4 and annotate the classes to separate them. 3: Use a file naming convention to tell what a class is , i.e. AdapterATest and AdapterAIntergrationTest. 3 has the issue that Eclipse has the option to "Run all tests in the selected project/package or folder". So it would make it very hard to just run the integration tests. 2: runs the risk that developers might start writing integration tests in unit test classes and it just gets messy. 1: Seems like the neatest solution, but my gut says there must be a better solution out there. So that is my question, how do you lot break apart integration tests and proper unit tests?

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• Why does Cut/Paste of form components sometimes stop working in Delphi 2007 IDE?

  - by robsoft

  This is driving me crazy. I'm not going to take it anymore. I'm going to ask, even at the risk of eternal public humiliation! (If it's something really obvious or that I've done to the system myself). For reasons I've never quite had the patience to work out, every so often the form I'm working on in Delphi 2007's visual form editor goes 'pseudo-read-only'; I can add new components to the form, I can move/resize existing ones (and change any properties in the Object Inspector), and I can select a component and 'copy' it to the clipboard. But I'm completely unable to cut a component from the form, or paste a new copy down. I don't believe it's to do with the 'Lock Controls' Edit menu option as I can toggle this on or off and it has the effect it's supposed to - this disappearance of Cut & Paste happens on the right-click context menu, from the keyboard and from the main Edit menu - it's as if the form has become read only to thing to do with the clipboard. If I close the form in the IDE and then reopen it, everything starts working fine again (just as D1, D3, D5 and D7 always did for me, previously). I'm not going mad, as I'm sure I read something about why this happens on a newsgroup once and it's caught me out from time to time many many times in the last few months, but I've failed to find the newsgroup reference this evening and I've decided that, as more and more Delphi users seem to be making use of StackOverflow, it was worth asking here. Help - when I'm doing lots of form-work it drives me absolutely mad!

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• Reading from serial port with Boost Asio?

  - by trikri

  Hi! I'm going to check for incoming messages (data packages) on the serial port, using Boost Asio. Each message will start with a header that is one byte long, and will specify which type of the message has been sent. Each different type of message has an own length. The function I'm about to write should check for new incoming messages continually, and when it finds one it should read it, and then some other function should parse it. I thought that the code might look something like this: void check_for_incoming_messages() { boost::asio::streambuf response; boost::system::error_code error; std::string s1, s2; if (boost::asio::read(port, response, boost::asio::transfer_at_least(0), error)) { s1 = streambuf_to_string(response); int msg_code = s1[0]; if (msg_code < 0 || msg_code >= NUM_MESSAGES) { // Handle error, invalid message header } if (boost::asio::read(port, response, boost::asio::transfer_at_least(message_lengths[msg_code]-s1.length()), error)) { s2 = streambuf_to_string(response); // Handle the content of s1 and s2 } else if (error != boost::asio::error::eof) { throw boost::system::system_error(error); } } else if (error != boost::asio::error::eof) { throw boost::system::system_error(error); } } Is boost::asio::streambuf is the right thing to use? And how do I extract the data from it so I can parse the message? I also want to know if I need to have a separate thread which only calls this function, so that it get called more often? Isn't there a risk for loosing data in between two calls to the function otherwise, because so much data comes in that it can't be stored in the serial ports memory? I'm using Qt as a widget toolkit and I don't really know how long time it needs to process all it's events.

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• How to estimate the contribution of an individual to a software project?

  - by Amit Kumar

  I work on a software project and would like to estimate the percentage out of the total contribution that I have put in the development of the software. Is there some tool doing this? Such a tool can be useful for appraisals or negotiations, for example. After all, we work for money (yes, not only money, put the point remains). I think there is enough hand-waving for the most important things. The estimation is very subjective (at least to me now) but I do not know of any tool that provides even a subjective estimate. I know of Sloccount that spells out the total effort using the lines of code but not on per-developer basis. My idea of an ideal tool for this purpose would: measure the complexity of the code (more complex is more effort, but more effort is not necessarily more contribution) measure the decomposibility/flexibility of the software (more decomposable is better) how much library code is used -- using library code speeds up the development process, increases the associated risk and requires the developer to know from before or learn about the library. be intelligent enough to differentiate between "who wrote the code", "who copied the code" and "who indented the code". It is difficult to differentiate between the complexity in the implementation and the intrinsic complexity of the problem. Perhaps a comparison can be made with an equivalent open source counterpart if there is, or for each submodule separately. If there is no such tool, is there no merit in having such a tool? Or do you believe in "I do work, I do not measure"? It takes time after all. Perhaps the project manager should do this estimation continuously, say, weekly. Are there any standards? Yes, standardization is difficult because every project has a different goal, but difficult does not mean it is not useful.

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• Reduce number of config files to as few as possible

  - by Scott

  For most of my applications I use iBatis.Net for database access/modeling and log4Net for logging. In doing this, I need a number of *.config files for each project. For example, for a simple application I need to have the following *.config files: app.config ([AssemblyName].[Extention].config) [AssemblyName].SqlMap.config [AssemblyName].log4Net.config [AssemblyName].SqlMapProperties.config providers.config When these applications go from DEV to TEST to PRODUCTION environments, the settings contained in these files change depending on the environment. When the number of files get compounded by having 5-10 (or more) supporting executables per project, the work load on the infrastructure team (the ones doing the roll-outs to the different environments) gets rather high. We also have a high risk of one of the config files being missed, or a mistype in the config file. What is the best way to avoid these risks? Should I combine all of the config files into one file? (is that possible with iBatis?) I know that with VisualStudio 2010 they introduce transforms for these config files that allow the developer to setup all the settings for the different environments and then dynamically (depending on the build kicked off) the config files get updated to the correct versions. (VS 2010 - transforms) Thank you for any help that you can provide.

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• Sybase SQLAnywhere jConnect routines?

  - by jr

  I have a database which is part of a closed system and the end-user of the system would like me to write some reports using the data contains in a Sybase SQL Anywhere Database. The system doesn't provide the reports that they are looking for, but access to the data is available by connecting to this ASA database. The vendor of the software would likely prefer I not update the database and I am basically read-only as I am just doing some reporting. All is good, seal is not broken, warranty still intact, etc,etc.. My main problem is that I am using jConnect in order to read from the database, and jConnect requires some "jConnect Routines" to be installed into the database. I've found that I can make this happen by just doing an "Alter Database Upgrade JConnect On", but I just don't fully understand what this does and if there is any risks associated with it. So, my question is does anyone know exactly what jConnect routines are and how are they used? Is there any risk adding these to a database? Should I be worried about this?

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• Unit testing JSON output module, best practices

  - by Banang

  I am currently working on a module that takes one of our business objects and returns a json representation of that object to the caller. Due to limitations in our environment I am unable to use any existing json writer, so I have written my own, which is then used by the business object writer to serialize my objects. The json writer is tested in a way similar to this @Test public void writeEmptyArrayTest() { String expected = "[ ]"; writer.array().endArray(); assertEquals(expected, writer.toString()); } which is only manageable because of the small output each instruction produces, even though I keep feeling there must be a better way. The problem I am now facing is writing tests for the object writer module, where the output is much larger and much less manageable. The risk of spelling mistakes in the expected strings mucking up my tests seem too great, and writing code in this fashion seems both silly and unmanageable in a long term perspective. I keep feeling like I want to write tests to ensure that my tests are behaving correctly, and this feeling worries me. Therefore, is there a better way of doing this? Surely there must be? Does anyone know of any good literature in regard to this specific case (doesn't have to be json, but you know what I mean)? Grateful for all help.

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• Conditional required field validation in an ASP.net ListView

  - by Jim Dagg

  I'm having a heck of a time trying to figure out how to implement validation in a ListView. The goal is to require the user to enter text in the comments TextBox, but only if the CheckBox is checked. Downside is that these controls are in the EditTemplate of a ListView. Below is a snippet of the relevant code portion of the EditTemplate: <tr style="background-color: #00CCCC; color: #000000"> <td> Assume Risk? <asp:CheckBox ID="chkWaive" runat="server" Checked='<%# Bind("Waive") %>' /> </td> <td colspan="5"> <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="Comments required" ControlToValidate="txtComments" /> <asp:TextBox Width="95%" ID="txtComments" runat="server" Text='<%# Eval("Comment") %>'></asp:TextBox> </td> <td> <asp:Button ID="btnSave" runat="server" Text="Save" CommandName="Update" Width="100px" /> </td> </tr> Is there a way to do conditional validation using this method? If not, is there a way I could validate manually in the ItemUpdating event of the Listview, or somewhere else, and on a failure, alert the user of the error via a label or popup alert?

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• Find the flaws in the concept...

  - by Trindaz

  A web based web browser. Sounds silly right? Here's a use case. All comments about what could go wrong, and if anyone has tried and failed at this, very much wanted User goes to www.theBrowser.com and logs in with credentials specific to theBrowser.com. User tells theBrowser what their username and password for various sites are User goes to theBrowser.com/?uri=somesite.com theBrowser sends off the http request with User's log in details, then sends the http response back to User. This lets theBrowser do weird and wonderful functions like change colours / style sheets / etc. to every site that gets passed through it. From a technical stand point, storing username and password and passing them along is not a challenge for one user, but if there were a few, I'd have to use some kind of server based browser software to store a session per user logged in at theBrowser.com. How could I do that? Will I have to start from scratch? Obviously privacy and security are issues. Would theBrowser.com be too great a risk, even if users are fully warned? Cheers, Dave

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• How does one properly redefine self while avoiding the "Multiple methods named ..." warning?

  - by Elise van Looij

  In Apple's The Objective-C Programming Language: Defining a Class the section named "Redifining self" recommends that that class methods allocate and return instances use 'self' only to allocate an instance and then refer only to that instance. Thus, I have a number of subclasses, that have class methods along the lines of: + (id)scrollViewWithFrame: (NSRect)rectFrame { id newInstance = [[[self alloc] initWithFrame:rectFrame] autorelease]; [newInstance setHasHorizontalScroller: YES]; [newInstance setHasVerticalScroller: YES]; [newInstance setBorderType: NSNoBorder]; [newInstance setAutoresizingMask: (NSViewWidthSizable | NSViewHeightSizable)]; return newInstance; } The above is, of course, a subclass of NSScrollView. Unfortunately, Xcode 3.x all these NSView subclasses now raise warnings: "Warning: Multiple methods named '-setAutoresizingMask' found". I believe it has something to do with GCC 4.2, the settings of which I have not changed. The warning is correct, of course, since NSView and its various subclasses all implement setAutoresizingMask, but it is also unnecessary. Since they're only warnings, I ignore them but there is a risk that in between the thirty or so unnecessary ones, a really useful warning lurks which I simply don't see. So, what to do? I do want to adhere to good coding practices and I want to build warning-free apps -- how can I do both?

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• Idiomatic Scala way to deal with base vs derived class field names?

  - by Gregor Scheidt

  Consider the following base and derived classes in Scala: abstract class Base( val x : String ) final class Derived( x : String ) extends Base( "Base's " + x ) { override def toString = x } Here, the identifier 'x' of the Derived class parameter overrides the field of the Base class, so invoking toString like this: println( new Derived( "string" ).toString ) returns the Derived value and gives the result "string". So a reference to the 'x' parameter prompts the compiler to automatically generate a field on Derived, which is served up in the call to toString. This is very convenient usually, but leads to a replication of the field (I'm now storing the field on both Base and Derived), which may be undesirable. To avoid this replication, I can rename the Derived class parameter from 'x' to something else, like '_x': abstract class Base( val x : String ) final class Derived( _x : String ) extends Base( "Base's " + _x ) { override def toString = x } Now a call to toString returns "Base's string", which is what I want. Unfortunately, the code now looks somewhat ugly, and using named parameters to initialize the class also becomes less elegant: new Derived( _x = "string" ) There is also a risk of forgetting to give the derived classes' initialization parameters different names and inadvertently referring to the wrong field (undesirable since the Base class might actually hold a different value). Is there a better way? Edit: To clarify, I really only want the Base values; the Derived ones just seem necessary for initializing the Base ones. The example only references them to illustrate the ensuing issues. It might be nice to have a way to suppress automatic field generation if the derived class would otherwise end up hiding a base class field.

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• App session cookie not being created in Rails, sporadically

  - by James

  Hi everyone, This is an issue sporadically for very few users, however we haven't been able to replicate it. However I have now got a Chrome instance (Mac) which is reproducing the error (for some unknown reason), and I hope to not restart it until I have this nailed! Rails application, using memcached for session store. While the bug manifests in the _app_session_id cookie not being created, our javascript-generated cookie test and app-generated language cookies are being created successfully. This means that InvalidAuthenticityToken errors are thrown for every form that is submitted by those afflicted - people can't log into the app. The error occurs across all browsers - had reports for IE7 and Firefox (which most users use). Switching to another browser often fixes the issue (though not always), and standard cache-cookie-clear tactics do not. So now that I have got Chrome open which is having the same issue - in development, staging and live environments (meaning http and https). All other browsers are fine. I've restarted the servers and restarted memcached. I don't really want to restart Chrome - in the risk that the issue does go away with that (having said that, it hasn't worked for users). I've been tcpdumping the requests - and although I'll keep digging, I'd love it if anyone had any suggestions, places to start looking, anything. This is really painful ;) Thanks!

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• Wanted: How to reliably, consistently select an MKMapView annotation

  - by jdandrea

  After calling MKMapView's setCenterCoordinate:animated: method (without animation), I'd like to call selectAnnotation:animated: (with animation) so that the annotation pops out from the newly-centered pushpin. For now, I simply watch for mapViewDidFinishLoadingMap: and then select the annotation. However, this is problematic. For instance, this method isn't called when there's no need to load additional map data. In those cases, my annotation isn't selected. :( Very well. I could call this immediately after setting the center coordinate instead. Ahh, but in that case it's possible that there is map data to load (but it hasn't finished loading yet). I'd risk calling it too soon, with the animation becoming spotty at best. Thus, if I understand correctly, it's not a matter of knowing if my coordinate is visible, since it's possible to stray almost a screenful of distance and have to load new map data. Rather, it's a matter of knowing if new map data needs to be loaded, and then acting accordingly. Any ideas on how to accomplish this, or how to otherwise (reliably) select an annotation after re-centering the map view on the coordinate where that annotation lives? Clues appreciated - thanks!

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• Git checkout doesn't change anything, and it's getting very frustrating

  - by Josh

  I really like git. At least, I like the idea of git. Being able to checkout my master project as a separate branch where I can change whatever I want without risk of screwing everything else up is awesome. But it's not working. Every time I checkout a branch to another branch, make changes to the one branch, and then checkout the original branch, I still have all the files and changes that happened in the other branch. This is getting extremely frustrating. I've read that this can happen when you have files open in the IDE while doing this, but I've been pretty careful about that and both closed the files in the IDE, closed the IDE, and shut down my rails server before switching branches, and this still happens. Also, running 'git clean -f' either deletes everything that happened after some arbitrary commit (and randomly, at that), or, as in the latest case, didn't change anything back to its original state. I thought I was using git correctly, but at this point, I'm at my wit's end here. I'm trying to work with a bunch of experimental code using a stable version of my project, but I keep having to manually track down and fix all the changes I made. Any ideas or suggestions? git checkout -b photo_tagging git branch # to make sure it's right # make a bunch of changes, creations, etc git status # see what's changed since before git add . # approve of the changes, I guess, since if I do git commit after this, it says no changes git commit -m 'these are changes I made' git checkout master git branch #=> *master # look at files, tags_controller is still there, added in photo_tagging # and code added in photo_tagging branch are still there in *master This seems to happen whether I do a commit or not on the branch.

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• client-server syncing methodology [theoretical]

  - by Kenneth Ballenegger

  I'm in the progress of building an web-app that syncs with an iOS client. I'm currently tackling trying to figure out how to go about about syncing. I've come up with following two directions: I've got a fairly simple server web-app with a list of items. They are ordered by date modified and as such syncing the order does not matter. One direction I'm considering is to let the client deal with syncing. I've already got an API that lets the client get the data, as well as do certain actions on it, such as update, add or remove single items. I was considering: 1) on each sync asking the server for all items modified since the last successful sync and updating the local records based on what's returned by the server, and 2) building a persistent queue of create / remove / update requests on the client, and keeping them until confirmation by the server. The risk with this approach is that I'm basically asking each side to send changes to the other side, hoping it works smoothly, but risking a diversion at some point. This would probably be more bandwidth-efficient, though. The other direction I was considering was a more traditional model. I would have a "sync" process in which the client would send its whole list to the server (or a subset since last modified sync), the server would update the data on the server (by fixing conflicts by keeping the last modified item, and keeping deleted items with a deleted = 1 field), and the server would return an updated list of items (since last successful sync) which the client would then replace its data with. Thoughts?

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• Integrating Magento with SAP ECC 6.0 Backend

  - by ikarous

  I'm a freshly graduated (read: inexperienced) developer who's been tasked with determining the feasibility of integrating Magento with an SAP-based backend. No developer at our company has any experience working with either SAP or Magento, so I was hoping that the Stack Overflow community may be able to point me in the right direction with my research. We're a small company (four full-time developers) and the timeline on this project would be tight, so I'm trying to gather as much information as possible. The client has a tiered pricing structure, tax calculation logic, promotional deals, and automatic freight determination all implemented in an SAP ECC 6.0 system. They would like to migrate all their online stores over to Magento while continuing to utilize all existing functionality in SAP. The idea is to accomplish this by overriding certain modules in Magento to place remote calls to SAP BAPIs. I've investigated SAPRFC, which looks promising but relatively stale in terms of update frequency. Do any developers have experience using SAPRFC with SAP ECC 6.0 (with or without Magento integration)? If so, what were your experiences, and what were the biggest risk factors involved? Any comments, suggestions, or links to resources would be greatly appreciated.

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• Configure Windows firewall to prevent an application from listening on a specific port [closed]

  - by U-D13

  The issue: there are many applications struggling to listen on port 80 (Skype, Teamviewer et al.), and to many of them that even is not essential (in the sense that you can have a httpd running and blocking the http port, and the other application won't even squeak about being unable to open the port). What makes things worse, some of the apps are... Well, I suppose, that it's okay that the mentally impaired are being integrated in the society by giving them a job to do, but... Programming requires some intellectual effort, in my humble opinion... What I mean is that there is no way to configure the app not to use specific ports (that's what you get for using proprietary software) - you can either add it to windows firewall exceptions (and succumb to undesired port opening behavior) or not (and risk losing most - if not all - of the functionality). Technically, it is not impossible for the firewall to deny an application opening an incoming port even if the application is in the exception list. And if this functionality is built into the Windows firewall somewhere, there should be a way to activate it. So, what I want to know is: whether there exists such an option, and if it does how to activate it.

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• What harm can javascript do?

  - by The King

  I just happen to read the joel's blog here... So for example if you have a web page that says “What is your name?” with an edit box and then submitting that page takes you to another page that says, Hello, Elmer! (assuming the user’s name is Elmer), well, that’s a security vulnerability, because the user could type in all kinds of weird HTML and JavaScript instead of “Elmer” and their weird JavaScript could do narsty things, and now those narsty things appear to come from you, so for example they can read cookies that you put there and forward them on to Dr. Evil’s evil site. Since javascript runs on client end. All it can access or do is only on the client end. It can read informations stored in hidden fields and change them. It can read, write or manipulate cookies... But I feel, these informations are anyway available to him. (if he is smart enough to pass javascript in a textbox. So we are not empowering him with new information or providing him undue access to our server... Just curious to know whether I miss something. Can you list the things that a malicious user can do with this security hole. Edit : Thanks to all for enlightening . As kizzx2 pointed out in one of the comments... I was overlooking the fact that a JavaScript written by User A may get executed in the browser of User B under numerous circumstances, in which case it becomes a great risk.

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• chrome extension login security with iframe

  - by Weaver

  I should note, I'm not a chrome extension expert. However, I'm looking for some advice or high level solution to a security concern I have with my chrome extension. I've searched quite a bit but can't seem to find a concrete answer. The situation I have a chrome extension that needs to have the user login to our backend server. However, it was decided for design reasons that the default chrome popup balloon was undesirable. Thus I've used a modal dialog and jquery to make a styled popup that is injected with content scripts. Hence, the popup is injected into the DOM o the page you are visiting. The Problem Everything works, however now that I need to implement login functionality I've noticed a vulnerability: If the site we've injected our popup into knows the password fields ID they could run a script to continuously monitor the password and username field and store that data. Call me paranoid, but I see it as a risk. In fact,I wrote a mockup attack site that can correctly pull the user and password when entered into the given fields. My devised solution I took a look at some other chrome extensions, like Buffer, and noticed what they do is load their popup from their website and, instead, embed an iFrame which contains the popup in it. The popup would interact with the server inside the iframe. My understanding is iframes are subject to same-origin scripting policies as other websites, but I may be mistaken. As such, would doing the same thing be secure? TLDR To simplify, if I embedded an https login form from our server into a given DOM, via a chrome extension, are there security concerns to password sniffing? If this is not the best way to deal with chrome extension logins, do you have suggestions with what is? Perhaps there is a way to declare text fields that javascript can simply not interact with? Not too sure! Thank you so much for your time! I will happily clarify anything required.

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• Merging datasets based on 2 variables in SAS.

  - by John

  Hye Guys, my question is the following, i'm working with different databases, all contain information about 1000+ companies, a company is defined by its ticker code (the short version of the name( Ford as F) usually seen on stock quotation boards). Aside from the ticker code to merge on I also have to merge on the time, I used month as a count variable throughout my time series. The final purpose is to have a regression in the kind of Y(jt) = c + X(jt) +X1(jt) etc with j = company (ticker) and t = time (month). So imagine I have 2 databases, one which is the base database with variables such as Tickers, months, beta's of a company (risk measure) etc and a second database which has an extra variable (let's say market capitalisation). What I want to do then is to merge these 2 databases based on the ticker and the month. Example: Base database: Ticker __ Month __ Betas AA __ 4 __ 1.2 BB __ 8 __ 1.18 Second database: Ticker __ Month __ MCAP AA __ 4 __ 8542 BB __ 6 __ 1245 Then after merge I would like to have something like this: Ticker __ Month _ Betas ___ MCAP AA __ 4 _ 1.2 ___ 8542 So all observations that do not match BOTH date and ticker have to be dropped, I'm sure this is possible, just can't find the right type of code. Thanks! PS: I'm guessing the underscars have something to do with font layout but both the bold as italic is supposed to be normal :)

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• Cassandra hot keyspace structure change

  - by Pierre

  Hello. I'm currently running a 12-node Cassandra cluster storing 4TB of data, with a replication factor set to 3. For the needs of an application update, we need to change the configuration of our keyspace, and we'd like to avoid any downtime if possible. I read on a mailing list that the best way to do it is to: Kill cassandra process on one server of the cluster Start it again, wait for the commit log to be written on the disk, and kill it again Make the modifications in the storage.xml file Rename or delete the files in the data directories according to the changes we made Start cassandra Goto 1 with next server on the list My questions would be: Did I understand the process well? Is there any risk of data corruption? During the process, there will be servers with different versions of the storage.xml file in the same cluser, same keyspace. Is it a problem? Same question as above if we not only add, rename and remove ColumnFamilies, but if we change the CompareWith parameter / transform an existing column family into a super one. Or do we need to change the name? Thank you for your answers. It's the first time I'll do this, and I'm a little bit scared.

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• Beyond core java

  - by Paul

  Coming to the end of the first year of my CS degree, we've done some Java but just the core stuff; manipulating strings and arrays, inheritance, implementing logic etc. I visit this website daily and I see so much stuff that is beyond me; using frameworks; managing databases etc. It makes me feel like I've just learned the syntax of Java, and there is so much more to do with it. My question is though, how do I get there? I don't think I'm advanced enough to join an open source project, which seems to be suggested often (though I'd love to) and I've looked at other similar questions on here (like this one) but even then I don't think that'd work for me.. firstly, could somebody try give me some commonly used frameworks etc and how and what they are used for? Where would be a good place to start? How did you get started in using the things you do? Or perhaps you think I'm going down the wrong route. Should I learn another language, and just wait until the moment occurs where it's clear what I should be doing? I'm only in the first year of my degree, so far we've lightly covered Haskell and Java, and I've done a little HTML and CSS in my free time. I know that next year we cover python, so perhaps I should just wait till then and see if I prefer that? I feel like I also risk learning something in depth and then never using it... I suppose I'm also asking for personal experiences; was there a point where you felt you'd exceeded the basic grasp of a language (does not necessarily have to be Java related) and reach a more "advanced" level? I guess I'll put subjective tag on this, but really I just want to know how to get beyond the basic understanding of a language.

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