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  • Stop trying to be perfect

    - by Kyle Burns
    Yes, Bob is my uncle too.  I also think the points in the Manifesto for Software Craftsmanship (manifesto.softwarecraftsmanship.org) are all great.  What amazes me is that tend to confuse the term “well crafted” with “perfect”.  I'm about to say something that will make Quality Assurance managers and many development types as well until you think about it as a craftsman – “Stop trying to be perfect”. Now let me explain what I mean.  Building software, as with building almost anything, often involves a series of trade-offs where either one undesired characteristic is accepted as necessary to achieve another desired one (or maybe stave off one that is even less desirable) or a desirable characteristic is sacrificed for the same reasons.  This implies that perfection itself is unattainable.  What is attainable is “sufficient” and I think that this really goes to the heart both of what people are trying to do with Agile and with the craftsmanship movement.  Simply put, sufficient software drives the greatest business value.   I've been in many meetings where “how can we keep anything from ever going wrong” has become the thing that holds us in analysis paralysis.  I've also been the guy trying way too hard to perfect some function to make sure that every edge case is accounted for.  Somewhere in there, something a drill instructor said while I was in boot camp occurred to me.  In response to being asked a question by another recruit having to do with some edge case (I can barely remember the context), he said “What if grasshoppers had machine guns?  Would the birds still **** with them?”  It sounds funny, but there's a lot of wisdom in those words.   “Sufficient” is different for every situation and it’s important to understand what sufficient means in the context of the work you’re doing.  If I’m writing a timesheet application (and please shoot me if I am), I’m going to have a much higher tolerance for imperfection than if you’re writing software to control life support systems on spacecraft.  I’m also likely to have less need for high volume performance than if you’re writing software to control stock trading transactions.   I’d encourage anyone who has read this far to instead of trying to be perfect, try to create software that is sufficient in every way.  If you’re working to make a component that is sufficient “better”, ask yourself if there is any component left that is not yet sufficient.  If the answer is “yes” you’re working on the wrong thing and need to adjust.  If the answer is “no”, why aren’t you shipping and delivering business value?

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  • Why is my laptop so sluggish? Or Damn You Facebook and Twitter! Or All Hail Chrome!

    - by John Conwell
    In the past three weeks, I've noticed that my laptop (dual core 2.1GHz, 2Gb RAM) has become amazingly sluggish.  I only uses for communications and data lookup workflows, so the slowness was tolerable.  But today I finally got fed up with the suckyness and decided to get to the root of the problem (I do have strong performance roots after all). It actually didn't take all that long to figure it out.  About a year ago I converted to Google Chrome (away from FireFox).  One of the great tools Chrome has is a "Task Manager" tool, that gives you Windows Task Manager like details for all the tabs open in the browser (Shift + Esc).  Since every tab runs in its own process, its easy from Task Manager (both Windows or Chrome) to identify and kill a single performance offending tab.  This is unlike IE, where you only get aggregate data about all tabs open.  Anyway, I digress.  Today my laptop sucked.  Windows Task Manager told me that I had two memory hogging Chrome tabs, but couldn't tell me which web page those tabs are showing.  Enter Chrome Task Manager which tells you the page title, along with CPU, memory and network utilization of each tab.  Enter my amazement.  Turns out Facebook was using just shy of half a Gb of RAM.  Half a Gigabyte!  That's 512 Megabytes!524,288 Kilobytes! 536,870,912 Bytes!  Or 4,294,967,296 Bits!  In other words, that's a frackin boat load of memory.  Now consider that Facebook is running on pretty much 96.3% (statistics based on absolutely nothing) of every house hold desktop, laptop, netbook, and mobile device in America, that is pretty horrific! And I wasn't playing any Facebook games like FarmWars or MafiaVille.  I just had my normal, default home page up showing me who just had breakfast, or just got finished with their morning run. I'm sorry...let me say that again...HALF A GIG OF RAM!  That is just unforgivable. I can just see my mom calling me up:  Mom: "John...I think I need a new computer.  Mine is really slow these days" John: "What do you have running?" Mom: "Oh, just Facebook" John: "Ok, close Facebook and tell me how fast your computer feels" Mom: "Well...I don't know how fast it is.  All I do is use Facebook" John: "Ok Mom, I'll send you a new computer by Tuesday" Oh yea...and the other offending web page?  It was Twitter, using a quarter of a Gigabyte. God I love social networks!

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  • Have you used the ExecutionValue and ExecValueVariable properties?

    The ExecutionValue execution value property and it’s friend ExecValueVariable are a much undervalued feature of SSIS, and many people I talk to are not even aware of their existence, so I thought I’d try and raise their profile a bit. The ExecutionValue property is defined on the base object Task, so all tasks have it available, but it is up to the task developer to do something useful with it. The basic idea behind it is that it allows the task to return something useful and interesting about what it has performed, in addition to the standard success or failure result. The best example perhaps is the Execute SQL Task which uses the ExecutionValue property to return the number of rows affected by the SQL statement(s). This is a very useful feature, something people often want to capture into a variable, and start using the result set options to do. Unfortunately we cannot read the value of a task property at runtime from within a SSIS package, so the ExecutionValue property on its own is a bit of a let down, but enter the ExecValueVariable and we have the perfect marriage. The ExecValueVariable is another property exposed through the task (TaskHost), which lets us select a SSIS package variable. What happens now is that when the task sets the ExecutionValue, the interesting value is copied into the variable we set on the ExecValueVariable property, and a variable is something we can access and do something with. So put simply if the ExecutionValue property value is of interest, make sure you create yourself a package variable and set the name as the ExecValueVariable. Have  look at the 3 step guide below: 1 Configure your task as normal, for example the Execute SQL Task, which here calls a stored procedure to do some updates. 2 Create variable of a suitable type to match the ExecutionValue, an integer is used to match the result we want to capture, the number of rows. 3 Set the ExecValueVariable for the task, just select the variable we created in step 2. You need to do this in Properties grid for the task (Short-cut key, select the task and press F4) Now when we execute the sample task above, our variable UpdateQueueRowCount will get the number of rows we updated in our Execute SQL Task. I’ve tried to collate a list of tasks that return something useful via the ExecutionValue and ExecValueVariable mechanism, but the documentation isn’t always great. Task ExecutionValue Description Execute SQL Task Returns the number of rows affected by the SQL statement or statements. File System Task Returns the number of successful operations performed by the task. File Watcher Task Returns the full path of the file found Transfer Error Messages Task Returns the number of error messages that have been transferred Transfer Jobs Task Returns the number of jobs that are transferred Transfer Logins Task Returns the number of logins transferred Transfer Master Stored Procedures Task Returns the number of stored procedures transferred Transfer SQL Server Objects Task Returns the number of objects transferred WMI Data Reader Task Returns an object that contains the results of the task. Not exactly clear, but I assume it depends on the WMI query used.

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  • GWT: Generate more complete crawl error report

    - by Mike
    I'm a developer in charge of managing Webmasters and related issues (including correcting crawl errors) for dozens (hundreds, maybe?) of active sites and as part of my duties I create a report of every discrepancy, including all pages generating a 404 and all pages that link to those pages. Currently within Webmaster Tools I'm able to download a csv file of all pages with a 404 response, but I'm then having to manually click on every single one of those links and copy the "linked from" field to paste into my spreadsheet. This is extremely tedious and seems unnecessary; I would expect the ability to download all that data at once. I'm ultimately looking for the end result of one csv file that has every url with a 404, but also has every url that links to each one of them. Am I overlooking this functionality somewhere or does anyone have a good solution? Edit 1 (2/11/2013): Example of what the csv output looks like now: URL,Response Code,News Error,Detected,Category http://www.abcdef.com/123.php,404,,11/12/13,Not found http://www.abcdef.com/456.php,404,,11/12/13,Not found Which is great, but let's say 123.php has 5 pages that link to it. Now I have to duplicate that row in my spreadsheet 4 more times, then go into Webmasters, get all the url's that link to the page, and add that data to my spreadsheet. The output I would prefer: URL,Response Code,Linked From,News Error,Detected,Category http://www.abcdef.com/123.php,404,http://www.ghijkl.com/naughtypage1.php,,11/12/13,Not found http://www.abcdef.com/123.php,404,http://www.ghijkl.com/naughtypage2.php,,11/12/13,Not found http://www.abcdef.com/123.php,404,http://www.ghijkl.com/naughtypage3.php,,11/12/13,Not found http://www.abcdef.com/456.php,404,http://www.ghijkl.com/naughtypage1.php,,11/12/13,Not found http://www.abcdef.com/456.php,404,http://www.ghijkl.com/naughtypage2.php,,11/12/13,Not found http://www.abcdef.com/456.php,404,http://www.ghijkl.com/naughtypage3.php,,11/12/13,Not found Note the (hypothetical) addition of a "Linked From" column, as well as the fact there are only 2 unique URL's now (like before) but all of the "Linked To" pages are shown in one report. Edit 2 (2/12/2013): To clarify, my question is less about detecting and correcting 404's, but more about generating a report of what Google has listed as errors. Oftentimes, these errors aren't even valid anymore but I still need documentation to show that Google detected a problem and that problem is now fixed. Many of the "linked from" url's I find are actually outdated, cached resources. For example, I'll frequently see that the linked-from url is the sitemap, which is actually an old sitemap cached by Google that points to an old page. Neither the sitemap or old page exist, but they still appear in my crawl error reports because they are cached resources.

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  • 3D terrain map with Hexagon Grids (XNA)

    - by Rob
    I'm working on a hobby project (I'm a web/backend developer by day) and I want to create a 3D Tile (terrain) engine. I'm using XNA, but I can use MonoGame, OpenGL, or straight DirectX, so the answer does not have to be XNA specific. I'm more looking for some high level advice on how to approach this problem. I know about creating height maps and such, there are thousands of references out there on the net for that, this is a bit more specific. I'm more concerned with is the approach to get a 3D hexagon tile grid out of my terrain (since the terrain, and all 3d objects, are basically triangles). The first approach I thought about is to basically draw the triangles on the screen in the following order (blue numbers) to give me the triangles for terrain (black triangles) and then make hexes out of the triangles (red hex). http://screencast.com/t/ebrH2g5V This approach seems complicated to me since i'm basically having to draw 4 different types of triangles. The next approach I thought of was to use the existing triangles like I did for a square grid and get my hexes from 6 triangles as follows http://screencast.com/t/w9b7qKzVJtb8 This seems like the easier approach to me since there are only 2 types of triangles (i would have to play with the heights and widths to get a "perfect" hexagon, but the idea is the same. So I'm looking for: 1) Any suggestions on which approach I should take, and why. 2) How would I translate mouse position to a hexagon grid position (especially when moving the camera around), for example in the second image if the mouse pointer were the green circle, how would I determine to highlight that hexagon and then translating that into grid coordinates (assuming it is 0,0)? 3) Any references, articles, books, etc - to get me going in the right direction. Note: I've done hex grid's and mouse-grid coordinate conversion before in 2d. looking for some pointers on how to do the same in 3d. The result I would like to achieve is something similar to the following: http :// www. youtube .com / watch?v=Ri92YkyC3fw (sorry about the youtube link, but it will only let me post 2 links in this post... same rep problem i mention below...) Thanks for any help! P.S. Sorry for not posting the images inline, I apparently don't have enough rep on this stack exchange site.

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  • Class instance clustering in object reference graph for multi-entries serialization

    - by Juh_
    My question is on the best way to cluster a graph of class instances (i.e. objects, the graph nodes) linked by object references (the -directed- edges of the graph) around specifically marked objects. To explain better my question, let me explain my motivation: I currently use a moderately complex system to serialize the data used in my projects: "marked" objects have a specific attributes which stores a "saving entry": the path to an associated file on disc (but it could be done for any storage type providing the suitable interface) Those object can then be serialized automatically (eg: obj.save()) The serialization of a marked object 'a' contains implicitly all objects 'b' for which 'a' has a reference to, directly s.t: a.b = b, or indirectly s.t.: a.c.b = b for some object 'c' This is very simple and basically define specific storage entries to specific objects. I have then "container" type objects that: can be serialized similarly (in fact their are or can-be "marked") they don't serialize in their storage entries the "marked" objects (with direct reference): if a and a.b are both marked, a.save() calls b.save() and stores a.b = storage_entry(b) So, if I serialize 'a', it will serialize automatically all objects that can be reached from 'a' through the object reference graph, possibly in multiples entries. That is what I want, and is usually provides the functionalities I need. However, it is very ad-hoc and there are some structural limitations to this approach: the multi-entry saving can only works through direct connections in "container" objects, and there are situations with undefined behavior such as if two "marked" objects 'a'and 'b' both have a reference to an unmarked object 'c'. In this case my system will stores 'c' in both 'a' and 'b' making an implicit copy which not only double the storage size, but also change the object reference graph after re-loading. I am thinking of generalizing the process. Apart for the practical questions on implementation (I am coding in python, and use Pickle to serialize my objects), there is a general question on the way to attach (cluster) unmarked objects to marked ones. So, my questions are: What are the important issues that should be considered? Basically why not just use any graph parsing algorithm with the "attach to last marked node" behavior. Is there any work done on this problem, practical or theoretical, that I should be aware of? Note: I added the tag graph-database because I think the answer might come from that fields, even if the question is not.

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  • How do I get long command lines to wrap to the next line?

    - by BrianH
    Edit It was my .bashrc file. I've copied the same profile from machine to machine, and I used special characters in my $PS1 that are somehow throwing it off. I'm now sticking with the standard bash variables for my $PS1. Thanks to @ændrük for the tip on the .bashrc! ...End Edit... Something I have noticed in Ubuntu for a long time that has been frustrating to me is when I am typing a command at the command line that gets longer (wider) than the terminal width, instead of wrapping to a new line, it goes back to column 1 on the same line and starts over-writing the beginning of my command line. (It doesn't actually overwrite the actual command, but visually, it is overwriting the text that was displayed). It's hard to explain without seeing it, but let's say my terminal was 20 characters wide (Mine is more like 120 characters - but for the sake of an example), and I want to echo the English alphabet. What I type is this: echo abcdefghijklmnopqrstuvwxyz But what my terminal looks like before I hit the key is: pqrstuvwxyzghijklmno When I hit enter, it echos abcdefghijklmnopqrstuvwxyz so I know the command was received properly. It just wrapped my typing after the "o" and started over on the same line. What I would expect to happen, if I typed this command in on a terminal that was only 20 characters wide would be this: echo abcdefghijklmno pqrstuvwxyz Background: I am using bash as my shell, and I have this line in my ~/.bashrc: set -o vi to be able to navigate the command line with VI commands. I am currently using Ubuntu 10.10 server, and connecting to the server with Putty. In any other environment I have worked in, if I type a long command line, it will add a new line underneath the line I am working on when my command gets longer than the terminal width and when I keep typing I can see my command on 2 different lines. But for as long as I can remember using Ubuntu, my long commands only occupy 1 line. This also happens when I am going back to previous commands in the history (I hit Esc, then 'K' to go back to previous commands) - when I get to a previous command that was longer than the terminal width, the command line gets mangled and I cannot tell where I am at in the command. The only work-around I have found to see the entire long command is to hit "Esc-V", which opens up the current command in a VI editor. I don't think I have anything odd in my .bashrc file. I commented out the "set -o vi" line, and I still had the problem. I downloaded a fresh copy of Putty and didn't make any changes to the configuration - I just typed in my host name to connect, and I still have the problem, so I don't think it's anything with Putty (unless I need to make some config changes) Has anyone else had this problem, and can anyone think of how to fix it? Thanks in advance! Brian

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  • How can I convince IE to honor my explicit instructions to make a table column X pixels wide? [migrated]

    - by AnthonyWJones
    Please consider this small but complete chunk of HTML: <!DOCTYPE html > <html> <head> <title>Test</title> <style type="text/css"> span {overflow:hidden; white-space:nowrap; } td {overflow:hidden; text-overflow:ellipsis} </style> </head> <body> <table cellspacing="0" > <tbody> <tr> <td nowrap="nowrap" style="max-width:30px; width:30px; white-space:nowrap; "><span>column 1</span></td> <td nowrap="nowrap" style="max-width:30px; width:30px; white-space:nowrap; "><span>column 2</span></td> <td nowrap="nowrap" style="max-width:30px; width:30px; white-space:nowrap; "><span>column 3</span></td> </tr> </tbody> </table> </body> </html> If you render the above in Chrome you'll see the effect I'm looking for. However render it in IE8 or 9 the width and/or max-width is ignored. So my question is how do get IE to simply let me specify the width of a cell explicitly? BTW, I've tried various combinations of table-layout:fixed and using colgroup with cols and all sorts, nothing I've tried convinces IE to what I'm clearly asking it to explicitly do? If I had any hair before starting this I wouldn't have any left by now.

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  • I can't install Ubuntu 12.04.1 on iMac G5

    - by user89004
    So, I have this iMac G5 that doesn't have iSight, only a small light sensor I think undernieth, machine model 8.2. I tried burning a Ubuntu 12.04.1 PowerPC 64bit .iso to a cd but the computer just won't boot it, I don't know why. Next I tried with a USB but it wouldn't let me boot that either, I created the usb on my dad's win7 laptop as the process was way easier than on freakin Mac or Ubuntu (no command typing AT ALL on windows) I'm able to get into openfirmware and type boot usb and it does show some weird writing that scrolls so fast I can't see anything and then it just gives me this huge no sign like a stop sign and freezez. The sign is grey and the line in the middle is tilted towards the left. An other issue I'm having with hdiutil is that I can't convert the stupid .iso I just downloaded into a .img because the file keeps on dissapearing right when it's done converting it. I used the syntax from Ubuntu support how to create a bootable usb drive under Mac OS X. I even didn't include the 2 stupid ~ that are shown in the syntax that are completly worthless, God only know why they put them there, and I even tried running the whole thing as root with sudo su before the command. The funny thing is that if I convert something smaller it works. The command I was using is hdiutil convert -format UDRW -o /path/to/target.img /path/to/ubuntu.iso I even tried hdiutil convert /path/to/ubuntu.iso -format UDRW -o /path/to/target.img but the same thing happens, the dummy .img.dmg file dissapears when the conversion is done no matter where I set the output file to go. I have tried several different folders, the same thing happens with all of them. I also tried burning a Ubuntu mini iso on a cd, can't remember if it was 11.10 or 12.10 but even thoguh holding c when the iMac boots up does show me the cd and I can boot from it, I get this weird error upon hitting install, it says something like invalid memory access, release keys and error strings I can't read. I don't have any original DVDs from this iMac and can't run hardware diagnostics. WHatever option I try at the command prompt from the mini ubuntu cd I get the same result, error code and openfirmware backdrop that's frozen. I noticed that the pen drive I created on my dads Win7 laptop is formated with MS-DOS but I can still mount it no problem, so it shouldn't have a problem booting it, right? I used the advice on ubuntu.com to make it, from here. Also, my partition is HFS+ so I can't use it as a hard drive and boot from it. I don' have 2 partitions either, just one HDD, one partition. Please help!!!

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  • What if I can't make my unit test fail in "Red, Green, Refactor" of TDD?

    - by Joshua Harris
    So let's say that I have a test: @Test public void MoveY_MoveZero_DoesNotMove() { Point p = new Point(50.0, 50.0); p.MoveY(0.0); Assert.assertAreEqual(50.0, p.Y); } This test then causes me to create the class Point: public class Point { double X; double Y; public void MoveY(double yDisplace) { throw new NotYetImplementedException(); } } Ok. It fails. Good. Then I remove the exception and I get green. Great, but of course I need to test if it changes value. So I write a test that calls p.MoveY(10.0) and checks if p.Y is equal to 60.0. It fails, so then I change the function to look like so: public void MoveY(double yDisplace) { Y += yDisplace; } Great, now I have green again and I can move on. I've tested not moving and moving in the positive direction, so naturally I should test a negative value. The only problem with this test is that if I wrote the test correctly, then it doesn't fail at first. That means that I didn't fit the principle of "Red, Green, Refactor." Of course, This is a first-world problem of TDD, but getting a fail at first is helpful in that it shows that your test can fail. Otherwise this seemingly innocent test that is just passing for incorrect reasons could fail later because it was written wrong. That might not be a problem if it happened 5 minutes later, but what if it happens to the poor-sap that inheirited your code two years later. What he knows is that MoveY does not work with negative values because that is what the test is telling him. But, it really could work and just be a bug in the test. I don't think that would happen in this particular case because the code sample is so simple, but if it were a large complicated system that might not be the case. It seems crazy to say that I want to fail my tests, but that is an important step in TDD, for good reasons.

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  • What do you do when practical problems get in the way of practical goals?

    - by P.Brian.Mackey
    UPDATE Source control is good to use. Sometimes, real world issues make it impractical to use. For example: If the team is not used to using source control, training problems can arise If a team member directly modifies code on the server, various issues can arise. Merge problems, lack of history, etc Let's say there's a project that is way out of sync. The physical files on the server differ in unknown ways over ~100 files. Merging would take not only a great knowledge of the project, but is also well beyond the ability to complete in the given time. Other projects are falling out of sync. Developers continue to have a distrust of source control and therefore compound the issue by not using source control. Developers argue that using source control is wasteful because merging is error prone and difficult. This is a difficult point to argue, because when source control is being so badly mis-used and source control continually bypassed, it is error prone indeed. Therefore, the evidence "speaks for itself" in their view. Developers argue that directly modifying source control saves time. This is also difficult to argue. Because the merge required to synchronize the code to start with is time consuming, across ~10 projects. Permanent files are often stored in the same directory as the web project. So publishing (full publish) erases these files that are not in source control. This also drives distrust for source control. Because "publishing breaks the project". Fixing this (moving stored files out of the solution subfolders) takes a great deal of time and debugging as these locations are not set in web.config and often exist across multiple code points. So, the culture persists itself. Bad practice begets more bad practice. Bad solutions drive new hacks to "fix" much deeper, much more time consuming problems. Servers, hard drive space are extremly difficult to come by. Yet, user expectations are rising. What can be done in this situation?

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  • Synchronizing ODSEE and OUD

    - by Etienne Remillon
    When it comes to synchronizing between ODSEE and OUD, what should be the best options ? Couple  options are available - Use one of OUD internal capability called Replication Gateway - Use our synchronization tool called Directory Integration Platform part of Oracle Directory Services Plus - Manuel export and import Let's check pro and cons on each method. Replication Gateway is the natural, out of the box solution to perform the task. We created this as a feature of OUD because it works at our replication protocol level. The gateway perform the required adaptation between the ODSEE's replication protocol and OUD's one. The benefits of doing this is that it provide strong consistency between the to type of directories. This fully leverage conflict management implemented in the replication protocols to ensure that changes are applied in a coherent and ordered manner. It does not require specific modification on existing ODSEE production instances such as turning on "retro changelog". Changes are propagated at near speed of replication in both directions. Replication Gateway can also synchronize information that are stored internally in the directory server such as "xxxxx" account locking managed at ODSEE server level and not via the nsyyyy attribute. OUD replication gateway does no require any specific tools or installation specific procedure. It is manged like other OUD component with monitoring and configuration via the standard console. OUD Replication Gateway does not perform adaptation between ODSEE and OUD. Using Directory Integration Protocol as external component to OUD, brings flexibility in remapping and transformations between ODSEE and OUD. There is a price to pay in using DIP to perform the synchronization task. You will have to turn on the retro change log to get access to changes on the ODSEE side (this will impact disk and CPU usage and performances which could be a serious challenge for your existing ODSEE environment (if you have not provisioned additional hardware and instances). You will not benefits of conflict resolution management and this might have to be addressed at application level, which is not always possible to implement. Using export and import seams very simple, but this methodology cannot ensure an highly available deployment with up to date entries on booth sides. This solution can be used if full HA with up-to-date data is not needed (during synchronization time). It often used  if data-cleaning need to take place to avoid polluting a new environment with old un-necessary data.

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  • Programming Language, Turing Completeness and Turing Machine

    - by Amumu
    A programming language is said to be Turing Completeness if it can successfully simulate a universal TM. Let's take functional programming language for example. In functional programming, function has highest priority over anything. You can pass functions around like any primitives or objects. This is called first class function. In functional programming, your function does not produce side effect i.e. output strings onto screen, change the state of variables outside of its scope. Each function has a copy of its own objects if the objects are passed from the outside, and the copied objects are returned once the function finishes its job. Each function written purely in functional style is completely independent to anything outside of it. Thus, the complexity of the overall system is reduced. This is referred as referential transparency. In functional programming, each function can have its local variables kept its values even after the function exits. This is done by the garbage collector. The value can be reused the next time the function is called again. This is called memoization. A function usually should solve only one thing. It should model only one algorithm to answer a problem. Do you think that a function in a functional language with above properties simulate a Turing Machines? Functions (= algorithms = Turing Machines) are able to be passed around as input and returned as output. TM also accepts and simulate other TMs Memoization models the set of states of a Turing Machine. The memorized variables can be used to determine states of a TM (i.e. which lines to execute, what behavior should it take in a give state ...). Also, you can use memoization to simulate your internal tape storage. In language like C/C++, when a function exits, you lose all of its internal data (unless you store it elsewhere outside of its scope). The set of symbols are the set of all strings in a programming language, which is the higher level and human-readable version of machine code (opcode) Start state is the beginning of the function. However, with memoization, start state can be determined by memoization or if you want, switch/if-else statement in imperative programming language. But then, you can't Final accepting state when the function returns a value, or rejects if an exception happens. Thus, the function (= algorithm = TM) is decidable. Otherwise, it's undecidable. I'm not sure about this. What do you think? Is my thinking true on all of this? The reason I bring function in functional programming because I think it's closer to the idea of TM. What experience with other programming languages do you have which make you feel the idea of TM and the ideas of Computer Science in general? Can you specify how you think?

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  • Can't save data for a member in a data form

    - by RahulS
    Implied sharing is an old thing everyone knows the reasons and solutions of that, still little theory about that: With Essbase implied sharing, some members are shared even if you do not explicitly set them as shared. These members are implied shared members. When an implied share relationship is created, each implied member assumes the other member’s value. Essbase assumes (or implies) a shared member relationship in these situations: 1. A parent has only one child 2. A parent has only one child that consolidates to the parent In a Planning form that contains members with an implied sharing relationship, when a value is added for the parent, the child assumes the same value after the form is saved. Likewise, if a value is added for the child, the parent usually assumes the same value after a form is saved.For example, when a calculation script or load rule populates an implied share member, the other implied share member assumes the value of the member populated by the calculation script or load rule. The last value calculated or imported takes precedence. The result is the same whether you refer to the parent or the child as a variable in a calculation script. For more information have a look at: http://docs.oracle.com/cd/E17236_01/epm.1112/hp_admin_11122/ch14s11.html Now the issue which we are going to talk about is We loose data on save even when the parent is dynamic calc and has a single child. A dynamic calc parent to a single child:  If we design the form with following selection: In the data form we will find parent below the member and this is by design whenever you make a selection using commands to select all the member below parent, always children will appear before the parent: Lets try to enter data, Save it Now, try to change the way we selected members Here we go: Now the question again why this behavior: 1. Data from Planning data form passes to Essbase row by row, 2. Because in data form the child member appears before the parent, 3. First, data goes to Essbase for child (SingleStoreChild), 4. Then when Planning passes the data for parent there was #Missing or No data,  5. Over writes the data to #missing. PS: As we know that dynamic calc members are calculated on the fly they are not allocated with any memory in the Essbase, here the parent was dynamic calc and it was pointing to same memory as child in the background, when Planning was passing data to Essbase for second row it has updated the child with missing data.(Little confusing, let me know if you need more explanation) 6. As one of the solutions just change the order of appearance of parent and child. Cheers..!!! Rahul S. https://www.facebook.com/pages/HyperionPlanning/117320818374228

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  • Reporting on common code smells : A POC

    - by Dave Ballantyne
    Over the past few blog entries, I’ve been looking at parsing TSQL scripts in a variety of ways for a variety of tasks.  In my last entry ‘How to prevent ‘Select *’ : The elegant way’, I looked at parsing SQL to report upon uses of SELECT *.  The obvious question leading on from this is, “Great, what about other code smells ?”  Well, using the language service parser to do that was turning out to be a bit of a hard job,  sure I was getting tokens but no real context.  I wasn't even being told when an end of statement had been reached. One of the other parsing options available from Microsoft is exposed in the assembly ‘Microsoft.SqlServer.TransactSql.ScriptDom’,  this is ,I believe, installed with the client development tools with SQLServer.  It is much more feature rich than the original parser I had used and breaks a TSQL script into intuitive classes for analysis. So, what sort of smells can I now find using it ?  Well, for an opening gambit quite a nice little list. Use of NOLOCK Set of READ UNCOMMITTED Use of SELECT * Insert without column references Explicit datatype conversion on Sargs Cross server selects Non use of two-part naming convention Table and Query hint usage Changes in set options Use of single line comments Use of ordinal column positions in ORDER BY clause Now, lets not argue the point that “It depends” as smells on some of these, but as an academic exercise it is quite interesting.  The code is available from this link :https://www.dropbox.com/s/rfk32sou4fzl2cw/TSQLDomTest.zip  All the usual disclaimers apply to this code, I cannot be held responsible for anything ranging from mild annoyance through to universe destruction due to the use of this code or examples. The zip file contains a powershell script and my test cases.  The assembly used requires .Net 4 to run, which means that you will need powershell 3 ( though im running through PowerGUI and all works ok ) .  The code searches for all .sql files in the folder hierarchy for the workingpath,  you can override this if you want by simply changing the $Folder variable, and processes each in turn for the smells.  Feedback is not great at the moment, all it does is output to an xml file (Smells.xml) the offset position and a description of the smell found. Right now, I am interested in your feedback.  What do you think ?  Is this (or should it be) more than an academic exercise ?  Can tooling such as this be used as some form of code quality measure ?  Does it Work ? Do you have a case listed above which is not being reported ? Do you have a case that you would love to be reported ? Let me know , please mailto: [email protected]. Thanks

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  • Walmart's Mobile Self-Checkout

    - by David Dorf
    Reuters recently reported that Walmart was testing an iPhone-based self-checkout at a store near its headquarters.  Consumers scan items as they're placed in the physical basket, then the virtual basket is transferred to an existing self-checkout station where payment is tendered.  A very solid solution, but not exactly original. Before we go further, let's look at the possible cost savings for Walmart.  According to the article: Pushing more shoppers to scan their own items and make payments without the help of a cashier could save Wal-Mart millions of dollars, Chief Financial Officer Charles Holley said on March 7. The company spends about $12 million in cashier wages every second at its Walmart U.S. stores. Um, yeah. Using back-of-the-napkin math, I calculated Walmart's cashiers are making $157k per hour.  A more accurate statement would be saving $12M per year for each second saved on the average transaction time.  So if this self-checkout approach saves 2 seconds per transaction on average, Walmart would save $24M per year on labor.  Maybe.  Sometimes that savings will be used to do other tasks in the store, so it may not directly translate to less employees. When I saw this approach demonstrated in Sweden, there were a few differences, which may or may not be in Walmart's plans.  First, the consumers were identified based on their loyalty card.  In order to offset the inevitable shrink, retailers need to save on labor but also increase basket size, typically via in-aisle promotions.  As they scan items, retailers should target promos, and that's easier to do if you know some shopping history.  Last I checked, Walmart had no loyalty program. Second, at the self-checkout station consumers were randomly selected for an audit in which they must re-scan all the items just like you do at a typical self-checkout.  If you were found to be stealing, your ability to use the system can be revoked.  That's a tough one in the US, especially when the system goes wrong, either by mistake or by lying.  At least in my view, the Swedes are bit more trustworthy than the people of Walmart. So while I think the idea of mobile self-checkout has merit, perhaps its not right for Walmart.

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  • Who should control navigation in an MVVM application?

    - by SonOfPirate
    Example #1: I have a view displayed in my MVVM application (let's use Silverlight for the purposes of the discussion) and I click on a button that should take me to a new page. Example #2: That same view has another button that, when clicked, should open up a details view in a child window (dialog). We know that there will be Command objects exposed by our ViewModel bound to the buttons with methods that respond to the user's click. But, what then? How do we complete the action? Even if we use a so-called NavigationService, what are we telling it? To be more specific, in a traditional View-first model (like URL-based navigation schemes such as on the web or the SL built-in navigation framework) the Command objects would have to know what View to display next. That seems to cross the line when it comes to the separation of concerns promoted by the pattern. On the other hand, if the button wasn't wired to a Command object and behaved like a hyperlink, the navigation rules could be defined in the markup. But do we want the Views to control application flow and isn't navigation just another type of business logic? (I can say yes in some cases and no in others.) To me, the utopian implementation of the MVVM pattern (and I've heard others profess this) would be to have the ViewModel wired in such a way that the application can run headless (i.e. no Views). This provides the most surface area for code-based testing and makes the Views a true skin on the application. And my ViewModel shouldn't care if it displayed in the main window, a floating panel or a child window, should it? According to this apprach, it is up to some other mechanism at runtime to 'bind' what View should be displayed for each ViewModel. But what if we want to share a View with multiple ViewModels or vice versa? So given the need to manage the View-ViewModel relationship so we know what to display when along with the need to navigate between views, including displaying child windows / dialogs, how do we truly accomplish this in the MVVM pattern?

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  • Calling home, receiving calls and smartphone data from the US

    - by Rob Farley
    I got asked about calling home from the US, by someone going to the PASS Summit. I found myself thinking “there should be a blog post about this”... The easiest way to phone home is Skype - no question. Use WiFi, and if you’re calling someone who has Skype on their phone at the other end, it’s free. Even if they don’t, it’s still pretty good price-wise. The PASS Summit conference centre has good WiFI, as do the hotels, and plenty of other places (like Starbucks). But if you’re used to having data all the time, particularly when you’re walking from one place to another, then you’ll want a sim card. This also lets you receive calls more easily, not just solving your data problem. You’ll need to make sure your phone isn’t locked to your local network – get that sorted before you leave. It’s no trouble to drop by a T-mobile or AT&T store and getting a prepaid sim. You can’t get one from the airport, but if the PASS Summit is your first stop, there’s a T-mobile store on 6th in Seattle between Pine & Pike, so you can see it from the Sheraton hotel if that’s where you’re staying. AT&T isn’t far away either. But – there’s an extra step that you should be aware of. If you talk to one of these US telcos, you’ll probably (hopefully I’m wrong, but this is how it was for me recently) be told that their prepaid sims don’t work in smartphones. And they’re right – the APN gets detected and stops the data from working. But luckily, Apple (and others) have provided information about how to change the APN, which has been used by a company based in New Zealand to let you get your phone working. Basically, you send your phone browser to http://unlockit.co.nz and follow the prompts. But do this from a WiFi place somewhere, because you won’t have data access until after you’ve sorted this out... Oh, and if you get a prepaid sim with “unlimited data”, you will still need to get a Data Feature for it. And just for the record – this is WAY easier if you’re going to the UK. I dropped into a T-mobile shop there, and bought a prepaid sim card for five quid, which gave me 250MB data and some (but not much) call credit. In Australia it’s even easier, because you can buy data-enabled sim cards that work in smartphones from the airport when you arrive. I think having access to data really helps you feel at home in a different place. It means you can pull up maps, see what your friends are doing, and more. Hopefully this post helps, but feel free to post comments with extra information if you have it. @rob_farley

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  • Quick run through of the WP7 Developer Tools January 2011

    - by mbcrump
    In case you haven’t heard the latest WP7 Developers Tool update was released yesterday and contains a few goodies. First you need to go and grab the bits here. You can install them in any order, but I installed the WindowsPhoneDeveloperResources_en-US_Patch1.msp first. Then the VS10-KB2486994-x86.exe. They install silently. In other words, you would need to check Programs and Features and look in Installed Updates to see if they installed successfully. Like the screenshot below: Once you get them installed you can try out a few new features. Like Copy and Paste. Just fire up your application and put a TextBox on it and Select the Text and you will have the option highlighted in red above the text. Once you select it you will have the option to paste it. (see red rectangle below). Another feature is the Windows Phone Capability Detection Tool – This tool detects the phone capabilities used by your application. This will prevent you from submitting an app to the marketplace that says it uses x feature but really does not. How do you use it? Well navigate out to either directory: %ProgramFiles%\Microsoft SDKs\Windows Phone\v7.0\Tools\CapDetect %ProgramFiles (x86)%\Microsoft SDKs\Windows Phone\v7.0\Tools\CapDetect and run the following command: CapabilityDetection.exe Rules.xml YOURWP7XAPFILEOUTPUTDIRECTORY So, in my example you will see my app only requires the ID_CAP_MICROPHONE. Let’s see what the WmAppManifest.xml says in our WP7 Project: Whoa! That’s a lot of extra stuff we don’t need. We can delete unused capabilities safely now. Some of the other fixes are: (Copied straight from Microsoft) Fixes a text selection bug in pivot and panorama controls. In applications that have pivot or panorama controls that contain text boxes, users can unintentionally change panes when trying to copy text. To prevent this problem, open your application, recompile it, and then resubmit it to the Windows Phone Marketplace. Windows Phone Connect Tool – Allows you to connect your phone to a PC when Zune® software is not running and debug applications that use media APIs. For more information, see How to: Use the Connect Tool. Updated Bing Maps Silverlight Control – Includes improvements to gesture performance when using Bing™ Maps Silverlight® Control. Windows Phone Developer Tools Fix allowing deployment of XAP files over 64 MB in size to physical phone devices for testing and debugging. That’s pretty much it. Thanks again for reading my blog!  Subscribe to my feed CodeProject

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  • Web Development Goes Pre-Visual InterDev

    - by Ken Cox [MVP]
    As a longtime and hardcore ASP.NET webforms developer, I’m finding the new client-side development world a bit of a grind.  I love learning new technologies, but I can’t help feeling we’ve regressed and lost our old RAD advantage as we move heavy lifting to the client. For my latest project, I’m using Telerik’s KendoUI in Visual Studio 2012. To say I feel clumsy writing this much JavaScript is an understatement. It seems like the only safe way to ‘write’ this code is by copying a working snippet from someone else and pasting it into my HTML page.  For me, JavaScript has largely been for small UI tasks like client-side validation and a bit of AJAX – and often emitted by a server-side control. I find myself today lost in nests of curly braces that Ctrl+K, Ctrl+D doesn’t seem to understand that well either. IntelliSense, my old syntax saviour, doesn’t seem to have kept up with this cobweb of code either. Code completion? Not seeing it. As I fumbled about this evening, I thought about how web development rocketed forward when Microsoft introduced Visual InterDev. Its Design-Time Controls (DTCs) changed the way we created sites. All the iterations of Visual Studio have enhanced that server-side experience where you let a tool write the bulk of the code and manually finesse it from there. What happened? Why am I typing  properties and values (especially default values!) into VS 2012 to get a client-side grid on a page? Where are the drag and drop objects that traditionally provided 70 percent of the mark-up and configuration?  Did we forget how to write Property Pages where you enter a value and the correct syntax appears magically in the source code? To me, the tooling was looking the other way as the scene shifted from server-side code to nimble client-side script. It’ll have to catch up. Although JavaScript is the lingua franca of web browsers, the language is unwieldy, tough to maintain, and messy to debug. If a .NET JIT compiler can turn our VB, F#, and C# source code into an Intermediate Language that executes on a computer, I don’t see why there can’t be a client-side compiler that turns a .NET language into JavaScript that browsers can consume.

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  • Help with Collision of spawned object(postion fixed) with objects that there are translating on screen

    - by Amrutha
    Hey guys I am creating a game using Corona SDK and so coding it in Lua. So there are 2 separate functions, To translate the hit objects and change their color when they are tapped The link below is the code I am using to for the first function http://developer.anscamobile.com/sample-code/fishies Spawn objects that will hit the translating objects on collision. Alos on collision the spawned object disappears and the translating object bears a color(indicating the collision). In addition the size of this spawned object is dependent on i/p volume level. The function I have written is as follows, --VOICE INPUT CODE local r = media.newRecording() r:startRecording() r:startTuner() --local function newBar() -- local bar = display.newLine( 0, 0, 1, 0 ) -- bar:setColor( 0, 55, 100, 20 ) -- bar.width = 5 -- bar.y=400 -- bar.x=20 -- return bar --end local c1 = display.newImage("str-minion-small.png") c1.isVisible=false local c2 = display.newImage("str-minion-mid.png") c2.isVisible=false local c3 = display.newImage("str-minion-big.png") c3.isVisible=false --SPAWNING local function spawnDisk( event ) local phase = event.phase local volumeBar = display.newLine( 0, 0, 1, 0 ) volumeBar.y = 400 volumeBar.x = 20 -- volumeBar.isVisible=false local v = 20*math.log(r:getTunerVolume()) local MINTHRESH = 30 local LEFTMARGIN = 20 local v2 = MINTHRESH + math.max (v, -MINTHRESH) v2 = (display.contentWidth - 1 * LEFTMARGIN ) * v2 / MINTHRESH volumeBar.xScale = math.max ( 20, v2 ) local l = volumeBar.xScale local cnt1 = 0 local cnt2 = 0 local cnt3 = 0 local ONE =1 local val = event.numTaps --local px=event.x --local py=event.y if "ended" == phase then --audio.play( popSound ) --myLabel.isVisible = false if l > 50 and l <=150 then -- c1:setFillColor(10,105,0) -- c1.isVisible=false c1.x=math.random( 10, 450 ) c1.y=math.random( 10, 300 ) physics.addBody( c1, { density=1, radius=10.0 } ) c1.isVisible=true cnt1= cnt1+ ONE return c1 elseif l > 100 and l <=250 then --c2:setFillColor(200,10,0) c2.x=math.random( 10, 450 ) c2.y=math.random( 10, 300 ) physics.addBody( c2, { density=2, radius=9000.0 } ) c2.isVisible=true cnt2= cnt2+ ONE return c2 elseif l >=250 then c3.x=math.random( 40, 450 ) c3.y=math.random( 40, 300 ) physics.addBody( c3, { density=2, radius=7000.0 , bounce=0.0 } ) c3.isVisible=true cnt3= cnt3+ ONE return c3 end end end buzzR:addEventListener( "touch", spawnDisk ) -- touch the screen to create disks Now both functions work fine independently but there is no collision happening. Its almost as if the translating object and the spawn object are on different layers. The translating object passes through the spawn object freely. Can anyone please tell me how to resolve this problem. And how can I get them to collide. Its my first attempt at game development, that too for a mobile platform so would appreciate all help. Also if I have not been specific do let me know. I ll try to frame the query better :). Thanks in advance.

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  • Understanding clojure keywords

    - by tjb1982
    I'm taking my first steps with Clojure. Otherwise, I'm somewhat competent with JavaScript, Python, Java, and a little C. I was reading this artical that describes destructuring vectors and maps. E.g. => (def point [0 0]) => (let [[x y] point] => (println "the coordinates are:" x y)) the coordinates are: 0 0 but I'm having a difficult time understanding keywords. At first glance, they seem really simple, as they just evaluate to themselves: => :test :test But they seem to be used is so many different ways and I don't understand how to think about them. E.g., you can also do stuff like this: => (defn full-name [& {first :first last :last}] => (println first last)) => (full-name :first "Tom" :last "Brennan") Tom Brennan nil This doesn't seem intuitive to me. I would have guessed the arguments should have been something more like: (full-name {:first "Tom" :last "Brennan"}) because it looks like in the function definition that you're saying "no required arguments, but a variable number of arguments comes in the form of a single map". But it seems more like you're saying "no required arguments, but a variable number of arguments comes which should be a list of alternating keywords and values... ?" I'm not really sure how to wrap my brain around this. Also, things like this confuse me too: => (def population {:humans 5 :zombies 1000}) => (:zombies population) 1000 => (population :zombies) 1000 How do maps and keywords suddenly become functions? If I could get some clarification on the use of keywords in these two examples, that would be really helpful. Update I've also seen http://stackoverflow.com/questions/3337888/clojure-named-arguments and while the accepted answer is a great demonstration of how to use keywords with destructuring and named arguments, I'm really looking more for understanding how to think about them--why the language is designed this way and how I can best internalize their use.

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  • Meaning of Crawl errors

    - by com
    My question is about definition of Crawl errors in Google Webmaster Tools. Crawl errors is devided into few sections. Let's first consider HTTP section. I assume that all broken links in this section was somehow found by crawler, this is not the links from sitemap. If all this links was found by scanning pages from sitemap for links, why it doesn't mention what was the source page, like in sitemap section with column Linked From. Please correct me if I am wrong. Sitemap section. Looks like all those links came from my sitemap. But there is Linked From column, I already know, that all those broken links is from sitemap, so in order to fix the error, I should revise my sitemap. Am I wrong? Not followed section. I don't know what does it mean. Looks like it accumulates all links that caused redirect, but for some reason Google considers all those redirect as wrong redirect. Do you know if there are any set of rules how to determine wrong redirect. Actually I found were was my mistake, I tried to normalize URL and redirect it to the right URL, but I did normalization in a wrong way. Not found section. This section like HTTP section but with 404 errors. This section has Linked From column. But very often Linked From has unavailable. What does it mean, Google can not say me how it found this non existing page. How this section related to sitemap section. Does this section contains all 404 links from sitemap too. But there is too many 404 links, much more than in sitemap. I tried to take a look what we have in Linked From, and I saw that this link came from sitemap two month ago. But why Google keeps it indexed, the link is already dead, new sitemap doesn't have it. If there is any expire date for old links? Unreachable section. Looks like this section for 500 errors. This section doesn't contain Linked From column. There are too many completely meaningless links, I really don't know where this stuff came from, and without Linked From I am not able to figure out how to deal with it. Sorry for such a big topic, but I just want to make it clear, what every section stands for, because it's extremely crucial in order to deal with all those problems. Hopefully it will be useful not just for me. Thanks!

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  • Function Folding in #PowerQuery

    - by Darren Gosbell
    Originally posted on: http://geekswithblogs.net/darrengosbell/archive/2014/05/16/function-folding-in-powerquery.aspxLooking at a typical Power Query query you will noticed that it's made up of a number of small steps. As an example take a look at the query I did in my previous post about joining a fact table to a slowly changing dimension. It was roughly built up of the following steps: Get all records from the fact table Get all records from the dimension table do an outer join between these two tables on the business key (resulting in an increase in the row count as there are multiple records in the dimension table for each business key) Filter out the excess rows introduced in step 3 remove extra columns that are not required in the final result set. If Power Query was to execute a query like this literally, following the same steps in the same order it would not be overly efficient. Particularly if your two source tables were quite large. However Power Query has a feature called function folding where it can take a number of these small steps and push them down to the data source. The degree of function folding that can be performed depends on the data source, As you might expect, relational data sources like SQL Server, Oracle and Teradata support folding, but so do some of the other sources like OData, Exchange and Active Directory. To explore how this works I took the data from my previous post and loaded it into a SQL database. Then I converted my Power Query expression to source it's data from that database. Below is the resulting Power Query which I edited by hand so that the whole thing can be shown in a single expression: let     SqlSource = Sql.Database("localhost", "PowerQueryTest"),     BU = SqlSource{[Schema="dbo",Item="BU"]}[Data],     Fact = SqlSource{[Schema="dbo",Item="fact"]}[Data],     Source = Table.NestedJoin(Fact,{"BU_Code"},BU,{"BU_Code"},"NewColumn"),     LeftJoin = Table.ExpandTableColumn(Source, "NewColumn"                                   , {"BU_Key", "StartDate", "EndDate"}                                   , {"BU_Key", "StartDate", "EndDate"}),     BetweenFilter = Table.SelectRows(LeftJoin, each (([Date] >= [StartDate]) and ([Date] <= [EndDate])) ),     RemovedColumns = Table.RemoveColumns(BetweenFilter,{"StartDate", "EndDate"}) in     RemovedColumns If the above query was run step by step in a literal fashion you would expect it to run two queries against the SQL database doing "SELECT * …" from both tables. However a profiler trace shows just the following single SQL query: select [_].[BU_Code],     [_].[Date],     [_].[Amount],     [_].[BU_Key] from (     select [$Outer].[BU_Code],         [$Outer].[Date],         [$Outer].[Amount],         [$Inner].[BU_Key],         [$Inner].[StartDate],         [$Inner].[EndDate]     from [dbo].[fact] as [$Outer]     left outer join     (         select [_].[BU_Key] as [BU_Key],             [_].[BU_Code] as [BU_Code2],             [_].[BU_Name] as [BU_Name],             [_].[StartDate] as [StartDate],             [_].[EndDate] as [EndDate]         from [dbo].[BU] as [_]     ) as [$Inner] on ([$Outer].[BU_Code] = [$Inner].[BU_Code2] or [$Outer].[BU_Code] is null and [$Inner].[BU_Code2] is null) ) as [_] where [_].[Date] >= [_].[StartDate] and [_].[Date] <= [_].[EndDate] The resulting query is a little strange, you can probably tell that it was generated programmatically. But if you look closely you'll notice that every single part of the Power Query formula has been pushed down to SQL Server. Power Query itself ends up just constructing the query and passing the results back to Excel, it does not do any of the data transformation steps itself. So now you can feel a bit more comfortable showing Power Query to your less technical Colleagues knowing that the tool will do it's best fold all the  small steps in Power Query down the most efficient query that it can against the source systems.

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  • Design for an interface implementation that provides additional functionality

    - by Limbo Exile
    There is a design problem that I came upon while implementing an interface: Let's say there is a Device interface that promises to provide functionalities PerformA() and GetB(). This interface will be implemented for multiple models of a device. What happens if one model has an additional functionality CheckC() which doesn't have equivalents in other implementations? I came up with different solutions, none of which seems to comply with interface design guidelines: To add CheckC() method to the interface and leave one of its implementations empty: interface ISomeDevice { void PerformA(); int GetB(); bool CheckC(); } class DeviceModel1 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } public bool CheckC() { bool res; // assign res a value based on some validation return res; } } class DeviceModel2 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } public bool CheckC() { return true; // without checking anything } } This solution seems incorrect as a class implements an interface without truly implementing all the demanded methods. To leave out CheckC() method from the interface and to use explicit cast in order to call it: interface ISomeDevice { void PerformA(); int GetB(); } class DeviceModel1 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } public bool CheckC() { bool res; // assign res a value based on some validation return res; } } class DeviceModel2 : ISomeDevice { public void PerformA() { // do stuff } public int GetB() { return 1; } } class DeviceManager { private ISomeDevice myDevice; public void ManageDevice(bool newDeviceModel) { myDevice = (newDeviceModel) ? new DeviceModel1() : new DeviceModel2(); myDevice.PerformA(); int b = myDevice.GetB(); if (newDeviceModel) { DeviceModel1 newDevice = myDevice as DeviceModel1; bool c = newDevice.CheckC(); } } } This solution seems to make the interface inconsistent. For the device that supports CheckC(): to add the logic of CheckC() into the logic of another method that is present in the interface. This solution is not always possible. So, what is the correct design to be used in such cases? Maybe creating an interface should be abandoned altogether in favor of another design?

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