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  • Should a g_object_new have a matching g_object_unref?

    - by legends2k
    I'm using libnotify to show desktop notifications in my application; notify_notification_new() returns a NotifyNotification*, which should be passed as the first param to further function calls of the notification library. There is no notify_notification_free() which frees the pointer it returns. I looked up the source of notify_notification_new() and internally it does a g_object_new(), gets a GObject* and returns it as a NotfiyNotification*, so when my application does the clean up, should I call a g_object_unref() on the pointer returned by notify_notification_new()?

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  • Implement dictionary using java

    - by ahmad
    Task Dictionary ADT The dictionary ADT models a searchable collection of key-element entries Multiple items with the same key are allowed Applications: word-definition pairs Dictionary ADT methods: find(k): if the dictionary has an entry with key k, returns it, else, returns null findAll(k): returns an iterator of all entries with key k insert(k, o): inserts and returns the entry (k, o) remove(e): remove the entry e from the dictionary size(), isEmpty() Operation Output Dictionary insert(5,A) (5,A) (5,A) insert(7,B) (7,B) (5,A),(7,B) insert(2,C) (2,C) (5,A),(7,B),(2,C) insert(8,D) (8,D) (5,A),(7,B),(2,C),(8,D) insert(2,E) (2,E) (5,A),(7,B),(2,C),(8,D),(2,E) find(7) (7,B) (5,A),(7,B),(2,C),(8,D),(2,E) find(4) null (5,A),(7,B),(2,C),(8,D),(2,E) find(2) (2,C) (5,A),(7,B),(2,C),(8,D),(2,E) findAll(2) (2,C),(2,E) (5,A),(7,B),(2,C),(8,D),(2,E) size() 5 (5,A),(7,B),(2,C),(8,D),(2,E) remove(find(5)) (5,A) (7,B),(2,C),(8,D),(2,E) find(5) null (7,B),(2,C),(8,D),(2,E) Detailed explanation: NO Specific requirements: please Get it done i need HELP !!!

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  • What does the ^ operator do in Java?

    - by joroj
    What function does the "^" operator serve in Java? When I try this: int a = 5^n; ...it gives me: for n = 5, returns 0 for n = 4, returns 1 for n = 6, returns 3 ...so I guess it doesn't indicate exponentiation. But what is it then?

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  • Why is PHP date() adding +1 hour in diff calculation?

    - by Lex
    Hi there, I've got kind of a tricky question, I already searched every related question on Stackoverflow and neither solved my conundrum, although I think I'm running in circles, so here's the question: I've got this code: $val = (strtotime('2010-03-22 10:05:00')-strtotime('2010-03-22 09:00:00')) This returns correctly $val = 3900 (3600 seconds = 1 hour, 300 seconds = 5 mins) But doing this: echo date("H:i",$val)."<br>"; returns 02:05 even doing this: echo date("H:i",3900)."<br>"; returns 02:05 (just to be naively sure) Doing this: echo date("H:i eTO",3900)."<br>"; returns 02:05 System/LocaltimeCET+0100 Which is correct, my timezone is CET and is +1. What's going on? Is date() correcting the timezone for some reason? Or am I doing anything wrong?

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  • Problem finding the difference in days between two dates

    - by James
    I have been using a tidy little routine that I found here to calculate the difference in days between two dates in AS3. I am getting some strange results and I am wondering if any of you inter-codal-mega-lords can shed some light? Why is Q1 of 2010 coming up one day short, when in all other cases the routine is performing fine? Many thanks in advance to anyone who can help! function countDays( startDate:Date, endDate:Date ):int { var oneDay:int = 24*60*60*1000; // hours*minutes*seconds*milliseconds var diffDays:int = Math.abs((startDate.getTime() - endDate.getTime())/(oneDay)); return diffDays; } countDays( new Date( 2010, 00, 01 ), new Date( 2011, 00, 01 ) ); // returns 365, which is correct countDays( new Date( 2010, 00, 01 ), new Date( 2010, 03, 01 ) ); // returns 89, which is 1 day short countDays( new Date( 2010, 03, 01 ), new Date( 2010, 06, 01 ) ); // returns 91, which is correct countDays( new Date( 2010, 06, 01 ), new Date( 2010, 09, 01 ) ); // returns 92, which is correct countDays( new Date( 2010, 09, 01 ), new Date( 2011, 00, 01 ) ); // returns 92, which is correct

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  • Why does document.evaluate succeed in Firebug but fail in Selenium?

    - by anil
    browser.getEval function in selenium makes iterateNext return null ..Otherwise in firebug it returns a value(same script) document.evaluate("//button[text()='Save']", document, null, XPathResult.ANY_TYPE, null) .iterateNext() .disabled; returns true But browser.getEval("document.evaluate(\"//button[text()='Save']\", document, null, XPathResult.ANY_TYPE, null) .iterateNext() .disabled;"); returns that error as : "com.thoughtworks.selenium.SeleniumException: ERROR: Threw an exception: res.iterateNext() is null "

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  • Partially Modifying an XML serialized document.

    - by Stacey
    I have an XML document, several actually, that will be editable via a front-end UI. I've discovered a problem with this approach (other than the fact that it is using xml files instead of a database... but I cannot change that right now). If one user makes a change while another user is in the process of making a change, then the second one's changes will overwrite the first. I need to be able to request objects from the xml files, change them, and then submit the changes back to the xml file without re-writing the entire file. I've got my entire xml access class posted here (which was formed thanks to wonderful help from stackoverflow!) using System; using System.Linq; using System.Collections; using System.Collections.Generic; namespace Repositories { /// <summary> /// A file base repository represents a data backing that is stored in an .xml file. /// </summary> public partial class Repository<T> : IRepository { /// <summary> /// Default constructor for a file repository /// </summary> public Repository() { } /// <summary> /// Initialize a basic repository with a filename. This will have to be passed from a context to be mapped. /// </summary> /// <param name="filename"></param> public Repository(string filename) { FileName = filename; } /// <summary> /// Discovers a single item from this repository. /// </summary> /// <typeparam name="TItem">The type of item to recover.</typeparam> /// <typeparam name="TCollection">The collection the item belongs to.</typeparam> /// <param name="expression"></param> /// <returns></returns> public TItem Single<TItem, TCollection>(Predicate<TItem> expression) where TCollection : IDisposable, IEnumerable<TItem> { using (var list = List<TCollection>()) { return list.Single(i => expression(i)); } } /// <summary> /// Discovers a collection from the repository, /// </summary> /// <typeparam name="TCollection"></typeparam> /// <returns></returns> public TCollection List<TCollection>() where TCollection : IDisposable { using (var list = System.Xml.Serializer.Deserialize<TCollection>(FileName)) { return (TCollection)list; } } /// <summary> /// Discovers a single item from this repository. /// </summary> /// <typeparam name="TItem">The type of item to recover.</typeparam> /// <typeparam name="TCollection">The collection the item belongs to.</typeparam> /// <param name="expression"></param> /// <returns></returns> public List<TItem> Select<TItem, TCollection>(Predicate<TItem> expression) where TCollection : IDisposable, IEnumerable<TItem> { using (var list = List<TCollection>()) { return list.Where( i => expression(i) ).ToList<TItem>(); } } /// <summary> /// Attempts to save an entire collection. /// </summary> /// <typeparam name="TCollection"></typeparam> /// <param name="collection"></param> /// <returns></returns> public Boolean Save<TCollection>(TCollection collection) { try { // load the collection into an xml reader and try to serialize it. System.Xml.XmlDocument xDoc = new System.Xml.XmlDocument(); xDoc.LoadXml(System.Xml.Serializer.Serialize<TCollection>(collection)); // attempt to flush the file xDoc.Save(FileName); // assume success return true; } catch { return false; } } internal string FileName { get; private set; } } public interface IRepository { TItem Single<TItem, TCollection>(Predicate<TItem> expression) where TCollection : IDisposable, IEnumerable<TItem>; TCollection List<TCollection>() where TCollection : IDisposable; List<TItem> Select<TItem, TCollection>(Predicate<TItem> expression) where TCollection : IDisposable, IEnumerable<TItem>; Boolean Save<TCollection>(TCollection collection); } }

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  • Unit Testing: hard dependency MessageBox.Show()

    - by Sean B
    What ways can the SampleConfirmationDialog be unit tested? The SampleConfirmationDialog would be exercised via acceptance tests, however how could we unit test it, seeing as MessageBox is not abstract and no matching interface? public interface IConfirmationDialog { /// <summary> /// Confirms the dialog with the user /// </summary> /// <returns>True if confirmed, false if not, null if cancelled</returns> bool? Confirm(); } /// <summary> /// Implementation of a confirmation dialog /// </summary> public class SampleConfirmationDialog : IConfirmationDialog { /// <summary> /// Confirms the dialog with the user /// </summary> /// <returns>True if confirmed, false if not, null if cancelled</returns> public bool? Confirm() { return MessageBox.Show("do operation x?", "title", MessageBoxButton.YesNo, MessageBoxImage.Question) == MessageBoxResult.Yes; } }

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  • custom ListView --Null pointer exception

    - by raghs
    this code throws a Null pointer exception. It was thrown by getChildAt(i). The getCount() returns the number of items in listView. But getChildAt(i) returns only if item is present in current list view. For example in a scrollable list view assume that there are 20 items. The getCount() returns 20. But getChildAt(20) returns null. Because it doesnot fit in listview. How to solve this problem?? int i,j=object.getCount(); View v=getListView(); CheckBox chk=null; for(i=0;i<j;i++) { chk=((CheckBox)((ViewGroup) v).getChildAt(i).findViewById(R.id.checkBox1)); if(chk.isChecked()) { //download the contents to specific folder in sd card } }

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  • If Else Conditionals within Function in JavaScript

    - by Antoine-Laurent Lavoisier
    I'm having issues with conditionals. I want to return the index where pattern starts in string (or -1 if not found). The search is to be case sensitive if the 3rd parameter is true otherwise it is case insensitive. Examples index("abAB12","AB",true) returns 2 but index("abAB12","AB",false) returns 0 index("abAB12","BA",true) returns -1 and index("abAB12","BA",false) returns 1 Any idea how I can accomplish this? This is my code so far var s = "abAB12" var p = "AB" var cs = true function index(string, pattern, caseSensitive) { if (pattern) { var found = false; if (caseSensitive = false) { if (string.indexOf(pattern.) >= 0) { found = true; } return (found); else { return (""); } } else if (caseSensitive = true) { if (string.toLowerCase().indexOf(pattern.toLowerCase()) >= 0) { found = true; } return (found); } else { return (""); } } } alert(index(s, p, cs)); Fiddle at http://jsfiddle.net/AfDFb/1/

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  • MySQL function return more than 1 row

    - by bobobobo
    I'd like to write a MySQL stored function that returns multiple rows of data. Is this possible? It seems to be locked at 1 row -- can't even return 0 rows. For example DELIMITER // create function go() RETURNS int deterministic NO SQL BEGIN return null ; -- this doesn't return 0 rows! it returns 1 row -- return 0 ; END // DELIMITER ; Returning null from a MySQL stored proc though, doesn't return 0 rows.. it returns 1 row with the value null in it. Can I return 0, or more than 1 row from a MySQL function, how?

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  • Will an optimizing compiler remove calls to a method whose result will be multiplied by zero?

    - by Tim R.
    Suppose you have a computationally expensive method, Compute(p), which returns some float, and another method, Falloff(p), which returns another float from zero to one. If you compute Falloff(p) * Compute(p), will Compute(p) still run when Falloff(p) returns zero? Or would you need to write a special case to prevent Compute(p) from running unnecessarily? Theoretically, an optimizing compiler could determine that omitting Compute when Falloff returns zero would have no effect on the program. However, this is kind of hard to test, since if you have Compute output some debug data to determine whether it is running, the compiler would know not to omit it because of that debug info, resulting in sort of a Schrodinger's cat situation. I know the safe solution to this problem is just to add the special case, but I'm just curious.

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  • A 16-digit hashing function

    - by Aly
    Is there a hash function that returns a 16-digit hex value (as MD5 returns 32-digit), or is there a library (for C++) in which I can use MD5 or SHA-1 which returns a 16-digit value

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  • Stay on current page after POST

    - by DogPooOnYourShoe
    I have a form which once the Submit button is pressed, it goes to a blank page and returns any error messages on that blank page. However I have a website template and I wish that my script is run, and returns the the page which did the action POST and puts any error messages on that page. Example of what is happening: PAGE REQUESTS POST ---- SCRIPT RUNS --- RETURNS ERROR MESSAGE What I want it to do is: PAGE REQUESTS POST --- SCRIPT RUNS ---- GOES TO THE PAGE WHICH REQUESTED POST ---- SHOWS ANY ERROR MESSAGES WHICH THE SCRIPT PICKED OUT.

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  • who uses a TCP port?

    - by dijxtra
    One of gen_servers in my app call gen_tcp:listen(Port, [{active, true}]). First time I run unit test, it returns {ok, Socket}, but second time I run the same unit test, it returns an {error, eaddrinuse}, but lsof -i TCP returns nothing. Also, when the same unit_test is run twice on another machine (WinXP), it works as expected (that is, returns {ok, Socket} both times). Therefore, my gen_server obviously releases the port, but Erlang somehow doesn't know that. So, how can I figure out who does Erlang think uses this address?

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  • java packets byte

    - by user303289
    Guys, I am implementing a protocol in one of the wireless project. I am stucked at one point. In of the java file i am suppose to receive a packet and that packet is 12 byte packet and I have to write different functions for reading different parts of packets and convert it to diferent type. Like I want first four byte in one of the function and convert it to int, next two bytes in string. and again next two in string, last two hop in string and followed by last two int. I want follwing function to implement: // here is the interface /* FloodingData should use methods defined in this class. */ class FloodingPacket{ public static void main(String arg[]){ byte FloodingPack[]; // just for example to test in code FloodingPack=new byte[12]; interface IFloodingPacket { // Returns the unique sequence number for the packet int getSequenceNumber() ; // Returns the source address for the packet String getSourceAddress(); // Returns the destination address for the packet String getDestinationAddress(); // Returns the last hop address for the packet String getLastHopAddress(); // Sets the last hop address to the address of the node // which the packet was received from void updateLastHopAddress(); // Returns the entire packet in bytes (for sending) byte[] getBytes(); // Sets the bytes of the packet (for receiving) void setBytes(byte[] packet); }

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  • Sending a message to nil?

    - by Ryan Delucchi
    As a Java developer who is reading Apple's Objective-C 2.0 documentation: I wonder as to what sending a message to nil means - let alone how it is actually useful. Taking an excerpt from the documentation: There are several patterns in Cocoa that take advantage of this fact. The value returned from a message to nil may also be valid: If the method returns an object, any pointer type, any integer scalar of size less than or equal to sizeof(void*), a float, a double, a long double, or a long long, then a message sent to nil returns 0. If the method returns a struct, as defined by the Mac OS X ABI Function Call Guide to be returned in registers, then a message sent to nil returns 0.0 for every field in the data structure. Other struct data types will not be filled with zeros. If the method returns anything other than the aforementioned value types the return value of a message sent to nil is undefined. Has Java rendered my brain incapable of grokking the explanation above? Or is there something that I am missing that would make this as clear as glass? Note: Yes, I do get the idea of messages/receivers in Objective-C, I am simply confused about a receiver that happens to be nil.

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  • How to find where error is.

    - by gurugio
    How can I find where the error occurs? In C language, the return value means what error occurs, such as failure to open file or memory allocation. There is no information where the error occurs. For example, function 'foo' calls A,B,C,D. If foo returns an error value, it might be return value of A or B or C or D. I cannot find what function returns error. I have to run debugger or add some codes to find what function returns error.

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  • DropDownList and SelectListItem Array Item Updates in MVC

    - by Rick Strahl
    So I ran into an interesting behavior today as I deployed my first MVC 4 app tonight. I have a list form that has a filter drop down that allows selection of categories. This list is static and rarely changes so rather than loading these items from the database each time I load the items once and then cache the actual SelectListItem[] array in a static property. However, when we put the site online tonight we immediately noticed that the drop down list was coming up with pre-set values that randomly changed. Didn't take me long to trace this back to the cached list of SelectListItem[]. Clearly the list was getting updated - apparently through the model binding process in the selection postback. To clarify the scenario here's the drop down list definition in the Razor View:@Html.DropDownListFor(mod => mod.QueryParameters.Category, Model.CategoryList, "All Categories") where Model.CategoryList gets set with:[HttpPost] [CompressContent] public ActionResult List(MessageListViewModel model) { InitializeViewModel(model); busEntry entryBus = new busEntry(); var entries = entryBus.GetEntryList(model.QueryParameters); model.Entries = entries; model.DisplayMode = ApplicationDisplayModes.Standard; model.CategoryList = AppUtils.GetCachedCategoryList(); return View(model); } The AppUtils.GetCachedCategoryList() method gets the cached list or loads the list on the first access. The code to load up the list is housed in a Web utility class. The method looks like this:/// <summary> /// Returns a static category list that is cached /// </summary> /// <returns></returns> public static SelectListItem[] GetCachedCategoryList() { if (_CategoryList != null) return _CategoryList; lock (_SyncLock) { if (_CategoryList != null) return _CategoryList; var catBus = new busCategory(); var categories = catBus.GetCategories().ToList(); // Turn list into a SelectItem list var catList= categories .Select(cat => new SelectListItem() { Text = cat.Name, Value = cat.Id.ToString() }) .ToList(); catList.Insert(0, new SelectListItem() { Value = ((int)SpecialCategories.AllCategoriesButRealEstate).ToString(), Text = "All Categories except Real Estate" }); catList.Insert(1, new SelectListItem() { Value = "-1", Text = "--------------------------------" }); _CategoryList = catList.ToArray(); } return _CategoryList; } private static SelectListItem[] _CategoryList ; This seemed normal enough to me - I've been doing stuff like this forever caching smallish lists in memory to avoid an extra trip to the database. This list is used in various places throughout the application - for the list display and also when adding new items and setting up for notifications etc.. Watch that ModelBinder! However, it turns out that this code is clearly causing a problem. It appears that the model binder on the [HttpPost] method is actually updating the list that's bound to and changing the actual entry item in the list and setting its selected value. If you look at the code above I'm not setting the SelectListItem.Selected value anywhere - the only place this value can get set is through ModelBinding. Sure enough when stepping through the code I see that when an item is selected the actual model - model.CategoryList[x].Selected - reflects that. This is bad on several levels: First it's obviously affecting the application behavior - nobody wants to see their drop down list values jump all over the place randomly. But it's also a problem because the array is getting updated by multiple ASP.NET threads which likely would lead to odd crashes from time to time. Not good! In retrospect the modelbinding behavior makes perfect sense. The actual items and the Selected property is the ModelBinder's way of keeping track of one or more selected values. So while I assumed the list to be read-only, the ModelBinder is actually updating it on a post back producing the rather surprising results. Totally missed this during testing and is another one of those little - "Did you know?" moments. So, is there a way around this? Yes but it's maybe not quite obvious. I can't change the behavior of the ModelBinder, but I can certainly change the way that the list is generated. Rather than returning the cached list, I can return a brand new cloned list from the cached items like this:/// <summary> /// Returns a static category list that is cached /// </summary> /// <returns></returns> public static SelectListItem[] GetCachedCategoryList() { if (_CategoryList != null) { // Have to create new instances via projection // to avoid ModelBinding updates to affect this // globally return _CategoryList .Select(cat => new SelectListItem() { Value = cat.Value, Text = cat.Text }) .ToArray(); } …}  The key is that newly created instances of SelectListItems are returned not just filtered instances of the original list. The key here is 'new instances' so that the ModelBinding updates do not update the actual static instance. The code above uses LINQ and a projection into new SelectListItem instances to create this array of fresh instances. And this code works correctly - no more cross-talk between users. Unfortunately this code is also less efficient - it has to reselect the items and uses extra memory for the new array. Knowing what I know now I probably would have not cached the list and just take the hit to read from the database. If there is even a possibility of thread clashes I'm very wary of creating code like this. But since the method already exists and handles this load in one place this fix was easy enough to put in. Live and learn. It's little things like this that can cause some interesting head scratchers sometimes…© Rick Strahl, West Wind Technologies, 2005-2012Posted in MVC  ASP.NET  .NET   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Get vertex colors from fbx (OpenGL, FBX SDK)

    - by instancedName
    I'm kinda stuck with this one. I managed to get vertex positions, indices, normals, but I don't quite understand how te get vertex colors. I need them to fill my buffer. I tried funcion mesh-GetElementVertexColorCount() and then to iterate trough all of them, but it returns zero. I alse tried to get layer, and then use layer-GetVertexColors(), but it returns NULL pointer. Can anyone help me with this one?

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  • AdvancedFormatProvider: Making string.format do more

    - by plblum
    When I have an integer that I want to format within the String.Format() and ToString(format) methods, I’m always forgetting the format symbol to use with it. That’s probably because its not very intuitive. Use {0:N0} if you want it with group (thousands) separators. text = String.Format("{0:N0}", 1000); // returns "1,000"   int value1 = 1000; text = value1.ToString("N0"); Use {0:D} or {0:G} if you want it without group separators. text = String.Format("{0:D}", 1000); // returns "1000"   int value2 = 1000; text2 = value2.ToString("D"); The {0:D} is especially confusing because Microsoft gives the token the name “Decimal”. I thought it reasonable to have a new format symbol for String.Format, "I" for integer, and the ability to tell it whether it shows the group separators. Along the same lines, why not expand the format symbols for currency ({0:C}) and percent ({0:P}) to let you omit the currency or percent symbol, omit the group separator, and even to drop the decimal part when the value is equal to the whole number? My solution is an open source project called AdvancedFormatProvider, a group of classes that provide the new format symbols, continue to support the rest of the native symbols and makes it easy to plug in additional format symbols. Please visit https://github.com/plblum/AdvancedFormatProvider to learn about it in detail and explore how its implemented. The rest of this post will explore some of the concepts it takes to expand String.Format() and ToString(format). AdvancedFormatProvider benefits: Supports {0:I} token for integers. It offers the {0:I-,} option to omit the group separator. Supports {0:C} token with several options. {0:C-$} omits the currency symbol. {0:C-,} omits group separators, and {0:C-0} hides the decimal part when the value would show “.00”. For example, 1000.0 becomes “$1000” while 1000.12 becomes “$1000.12”. Supports {0:P} token with several options. {0:P-%} omits the percent symbol. {0:P-,} omits group separators, and {0:P-0} hides the decimal part when the value would show “.00”. For example, 1 becomes “100 %” while 1.1223 becomes “112.23 %”. Provides a plug in framework that lets you create new formatters to handle specific format symbols. You register them globally so you can just pass the AdvancedFormatProvider object into String.Format and ToString(format) without having to figure out which plug ins to add. text = String.Format(AdvancedFormatProvider.Current, "{0:I}", 1000); // returns "1,000" text2 = String.Format(AdvancedFormatProvider.Current, "{0:I-,}", 1000); // returns "1000" text3 = String.Format(AdvancedFormatProvider.Current, "{0:C-$-,}", 1000.0); // returns "1000.00" The IFormatProvider parameter Microsoft has made String.Format() and ToString(format) format expandable. They each take an additional parameter that takes an object that implements System.IFormatProvider. This interface has a single member, the GetFormat() method, which returns an object that knows how to convert the format symbol and value into the desired string. There are already a number of web-based resources to teach you about IFormatProvider and the companion interface ICustomFormatter. I’ll defer to them if you want to dig more into the topic. The only thing I want to point out is what I think are implementation considerations. Why GetFormat() always tests for ICustomFormatter When you see examples of implementing IFormatProviders, the GetFormat() method always tests the parameter against the ICustomFormatter type. Why is that? public object GetFormat(Type formatType) { if (formatType == typeof(ICustomFormatter)) return this; else return null; } The value of formatType is already predetermined by the .net framework. String.Format() uses the StringBuilder.AppendFormat() method to parse the string, extracting the tokens and calling GetFormat() with the ICustomFormatter type. (The .net framework also calls GetFormat() with the types of System.Globalization.NumberFormatInfo and System.Globalization.DateTimeFormatInfo but these are exclusive to how the System.Globalization.CultureInfo class handles its implementation of IFormatProvider.) Your code replaces instead of expands I would have expected the caller to pass in the format string to GetFormat() to allow your code to determine if it handles the request. My vision would be to return null when the format string is not supported. The caller would iterate through IFormatProviders until it finds one that handles the format string. Unfortunatley that is not the case. The reason you write GetFormat() as above is because the caller is expecting an object that handles all formatting cases. You are effectively supposed to write enough code in your formatter to handle your new cases and call .net functions (like String.Format() and ToString(format)) to handle the original cases. Its not hard to support the native functions from within your ICustomFormatter.Format function. Just test the format string to see if it applies to you. If not, call String.Format() with a token using the format passed in. public string Format(string format, object arg, IFormatProvider formatProvider) { if (format.StartsWith("I")) { // handle "I" formatter } else return String.Format(formatProvider, "{0:" + format + "}", arg); } Formatters are only used by explicit request Each time you write a custom formatter (implementer of ICustomFormatter), it is not used unless you explicitly passed an IFormatProvider object that supports your formatter into String.Format() or ToString(). This has several disadvantages: Suppose you have several ICustomFormatters. In order to have all available to String.Format() and ToString(format), you have to merge their code and create an IFormatProvider to return an instance of your new class. You have to remember to utilize the IFormatProvider parameter. Its easy to overlook, especially when you have existing code that calls String.Format() without using it. Some APIs may call String.Format() themselves. If those APIs do not offer an IFormatProvider parameter, your ICustomFormatter will not be available to them. The AdvancedFormatProvider solves the first two of these problems by providing a plug-in architecture.

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  • Using a WCF Message Inspector to extend AppFabric Monitoring

    - by Shawn Cicoria
    I read through Ron Jacobs post on Monitoring WCF Data Services with AppFabric http://blogs.msdn.com/b/endpoint/archive/2010/06/09/tracking-wcf-data-services-with-windows-server-appfabric.aspx What is immediately striking are 2 things – it’s so easy to get monitoring data into a viewer (AppFabric Dashboard) w/ very little work.  And the 2nd thing is, why can’t this be a WCF message inspector on the dispatch side. So, I took the base class WCFUserEventProvider that’s located in the WCF/WF samples [1] in the following path, \WF_WCF_Samples\WCF\Basic\Management\AnalyticTraceExtensibility\CS\WCFAnalyticTracingExtensibility\  and then created a few classes that project the injection as a IEndPointBehavior There are just 3 classes to drive injection of the inspector at runtime via config: IDispatchMessageInspector implementation BehaviorExtensionElement implementation IEndpointBehavior implementation The full source code is below with a link to the solution file here: [Solution File] using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.ServiceModel.Dispatcher; using System.ServiceModel.Channels; using System.ServiceModel; using System.ServiceModel.Configuration; using System.ServiceModel.Description; using Microsoft.Samples.WCFAnalyticTracingExtensibility; namespace Fabrikam.Services { public class AppFabricE2EInspector : IDispatchMessageInspector { static WCFUserEventProvider evntProvider = null; static AppFabricE2EInspector() { evntProvider = new WCFUserEventProvider(); } public object AfterReceiveRequest( ref Message request, IClientChannel channel, InstanceContext instanceContext) { OperationContext ctx = OperationContext.Current; var opName = ctx.IncomingMessageHeaders.Action; evntProvider.WriteInformationEvent("start", string.Format("operation: {0} at address {1}", opName, ctx.EndpointDispatcher.EndpointAddress)); return null; } public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState) { OperationContext ctx = OperationContext.Current; var opName = ctx.IncomingMessageHeaders.Action; evntProvider.WriteInformationEvent("end", string.Format("operation: {0} at address {1}", opName, ctx.EndpointDispatcher.EndpointAddress)); } } public class AppFabricE2EBehaviorElement : BehaviorExtensionElement { #region BehaviorExtensionElement /// <summary> /// Gets the type of behavior. /// </summary> /// <value></value> /// <returns>The type that implements the end point behavior<see cref="T:System.Type"/>.</returns> public override Type BehaviorType { get { return typeof(AppFabricE2EEndpointBehavior); } } /// <summary> /// Creates a behavior extension based on the current configuration settings. /// </summary> /// <returns>The behavior extension.</returns> protected override object CreateBehavior() { return new AppFabricE2EEndpointBehavior(); } #endregion BehaviorExtensionElement } public class AppFabricE2EEndpointBehavior : IEndpointBehavior //, IServiceBehavior { #region IEndpointBehavior public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) {} public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime) { throw new NotImplementedException(); } public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher) { endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new AppFabricE2EInspector()); } public void Validate(ServiceEndpoint endpoint) { ; } #endregion IEndpointBehavior } }     [1] http://www.microsoft.com/downloads/details.aspx?FamilyID=35ec8682-d5fd-4bc3-a51a-d8ad115a8792&displaylang=en

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  • Fun with Aggregates

    - by Paul White
    There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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