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  • Selector to select third list item?

    - by Richard Knop
    Suppose a HTML markup like this: <ul> <li>List item 1</li> <li>List item 2</li> <li>List item 3</li><!-- I want to select only this --> </ul> Would it be possible to select only the third list item in the unordered list element? I've been browsing the jQuery documentation but I can't find any selector that could do this.

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  • JQuery Selector - Select this, not that?

    - by JasonS
    Hi, I have created a script which is surprisingly working. (I do not do much JavaScript) What I have is a load of images listed within a div. These images are hidden. JQuery gets the properties of the images and puts them into an array. When the body is clicked, the background image of the page changes. This works nicely. However, I now have a problem. There are several elements which I shouldn't change the background when they are clicked. Namely, navigation, footer and caption. How do I create a selector which makes the body clickable, yet ignores clicks on the above 3 div's?

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  • Jquery taconite selector with character that needs to be escaped

    - by hdx
    I'm using the jquery taconite plugin to make an ajax request that will replace a certain element in my page, however the element has an id like "email.subject".. I can select it just fine if I do '$("email\\.subject")', but when I try to use the taconite plugin like this: <taconite> <replaceWith select="#email\\.subject"> JUCA </replaceWith> </taconite> The plugin log says: [taconite] No matching targets for selector: #email\\.subject How can I make this work?

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  • jQuery selector question

    - by Jakey
    I have a span and an anchor inside a table cell. I have the anchor set up to show a tooltip. I would like the text inside the span to be used for the tooltip. How can I select this text in jQuery? <td class="row-head" colspan="5"><span class="tip-text">Complete Coverage</span><a href="#" class="help"></a></td> JQuery code - the current selector always finds the first instance only for all tips. $(document).ready(function() { $('.help').qtip({ style: { name: 'cream', tip: true }, content: { text: $(this).find('span.tip-text').html() } }); }); Thanks

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  • jQuery li:has(ul) selector issue

    - by sushil bharwani
    I was creating a tree using UL LI list and jQuery. I used a jQuery Selector jQuery(li:has(ul)) to find all the list nodes having childs and then added a click event to it. jQuery(li:has(ul)).click(function(event) { jQuery(this).children.toggle(); jQuery(this).css("cursor","hand"); }); This works for me except i dont understand why i get a cursor hand and click event triggering even when i take mouse pointer to childs of my selected li <li> Parent // it works here that is fine <ul> <li> child1 // it works here i dont understand need explanation </li> <li> child2 // it works here i dont understand need explanation </li> </ul> </li>

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  • Define keyref selector based on element type in XPath

    - by Robert Sirre
    Let's say I have an XML file that will look like this: <a> <b d="value1"/> <c d="value2"/> </a> In the XSD file that defines the structure of this XML file I defined the elements by name 'b' and 'c' to be of the same type (and the type requires attribute 'd'). Let's say that I want to make a keyReference of all elements of the type that both 'b' and 'c' are, is there any way in XPath to do this? At the definition of the type of 'a' I would expect something like this: <xs:keyref name="myReferenceName" refer="keyToReferTo"> <xs:selector xpath="[@type='typenameof elements b and c?']"/> <xs:field xpath="@d"/> </xs:keyref> Is something like this possible, or is XPath, even in the XSD, schema-unaware?

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  • jQuery child selector expression

    - by Saiful
    <div id="div"> <div> <!-- first level --> <div> <!-- second level --> <div>1.1</div> <!-- third level --> <div>1.2</div> </div> <div> <div></div> <div>2.2</div> </div> </div> </div> What are the jQuery selector expressions for selecting the followings: 1. div commented by first level 2. divs commented by second level 3. divs commented by third level

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  • jquery :not selector not working in next() method

    - by Richard
    what is the next best thing to use when you want to select the next li item, but not the one that has someClassName. The not selector returns an empty array! or is this a case off using filter? <li class="first">pickle</> <li class="someClassName">tomato</li> <li>chicken</> <li>cocosnut</> var current = $('ul.items li.first'); var next = current.next(':not(li.someClassName)'); thanks, Richard

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  • unrecognized selector sent to instance

    - by iamsmug
    My app works fine in the simulator but when I run it on my phone I get this error: 2010-04-05 21:32:45.119 Top Banana[119:207] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* -[MethodViewController setReferringObject:]: unrecognized selector sent to instance 0x16e930' It happens here: -(void)method { [UIView beginAnimations:@"View Flip" context:nil]; [UIView setAnimationDuration:0.50]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; [UIView setAnimationTransition: UIViewAnimationTransitionFlipFromRight forView:self.navigationController.view cache:NO]; MethodViewController *methodViewController = [[MethodViewController alloc] initWithNibName:@"MethodViewController" bundle:0]; NSManagedObject *selectedObject = self.referringObject; methodViewController.referringObject = selectedObject; [self.navigationController pushViewController:methodViewController animated:NO]; methodViewController.title = @"Method"; [UIView commitAnimations]; [MethodViewController release]; } It crashes on this line: methodViewController.referringObject = selectedObject; Not sure how to resolve this as it works in the simulator, I'm sure it is fairly basic to fix, any help will be appreciated.

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  • jQuery sibling selector?

    - by Brett
    Hi, I have a table which I'm trying to do a pricing list, that auto-computes the tax component.. I'm getting the value from price_1, applying a math cal, and saving it to tax_1. I could read the number of the end of the id, but hopefully there is a cleaner way with jQuery. E.g. I would have a lot of fields like.. price_1 price_2 price_3 tax_1 tax_2 tax_3 etc... I can use the following code to call jQuery on change of a price, and get the value of that price. How do I update the tax field next to it? should I use a sibling selector or something?? $('#pricing').delegate("input", "change", function(){ $(this).val() /* the value of the price */; })

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  • jQuery basics - selector

    - by rkrauter
    I feel dumb.. Why is my "header" div not being selected? It's background color is not being changed. I am learning about the + operator so I am not looking for a different selector. E + F an F element immediately preceded by an E element $("#divA + div").css("background-color", "red"); Html <div id="divA"> <div> Header</div> Lorem Ipsum is simply dummy text of the printing and typesetting industry. </div> Thanks!

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  • jQuery text attribute selector

    - by Shagglez
    I am trying to use the text attribute as a selector, but I can't quite grasp the behaviour, would really appreciate if someone could explain. For example given <span class="span_class"><a class="a_class">text</a></span>, $('a.a_class').text() gives "text" as expected. However $('a.a_class[text]') wouldn't match any elements, and neither would $('span.span_class > a.a_class[text]'), but $('span.span_class* > a.a_class[text]') would (although not in IE). The only workaround I can think of for IE, is loop through all anchors contained in a span, use .text() on each and match it against a certain criteria, but it seems slower than using in-built selectors. Anyone have better ideas?

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  • turn off disable the performance cache

    - by jessie
    OK I run a streaming website and my CMS is giving me an error when uploading videos "Failed To Find Flength File" ok so I did some research. The answer I got from the coder was below. I did do all that, but the only thing I could not do is turn off what he refers to as performance cache, talked about in the last sentence... I am on a Cent OS Assuming the script is set up properly, you are probably dealing with some kind of write-caching. Some servers perform write-caching which prevents writing out the flength file or the entire CGITemp file during the upload. The flength file or the CGITemp file do not actually hit the disk until the upload is complete, making it worthless for reporting on progress during the upload. This may be fixed using a .htaccess file assuming your host supports them. Here is a link to an excellent tutorial on using .htaccess files. I strongly recommend giving it a quick read before attempting to install your own .htaccess file. 1. A mod_security module for Apache. To fix it just create a file called .htaccess (that's a period followed by "htaccess") and put the following lines in that file. Upload the file into the directory where the Uber-Uploader CGI ".pl" scripts resides, or in some directory above it (like your server's DOCUMENT_ROOT, i.e. the top-level of your webspace). htaccess files must be uploaded as ASCII mode, not BINARY. You may need to CHMOD the htaccess file to 644 or (RW-R--R--). # Turn off mod_security filtering. SecFilterEngine Off # The below probably isn't needed, # but better safe than sorry. SecFilterScanPOST Off If the above method does not work, try putting the following lines into the file SetEnvIfNoCase Content-Type \ "^multipart/form-data;" "MODSEC_NOPOSTBUFFERING=Do not buffer file uploads" mod_gzip_on No 2. "Performance Cache" enabled on OS X SERVER. If you're running OS X Server and the progress bar isn't working, it could be because of "performance caching." Apparently if ANY of your hosted sites are using performance caching, then by default, all sites (domains) will attempt to. The fix then is to disable the performance cache on all hosted sites.

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  • CSS Selector Issue

    - by YsoL8
    Hello html body .home blog logged-in div #wrapper div #page div .cats I have a problem with selecting unordered lists (i.e ul li.class-name class-name-number) at the above dom location in CSS. I am working with a wordpress theme. Basically could I have suggestions for the correct selector to use in order to influence this tag? I can provide a simplified html structure if it will help. I've tried a number of selectors along the lines of: (sometimes)#page (# or .)cats (sometimes)ul li(sometimes with class name) EDIT: I've tried the selectors suggested in the wordpress docs. Thanks!

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  • Quick question about jQuery selector content efficiency

    - by serg
    I am loading HTML page through ajax and then doing a bunch of searches using selectors: $.ajax({ ... dataType: "html", success: function(html) { $("#id1", html); $(".class", html); //... } } Should I extract $(html) into a variable and use it as a content, or it doesn't matter (from performance point)? success: function(html) { $html = $(html); $("#id1", $html); $(".class", $html); //... }

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  • CSS3 selector to find the 2nd div of the same class

    - by mpeters
    I need a CSS selector that can find the 2nd div of 2 that has the same class. I've looked at nth-child() but it's not what I want since I can't see a way to further clarify what class I want. These 2 divs will be siblings in the document if that helps. My HTML looks something like this: <div class="foo">...</div> <div class="bar">...</div> <div class="baz">...</div> <div class="bar">...</div> And I want the 2nd div.bar (or the last div.bar would work too).

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  • jQuery selector - style values

    - by kender
    I got a series of divs like this: <div class="message" style="padding-left: 0px;">...</div> <div class="message" style="padding-left: 20px;">...</div> <div class="message" style="padding-left: 20px;">...</div> <div class="message" style="padding-left: 40px;">...</div> <div class="message" style="padding-left: 20px;">...</div> And I would like to make a selector that would get me the divs with padding greater then 20px. Would it be possible with just using jquery? Or I should modify my html tree and add some attribute that would distinguish those elemenents with high padding value?

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  • Is a selector like *+* safe to use?

    - by mcmullins
    I recently came across this CSS selector while trying to find a way to easily space out major blog elements such as paragraphs and images. An example of its use would be something like this: .post *+* {margin-top: 15px;} /* or... */ .post > *+* {margin-top: 15px;} /* if you don't want the margin to apply to nested elements */ At first glance, it seemed pretty useful. So my question is: What downsides are there to using these selectors? Specifically: What's the browser support like for this? Are there any cases you wouldn't want an even margin spacing between elements in an article and if not, is it easier to declare this first and then overwrite or simply declare each element individually? Does this have performance issues since you're selecting everything twice?

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  • Select lowest nested selector when clicked

    - by rikAtee
    I would like to click $('.sub-menu') selector and return the lowerst nested item that was clicked, rather than the highest. e.g., when I click "enlish", "root" is returned becasue "english" is a child of "root". I want "english" returned when I select "english". <div ID="browse_container"> <div class="sub-menu">Root <div class="sub-menu">English</div> <div class="sub-menu">Maths <div class="sub-menu">Year 1</div> <div class="sub-menu">Year 2</div> </div> <div class="sub-menu">? Science</div> </div> </div> my script is simply: $('.sub-menu, #root').on('click', function(event){ alert($(this).text()) });

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  • why my test performance class gives me inconsistent results even after proper warm-up?

    - by colinfang
    i made a class which helps me measure time for any methods in Ticks. Basically, it runs testing method 100x, and force GC, then it records time taken for another 100x method runs. x64 release ctrl+f5 VS2012/VS2010 the results are following: 2,914 2,909 2,913 2,909 2,908 2,907 2,909 2,998 2,976 2,855 2,446 2,415 2,435 2,401 2,402 2,402 2,399 2,401 2,401 2,400 2,399 2,400 2,404 2,402 2,401 2,399 2,400 2,402 2,404 2,403 2,401 2,403 2,401 2,400 2,399 2,414 2,405 2,401 2,407 2,399 2,401 2,402 2,401 2,404 2,401 2,404 2,405 2,368 1,577 1,579 1,626 1,578 1,576 1,578 1,577 1,577 1,576 1,578 1,576 1,578 1,577 1,578 1,576 1,578 1,577 1,579 1,585 1,576 1,579 1,577 1,579 1,578 1,579 1,577 1,578 1,577 1,578 1,576 1,578 1,577 1,578 1,599 1,579 1,578 1,582 1,576 1,578 1,576 1,579 1,577 1,578 1,577 1,591 1,577 1,578 1,578 1,576 1,578 1,576 1,578 As you can see there are 3 phases, first is ~2,900, second is ~2,400, then ~1,550 What might be the reason to cause it? the test performance class code follows: public static void RunTests(Func<long> myTest) { const int numTrials = 100; Stopwatch sw = new Stopwatch(); double[] sample = new double[numTrials]; Console.WriteLine("Checksum is {0:N0}", myTest()); sw.Start(); myTest(); sw.Stop(); Console.WriteLine("Estimated time per test is {0:N0} ticks\n", sw.ElapsedTicks); for (int i = 0; i < numTrials; i++) { myTest(); } GC.Collect(); string testName = myTest.Method.Name; Console.WriteLine("----> Starting benchmark {0}\n", myTest.Method.Name); for (int i = 0; i < numTrials; i++) { sw.Restart(); myTest(); sw.Stop(); sample[i] = sw.ElapsedTicks; } double testResult = DataSetAnalysis.Report(sample); for (int j = 0; j < numTrials; j = j + 5) Console.WriteLine("{0,8:N0} {1,8:N0} {2,8:N0} {3,8:N0} {4,8:N0}", sample[j], sample[j + 1], sample[j + 2], sample[j + 3], sample[j + 4]); Console.WriteLine("\n----> End of benchmark"); }

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  • jquery selector for td in a table

    - by ooo
    i want to get a event that will fire when i click inside a td of a html table i had this: ('td').live('click', function() { alert($(this).attr('id')); }); which works but this fires inside the 'th" cells as well (not sure why). is there any selector that just fires inside td's and not th's. I tried this: ('tbody td').live('click', function() { alert($(this).attr('id')); }); but that didn't seems to stop this firing for the th's.

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  • css selector on IE

    - by user121196
    I'm using .class1.class2 .class3 selector, works fine in FF, but on IE7, it doesn't work. In the css below, the second style is always shown in IE. any solution? <STYLE type="text/css"> .test1.test2 .test3{ width:90px; height:100px; } .test4.test2 .test3{ width:900px; height:100px; } </style> <div class="test1 test2"> <button value="test" class="test3"/> </div>

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  • Web Site Performance and Assembly Versioning – Part 2 Versioning Combined Files Using Subversion

    - by capgpilk
    Ok so it took a while to post this second part. Many apologies, we had a big roll out of a new platform at work and many things had to get sidelined. So this is the second part in a short series of website performance and using versioning to help improve it. Minification and Concatination of JavaScript and CSS Files Versioning Combined Files Using Subversion – this post Versioning Combined Files Using Mercurial – published shortly In the previous post we used AjaxMin to shrink js and css files then concatenated them into one file each which had the file name of site-script.combined.min.js and site-style.combined.min.css. These file names are fine, but you can configure IIS 7 to cache these static files and so lower the amount of data transferred between server and client. This is done by editing the response headers in IIS. 1. In IIS7 Manager, choose the directory where these files are located and select HTTP Response Headers. 2. Check the Expire Web Content and set a time period well into the future. 3. When refreshing the web page, the server will respond with HTTP 304 forcing the browser to retrieve the file from its cache. 4. As can be seen in FireBug, the Cache-Control header has a max age of 31536000 seconds which equates to 365 days.   The server will always send this HTTP 304 message unless the file changes forcing it to send new content. To help force this we can change the file name based on the latest build using the SVN revision number in the filename. So we have lowered data transfer on content that hasn’t changed, but forced it to be sent when you have made a change to the css or js files. Now to get the SVN revision number in to the file name. 1. Import the MSBuildCommunityTasks targets which can be dowloaded from here. 1: <Import Project="$(MSBuildExtensionsPath) 2: \MSBuildCommunityTasks 3: \MSBuild.Community.Tasks.Targets" /> 2. Edit the BeforeBuild target to call out to svn and get the latest revision 1: <SvnVersion LocalPath="$(MSBuildProjectDirectory)" 2: ToolPath="$(ProgramFiles)\VisualSVN Server\bin"> 3: <Output TaskParameter="Revision" PropertyName="Revision" /> 4: </SvnVersion> 3. Set it to update the project AssemblyInfo.cs file for the svn revision. 1: <FileUpdate Files="Properties\AssemblyInfo.cs" 2: Regex="(\d+)\.(\d+)\.(\d+)\.(\d+)" 3: ReplacementText="$1.$2.$3.$(Revision)" /> 4. Now edit the AfterBuild target to get the full dll version. You could combine these two steps and just get the version from svn, I am working on one project that updates the AssemblyInfo file and another project that allows manual editing of the file, but needs that version within the file name; so I just combined the two for this post. 1: <MSBuild.ExtensionPack.Framework.Assembly 2: TaskAction="GetInfo" 3: NetAssembly="$(OutputPath)\mydll.dll"> 4: <Output TaskParameter="OutputItems" ItemName="Info" /> 5: </MSBuild.ExtensionPack.Framework.Assembly> 6: <Message Text="Version: %(Info.AssemblyVersion)" 7: Importance="High" /> 5. Use this Info.AssemblyVersion to write out the combined css and js files as described in the last post. 1: <WriteLinestoFile File="Scripts\site-%(Info.AssemblyVersion).combined.min.js" 2: Lines="@(JSLinesSite)" Overwrite="true" />   In the next post I will cover doing the same, but for a Mercurial repository.

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  • quick look at: dm_db_index_physical_stats

    - by fatherjack
    A quick look at the key data from this dmv that can help a DBA keep databases performing well and systems online as the users need them. When the dynamic management views relating to index statistics became available in SQL Server 2005 there was much hype about how they can help a DBA keep their servers running in better health than ever before. This particular view gives an insight into the physical health of the indexes present in a database. Whether they are use or unused, complete or missing some columns is irrelevant, this is simply the physical stats of all indexes; disabled indexes are ignored however. In it’s simplest form this dmv can be executed as:   The results from executing this contain a record for every index in every database but some of the columns will be NULL. The first parameter is there so that you can specify which database you want to gather index details on, rather than scan every database. Simply specifying DB_ID() in place of the first NULL achieves this. In order to avoid the NULLS, or more accurately, in order to choose when to have the NULLS you need to specify a value for the last parameter. It takes one of 4 values – DEFAULT, ‘SAMPLED’, ‘LIMITED’ or ‘DETAILED’. If you execute the dmv with each of these values you can see some interesting details in the times taken to complete each step. DECLARE @Start DATETIME DECLARE @First DATETIME DECLARE @Second DATETIME DECLARE @Third DATETIME DECLARE @Finish DATETIME SET @Start = GETDATE() SELECT * FROM [sys].[dm_db_index_physical_stats](DB_ID(), NULL, NULL, NULL, DEFAULT) AS ddips SET @First = GETDATE() SELECT * FROM [sys].[dm_db_index_physical_stats](DB_ID(), NULL, NULL, NULL, 'SAMPLED') AS ddips SET @Second = GETDATE() SELECT * FROM [sys].[dm_db_index_physical_stats](DB_ID(), NULL, NULL, NULL, 'LIMITED') AS ddips SET @Third = GETDATE() SELECT * FROM [sys].[dm_db_index_physical_stats](DB_ID(), NULL, NULL, NULL, 'DETAILED') AS ddips SET @Finish = GETDATE() SELECT DATEDIFF(ms, @Start, @First) AS [DEFAULT] , DATEDIFF(ms, @First, @Second) AS [SAMPLED] , DATEDIFF(ms, @Second, @Third) AS [LIMITED] , DATEDIFF(ms, @Third, @Finish) AS [DETAILED] Running this code will give you 4 result sets; DEFAULT will have 12 columns full of data and then NULLS in the remainder. SAMPLED will have 21 columns full of data. LIMITED will have 12 columns of data and the NULLS in the remainder. DETAILED will have 21 columns full of data. So, from this we can deduce that the DEFAULT value (the same one that is also applied when you query the view using a NULL parameter) is the same as using LIMITED. Viewing the final result set has some details that are worth noting: Running queries against this view takes significantly longer when using the SAMPLED and DETAILED values in the last parameter. The duration of the query is directly related to the size of the database you are working in so be careful running this on big databases unless you have tried it on a test server first. Let’s look at the data we get back with the DEFAULT value first of all and then progress to the extra information later. We know that the first parameter that we supply has to be a database id and for the purposes of this blog we will be providing that value with the DB_ID function. We could just as easily put a fixed value in there or a function such as DB_ID (‘AnyDatabaseName’). The first columns we get back are database_id and object_id. These are pretty explanatory and we can wrap those in some code to make things a little easier to read: SELECT DB_NAME([ddips].[database_id]) AS [DatabaseName] , OBJECT_NAME([ddips].[object_id]) AS [TableName] … FROM [sys].[dm_db_index_physical_stats](DB_ID(), NULL, NULL, NULL, NULL) AS ddips  gives us   SELECT DB_NAME([ddips].[database_id]) AS [DatabaseName] , OBJECT_NAME([ddips].[object_id]) AS [TableName], [i].[name] AS [IndexName] , ….. FROM [sys].[dm_db_index_physical_stats](DB_ID(), NULL, NULL, NULL, NULL) AS ddips INNER JOIN [sys].[indexes] AS i ON [ddips].[index_id] = [i].[index_id] AND [ddips].[object_id] = [i].[object_id]     These handily tie in with the next parameters in the query on the dmv. If you specify an object_id and an index_id in these then you get results limited to either the table or the specific index. Once again we can place a  function in here to make it easier to work with a specific table. eg. SELECT * FROM [sys].[dm_db_index_physical_stats] (DB_ID(), OBJECT_ID(‘AdventureWorks2008.Person.Address’) , 1, NULL, NULL) AS ddips   Note: Despite me showing that functions can be placed directly in the parameters for this dmv, best practice recommends that functions are not used directly in the function as it is possible that they will fail to return a valid object ID. To be certain of not passing invalid values to this function, and therefore setting an automated process off on the wrong path, declare variables for the OBJECT_IDs and once they have been validated, use them in the function: DECLARE @db_id SMALLINT; DECLARE @object_id INT; SET @db_id = DB_ID(N’AdventureWorks_2008′); SET @object_id = OBJECT_ID(N’AdventureWorks_2008.Person.Address’); IF @db_id IS NULL BEGINPRINT N’Invalid database’; ENDELSE IF @object_id IS NULL BEGINPRINT N’Invalid object’; ENDELSE BEGINSELECT * FROM sys.dm_db_index_physical_stats (@db_id, @object_id, NULL, NULL , ‘LIMITED’); END; GO In cases where the results of querying this dmv don’t have any effect on other processes (i.e. simply viewing the results in the SSMS results area)  then it will be noticed when the results are not consistent with the expected results and in the case of this blog this is the method I have used. So, now we can relate the values in these columns to something that we recognise in the database lets see what those other values in the dmv are all about. The next columns are: We’ll skip partition_number, index_type_desc, alloc_unit_type_desc, index_depth and index_level  as this is a quick look at the dmv and they are pretty self explanatory. The final columns revealed by querying this view in the DEFAULT mode are avg_fragmentation_in_percent. This is the amount that the index is logically fragmented. It will show NULL when the dmv is queried in SAMPLED mode. fragment_count. The number of pieces that the index is broken into. It will show NULL when the dmv is queried in SAMPLED mode. avg_fragment_size_in_pages. The average size, in pages, of a single fragment in the leaf level of the IN_ROW_DATA allocation unit. It will show NULL when the dmv is queried in SAMPLED mode. page_count. Total number of index or data pages in use. OK, so what does this give us? Well, there is an obvious correlation between fragment_count, page_count and avg_fragment_size-in_pages. We see that an index that takes up 27 pages and is in 3 fragments has an average fragment size of 9 pages (27/3=9). This means that for this index there are 3 separate places on the hard disk that SQL Server needs to locate and access to gather the data when it is requested by a DML query. If this index was bigger than 72KB then having it’s data in 3 pieces might not be too big an issue as each piece would have a significant piece of data to read and the speed of access would not be too poor. If the number of fragments increases then obviously the amount of data in each piece decreases and that means the amount of work for the disks to do in order to retrieve the data to satisfy the query increases and this would start to decrease performance. This information can be useful to keep in mind when considering the value in the avg_fragmentation_in_percent column. This is arrived at by an internal algorithm that gives a value to the logical fragmentation of the index taking into account the multiple files, type of allocation unit and the previously mentioned characteristics if index size (page_count) and fragment_count. Seeing an index with a high avg_fragmentation_in_percent value will be a call to action for a DBA that is investigating performance issues. It is possible that tables will have indexes that suffer from rapid increases in fragmentation as part of normal daily business and that regular defragmentation work will be needed to keep it in good order. In other cases indexes will rarely become fragmented and therefore not need rebuilding from one end of the year to another. Keeping this in mind DBAs need to use an ‘intelligent’ process that assesses key characteristics of an index and decides on the best, if any, defragmentation method to apply should be used. There is a simple example of this in the sample code found in the Books OnLine content for this dmv, in example D. There are also a couple of very popular solutions created by SQL Server MVPs Michelle Ufford and Ola Hallengren which I would wholly recommend that you review for much further detail on how to care for your SQL Server indexes. Right, let’s get back on track then. Querying the dmv with the fifth parameter value as ‘DETAILED’ takes longer because it goes through the index and refreshes all data from every level of the index. As this blog is only a quick look a we are going to skate right past ghost_record_count and version_ghost_record_count and discuss avg_page_space_used_in_percent, record_count, min_record_size_in_bytes, max_record_size_in_bytes and avg_record_size_in_bytes. We can see from the details below that there is a correlation between the columns marked. Column 1 (Page_Count) is the number of 8KB pages used by the index, column 2 is how full each page is (how much of the 8KB has actual data written on it), column 3 is how many records are recorded in the index and column 4 is the average size of each record. This approximates to: ((Col1*8) * 1024*(Col2/100))/Col3 = Col4*. avg_page_space_used_in_percent is an important column to review as this indicates how much of the disk that has been given over to the storage of the index actually has data on it. This value is affected by the value given for the FILL_FACTOR parameter when creating an index. avg_record_size_in_bytes is important as you can use it to get an idea of how many records are in each page and therefore in each fragment, thus reinforcing how important it is to keep fragmentation under control. min_record_size_in_bytes and max_record_size_in_bytes are exactly as their names set them out to be. A detail of the smallest and largest records in the index. Purely offered as a guide to the DBA to better understand the storage practices taking place. So, keeping an eye on avg_fragmentation_in_percent will ensure that your indexes are helping data access processes take place as efficiently as possible. Where fragmentation recurs frequently then potentially the DBA should consider; the fill_factor of the index in order to leave space at the leaf level so that new records can be inserted without causing fragmentation so rapidly. the columns used in the index should be analysed to avoid new records needing to be inserted in the middle of the index but rather always be added to the end. * – it’s approximate as there are many factors associated with things like the type of data and other database settings that affect this slightly.  Another great resource for working with SQL Server DMVs is Performance Tuning with SQL Server Dynamic Management Views by Louis Davidson and Tim Ford – a free ebook or paperback from Simple Talk. Disclaimer – Jonathan is a Friend of Red Gate and as such, whenever they are discussed, will have a generally positive disposition towards Red Gate tools. Other tools are often available and you should always try others before you come back and buy the Red Gate ones. All code in this blog is provided “as is” and no guarantee, warranty or accuracy is applicable or inferred, run the code on a test server and be sure to understand it before you run it on a server that means a lot to you or your manager.

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  • SQL SERVER – SQL Server Misconceptions and Resolution – A Practical Perspective – TechEd 2012 India

    - by pinaldave
    TechEd India 2012 is just around the corner and I will be presenting there in two different sessions. On the very first day of this event, my presentation will be all about SQL Server Misconceptions and Resolution – A Practical Perspective. The dictionary tells us that a “misconception” means a view or opinion that is incorrect and is based on faulty thinking or understanding. In SQL Server, there are so many misconceptions. In fact, when I hear some of these misconceptions, I feel like fainting at that very moment! Seriously, at one time, I came across the scenario where instead of using INSERT INTO…SELECT, the developer used CURSOR believing that cursor is faster (duh!). Here is the link the blog post related to this. Pinal and Vinod in 2009 I have been presenting in TechEd India for last three years. This is my fourth opportunity to present a technical session on SQL Server. Just like the previous years, I decided to present something different. Here is a novelty of this year: I will be presenting this session with Vinod Kumar. Vinod Kumar and I have a great synergy when we work together. So far, we have written one SQL Server Interview Questions and Answers book and 2 video courses: (1) SQL Server Questions and Answers (2) SQL Server Performance: Indexing Basics. Pinal and Vinod in 2011 When we sat together and started building an outline for this course, we had many options in mind for this tango session. However, we have decided that we will make this session as lively as possible while keeping it natural at the same time. We know our flow and we know our conversation highlight, but we do not know what exactly each of us is going to present. We have decided to challenge each other on stage and push each other’s knowledge to the verge. We promise that the session will be entertaining with lots of SQL Server trivia, tips and tricks. Here are the challenges that I’ll take on: I will puzzle Vinod with my difficult questions I will present such misconception that Vinod will have no resolution for it. I need your help.  Will you help me stump Vinod? If yes, come and attend our session and join me to prove that together we are superior (a friendly brain clash, but we must win!). SQL Server enthusiasts and SQL Server fans are going to have gala time at #TechEdIn as we have a very solid lineup of the speaker and extremely interesting sessions at TechEdIn. Read the complete blog post of Vinod. Session Details Title: SQL Server Misconceptions and Resolution – A Practical Perspective (Add to Calendar) Abstract: “Earth is flat”! – An ancient common misconception, which has been proven incorrect as we progressed in modern times. In this session we will see various database misconceptions prevailing and their resolution with the aid of the demos. In this unique session audience will be part of the conversation and resolution. Date and Time: March 21, 2012, 15:15 to 16:15 Location: Hotel Lalit Ashok - Kumara Krupa High Grounds, Bengaluru – 560001, Karnataka, India. Add to Calendar Please submit your questions in the comments area and I will be for sure discussing them during my session. If I pick your question to discuss during my session, here is your gift I commit right now – SQL Server Interview Questions and Answers Book. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Interview Questions and Answers, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: TechEd, TechEdIn

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