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  • Big Data Learning Resources

    - by Lara Rubbelke
    I have recently had several requests from people asking for resources to learn about Big Data and Hadoop. Below is a list of resources that I typically recommend. I'll update this list as I find more resources. Let's crowdsource this... Tell me your favorite resources and I'll get them on the list! Books and Whitepapers Planning for Big Data Free e-book Great primer on the general Big Data space. This is always my recommendation for people who are new to Big Data and are trying to understand it....(read more)

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  • Speaking this week at Richmond SQL Server User Group

    - by drsql
    Thursday night, at 6:00 (or so) I will be speaking in Richmond ( http://richmondsql.org/cs2007/ ), talking about How to Implement a Hierarchy using SQL Server. The abstract is: One of the most common structures you will come across in the real world is a hierarchy (either a single parent "tree" or a multi-parent "graph"). Many systems will implement the obvious examples, such as a corporate managerial structure or a bill of materials. It turns out that almost any many-to-many relationship can be...(read more)

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  • Cloud Computing: Start with the problem

    - by BuckWoody
    At one point in my life I would build my own computing system for home use. I wanted a particular video card, a certain set of drives, and a lot of memory. Not only could I not find those things in a vendor’s pre-built computer, but those were more expensive – by a lot. As time moved on and the computing industry matured, I actually find that I can buy a vendor’s system as cheaply – and in some cases far more cheaply – than I can build it myself.   This paradigm holds true for almost any product, even clothing and furniture. And it’s also held true for software… Mostly. If you need an office productivity package, you simply buy one or use open-sourced software for that. There’s really no need to write your own Word Processor – it’s kind of been done a thousand times over. Even if you need a full system for customer relationship management or other needs, you simply buy one. But there is no “cloud solution in a box”.  Sure, if you’re after “Software as a Service” – type solutions, like being able to process video (Windows Azure Media Services) or running a Pig or Hive job in Hadoop (Hadoop on Windows Azure) you can simply use one of those, or if you just want to deploy a Virtual Machine (Windows Azure Virtual Machines) you can get that, but if you’re looking for a solution to a problem your organization has, you may need to mix Software, Infrastructure, and perhaps even Platforms (such as Windows Azure Computing) to solve the issue. It’s all about starting from the problem-end first. We’ve become so accustomed to looking for a box of software that will solve the problem, that we often start with the solution and try to fit it to the problem, rather than the other way around.  When I talk with my fellow architects at other companies, one of the hardest things to get them to do is to ignore the technology for a moment and describe what the issues are. It’s interesting to monitor the conversation and watch how many times we deviate from the problem into the solution. So, in your work today, try a little experiment: watch how many times you go after a problem by starting with the solution. Tomorrow, make a conscious effort to reverse that. You might be surprised at the results.

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  • links for 2011-01-31

    - by Bob Rhubart
    Do (Software) Architects Architect? "The first question, is 'Why is architect being used as a verb?' Mirriam-Webster dictionary does not contain a definition of architect as a verb, nor do many other recognized dictionaries." -- TheCPUWizard (tags: softwarearchitecture) Oracle Business Intelligence Blog: Gartner Magic Quadrant for BI Platforms 2011 "Oracle customers indicate they deploy the Oracle Business Intelligence Suite Enterprise Edition (OBIEE) platform to support among the most complex deployments in our survey." - Gartner (tags: oracle businessintelligence gartner) Oracle BI Server Modeling, Part 1- Designing a Query Factory (Oracle BI Foundation) Bob Ertl lays the groundwork for Business Intelligence modeling concepts with a look at "the big picture of how the BI Server fits into the system, and how the CEIM controls the query processing." (tags: oracle otn businessintelligence) Tom Graves: Modelling people in enterprise-architecture Tom says: "One of the key characteristics of ‘crossing the chasm’ to a viable whole-of-enterprise architecture is the explicit inclusion of people. In short, we need to be able to model and map where people fit in relation to the architecture. But there’s a catch. A big catch." (tags: entarch) Java developer webcasts for customers and partners (SOA Partner Community Blog) Jurgen Kress shares info on several upcoming online events focused on WebLogic. (tags: weblogic oracle otn soa) Business SOA: Data Services are bogus, Information services are real Steve Jones says: "The other day when I was talking about MDM a bright spark pointed out that I hated data services but wasn't MDM just about data services?" (tags: SOA MDM) Andrejus Baranovskis's Blog: Configuring Missing Contribution Folders for Oracle UCM 11g and WebCenter 11g PS3 Andrejus says: "After doing some research on UCM, we found that Folders_g component must be configured in UCM, for Contribution Folders to be enabled." (tags: oracle otn oracleace UCM webcenter enterprise2.0) Wim Coekaerts: Converting an Oracle VM VirtualBox VM into an Oracle VM Server image Wim Coekaerts offers a few simple steps to convert an existing Oracle VM VirtualBox image.  (tags: oracle otn virtualization virtualbox) Stefan Hinker: Secure Deployment of Oracle VM Server for SPARC This new paper from Stefan Hinker will help you understand the general security concerns in virtualized environments as well as the specific additional threats that arise out of them. (tags: oracle otn SPARC virtualization enterprisearchitecture) The EA Roadmap to Rationalize, Standardize, and Consolidate the IT Portfolio Enterprise IT is in a state of constant evolution. As a result, business processes and technologies become increasingly more difficult to change and more costly to keep up-to-date. (tags: entarch oracle otn)

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  • [OT] Gates Millenium Scholars scholarship program

    - by John Paul Cook
    Here's a notice about scholarship opportunities that many students may miss because of being out for the holidays. If you know a bright, deserving student, please alert him or her to this outstanding scholarship opportunity. Here is what I want for Christmas from you, my readers. I want to see LOTS of comments about how you informed a student about this scholarship or otherwise got the word out. Dear Student, The Bill & Melinda Gates Foundation proudly announces the 2011 Gates Millennium Scholars...(read more)

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  • SQL Saturday #274 Slovenia

    - by Dejan Sarka
    Yes, here it is SQL Saturday #274 is coming to Slovenia (#sqlsatSlovenia). The event will take place on Saturday, December 21st, at company pixi* labs, Informacijske tehnologije, d.o.o. Poslovna cona A 2 SI-4208 Šencur This company generously offered to host the event. We, the whole Slovenian SQL Server community, are very grateful for this. At this time, a call for speakers went out, and we are already getting the first proposals. We are especially happy that we will get possibility to show the foreign speakers how beautiful Slovenia and especially the capital Ljubljana is in December. Expect a lot of partying right on the streets, no matter of weather. Be prepared, we have slightly weird customs when it comes to drinks. For example, our regular special discount offer is not three drinks for the price of two; it is six drinks for the price of five. If you are a speaker or want to become one, consider sending a proposal. Since most of the sessions will be held in English and you don’t want to speak, consider coming as a visitor as well. Or maybe you would be interested to become a sponsor. Although we are targeting a low budgeted event, any kind of sponsorship is very welcome. Please feel free to contact the organizers if you are interested to become a sponsor: Matija Lah – [email protected], Mladen Prajdic - [email protected], or Dejan Sarka  - [email protected]. Looking forward to see you all!

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  • When the obvious answer is obviously wrong

    - by John Paul Cook
    This post is about how simple math in T-SQL can produce undesirable results, but first we begin with a math quiz. Answer the following as quickly as possible: You just read pages 100-300 of a book. How many pages did you read? QUICKLY NOW! For those of you who answered 200 pages, I have a new question: Which page did you not read? There were 201 pages to read. If you read 200 pages, you skipped a page! What your answer be if I asked you how many pages did you read if you read pages 1-3? Three pages!...(read more)

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  • MDW Reports–New Source Code ZIP File Available

    - by billramo
    In my MDW Reports series, I attached V1 of the RDL files in my post - May the source be with you! MDW Report Series Part 6–The Final Edition. Since that post, Rachna Agarwal from MSIT in India updated the RDL files that are ready to go in a single ZIP. The reports assume that they will ne uploaded to the Report Manager’s root folder and use a shared data source named MDW. The reports also integrate with the new Query Hash Statistics reports. You can download them from my SQLBlog.com download site.

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  • SQLSaturday #69 - Philly Love

    - by Mike C
    Thanks to the Philly SQL Server User Group (PSSUG) and to everyone who attended SQLSaturday #69 in the City of Brotherly Love yesterday. It was a great event with a lot of great people. My presentations are available for download at the links below: http://www.sqlsaturday.com/viewsession.aspx?sat=69&sessionid=3333 http://www.sqlsaturday.com/viewsession.aspx?sat=69&sessionid=3334 I just went through my speaker evaluations, and I'm happy to report the response was pretty positive across the...(read more)

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  • What permissions are required for SET IDENTITY_INSERT ON?

    - by AaronBertrand
    SQL Server 2000's SET IDENTITY_INSERT ON topic says: Execute permissions default to the sysadmin fixed server role, and the db_owner and db_ddladmin fixed database roles, and the object owner. While the SET IDENTITY_INSERT topic for SQL Server 2005 (and up) says: User must own the object, or be a member of the sysadmin fixed server role, or the db_owner and db_ddladmin fixed database roles. This was clearly adapted from the 2000 books online and re-written by someone who misinterpreted "db_owner...(read more)

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  • Installing Microsoft Atlanta

    - by John Paul Cook
    Since my previous post on Microsoft Atlanta, I've been asked how someone can get started with it. Go to https://www.microsoftatlanta.com/ and click the Create Account button using a Windows Live id such as a Hotmail account. If you don’t have Silverlight installed, you’ll be prompted to install it somewhere along the way. I encourage you to install Atlanta and try it out. The product is still being developed and your early feedback can make a difference. When you click Download Registration Certificate...(read more)

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  • FIX: A network error occurred during SQL Server Native Client installation

    - by Greg Low
    One of the things that I have been pestering the SQL team to do is to name their updates according to what is contained in them. For example, instead of just: sqlncli.msi What I'd prefer is that the file was called something like: SQLServerNativeClient2k8SP1CU3x64.msi So I normally rename them as soon as I receive them, to avoid confusion in future. However, today I found that doing so caused me a problem. After renaming the file, and installing it, the installation failed with the error: " A network...(read more)

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  • SQL Server 2008 R2: StreamInsight changes at RTM: Count Windows

    - by Greg Low
    Another interesting change in the RTM version of StreamInsight is the addition of a new window type. Count Windows aren't time based but are based on counting a number of events. The window type provided in this release is called CountByStartTimeWindow. Based on that name, you'd have to presume we might get other types of count windows in the future. This new window type takes two parameters. The first is the number of events. The second is an output policy, similar to the policies now required for...(read more)

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  • Updatable columnstore index, sp_spaceused and sys.partitions

    - by Michael Zilberstein
    Columnstore index in SQL Server 2014 contains 2 new important features: it can be clustered and it is updateable. So I decided to play with both. As a “control group” I’ve taken my old columnstore index demo from one of the ISUG (Israeli SQL Server Usergroup) sessions. The script itself isn’t important – it creates partition function with 7 partitions (actually 8 but one remains empty), table on it and populates the table with 63 million rows – 9 million in each partition. So I used the same script...(read more)

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  • SQLPass NomCom election: Why I voted twice

    - by Hugo Kornelis
    Did you already cast your votes for the SQLPass NomCom election ? If not, you really should! Your vote can make a difference, so don’t let it go to waste. The NomCom is the group of people that prepares the elections for the SQLPass Board of Directors. With the current election procedures, their opinion carries a lot of weight. They can reject applications, and the order in which they present candidates can be considered a voting advice. So use care when casting your votes – you are giving a lot...(read more)

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  • WUXGA revisited

    - by John Paul Cook
    I previously blogged about my search for a 17” 1920x1200 laptop. The only one I could find was a 17” MacBook Pro, which has been an excellent machine for running Windows and SQL Server. It is no longer made. Apple has a few refurbished ones available. Just be sure to get a matte display if you buy one. If you want WUXGA resolution or better in a laptop, your only off the shelf option is now the 15” MacBook Pro with the Retina display, which is 2880x1800. This exceeds the resolution of my 30” 2560x1600...(read more)

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  • Extracting GPS Data from JPG files

    - by Peter W. DeBetta
    I have been very remiss in posting lately. Unfortunately, much of what I do now involves client work that I cannot post. Fortunately, someone asked me how he could get a formatted list (e.g. tab-delimited) of files with GPS data from those files. He also added the constraint that this could not be a new piece of software (company security) and had to be scriptable. I did some searching around, and found some techniques for extracting GPS data, but was unable to find a complete solution. So, I did...(read more)

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  • Using SPServices &amp; jQuery to Find My Stuff from Multi-Select Person/Group Field

    - by Mark Rackley
    Okay… quick blog post for all you SPServices fans out there. I needed to quickly write a script that would return all the tasks currently assigned to me.  I also wanted it to return any task that was assigned to a group I belong to. This can actually be done with a CAML query, so no big deal, right?  The rub is that the “assigned to” field is a multi-select person or group field. As far as I know (and I actually know so little) you cannot just write a CAML query to return this information. If you can, please leave a comment below and disregard the rest of this blog post… So… what’s a hacker to do? As always, I break things down to their most simple components (I really love the KISS principle and would get it tattooed on my back if people wouldn’t think it meant “Knights In Satan’s Service”. You really gotta be an old far to get that reference).  Here’s what we’re going to do: Get currently logged in user’s name as it is stored in a person field Find all the SharePoint groups the current user belongs to Retrieve a set of assigned tasks from the task list and then find those that are assigned to current  user or group current user belongs to Nothing too hairy… So let’s get started Some Caveats before I continue There are some obvious performance implications with this solution as I make a total of four SPServices calls and there’s a lot of looping going on. Also, the CAML query in this blog has NOT been optimized. If you move forward with this code, tweak it so that it returns a further subset of data or you will see horrible performance if you have a few hundred entries in your task list. Add a date range to the CAML or something. Find some way to limit the results as much as possible. Lastly, if you DO have a better solution, I would like you to share. Iron sharpens iron and all…   Alright, let’s really get started. Get currently logged in user’s name as it is stored in a person field First thing we need to do is understand how a person group looks when you look at the XML returned from a SharePoint Web Service call. It turns out it’s stored like any other multi select item in SharePoint which is <id>;#<value> and when you assign a person to that field the <value> equals the person’s name “Mark Rackley” in my case. This is for Windows Authentication, I would expect this to be different in FBA, but I’m not using FBA. If you want to know what it looks like with FBA you can use the code in this blog and strategically place an alert to see the value.  Anyway… I need to find the name of the user who is currently logged in as it is stored in the person field. This turns out to be one SPServices call: var userName = $().SPServices.SPGetCurrentUser({                     fieldName: "Title",                     debug: false                     }); As you can see, the “Title” field has the information we need. I suspect (although again, I haven’t tried) that the Title field also contains the user’s name as we need it if I was using FBA. Okay… last thing we need to do is store our users name in an array for processing later: myGroups = new Array(); myGroups.push(userName); Find all the SharePoint groups the current user belongs to Now for the groups. How are groups returned in that XML stream?  Same as the person <ID>;#<Group Name>, and if it’s a mutli select it’s all returned in one big long string “<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>”.  So, how do we find all the groups the current user belongs to? This is also a simple SPServices call. Using the “GetGroupCollectionFromUser” operation we can find all the groups a user belongs to. So, let’s execute this method and store all our groups. $().SPServices({       operation: "GetGroupCollectionFromUser",       userLoginName: $().SPServices.SPGetCurrentUser(),       async: false,       completefunc: function(xData, Status) {          $(xData.responseXML).find("[nodeName=Group]").each(function() {                 myGroups.push($(this).attr("Name"));          });         }     }); So, all we did in the above code was execute the “GetGroupCollectionFromUser” operation and look for the each “Group” node (row) and store the name for each group in our array that we put the user’s name in previously (myGroups). Now we have an array that contains the current user’s name as it will appear in the person field XML and  all the groups the current user belongs to. The Rest Now comes the easy part for all of you familiar with SPServices. We are going to retrieve our tasks from the Task list using “GetListItems” and look at each entry to see if it belongs to this person. If it does belong to this person we are going to store it for later processing. That code looks something like this: // get list of assigned tasks that aren't closed... *modify the CAML to perform better!*             $().SPServices({                   operation: "GetListItems",                   async: false,                   listName: "Tasks",                   CAMLViewFields: "<ViewFields>" +                             "<FieldRef Name='AssignedTo' />" +                             "<FieldRef Name='Title' />" +                             "<FieldRef Name='StartDate' />" +                             "<FieldRef Name='EndDate' />" +                             "<FieldRef Name='Status' />" +                             "</ViewFields>",                   CAMLQuery: "<Query><Where><And><IsNotNull><FieldRef Name='AssignedTo'/></IsNotNull><Neq><FieldRef Name='Status'/><Value Type='Text'>Completed</Value></Neq></And></Where></Query>",                     completefunc: function (xData, Status) {                         var aDataSet = new Array();                        //loop through each returned Task                         $(xData.responseXML).find("[nodeName=z:row]").each(function() {                             //store the multi-select string of who task is assigned to                             var assignedToString = $(this).attr("ows_AssignedTo");                             found = false;                            //loop through the persons name and all the groups they belong to                             for(var i=0; i<myGroups.length; i++) {                                 //if the person's name or group exists in the assigned To string                                 //then the task is assigned to them                                 if (assignedToString.indexOf(myGroups[i]) >= 0){                                     found = true;                                     break;                                 }                             }                             //if the Task belongs to this person then store or display it                             //(I'm storing it in an array)                             if (found){                                 var thisName = $(this).attr("ows_Title");                                 var thisStartDate = $(this).attr("ows_StartDate");                                 var thisEndDate = $(this).attr("ows_EndDate");                                 var thisStatus = $(this).attr("ows_Status");                                                                  var aDataRow=new Array(                                     thisName,                                     thisStartDate,                                     thisEndDate,                                     thisStatus);                                 aDataSet.push(aDataRow);                             }                          });                          SomeFunctionToDisplayData(aDataSet);                     }                 }); Some notes on why I did certain things and additional caveats. You will notice in my code that I’m doing an AssignedToString.indexOf(GroupName) to see if the task belongs to the person. This could possibly return bad results if you have SharePoint Group names that are named in such a way that the “IndexOf” returns a false positive.  For example if you have a Group called “My Users” and a group called “My Users – SuperUsers” then if a user belonged to “My Users” it would return a false positive on executing “My Users – SuperUsers”.IndexOf(“My Users”). Make sense? Just be aware of this when naming groups, we don’t have this problem. This is where also some fine-tuning can probably be done by those smarter than me. This is a pretty inefficient method to determine if a task belongs to a user, I mean what if a user belongs to 20 groups? That’s a LOT of looping.  See all the opportunities I give you guys to do something fun?? Also, why am I storing my values in an array instead of just writing them out to a Div? Well.. I want to pass my data to a jQuery library to format it all nice and pretty and an Array is a great way to do that. When all is said and done and we put all the code together it looks like:   $(document).ready(function() {         var userName = $().SPServices.SPGetCurrentUser({                     fieldName: "Title",                     debug: false                     });         myGroups = new Array();     myGroups.push(userName );       $().SPServices({       operation: "GetGroupCollectionFromUser",       userLoginName: $().SPServices.SPGetCurrentUser(),       async: false,       completefunc: function(xData, Status) {          $(xData.responseXML).find("[nodeName=Group]").each(function() {                 myGroups.push($(this).attr("Name"));          });                      // get list of assigned tasks that aren't closed... *modify this CAML to perform better!*             $().SPServices({                   operation: "GetListItems",                   async: false,                   listName: "Tasks",                   CAMLViewFields: "<ViewFields>" +                             "<FieldRef Name='AssignedTo' />" +                             "<FieldRef Name='Title' />" +                             "<FieldRef Name='StartDate' />" +                             "<FieldRef Name='EndDate' />" +                             "<FieldRef Name='Status' />" +                             "</ViewFields>",                   CAMLQuery: "<Query><Where><And><IsNotNull><FieldRef Name='AssignedTo'/></IsNotNull><Neq><FieldRef Name='Status'/><Value Type='Text'>Completed</Value></Neq></And></Where></Query>",                     completefunc: function (xData, Status) {                         var aDataSet = new Array();                         //loop through each returned Task                         $(xData.responseXML).find("[nodeName=z:row]").each(function() {                             //store the multi-select string of who task is assigned to                             var assignedToString = $(this).attr("ows_AssignedTo");                             found = false;                            //loop through the persons name and all the groups they belong to                             for(var i=0; i<myGroups.length; i++) {                                 //if the person's name or group exists in the assigned To string                                 //then the task is assigned to them                                 if (assignedToString.indexOf(myGroups[i]) >= 0){                                     found = true;                                     break;                                 }                             }                            //if the Task belongs to this person then store or display it                             //(I'm storing it in an array)                             if (found){                                 var thisName = $(this).attr("ows_Title");                                 var thisStartDate = $(this).attr("ows_StartDate");                                 var thisEndDate = $(this).attr("ows_EndDate");                                 var thisStatus = $(this).attr("ows_Status");                                                                  var aDataRow=new Array(                                     thisName,                                     thisStartDate,                                     thisEndDate,                                     thisStatus);                                 aDataSet.push(aDataRow);                             }                          });                          SomeFunctionToDisplayData(aDataSet);                     }                 });       }    });  }); Final Thoughts So, there you have it. Take it and run with it. Make it something cool (and tell me how you did it). Another possible way to improve performance in this scenario is to use a DVWP to display the tasks and use jQuery and the “myGroups” array from this blog post to hide all those rows that don’t belong to the current user. I haven’t tried it, but it does move some of the processing off to the server (generating the view) so it may perform better.  As always, thanks for stopping by… hope you have a Merry Christmas…

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  • 80% off for SQL Azure!

    - by Hugo Kornelis
    I have spent the last three days at SQLBits X in London – a truly great experience! There were lots of quality sessions, but I also enjoyed meeting new people and catching up with old friends. One of these friends (and I hope he’s still a friend after I post this) is Buck Woody . Not only a great and humorous speaker, but also a very nice fellow – for those who don’t mind being teased every now and then. When we were chatting, he told me that he was planning to announce a special access code to allow...(read more)

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  • Slides and demo code for Columnstore Index session

    - by Hugo Kornelis
    Almost a week has passed after SQLBits X in London , so I guess it’s about time for me to share the slides and demo code of my session on columnstore indexes. After all, I promised people I would do that – especially when I found out that I had enough demos prepared to fill two sessions! I made some changes to the demo code. I added extra comments, not only to the demos I could not explain and run during the session, but also to the rest, so that people who missed the session will also be able to...(read more)

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  • Windows in StreamInsight: Hopping vs. Snapshot

    - by Roman Schindlauer
    Three weeks ago, we explained the basic concept of windows in StreamInsight: defining sets of events that serve as arguments for set-based operations, like aggregations. Today, we want to discuss the so-called Hopping Windows and compare them with Snapshot Windows. We will compare these two, because they can serve similar purposes with different behaviors; we will discuss the remaining window type, Count Windows, another time. Hopping (and its syntactic-sugar-sister Tumbling) windows are probably the most straightforward windowing concept in StreamInsight. A hopping window is defined by its length, and the offset from one window to the next. They are aligned with some absolute point on the timeline (which can also be given as a parameter to the window) and create sets of events. The diagram below shows an example of a hopping window with length of 1h and hop size (the offset) of 15 minutes, hence creating overlapping windows:   Two aspects in this diagram are important: Since this window is overlapping, an event can fall into more than one windows. If an (interval) event spans a window boundary, its lifetime will be clipped to the window, before it is passed to the set-based operation. That’s the default and currently only available window input policy. (This should only concern you if you are using a time-sensitive user-defined aggregate or operator.) The set-based operation will be applied to each of these sets, yielding a result. This result is: A single scalar value in case of built-in or user-defined aggregates. A subset of the input payloads, in case of the TopK operator. Arbitrary events, when using a user-defined operator. The timestamps of the result are almost always the ones of the windows. Only the user-defined  operator can create new events with timestamps. (However, even these event lifetimes are subject to the window’s output policy, which is currently always to clip to the window end.) Let’s assume we were calculating the sum over some payload field: var result = from window in source.HoppingWindow( TimeSpan.FromHours(1), TimeSpan.FromMinutes(15), HoppingWindowOutputPolicy.ClipToWindowEnd) select new { avg = window.Avg(e => e.Value) }; Now each window is reflected by one result event:   As you can see, the window definition defines the output frequency. No matter how many or few events we got from the input, this hopping window will produce one result every 15 minutes – except for those windows that do not contain any events at all, because StreamInsight window operations are empty-preserving (more about that another time). The “forced” output for every window can become a performance issue if you have a real-time query with many events in a wide group & apply – let me explain: imagine you have a lot of events that you group by and then aggregate within each group – classical streaming pattern. The hopping window produces a result in each group at exactly the same point in time for all groups, since the window boundaries are aligned with the timeline, not with the event timestamps. This means that the query output will become very bursty, delivering the results of all the groups at the same point in time. This becomes especially obvious if the events are long-lasting, spanning multiple windows each, so that the produced result events do not change their value very often. In such a case, a snapshot window can remedy. Snapshot windows are more difficult to explain than hopping windows: they represent those periods in time, when no event changes occur. In other words, if you mark all event start and and times on your timeline, then you are looking at all snapshot window boundaries:   If your events are never overlapping, the snapshot window will not make much sense. It is commonly used together with timestamp modification, which make it a very powerful tool. Or as Allan Mitchell expressed in in a recent tweet: “I used to look at SnapshotWindow() with disdain. Now she is my mistress, the one I turn to in times of trouble and need”. Let’s look at a simple example: I want to compute the average of some value in my events over the last minute. I don’t want this output be produced at fixed intervals, but at soon as it changes (that’s the true event-driven spirit!). The snapshot window will include all currently active event at each point in time, hence we need to extend our original events’ lifetimes into the future: Applying the Snapshot window on these events, it will appear to be “looking back into the past”: If you look at the result produced in this diagram, you can easily prove that, at each point in time, the current event value represents the average of all original input event within the last minute. Here is the LINQ representation of that query, applying the lifetime extension before the snapshot window: var result = from window in source .AlterEventDuration(e => TimeSpan.FromMinutes(1)) .SnapshotWindow(SnapshotWindowOutputPolicy.Clip) select new { avg = window.Avg(e => e.Value) }; With more complex modifications of the event lifetimes you can achieve many more query patterns. For instance “running totals” by keeping the event start times, but snapping their end times to some fixed time, like the end of the day. Each snapshot then “sees” all events that have happened in the respective time period so far. Regards, The StreamInsight Team

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  • Do you know your DNS server?

    - by John Paul Cook
    If you don’t know your DNS server is valid, you need to find out before July 9. The FBI found rogue DNS servers and replaced them with clean, safe DNS servers to protect the public. These safe, clean servers will be turned off on July 9, 2012. If your computer was compromised to use the rogue servers, it will stop resolving DNS queries on July 9 when the clean servers are turned off. The FBI has provided full technical details at http://www.fbi.gov/news/stories/2011/november/malware_110911/DNS-changer-malware.pdf...(read more)

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  • Speaking at SQLSaturday #44 in Huntington Beach, CA (Los Angeles Area)

    - by Ben Nevarez
      I'll be presenting a session at SQLSaturday #44 in Huntington Beach, the first SQLSaturday on Southern California. The event takes place on Saturday, April 24 at the Golden West College on 15744 Goldenwest St, Huntington Beach, CA 92647.. For more information visit the following link   http://sqlsaturday.com/44/eventhome.aspx   My session is “How the Query Optimizer Works”. I hope to see you there. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Deletes that Split Pages and Forwarded Ghosts

    - by Paul White
    Can DELETE operations cause pages to split? Yes. It sounds counter-intuitive on the face of it; deleting rows frees up space on a page, and page splitting occurs when a page needs additional space. Nevertheless, there are circumstances when deleting rows causes them to expand before they can be deleted. The mechanism at work here is row versioning (extract from Books Online below): Isolation Levels The relationship between row-versioning isolation levels (the first bullet point) and page splits is...(read more)

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