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• Replication Services in a BI environment

  - by jorg

  In this blog post I will explain the principles of SQL Server Replication Services without too much detail and I will take a look on the BI capabilities that Replication Services could offer in my opinion. SQL Server Replication Services provides tools to copy and distribute database objects from one database system to another and maintain consistency afterwards. These tools basically copy or synchronize data with little or no transformations, they do not offer capabilities to transform data or apply business rules, like ETL tools do. The only “transformations” Replication Services offers is to filter records or columns out of your data set. You can achieve this by selecting the desired columns of a table and/or by using WHERE statements like this: SELECT <published_columns> FROM [Table] WHERE [DateTime] >= getdate() - 60 There are three types of replication: Transactional Replication This type replicates data on a transactional level. The Log Reader Agent reads directly on the transaction log of the source database (Publisher) and clones the transactions to the Distribution Database (Distributor), this database acts as a queue for the destination database (Subscriber). Next, the Distribution Agent moves the cloned transactions that are stored in the Distribution Database to the Subscriber. The Distribution Agent can either run at scheduled intervals or continuously which offers near real-time replication of data! So for example when a user executes an UPDATE statement on one or multiple records in the publisher database, this transaction (not the data itself) is copied to the distribution database and is then also executed on the subscriber. When the Distribution Agent is set to run continuously this process runs all the time and transactions on the publisher are replicated in small batches (near real-time), when it runs on scheduled intervals it executes larger batches of transactions, but the idea is the same. Snapshot Replication This type of replication makes an initial copy of database objects that need to be replicated, this includes the schemas and the data itself. All types of replication must start with a snapshot of the database objects from the Publisher to initialize the Subscriber. Transactional replication need an initial snapshot of the replicated publisher tables/objects to run its cloned transactions on and maintain consistency. The Snapshot Agent copies the schemas of the tables that will be replicated to files that will be stored in the Snapshot Folder which is a normal folder on the file system. When all the schemas are ready, the data itself will be copied from the Publisher to the snapshot folder. The snapshot is generated as a set of bulk copy program (BCP) files. Next, the Distribution Agent moves the snapshot to the Subscriber, if necessary it applies schema changes first and copies the data itself afterwards. The application of schema changes to the Subscriber is a nice feature, when you change the schema of the Publisher with, for example, an ALTER TABLE statement, that change is propagated by default to the Subscriber(s). Merge Replication Merge replication is typically used in server-to-client environments, for example when subscribers need to receive data, make changes offline, and later synchronize changes with the Publisher and other Subscribers, like with mobile devices that need to synchronize one in a while. Because I don’t really see BI capabilities here, I will not explain this type of replication any further. Replication Services in a BI environment Transactional Replication can be very useful in BI environments. In my opinion you never want to see users to run custom (SSRS) reports or PowerPivot solutions directly on your production database, it can slow down the system and can cause deadlocks in the database which can cause errors. Transactional Replication can offer a read-only, near real-time database for reporting purposes with minimal overhead on the source system. Snapshot Replication can also be useful in BI environments, if you don’t need a near real-time copy of the database, you can choose to use this form of replication. Next to an alternative for Transactional Replication it can be used to stage data so it can be transformed and moved into the data warehousing environment afterwards. In many solutions I have seen developers create multiple SSIS packages that simply copies data from one or more source systems to a staging database that figures as source for the ETL process. The creation of these packages takes a lot of (boring) time, while Replication Services can do the same in minutes. It is possible to filter out columns and/or records and it can even apply schema changes automatically so I think it offers enough features here. I don’t know how the performance will be and if it really works as good for this purpose as I expect, but I want to try this out soon!

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• Must partprobe before using drive?

  - by Jeff Welling

  This is a followup question to Cannot mount /dev/sdc1 on Debian 5.0, special device /dev/sdc1 doesn't exist Basically, I have 6 SATA hard drives in a machine and I'm trying to create a RAID6 array with them. When I try to run the mdadm command to create (with the verbose option) a raid array, I see messages like "mdadm: super1.x cannot open /dev/sdf1: No such device or address" which are resolved by doing partprobe /dev/sdf and then re-running the mdadm command. The problem is that I have to run partprobe after each reboot, and from experience I don't think this is normal behaviour -- on no other linux machine do I have to partprobe the device before I can use it. Something must be going wrong, but how do I troubleshoot this to find out what? Could this be caused by a hardware problem? Edit: Additional note - before I seemed to only have this problem with one drive, but now I'm having it with 3 drives.

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• Disable comments / Spam protection

  - by SamIAm

  My client site is built in Silverstripe, there is a news page, and it allows people to leave comments. Unfortunately we've got loads of spam emails. I'm new to this, is there any way we can disable the comment field by default? How do I do it? Alternatively is there easy way for me to install a spam protection? Thanks heaps. Sam Update - Because this is someone else's code, I just realised that they have some sort of spam protection already, so we are trying to disable comments now. I have manage to set no comment as default by changing file BlogEntry.php static $defaults = array( "ProvideComments" => true, 'ShowInMenus' => false ); to static $defaults = array( "ProvideComments" => false, //changed 'ShowInMenus' => false ); Am I on the right track to disable comments by default? Also how can I stop on the news page showing xxx comments link? eg Test Posted by Admin on 21 June 2011 | 3 Comments Tags: P This is a test.... 3 comments | Read the full post Thanks. S:)

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• amazon dynamoDB or MySQL for storing large arrays inside each row

  - by Logan Besecker

  I am trying to decide which database I should use for an application I'm making. I was leaning toward dynamoDB because of its scalability, but then I read in the documentation which said: there is a limit of 64 KB on the item size although it looks like MySQL has a similar restriction documented here This application will be storing a lot of data in two arrays, which could contain upwards of 10,000-100,000 strings in each. I estimate that these strings will each be somewhere around 20 characters long, so each element of the array will be around 40bytes and each array could be around 4MB. Given this predicament, what database on amazon AWS would you use; or how would you get around the limit of size per row? Thanks in advance, Logan Besecker

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• Using Table-Valued Parameters With SQL Server Reporting Services

  - by Jesse

  In my last post I talked about using table-valued parameters to pass a list of integer values to a stored procedure without resorting to using comma-delimited strings and parsing out each value into a TABLE variable. In this post I’ll extend the “Customer Transaction Summary” report example to see how we might leverage this same stored procedure from within an SQL Server Reporting Services (SSRS) report. I’ve worked with SSRS off and on for the past several years and have generally found it to be a very useful tool for building nice-looking reports for end users quickly and easily. That said, I’ve been frustrated by SSRS from time to time when seemingly simple things are difficult to accomplish or simply not supported at all. I thought that using table-valued parameters from within a SSRS report would be simple, but unfortunately I was wrong. Customer Transaction Summary Example Let’s take the “Customer Transaction Summary” report example from the last post and try to plug that same stored procedure into an SSRS report. Our report will have three parameters: Start Date – beginning of the date range for which the report will summarize customer transactions End Date – end of the date range for which the report will summarize customer transactions Customer Ids – One or more customer Ids representing the customers that will be included in the report The simplest way to get started with this report will be to create a new dataset and point it at our Customer Transaction Summary report stored procedure (note that I’m using SSRS 2012 in the screenshots below, but there should be little to no difference with SSRS 2008): When you initially create this dataset the SSRS designer will try to invoke the stored procedure to determine what the parameters and output fields are for you automatically. As part of this process the following dialog pops-up: Obviously I can’t use this dialog to specify a value for the ‘@customerIds’ parameter since it is of the IntegerListTableType user-defined type that we created in the last post. Unfortunately this really throws the SSRS designer for a loop, and regardless of what combination of Data Type, Pass Null Value, or Parameter Value I used here, I kept getting this error dialog with the message, "Operand type clash: nvarchar is incompatible with IntegerListTableType". This error message makes some sense considering that the nvarchar type is indeed incompatible with the IntegerListTableType, but there’s little clue given as to how to remedy the situation. I don’t know for sure, but I think that behind-the-scenes the SSRS designer is trying to give the @customerIds parameter an nvarchar-typed SqlParameter which is causing the issue. When I first saw this error I figured that this might just be a limitation of the dataset designer and that I’d be able to work around the issue by manually defining the parameters. I know that there are some special steps that need to be taken when invoking a stored procedure with a table-valued parameter from ADO .NET, so I figured that I might be able to use some custom code embedded in the report  to create a SqlParameter instance with the needed properties and value to make this work, but the “Operand type clash" error message persisted. The Text Query Approach Just because we’re using a stored procedure to create the dataset for this report doesn’t mean that we can’t use the ‘Text’ Query Type option and construct an EXEC statement that will invoke the stored procedure. In order for this to work properly the EXEC statement will also need to declare and populate an IntegerListTableType variable to pass into the stored procedure. Before I go any further I want to make one point clear: this is a really ugly hack and it makes me cringe to do it. Simply put, I strongly feel that it should not be this difficult to use a table-valued parameter with SSRS. With that said, let’s take a look at what we’ll have to do to make this work. Manually Define Parameters First, we’ll need to manually define the parameters for report by right-clicking on the ‘Parameters’ folder in the ‘Report Data’ window. We’ll need to define the ‘@startDate’ and ‘@endDate’ as simple date parameters. We’ll also create a parameter called ‘@customerIds’ that will be a mutli-valued Integer parameter: In the ‘Available Values’ tab we’ll point this parameter at a simple dataset that just returns the CustomerId and CustomerName of each row in the Customers table of the database or manually define a handful of Customer Id values to make available when the report runs. Once we have these parameters properly defined we can take another crack at creating the dataset that will invoke the ‘rpt_CustomerTransactionSummary’ stored procedure. This time we’ll choose the ‘Text’ query type option and put the following into the ‘Query’ text area: 1: exec('declare @customerIdList IntegerListTableType ' + @customerIdInserts + 2: ' EXEC rpt_CustomerTransactionSummary 3: @startDate=''' + @startDate + ''', 4: @endDate='''+ @endDate + ''', 5: @customerIds=@customerIdList')   By using the ‘Text’ query type we can enter any arbitrary SQL that we we want to and then use parameters and string concatenation to inject pieces of that query at run time. It can be a bit tricky to parse this out at first glance, but from the SSRS designer’s point of view this query defines three parameters: @customerIdInserts – This will be a Text parameter that we use to define INSERT statements that will populate the @customerIdList variable that is being declared in the SQL. This parameter won’t actually ever get passed into the stored procedure. I’ll go into how this will work in a bit. @startDate – This is a simple date parameter that will get passed through directly into the @startDate parameter of the stored procedure on line 3. @endDate – This is another simple data parameter that will get passed through into the @endDate parameter of the stored procedure on line 4. At this point the dataset designer will be able to correctly parse the query and should even be able to detect the fields that the stored procedure will return without needing to specify any values for query when prompted to. Once the dataset has been correctly defined we’ll have a @customerIdInserts parameter listed in the ‘Parameters’ tab of the dataset designer. We need to define an expression for this parameter that will take the values selected by the user for the ‘@customerIds’ parameter that we defined earlier and convert them into INSERT statements that will populate the @customerIdList variable that we defined in our Text query. In order to do this we’ll need to add some custom code to our report using the ‘Report Properties’ dialog: Any custom code defined in the Report Properties dialog gets embedded into the .rdl of the report itself and (unfortunately) must be written in VB .NET. Note that you can also add references to custom .NET assemblies (which could be written in any language), but that’s outside the scope of this post so we’ll stick with the “quick and dirty” VB .NET approach for now. Here’s the VB .NET code (note that any embedded code that you add here must be defined in a static/shared function, though you can define as many functions as you want): 1: Public Shared Function BuildIntegerListInserts(ByVal variableName As String, ByVal paramValues As Object()) As String 2: Dim insertStatements As New System.Text.StringBuilder() 3: For Each paramValue As Object In paramValues 4: insertStatements.AppendLine(String.Format("INSERT {0} VALUES ({1})", variableName, paramValue)) 5: Next 6: Return insertStatements.ToString() 7: End Function   This method takes a variable name and an array of objects. We use an array of objects here because that is how SSRS will pass us the values that were selected by the user at run-time. The method uses a StringBuilder to construct INSERT statements that will insert each value from the object array into the provided variable name. Once this method has been defined in the custom code for the report we can go back into the dataset designer’s Parameters tab and update the expression for the ‘@customerIdInserts’ parameter by clicking on the button with the “function” symbol that appears to the right of the parameter value. We’ll set the expression to: 1: =Code.BuildIntegerListInserts("@customerIdList ", Parameters!customerIds.Value)   In order to invoke our custom code method we simply need to invoke “Code.<method name>” and pass in any needed parameters. The first parameter needs to match the name of the IntegerListTableType variable that we used in the EXEC statement of our query. The second parameter will come from the Value property of the ‘@customerIds’ parameter (this evaluates to an object array at run time). Finally, we’ll need to edit the properties of the ‘@customerIdInserts’ parameter on the report to mark it as a nullable internal parameter so that users aren’t prompted to provide a value for it when running the report. Limitations And Final Thoughts When I first started looking into the text query approach described above I wondered if there might be an upper limit to the size of the string that can be used to run a report. Obviously, the size of the actual query could increase pretty dramatically if you have a parameter that has a lot of potential values or you need to support several different table-valued parameters in the same query. I tested the example Customer Transaction Summary report with 1000 selected customers without any issue, but your mileage may vary depending on how much data you might need to pass into your query. If you think that the text query hack is a lot of work just to use a table-valued parameter, I agree! I think that it should be a lot easier than this to use a table-valued parameter from within SSRS, but so far I haven’t found a better way. It might be possible to create some custom .NET code that could build the EXEC statement for a given set of parameters automatically, but exploring that will have to wait for another post. For now, unless there’s a really compelling reason or requirement to use table-valued parameters from SSRS reports I would probably stick with the tried and true “join-multi-valued-parameter-to-CSV-and-split-in-the-query” approach for using mutli-valued parameters in a stored procedure.

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• LSI RAID-on-chip with RAID6 over two SAS links goes red when HDD enclosure is powered cycled; how to recover?

  - by GregC

  I have a RAID6 array managed by LSI 9286-8e card. I also have Sans Digital 24-bay NexentaSTOR JBOD enclosure with SAS extender built-in. They are connected to separate UPS devices. Normally, I'd shut down the PC, leaving RAID6 in healthy state. But today the power to JBOD enclosure was cut but PC kept running. After restarting the PC, all disks in RAID6 have lit up RED, and the only option in LSI MegaRAID manager app was to reset each disk to unassigned, thereby loosing all data on RAID6 array. Thankfully, I am only testing, but how would I recover if this were to happen in production?

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• missing files after reassemble of RAID-5

  - by Kris_R

  I had to open my file-server's housing on Sunday to replace a faulty fan. What I didn't see was that one of the sata-cables was not properly connected. The 1st thing I did after a reboot was a check of the RAID status and it showed immediately that one drive is missing. Till this moment the device was not used (however it was mounted, so I'm not 100% sure that system did nothing). I stopped md0 and re-plugged the cable: mdadm --stop /dev/md0 poweroff After another reboot I checked the removed drive: mdadm --examine /dev/sdd1 ... Checksum : 3276bc1d - correct Events : 315782 Layout : left-symmetric Chunk Size : 32K Number Major Minor RaidDevice State this 0 8 49 0 active sync /dev/sdd1 0 0 8 49 0 active sync /dev/sdd1 1 1 8 65 1 active sync /dev/sde1 2 2 8 33 2 active sync /dev/sdc1 3 3 8 17 3 active sync /dev/sdb1 I was a bit surprised that it was shown as active (even if earlier mdadm said, that this device was removed from array) and its checksum was OK. I recreated RAID with: mdadm --assemble /dev/md0 --scan The command mdadm --detail /dev/md0 showed that all drives were running and system was in "clean" state. I mounted the device md0 and then came hic-cup. I wanted to work on one of the last files that I had been using before all the situation and it was not there. In another place I missed actually all files from the directory where I was working. As far as I can see most of the files that are older than a few days are intact but some newer ones are missing. Now the big question: what would be your advice? Is there a way to get these data? I thought about removing the drive that was earlier labeled by mdadm and rebuild array with another empty HDD. I've found that after re-assemble the "broken" drive has another label (changed from sdd to sdb). Can this have influence on rebuilt process? If yes, how to reassemble the array properly? I'm sure the SATA-cables are connected still in the same order to the controller. p.s. Please no advises like "restore from backup". I'm doing back-ups on Sunday's night and this happened in the late afternoon, so backup is not really options for me. p.s.s. I asked this question on Unix&Linux but no answer came up during last two days. I'm getting quite anxious. Sorry for duplicating if any of you reading the other forum.

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• What Raid should I use for Website Static Files / Content

  - by Simon

  I'm building a Web server (IIS7) and would like to know the best practice for storing static content and the uploaded files of website's users (predominantly pictures, but also other documents like pdf's). I will keep the operating System on a Raid 1 array. Where should I be keeping the actual website's pages & files, it's own static content, and that of it's users? Should I be placing this content on a seperate raid array, and if so which type? I was considering using SLC SSD's (Such as the Intel's X25-e) but the following issues came to light. Will the SLC SSD's give any improvement over a 2.5" 15k SAS Drive for this type of content? If I did use SSD's, I'm under the belief I would still need to use Raid for redundancy, yet I've heard Intel X25-e's don't support TRIM. Does this scrap them as a legitimate option?

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• IBM DB2 and the “'DbProviderFactories' section can only appear once per config” error

  - by Davide Mauri

  IBM doesn’t like MS. That’s a fact. And that’s why you can get your machine.config file (!!!) corrupted if you try to install IBM DB2 data providers on your server machine. If at some point, after having installed IBM DB2 data providers your SSIS packages or SSAS cubes or SSRS Reports starts to complain that 'DbProviderFactories' section can only appear once per config you may want to check into you machine.config, located in the %runtime install path%\Config http://msdn.microsoft.com/en-us/library/ms229697%28v=vs.71%29.aspx Almost surely you’ll find a IBM DB2 Provider into an additional DbProviderFactories section all alone. Poor guy. Remove the double DBProviderFactories entry, and merge everything inside only one section DBProviderFactories and after that everything will start to work again.

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• What is a “pretty and proper OO” way for handling sessions and authentication?

  - by asdfqwer

  Is coupling these two concepts a bad approach? As of right now I'm delegating all session handling and whether or not a user desires to logout in my config.inc file. As I was writing my Auth class I started wondering whether or not my Auth class should be taking care of most of the logic in my config.inc. Regardless, I'm sure there's a more elegant way of handling this... Here is what I have in my config.inc (also a large chunk of this code is based on a reply I found on SO except I can't find the source ._.): ini_set('session.name', 'SID'); # session management session_set_cookie_params(24*60*60); // set SID cookie lifetime session_start(); if(isset($_SESSION['LOGOUT']) { session_destroy(); // destroy session data $_SESSION = array(); // destroy session data sanity check setcookie('SID', '', time() - 24*60*60); // destroy session cookie data #header('Location: '.DOCROOT); } elseif(isset($_SESSION['SID_AUTH'])) { // verify user has authenticated if (!isset($_SESSION['SID_CREATED'])) { $_SESSION['SID_CREATED'] = time(); } elseif (time() - $_SESSION['SID_CREATED'] > 6*60*60) { // session started more than 6 hours ago session_regenerate_id(); // reset SID value $_SESSION['SID_CREATED'] = time(); // update creation time } if (isset($_SESSION['SID_MODIFIED']) && (time() - $_SESSION['SID_MODIFIED'] > 12*60*60)) { // last request was more than 12 hours ago session_destroy(); // destroy session data $_SESSION = array(); // destroy session data sanity check setcookie('SID', '', time() - 24*60*60); // destroy session cookie data } $_SESSION['SID_MODIFIED'] = time(); // update last activity time stamp }

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• Is There Anyway to Undo a Quick Initialize from a Perc6/i VD?

  - by Carlo71

  I stupidly fast initialized an existing Raid 5 Array Virtual disk with 10 Virtual Machines after creating a new Raid 5 Array. The VDs switched order on the list of the Perc Controller. My server is a PowerEdge R710 with a Perc 6/i Raid controller running ESXi 5.1. The Bios of the R710 and the Perc 6/i controller are both running the latest firmware. I tried the steps on this article: http://www.caseyfulton.com/dell-perc-6i-fast-initialize-how-to-restore/. However the BartPE just freezes on the Windows XP slapsh page. Does anybody know a full proof method? I have backups of the VMs, however I would like to avoid restoring all of them due to time constraint.

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• Tracking pages with variables in GA

  - by Imran

  Recently I have updated my site, it now passes a variable on some links like so... www.mysite.com/1234/?play=true I've noticed in Google Analytics it records www.mysite.com/1234/ and www.mysite.com/1234/?play=true as two different URL's. Is there a way to merge them because they are after all just one page, It makes "Top Content" for example hard to read because of dupilicates. I've read about something called canonical link tag which may help this? My blog has this already inserted into the head but it doesnt make a difference. Any suggestions?

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• Google I/O 2011: Large-scale Data Analysis Using the App Engine Pipeline API

  Google I/O 2011: Large-scale Data Analysis Using the App Engine Pipeline API Brett Slatkin The Pipeline API makes it easy to analyze complex data using App Engine. This talk will cover how to build multi-phase Map Reduce workflows; how to merge multiple large data sources with "join" operations; and how to build reusable analysis components. It will also cover the API's concurrency model, how to debug in production, and built-in testing facilities. From: GoogleDevelopers Views: 3320 17 ratings Time: 51:39 More in Science & Technology

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• Week in Geek: 50 Million Viruses and More on the Way Edition

  - by Asian Angel

  This week we learned how to backup and copy data between iOS devices, use Linux commands in Windows with Cygwin, boost email writing productivity with Microsoft Word Mail Merge, be more productive in Ubuntu using keyboard shortcuts, “restore the FTP service in XBMC, rename downloaded TV shows, access the Android Market in emulation”, and more Latest Features How-To Geek ETC How To Create Your Own Custom ASCII Art from Any Image How To Process Camera Raw Without Paying for Adobe Photoshop How Do You Block Annoying Text Message (SMS) Spam? How to Use and Master the Notoriously Difficult Pen Tool in Photoshop HTG Explains: What Are the Differences Between All Those Audio Formats? How To Use Layer Masks and Vector Masks to Remove Complex Backgrounds in Photoshop Enjoy Clutter-Free YouTube Video Viewing in Opera with CleanTube Bring Summer Back to Your Desktop with the LandscapeTheme for Chrome and Iron The Prospector – Home Dash Extension Creates a Whole New Browsing Experience in Firefox KinEmote Links Kinect to Windows Why Nobody Reads Web Site Privacy Policies [Infographic] Asian Temple in the Snow Wallpaper

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• SEO consequences for merging country sites in a .com

  - by Pekka

  I am in the process of refactoring a number of rental portals I've built for a company with locations in Austria, Germany, Switzerland, and the Netherlands. Instead of the current setting of each country site running under its own domain name: www.companyname.de www.companyname.ch www.companyname.at I would love to merge them all in this way: www.companyname.com/de www.companyname.com/ch www.companyname.com/at with the country TLDs doing a 301 redirect to the respective .com address. However, I have been repeatedly told not to do this due to likely problems with SEO - the business is very SEO dependent, and being a rental chain, needs to be strong in local results. So the question is: Is there an unavoidable hit in Search Engine Optimization when redirecting to a central .com domain? What measures can be taken to soften the blow? What comes to my mind is explicitly specifying a lang attribute in the html tag. Are there any other ways to specifically point out geographical location for sub-directories?

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• Joins in single-table queries

  - by Rob Farley

  Tables are only metadata. They don’t store data. I’ve written something about this before, but I want to take a viewpoint of this idea around the topic of joins, especially since it’s the topic for T-SQL Tuesday this month. Hosted this time by Sebastian Meine (@sqlity), who has a whole series on joins this month. Good for him – it’s a great topic. In that last post I discussed the fact that we write queries against tables, but that the engine turns it into a plan against indexes. My point wasn’t simply that a table is actually just a Clustered Index (or heap, which I consider just a special type of index), but that data access always happens against indexes – never tables – and we should be thinking about the indexes (specifically the non-clustered ones) when we write our queries. I described the scenario of looking up phone numbers, and how it never really occurs to us that there is a master list of phone numbers, because we think in terms of the useful non-clustered indexes that the phone companies provide us, but anyway – that’s not the point of this post. So a table is metadata. It stores information about the names of columns and their data types. Nullability, default values, constraints, triggers – these are all things that define the table, but the data isn’t stored in the table. The data that a table describes is stored in a heap or clustered index, but it goes further than this. All the useful data is going to live in non-clustered indexes. Remember this. It’s important. Stop thinking about tables, and start thinking about indexes. So let’s think about tables as indexes. This applies even in a world created by someone else, who doesn’t have the best indexes in mind for you. I’m sure you don’t need me to explain Covering Index bit – the fact that if you don’t have sufficient columns “included” in your index, your query plan will either have to do a Lookup, or else it’ll give up using your index and use one that does have everything it needs (even if that means scanning it). If you haven’t seen that before, drop me a line and I’ll run through it with you. Or go and read a post I did a long while ago about the maths involved in that decision. So – what I’m going to tell you is that a Lookup is a join. When I run SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 285; against the AdventureWorks2012 get the following plan: I’m sure you can see the join. Don’t look in the query, it’s not there. But you should be able to see the join in the plan. It’s an Inner Join, implemented by a Nested Loop. It’s pulling data in from the Index Seek, and joining that to the results of a Key Lookup. It clearly is – the QO wouldn’t call it that if it wasn’t really one. It behaves exactly like any other Nested Loop (Inner Join) operator, pulling rows from one side and putting a request in from the other. You wouldn’t have a problem accepting it as a join if the query were slightly different, such as SELECT sod.OrderQty FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail as sod on sod.SalesOrderID = soh.SalesOrderID WHERE soh.SalesPersonID = 285; Amazingly similar, of course. This one is an explicit join, the first example was just as much a join, even thought you didn’t actually ask for one. You need to consider this when you’re thinking about your queries. But it gets more interesting. Consider this query: SELECT SalesOrderID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276 AND CustomerID = 29522; It doesn’t look like there’s a join here either, but look at the plan. That’s not some Lookup in action – that’s a proper Merge Join. The Query Optimizer has worked out that it can get the data it needs by looking in two separate indexes and then doing a Merge Join on the data that it gets. Both indexes used are ordered by the column that’s indexed (one on SalesPersonID, one on CustomerID), and then by the CIX key SalesOrderID. Just like when you seek in the phone book to Farley, the Farleys you have are ordered by FirstName, these seek operations return the data ordered by the next field. This order is SalesOrderID, even though you didn’t explicitly put that column in the index definition. The result is two datasets that are ordered by SalesOrderID, making them very mergeable. Another example is the simple query SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276; This one prefers a Hash Match to a standard lookup even! This isn’t just ordinary index intersection, this is something else again! Just like before, we could imagine it better with two whole tables, but we shouldn’t try to distinguish between joining two tables and joining two indexes. The Query Optimizer can see (using basic maths) that it’s worth doing these particular operations using these two less-than-ideal indexes (because of course, the best indexese would be on both columns – a composite such as (SalesPersonID, CustomerID – and it would have the SalesOrderID column as part of it as the CIX key still). You need to think like this too. Not in terms of excusing single-column indexes like the ones in AdventureWorks2012, but in terms of having a picture about how you’d like your queries to run. If you start to think about what data you need, where it’s coming from, and how it’s going to be used, then you will almost certainly write better queries. …and yes, this would include when you’re dealing with regular joins across multiples, not just against joins within single table queries.

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• Sorting and Paging a Grid of Data in ASP.NET MVC

  This article is the fifth installment in an ongoing series on displaying a grid of data in an ASP.NET MVC application. Previous articles in this series examined how to sort, page, and filter a grid of data, but none have looked at combining one or more of these features in a single grid. This article and the next one show how to merge these features into a single grid. In particular, this article looks at displaying a grid that can handle both sorting and paging. The subsequent article will examine combining sorting, paging and filtering. Like with its predecessors, this article offers step-by-step instructions and includes a complete, working demo available for download at the end of the article. Read on to learn more! Read More >

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• What is a good way to store tilemap data?

  - by Stephen Tierney

  I'm developing a 2D platformer with some uni friends. We've based it upon the XNA Platformer Starter Kit which uses .txt files to store the tile map. While this is simple it does not give us enough control and flexibility with level design. Some examples: for multiple layers of content multiple files are required, each object is fixed onto the grid, doesn't allow for rotation of objects, limited number of characters etc. So I'm doing some research into how to store the level data and map file. This concerns only the file system storage of the tile maps, not the data structure to be used by the game while it is running. The tile map is loaded into a 2D array, so this question is about which source to fill the array from. Reasoning for DB: From my perspective I see less redundancy of data using a database to store the tile data. Tiles in the same x,y position with the same characteristics can be reused from level to level. It seems like it would simple enough to write a method to retrieve all the tiles that are used in a particular level from the database. Reasoning for JSON/XML: Visually editable files, changes can be tracked via SVN a lot easier. But there is repeated content. Do either have any drawbacks (load times, access times, memory etc) compared to the other? And what is commonly used in the industry? Currently the file looks like this: .................... .................... .................... .................... .................... .................... .................... .........GGG........ .........###........ .................... ....GGG.......GGG... ....###.......###... .................... .1................X. #################### 1 - Player start point, X - Level Exit, . - Empty space, # - Platform, G - Gem

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• How to set up RAID 1 on Dell PERC S300 With Existing OS Install

  - by Daniel Dugger

  We have a server that is being used in production, but it was not originally meant to. The main thing I want to add to it is a Dell PERC S300 RAID Card to have the main hard drive (Windows Server 2008 R2) mirrored on another hard drive. I can not initialize the disk and wipe the the OS to create the array and then re-install. Is there a way to create the array with a current hard drive, without affecting it, and just mirroring the drive? If that card is not an option, is there a card that would allow that? The server is a Dell PowerEdge T110 II.

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• Look up and string operation; fetch a value based on searching a partial string

  - by Sam

  I have 2 sets of data. One set to be filled up by fetching relevant data from a data array. DATA to be FILLED: Part#1 Part#2 ------ ------- 4021006 3808587 3870480 3083410 3873905 3890030 4002065 3699803 3930218 ARRAY OF DATA: Part#1 Part#2 ------ ------- 4021006;3808587 1 3808587 2 3870480;3083410;4002065 3 3083410 34 3873905 54 3890030 32 4002065;3930218 65 3699803 75 3930218 68 I need to match Part#1 and find Part#2. EXPECTED OUTPUT Part#1 Part#2 ------ ------- 4021006 1 3808587 1;2 3870480 3 3083410 3;4 3873905 54 3890030 32 4002065 3;65 3699803 75 3930218 65;68 Can anyone help.

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• How to remove individual webapps from Launcher

  - by Luis Alvarado

  Today my launcher looks like a long vertical bar of icons. I have 14 webapp icons on the launcher but there is no option to remove them or an option to no include them (Or even an option to merge them as I asked in a previous question). Is there an option, without having to disable the whole webapp idea, to remove individual webapps from the launcher. Forgot to add that the option to Unlock from Launcher does not appear, but only on the webapps. On the rest of the launcher icons it appears correctly. This is an image of the actual problem (Thanks to koma):

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• Software RAID 10 on Linux

  - by vpetersson

  For a long time, I've been thinking about switching to RAID 10 on a few servers. Now that Ubuntu 10.04 LTS is live, it's time for an upgrade. The servers I'm using are HP Proliant ML115 (very good value). It has four internal 3.5" slots. I'm currently using one drive for the system and a RAID5 array (software) for the remaining three disks. The problem is that this creates a single-point-of-failure on the boot drive. Hence I'd like to switch to a RAID10 array, as it would give me both better I/O performance and more reliability. The problem is only that good controller cards that supports RAID10 (such as 3Ware) cost almost as much as the server itself. Moreover software-RAID10 does not seem to work very well with Grub. What is your advice? Should I just keep running RAID5? Have anyone been able to successfully install a software RAID10 without boot issues?

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• Excel: count number of unique/distinct row in range with condition

  - by Bertvan

  I have a an excel sheet with: in Col A: week numbers in Col B: dates (timesheet entries) I need to know the number of days worked for each week, so I need to the number of unique date entries per week number. I found formula's (both array as non-array) that handle this for a fixed range, but I want to have the results in another column per week number. So, the result of the added dataset below would be (the colon is just for clarity): 14: 2 15: 3 17: 6 20: 2 21: 3 If this is the source data: 14: 4/04/2012 14: 4/04/2012 15: 10/04/2012 15: 10/04/2012 15: 11/04/2012 17: 26/04/2012 17: 26/04/2012 17: 26/04/2012 17: 26/04/2012 17: 27/04/2012 17: 27/04/2012 20: 14/05/2012 20: 14/05/2012 21: 23/05/2012 21: 23/05/2012 21: 25/05/2012

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• Something other than Vertex Welding with Texture Atlas?

  - by Tim Winter

  What options (in C# with XNA) would there be for texture usage in a procedural generated 3D world made of cubes to increase performance? Yes, it's like Minecraft. I've been doing a texture atlas and rendering faces individually (4 vertices per face), but I've also read in a couple places about using texture wrapping with two 1D atlases to merge adjacent faces with the same texture. If two or more adjacent faces share the same image, it'd be quite easy to wrap in this way reducing vertices by a large amount. My problem with this is having too many textures, swapping too often, and many image related things like non-power of 2 images. Is there a middle ground option between the 1D texture atlas trick and rendering 4 vertices per cube face? This is a picture of what I have currently (in wireframe). 4 vertices per face seems extremely inefficient to me.

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• Cannot reinstall MySql in 11.10 - ERROR: There's not enough space in /var/lib/mysql/

  - by Robin McCain

  I've tried it all (removing all the packages associated with MySQL) but keep getting stuff like this: Preconfiguring packages ... (Reading database ... 142196 files and directories currently installed.) Unpacking mysql-server-5.1 (from .../mysql-server-5.1_5.1.63-0ubuntu0.11.10.1_amd64.deb) ... ERROR: There's not enough space in /var/lib/mysql/ dpkg: error processing /var/cache/apt/archives/mysql-server-5.1_5.1.63-0ubuntu0.11.10.1_amd64.deb (--unpack): subprocess new pre-installation script returned error exit status 1 Errors were encountered while processing: /var/cache/apt/archives/mysql-server-5.1_5.1.63-0ubuntu0.11.10.1_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) Here is my drive space map. root@kyle:/# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/mapper/kyle-root 59361428 59021768 0 100% / udev 1014052 8 1014044 1% /dev tmpfs 409304 1476 407828 1% /run none 5120 0 5120 0% /run/lock none 1023256 0 1023256 0% /run/shm /dev/sda1 233191 46888 173862 22% /boot /dev/md0 1922858288 1048513192 776669500 58% /media/array The root volume actually only has about 10 gigabytes in use on the hard drive (which has a 60 gig partition). /dev/md0 is a 2 TB raid array.

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