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  • Which repo and version of Percona for Natty?

    - by thefella
    I'm wanting to drop in Percona instead of MySQL (5.1) on my Natty ubuntu server. I've added the keys and the repos. I've added a natty repo, even though it's not supposed to exist and it seems to be fine. The problem is when I go an apt-get install percona-server-server, it tells me that it depends on percona-server-server-5.5 and won't be installed. Should I just install 5.5 (over the top of mysql 5.1) or do I need to install percona 5.1? Or do I need to pick a different repo and let it decide?

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  • PHP not displaying any errors

    - by chutsu
    I've got ubuntu 10.04 installed, as well as: lighttpd mysql/php Now my problem is that my php scripts can be executed and has access to MySQL database, however I'm having problems getting php to display all errors when running. The result of a failed php run is a blank page. I tried setting the display errors on in php.ini in /etc/php5/cgi/php.ini I've also tried adding these two lines in the source to force errors on, to no avail. ini_set('display_errors', '1'); error_reporting(E_ALL); What should I do? Thanks

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  • Is it bad to have a very full hard drive on a high traffic database server?

    - by MikeN
    Running an Ubuntu server with MySQL for a high traffic production database server. Nothing else is running on the machine except the MySQL instance. We store daily database backups on the DB server, is there any performance hit or reason why we should keep the hard disk relatively empty? If the disk is filled up to 86%+ with the database and all of the backups, does it hurt performance at all? So would the DB server running with 86-90%+ full capacity perform less well in any way than the server running with only a 10% full disk? The total disk size on the server is over 1 TB so even 10% of the disk should be enough for basic O/S swapping and such.

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  • XAMPP won't start because I'm already running MySQL on port 3306

    - by JellicleCat
    I'm trying to start XAMPP, but it fails with only the word 'Busy' in the Control Panel console. I ran xampp/install/portcheck.bat to see if the ports were available, and I see that port 3306 is busy (because I'm running MySQL as a service on it). I suppose that XAMPP wants to take over and run MySQL on that port. Can anyone tell me how to get XAMPP to just make use of the existing server and not try to control it itself?

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  • PHP Runs Very Slow on IIS7. Need Help optimizing our config

    - by Kendor
    Am running a PHP based web app on our Windows 2008 cloud-based server. The app, which runs fine outside of our environment (e.g. a different IIS server), but is VERY slow in our environment. Based on googling this is a relatively common situation. I installed PHP and MySQL via the IIS web deployment method... Here's our setup: Windows 2008 Server Enterprise SP2 (32-bit) Microsoft-IIS/7.0 MySQL client version: mysqlnd 5.0.8-dev - 20102224 $Revision: 321634 $ PHP extension: mysqli Update for IIS 7.0 FastCGI Windows Cache Extension 1.1 for PHP 5.3 I had read elsewhere that ipv6 might be an issue, so I turned this off on the network adapter. The app is using: localhost as its connection Be easy on me, as I'm a bit green about some of these components... Also, rewriting the PHP app or modifying it is NOT an option. I'm reasonably SURE that our config is the issue.

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  • Apache Web Server character encoding

    - by OBY
    I've recently transferred my webapp from my localhost (LH) to a VPS, and have had hebrew chars-encoding probs since. Whenever I send a request with a heb-char it results in "?????" saved to the DB. My LH config was tomcat6, MySQL, and centOS 6.2, opened to the web. In the VPS env I'm behind an Apache Web Server, and the rest is quite the same (though I haven't done anything to its installation). Please note I already have had this problem before, on my LH when the request was sent from IE/chrome (not FF!). The solution was to apply a filter on the the context and change the char-type to UTF-8. My webapp content char-encode is utf-8, MySql server set to utf8 using charset utf8;, and my centOS set to iw_IL.UTF8 using export LANG=iw_IL.UTF8. When I use locale the bash output seems to be set correctly. Any suggestions?

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  • How to calculate unweighted averages in Excel PivotTable?

    - by yonatron
    I often make PivotTables in which each row contains a number of per-person average measures. I then want to look at the unweighted column average for each measure, and usually make some kind of chart from these. Because my individual cells are often averaged from different numbers of data points, the Grand Total row ends up being a weighted average, which I’m not interested in. So I usually make my own average row a few rows above the table to use for my charts. That’s not too much work, but there’s another problem. I often add a few more people’s worth of data to the PivotTables’ source, then refresh the tables. This means my average row needs to be updated to encompass more rows from the PivotTable. Not a huge deal with one table, but when I have lots of them across lots of sheets, I have to do find/replace on a whole bunch of formulas. So: is there a way to automatically get unweighted column averages in a PivotTable, such that when the table is refreshed, the averages don’t change locations and encompass the newly added (or removed) data Thanks

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  • Clustering with Vsphere and Apache load balacing

    - by Anonymous2011
    I was looking at Vsphere to automatically load balance my apache web servers, and mysql servers but will this actually do the job? I know it says it does auto load balancing but not actually sure it quite means what I want to achieve. Is there an easier way to set up a php-apache and mysql cluster within virtual machines? Or are there any guides to clustering? (I have tried googling without much luck) Any help towards understanding/setting up clustering and load balancing within virtual machines appreciated.

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  • PHP and MySQL on IIS7: can't find php_mcrypt.dll in php.ini

    - by user46250
    I have installed PHP with Microsoft Web PI. Then I installed mysql. According to http://learn.iis.net/page.aspx/353/install-and-configure-mysql-for-php-applications-on-iis-7/ I have to Uncomment the following lines by removing the semicolon: extension=php_mysqli.dll extension=php_mbstring.dll extension=php_mcrypt.dll But there is no extension=php_mcrypt.dll in php.ini installed by web PI so should I add it by hand then where ? and where should I check that php_mcrypt.dll exists ? Seems nobody knows, should better ask on Microsoft forum ?

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  • Reread partition table without rebooting?

    - by Teddy
    Sometimes, when resizing or otherwise mucking about with partitions on a disk, cfdisk will say: Wrote partition table, but re-read table failed. Reboot to update table. (This also happens with other partitioning tools, so I'm thinking this is a Linux issue rather than a cfdisk issue.) Why is this, and why does it only happens sometimes, and what can I do to avoid it? Note: Please assume that none of the partitions I am actually editing are opened, mounted or otherwise in use. Update: cfdisk uses ioctl(fd, BLKRRPART, NULL) to tell Linux to reread the partition table. Two of the other tools recommended so far (hdparm -z DEVICE, sfdisk -R DEVICE) does exactly the same thing. The partprobe DEVICE command, on the other hand, seems to use a new ioctl called BLKPG, which might be better; I don't know. (It also falls back on BLKRRPART if BLKPG fails.) BLKPG seems to be a "this partition has changed; here is the new size" operation, and it looked like partprobe called it individually on all the partitions on the device passed, so it should work if the individual partitions are unused. However, I have not had the opportunity to try it.

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  • mysqldump and wamp

    - by Adam
    I am running a wamp server and trying to use mysqldump to backup a mysql database I have. The following is the PHP code I am using to run mysqldump. exec("mysqldump backup -u$user -p$pass > $sql_file"); When I run the script the page just loads inifnately and the backup is not created. A blank file is being created so I know something is happening. Extra info: exec() is not disabled PHP is not running in safe mode Any ideas?? Win XP, WAMP, MYSQL 5.0.51b

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  • Can't access phpMyAdmin because of host, username and password

    - by Engprof
    everyone. When I try to access phpMyAdmin on Uniform Server I get the following error messages: " #1045 - Access denied for user 'root'@'localhost' (using password: YES) " " phpMyAdmin tried to connect to the MySQL server, and the server rejected the connection. You should check the host, username and password in your configuration and make sure that they correspond to the information given by the administrator of the MySQL server. " The funny thing is my username and password are both set to "root" and I have changed the IP address in the httpd.conf file to my Unique IP adddress, so I still don't know what the problem is. Could somebody please help me out? Any help would be much appreciated.

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  • Upgrading Fedora to Current Version - Dependent Applications Concerns

    - by nicorellius
    Is it possible to upgrade to Fedora 11 and still keep the server functional (it's running Fedora Core release 6 now, with MySQL 5.0, PHP 5.1 and Apache 2.2)? I have a Customer Relationship Management system on there and it is required on a daily basis. I am trying to figure out if I should upgrade (and whether that will cause huge problems) or if I should start over with a new OS (like Ubuntu) and install the CRM fresh, with updated version of MySQL, PHP, Apache, etc. I ask because I am not really the sysadmin, but have but put in charge of this server.

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  • Should we regularly schedule mysqlcheck (or databsae optimization)

    - by scatteredbomb
    We run a forum with some 2 million posts and I've noticed that if left untouched the overhead in the mySQL (as listed in phpMyAdmin) can get quite large (hundreds of megabytes). I'm wondering if scheduling a normal mysqlcheck to optimize the tables is good practice? Any reason not to do it, say, once a week at an off-peak hour? There was a time over the summer where our site was constantly crashing because mysql was using up all resources. That's when I noticed the huge amount of overhead and optimized the database and haven't had any problems since then with stability. I figured if that was helping alleviate the issues, I should just setup a cron to automatically do this.

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  • Is it safe to use up all memory on linux server, not leaving anything for the cache?

    - by Temnovit
    I have a CentOS server fully dedicated to MySQL 5.5 (with innodb tables mostly). Server has 32 GB RAM, SSD disks, and avarage memory usage looks like this: So about 25GB is in use and about 6.5GB is cached. I am experiencing performance problems with WRITE queries, so I was thinking, is this the optimal cache size? I might increase innodb buffer size, so that linux cache would become smaller, or decrease it, so it would be bigger. What is the optimal used/cached memory balance for busy MySQL server on linux?

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  • Access denied for user 'root@localhost' (using password:NO)

    - by murgatroid99
    I am attempting to install a network management package called cacti onto Ubuntu running under Windows Virtual PC. I attempted to install MySQL as it is one of cacti's dependencies. I can install and start the MySQL server, but whenever I try to access it in any other way, such as to change the password, I get the error message Access denied for user 'root@localhost' (using password:NO). I would like to know what is causing this and how to fix it. Edit: (just in case my comments are not visible) The answers from HD and Devin Ceartas did not work for me.

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  • How to copy a file to a remote server using the command line?

    - by cool_cs
    I am trying to copy a file from my desktop to my remote server using the sudo command. I am doing this from the remote machine since I know the password for this machine and I do not have a password for my local machine. sudo scp donj@localhost:/Desktop/my.cnf user@remotemachine:/app/MySQL/my.cnf This does not work however. I want to overwrite the my.cnf file in the MySQL directory. I tried the su command but I do not have the password to become a super user.

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  • Access denied for user 'root@localhost' (using password:NO)

    - by murgatroid99
    I am attempting to install a network management package called cacti onto Ubuntu running under Windows Virtual PC. I attempted to install MySQL as it is one of cacti's dependencies. I can install and start the MySQL server, but whenever I try to access it in any other way, such as to change the password, I get the error message Access denied for user 'root@localhost' (using password:NO). I would like to know what is causing this and how to fix it. Edit: (just in case my comments are not visible) The answers from HD and Devin Ceartas did not work for me.

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  • Open XML SDK 2.0 - Split table to new power point slide when content flows off current slide

    - by amurra
    I have a bunch of data that I need to export from a website to a power point presentation and have been using Open XML SDK 2.0 to perform this task. I have a power point presentation that I am putting through Open XML SDK 2.0 Productivity Tool to generate the template code that I can use to recreate the export. On one of those slides I have a table and the requirement is to add data to that table and break that table across multiple slides if the table exceeds the bottom of the slide. The approach I have taken is to determine the height of the table and if it exceeds the height of the slide, move that new content into the next slide. I have read Bryan and Jones blog on adding repeating data to a power point slide, but my scenario is a little different. They use the following code: A.Table tbl = current.Slide.Descendants<A.Table>().First(); A.TableRow tr = new A.TableRow(); tr.Height = heightInEmu; tr.Append(CreateDrawingCell(imageRel + imageRelId)); tr.Append(CreateTextCell(category)); tr.Append(CreateTextCell(subcategory)); tr.Append(CreateTextCell(model)); tr.Append(CreateTextCell(price.ToString())); tbl.Append(tr); imageRelId++; This won't work for me since they know what height to set the table row to since it will be the height of the image, but when adding in different amounts of text I do not know the height ahead of time so I just set tr.Heightto a default value. Here is my attempt at figuring at the table height: A.Table tbl = tableSlide.Slide.Descendants<A.Table>().First(); A.TableRow tr = new A.TableRow(); tr.Height = 370840L; tr.Append(PowerPointUtilities.CreateTextCell("This"); tr.Append(PowerPointUtilities.CreateTextCell("is")); tr.Append(PowerPointUtilities.CreateTextCell("a")); tr.Append(PowerPointUtilities.CreateTextCell("test")); tr.Append(PowerPointUtilities.CreateTextCell("Test")); tbl.Append(tr); tableSlide.Slide.Save(); long tableHeight = PowerPointUtilities.TableHeight(tbl); Here are the helper methods: public static A.TableCell CreateTextCell(string text) { A.TableCell tableCell = new A.TableCell( new A.TextBody(new A.BodyProperties(), new A.Paragraph(new A.Run(new A.Text(text)))), new A.TableCellProperties()); return tableCell; } public static Int64Value TableHeight(A.Table table) { long height = 0; foreach (var row in table.Descendants<A.TableRow>() .Where(h => h.Height.HasValue)) { height += row.Height.Value; } return height; } This correctly adds the new table row to the existing table, but when I try and get the height of the table, it returns the original height and not the new height. The new height meaning the default height I initially set and not the height after a large amount of text has been inserted. It seems the height only gets readjusted when it is opened in power point. I have also tried accessing the height of the largest table cell in the row, but can't seem to find the right property to perform that task. My question is how do you determine the height of a dynamically added table row since it doesn't seem to update the height of the row until it is opened in power point? Any other ways to determine when to split content to another slide while using Open XML SDK 2.0? I'm open to any suggestion on a better approach someone might have taken since there isn't much documentation on this subject.

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  • Get the Dynamic table data from gui in selenium webDriver

    - by Rabindra
    I am working on a web based Application that I am testing with Selenium. On one page the content is dynamically loaded in table. I want to get the Table data, i am geting a "org.openqa.selenium.NullPointerElementException" in this line. WebElement table = log.driver.findElement(By.xpath(tableXpath)); I tried the following complete code. public int selectfromtable(String tableXpath, String CompareValue, int columnnumber) throws Exception { WebElement table = log.driver.findElement(By.xpath(tableXpath)); List<WebElement> rows = table.findElements(By.tagName("tr")); int flag = 0; for (WebElement row : rows) { List<WebElement> cells = row.findElements(By.tagName("td")); if (!cells.isEmpty() && cells.get(columnnumber).getText().equals(CompareValue)) { flag = 1; Thread.sleep(1000); break; } else { Thread.sleep(2000); flag = 0; } } return flag; } I am calling the above method like String tableXpath = ".//*[@id='event_list']/form/div[1]/table/tbody/tr/td/div/table"; selectfromtable(tableXpath, eventType, 3); my html page is like <table width="100%"> <tbody style="overflow: auto; background-color: #FFFFFF"> <tr class="trOdd"> <td width="2%" align="center"> <td width="20%" align="center"> Account </td> <td width="20%" align="center"> Enter Collection </td> <td width="20%" align="center"> <td width="20%" align="center"> 10 </td> <td width="20%" align="center"> 1 </td> </tr> </tbody> <tbody style="overflow: auto; background-color: #FFFFFF"> <tr class="trEven"> <td width="2%" align="center"> <td width="20%" align="center"> Account </td> <td width="20%" align="center"> Resolved From Collection </td> <td width="20%" align="center"> <td width="20%" align="center"> 10 </td> <td width="20%" align="center"> 1 </td> </tr> </tbody> </table>

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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  • SQL SERVER – Updating Data in A Columnstore Index

    - by pinaldave
    So far I have written two articles on Columnstore Indexes, and both of them got very interesting readership. In fact, just recently I got a query on my previous article on Columnstore Index. Read the following two articles to get familiar with the Columnstore Index. They will give you a reference to the question which was asked by a certain reader: SQL SERVER – Fundamentals of Columnstore Index SQL SERVER – How to Ignore Columnstore Index Usage in Query Here is the reader’s question: ” When I tried to update my table after creating the Columnstore index, it gives me an error. What should I do?” When the Columnstore index is created on the table, the table becomes Read-Only table and it does not let any insert/update/delete on the table. The basic understanding is that Columnstore Index will be created on the table that is very huge and holds lots of data. If a table is small enough, there is no need to create a Columnstore index. The regular index should just help it. The reason why Columnstore index was needed is because the table was so big that retrieving the data was taking a really, really long time. Now, updating such a huge table is always a challenge by itself. If the Columnstore Index is created on the table, and the table needs to be updated, you need to know that there are various ways to update it. The easiest way is to disable the Index and enable it. Consider the following code: USE AdventureWorks GO -- Create New Table CREATE TABLE [dbo].[MySalesOrderDetail]( [SalesOrderID] [int] NOT NULL, [SalesOrderDetailID] [int] NOT NULL, [CarrierTrackingNumber] [nvarchar](25) NULL, [OrderQty] [smallint] NOT NULL, [ProductID] [int] NOT NULL, [SpecialOfferID] [int] NOT NULL, [UnitPrice] [money] NOT NULL, [UnitPriceDiscount] [money] NOT NULL, [LineTotal] [numeric](38, 6) NOT NULL, [rowguid] [uniqueidentifier] NOT NULL, [ModifiedDate] [datetime] NOT NULL ) ON [PRIMARY] GO -- Create clustered index CREATE CLUSTERED INDEX [CL_MySalesOrderDetail] ON [dbo].[MySalesOrderDetail] ( [SalesOrderDetailID]) GO -- Create Sample Data Table -- WARNING: This Query may run upto 2-10 minutes based on your systems resources INSERT INTO [dbo].[MySalesOrderDetail] SELECT S1.* FROM Sales.SalesOrderDetail S1 GO 100 -- Create ColumnStore Index CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_MySalesOrderDetail_ColumnStore] ON [MySalesOrderDetail] (UnitPrice, OrderQty, ProductID) GO -- Attempt to Update the table UPDATE [dbo].[MySalesOrderDetail] SET OrderQty = OrderQty +1 WHERE [SalesOrderID] = 43659 GO /* It will throw following error Msg 35330, Level 15, State 1, Line 2 UPDATE statement failed because data cannot be updated in a table with a columnstore index. Consider disabling the columnstore index before issuing the UPDATE statement, then rebuilding the columnstore index after UPDATE is complete. */ A similar error also shows up for Insert/Delete function. Here is the workaround. Disable the Columnstore Index and performance update, enable the Columnstore Index: -- Disable the Columnstore Index ALTER INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] DISABLE GO -- Attempt to Update the table UPDATE [dbo].[MySalesOrderDetail] SET OrderQty = OrderQty +1 WHERE [SalesOrderID] = 43659 GO -- Rebuild the Columnstore Index ALTER INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] REBUILD GO This time it will not throw an error while the update of the table goes successfully. Let us do a cleanup of our tables using this code: -- Cleanup DROP INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] GO TRUNCATE TABLE dbo.MySalesOrderDetail GO DROP TABLE dbo.MySalesOrderDetail GO In the next post we will see how we can use Partition to update the Columnstore Index. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Index, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Excel 2010: if( , , "") not treated the same as blank for pivot table group by date

    - by Confused
    I'm trying to group by date in an Excel 2010 pivot table. The column with dates (i.e., the one want to group by), should be the latest date of 2 other columns if neither is null, or blank. i.e., with a formula like: =IF(AND(A4 <> "", B4 <> ""), MAX(A4,B4), "") Normally, this ""in the IF() formula acts the same as an empty cell. In this case, it is preventing me from grouping by date in the Pivot Table. If I filter the date column by (Blanks), then clear the contents of all those cells, then the pivot table does group by date ok. i.e., "" is not being treated the same as an empty cell.

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  • Static Routes and the Routing Table

    - by TheD
    This is very much a learning question if someone would be happy to explain a couple of concepts. My question is - the default routing table that exists in, in my case, a default Windows 7 install, what do each of the routes in the table do? Here is a screenshot: The 10.128.4.0 is just a route I've added while messing. I understand from a question I posted on Superuser the first route is just a default route that will route all traffic for any IP to my default gateway on my Interface in use. But what about the others? And how would the routing table handle a machine with multiple NIC's, perhaps connected to two different networks, or maybe even two NIC's on the same network so a VM can have a physical Network card instead of each VM sharing the hosts. Thanks!

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  • How To Speed Up Adding Column To Large Table In Sql Server

    - by Chris
    I want to add a column to a Sql Server table with about 10M rows. I think this query would eventually finish adding the column I want: alter table T add mycol bit not null default 0 but it's been going for several hours already. Is there any shortcut to get a "not null default 0" column inserted into a large table? Or is this inherently really slow? This is Sql Server 2000. Later on I have to do something similar on Sql Server 2008.

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