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  • Disk partition errors after size change

    - by benjamin.d
    I increased the disk size of one of my VM when it was running. After a reboot, I get the following error message (at boot time): Mounting local filesystems...failed Now the VM is only accessible through ESX console (not through ssh), and nothing is working anymore.... I already tried to run fsck, but without success. The result of mount: The result of blkid: The result of fstab: Thanks for your help

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  • Why does Ubuntu 10.04 not see my hard drives?

    - by CT
    I am trying to install Ubuntu Desktop 10.04 64bit to a new machine. mobo = gigabyte x58a-ud3r cpu = i7 930 ssd = Kingston 64GB V+ hhd = wd 1tb black When the installation gets to the prepare partions step, no partitions are listed. Drives are recognized by BIOS and WinXP setup sees them. I have also tried Ubuntu 9.10. It does not see the drives also. Just searching around I found a suggestion to select "no dmraid" in additional options screen. This did not seem to help. Any ideas?

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  • Booting Windows from different partition than system

    - by szamil
    I have bought an SSD disk, but my laptop (Dell Precision M6300) refuse to use it as a target disk for windows (AHCPI on/off, BIOS up-to-date). I can't exchange the disk unfortunately... But fortunately, I've managed to install windows using USB disk case. The problem is, that when I put that disk as my internal drive it can't boot. (Disk read error, Three Finger Salute ... ) So I tried with Linux (openSUSE), I manage to install it as well, but when I tried to boot GRUB from internal drive I get errors again. (Should I try GRUB2?) I figured out that I can boot into that internal hard drive's openSUSE system using small USB drive with GRUB, kernel and image on it. So, I just run GRUB from USB drive, it loads necessary stuff from the USB drive and then continues from the internal drive. I want to do the same with Windows. But GRUB (rootnoverify and chainloader +1) does not boot my windows on internal drive. The question: is there any chance to copy the critical windows' boot files into the USB drive, to make it possible to boot from that USB drive, but continue booting from internal (different in general) drive? The USB drive would became a system hardware key! ;-) Disk: Plextor M5S 128GB Sata III, laptop has Sata II, but it's compatible anyway, right?

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  • FDE / SSD - partition and leave some unencrypted?

    - by Web Design Hero
    Just bought a used beast of a desktop pc. The system drive is setup as a Raid 0 SSD (Intel 510 SSD Drives) with 128 each. I will probably not have to many programs beyond office and maybe Adobe CS if I spring for it, I will be keeping big data on a regular hdd. My question is about setting up TrueCrypt with my configuration. I have not previously done full disk encryption, but I feel that its probably a good idea. I have done some speed tests using file containers on the hdd and the sdd with truecrypt. While there is a huge hit with the SSDs and Truecrypt, it still outperforms the hdd on its own by a good margin, so I think i will be okay for my needs with truecrypt. I have seen in a few places that they recommend partitioning the drive and leavign some of the SSD not inside truecrypt, does this really make a difference? If so, how much should I leave? Will there be any issue in the Raid0 configuration? I am not really concerned about all the wear leveling issue, rather loose data and be secure, but since I don't need all that space neccesarily, I would like to optimize my setup for security and speed.

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  • Best way to copy large amount of data between partitions

    - by skinp
    I'm looking to transfer data across 2 lv of an HP-UX server. I have a couple of those transfers to do, some of which are mostly binary (Oracle tablespace...) and some others are more text files (logs...). Used data size of the volumes is between 100Gb and 1Tb. Also, I will be changing the block size from 1K to 8K on some of these partitions... Things I'm looking for: Guarantees data integrity Fastest data transfer speed Keeps file ownership and permissions Right now, I've thought about dd, cp and rsync, but I'm not sure on the best one to use and the best way to use them...

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  • Shrink NTFS Partition Windows 2003

    - by Coops
    We have an iSCSI target provided by a CentOS server attached to a Windows Server 2003 Standard box, formatted in NTFS. My question is this - I know we can resize the backend block device fine (LVM et al.), however how do you tell Windows the NTFS filesystem has shrunk afterwards? [note we want to shrink]. I'm imagining a world of pain if it's not done correctly! This is a production box, so ideally we'd like the process to keep the drive mounted and online during the process, but downtime can be scheduled if need be. 90% of what I've found on the subject so far basically involves using the 'ntfsresize' command in Linux to do the job -- but surely Windows can do this itself? Cheers!

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  • Which is the recommended filesystem for VMware Server / ESXi?

    - by elitalon
    We have a couple of servers in office with VMware Server as virtualization solution. We are planning an upgrade of our infrastructure. Some servers will remain with VMware Server, but we want to migrate some others to VMware ESXi. In both cases we are making a fresh install, and I wonder if there any suggestion/guidelines regarding the host filesystem and its partitions. EDIT: We are using local storage instead of SAN/NAS external storage, because we are not sure if it is worth it to use them given our office size/requirements.

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  • mdadm lvm and ext4 slowness - How can I speed it up?

    - by beatbreaker
    I can't figure out why I'm getting such terrible times out of my mdadm and in particular the lvm partitions in it. I made the raid: mdadm --create --verbose /dev/md0 --level=5 --chunk=1024 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 # cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid5 sda1[0] sdd1[3] sdc1[2] sdb1[1] 2930279424 blocks level 5, 1024k chunk, algorithm 2 [4/4] [UUUU] I then created the physical volume, volume group, and logical volumes, I then formatted the logical volumes to ext4 using the following commands I got from here: http://busybox.net/~aldot/mkfs_stride.html mkfs.ext3 -b 4096 -E stride=256,stripe-width=768 /dev/datavg/blah Now I'm confused, I had these lvs running real quick before in mdadm but now that I've 'optimized' everything it's slower, eg, before: /dev/datavg/lv_audio: Timing buffered disk reads: 598 MB in 3.01 seconds = 198.85 MB/sec but now after: /dev/datavg/audio: Timing buffered disk reads: 198 MB in 3.00 seconds = 65.96 MB/sec That's pitiful! What's happened here? Did I not follow the instructions correctly? Can i reshape the ext4 partitons to default back to what they were? (I used defaults before and they were fine!)

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  • Accessing the partitions on an VLM volume

    - by projix
    Suppose you have an LVM volume /dev/vg0/mylv. You have presented this as a virtual disk to a virtualised or emulated guest system. During installation the guest system sees it as /dev/sda and partitions it into /dev/sda{1,2,5,6} and completes the installation. Now at some point you need to access those filesystems from within the host system, without running the guest system. fdisk sees these partitions just fine: # fdisk -l /dev/vg0/mylv Device Boot Start End Blocks Id System /dev/vg0/mylv1 2048 684031 340992 83 Linux /dev/vg0/mylv2 686078 20969471 10141697 5 Extended /dev/vg0/mylv5 686080 8290303 3802112 83 Linux /dev/vg0/mylv6 8292352 11980799 1844224 83 Linux However, the devices such as /dev/vg0/mylv1 do not actually exist. I guess that because they're within an LV, the OS does not recognise this type of nesting by default. Is there any way I can prod Linux so that /dev/vg0/mylv1 or equivalent appears and thus becomes mountable within the host system? I understand that it's possible with qemu-nbd, and will use this if necessary. However, I was hoping for something more direct if possible, rather than simulating a network block device and attaching that.

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  • Is it possible to have two HDD's, and both be primary?

    - by qwerty2
    Here is my configuration: C: - system/Windows XP HDD D: - empty I just added a new hard drive (D) and formatted it and made it a primary HDD. Since then Windows hasn't been able to boot. Is the computer able to have both the system and the new HDD as primary? If not, then that is why Windows isn't booting. If it IS possible, then I have no idea what the problem is. Any help or thoughts would be fantastic! thanks!

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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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  • ideas for algorithm? sorting a list randomly with emphasis on variety

    - by Steve Eisner
    I have a table of items with [ID,ATTR1,ATTR2,ATTR3]. I'd like to select about half of the items, but try to get a random result set that is NOT clustered. In other words, there's a fairly even spread of ATTR1 values, ATTR2 values, and ATTR3 values. This does NOT necessarily represent the data as a whole, in other words, the total table may be generally concentrated on certain attribute values, but I'd like to select a subset with more variety. The attributes are not inter-related, so there's not really a correlation between ATTR1 and ATTR2. Any ideas for an efficient algorithm? Thanks! I don't really even know how to search for this :)

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  • Need help displaying a dynamic table

    - by Gideon
    I am designing a job rota planner for a company and need help displaying a dynamic table containing the staff details. I have the following tables in MySQL database: Staff, Event, and Job. The staff table holds staff details (staffed, name, address...etc), the Event table (eventide, eventName, Fromdate, Todate...etc) and the Job table holds (Jobid, Jobdate, Eventid(fk), Staffid (fk)). I need to dynamically display the available staff list from the staff table when the user selects the EVENT and the DATE (3 drop downs: date, month, and year) from a PHP form. I need to display staff members that have not been assigned work on the selected date by checking the Jobdate in the Job table. I have been at this for all day and can't get around it. I am still learning PHP and would surely appreciate any help I can get. My current code displays all staff members when an event is selected: if(isset($_POST['submit'])) { $eventId = $_POST['eventradio']; } $timePeriod = $_POST['timeperiod']; $Day = $_POST['day']; $Month = $_POST['month']; $Year = $_POST['year']; $dateValue = $Year."-".$Month."-".$Day; $selectedDate = date("Y-m-d", strtotime($dateValue)); //construct the available staff list if ($selectedDate) { $staffsql = "SELECT s.StaffId, s.LastName, s.FirstName FROM Staff s WHERE s.StaffId NOT IN (SELECT J.StaffId FROM Job J WHERE J.JobDate != ".$selectedDate.")"; $staffResult = mysql_query($staffsql) or die (mysql_error()); } if ($staffResult){ echo "<p><table cellspacing='1' cellpadding='3'>"; echo "<th colspan=6>List of Available Staff</th>"; echo "</tr><tr><th> Select</th><th>Id</th><th></th><th>Last Name </th><th></th><th>First Name </th></tr>"; while ($staffarray = mysql_fetch_array($staffResult)) { echo "<tr onMouseOver= this.bgColor = 'red' onMouseOut =this.bgColor = 'white' bgcolor= '#FFFFFF'> <td align=center><input type='checkbox' name='selectbox[]' id='selectbox[]' value=".$staffarray['StaffId']."> </td><td align=left>".$staffarray['StaffId']." </td><td>&nbsp&nbsp</td><td align=center>".$staffarray['LastName']." </td><td>&nbsp&nbsp</td><td align=center>".$staffarray['FirstName']." </td></tr>"; } echo "</table>"; } else { echo "<br> The Staff list can not be displayed!"; } echo "</td></tr>"; echo "<tr><td></td>"; echo "<td align=center><input type='submit' name='Submit' value='Assign Staff'>&nbsp&nbsp"; echo "<input type='reset' value='Start Over'>"; echo "</td></tr>"; echo "</table>";

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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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  • How can I create a partition without the usage of Live CD nor USB?

    - by Ariel
    ¿Cómo crear una partición sin usar live CD ni USB? Is it possible to create a partition when using the system? When I try to do it on gParted, it seems that the options are disabled because of the disk is mounted and it cannot be unmounted because of I am using it in the system. I wish to create a new partition without removing or affecting the file system; just creating a new partition, but without the need to use a Live CD or USB. ¿Es posible crear una partición estando en el sistema? Ya que cuando lo intento desde GParted, al parecer están desactivadas las opciones porque la unidad está montada y no se puede desmontar ya que estoy usando el sistema. Quiero crear una nueva partición pero sin quitar o afectar el sistema de archivos; sólo crear una nueva partición, pero sin live CD o USB.

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  • Why does the first partition start at sector 34 when I choose "Guided - Use entire disk" during install?

    - by Kent
    After choosing "Guided - Use entire disk" during installation I find that the first partition starts on sector 34. Why that specific sector and not the first one? (parted) print Model: ATA WDC WD30EZRX-00M (scsi) Disk /dev/sda: 5860533168s Sector size (logical/physical): 512B/4096B Partition Table: gpt Number Start End Size File system Name Flags 1 34s 390659s 390626s fat32 boot 2 390660s 890660s 500001s ext2 3 890661s 5860533118s 5859642458s (parted) In case you prefer bytes as the unit: (parted) unit B (parted) print Model: ATA WDC WD30EZRX-00M (scsi) Disk /dev/sda: 3000592982016B Sector size (logical/physical): 512B/4096B Partition Table: gpt Number Start End Size File system Name Flags 1 17408B 200017919B 200000512B fat32 boot 2 200017920B 456018431B 256000512B ext2 3 456018432B 3000592956927B 3000136938496B

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  • How do I scan my windows partition for viruses from Ubuntu?

    - by Alvar
    I think I might have a virus on my windows partition and I want to scan it Ubuntu. Is this possible? I would like a program that is free. clamAV I tried clamAV but I couldn't find a setting for scaning my other partition that I have windows on, it scaned my Ubuntu disk and that was fine. Antivirus Within Windows I can't use my Windows partition since the virus make my laptop freeze every time I log in. And I don't want it to spread or make more damage than it might have done already.

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  • Is it Possible to Repair Boot Record on Windows Vista Partition on Dual Boot Ubuntu 12.04.02 LTS Install?

    - by PasBonRJB
    I recently successfully installed Ubuntu 12.04.02 Desktop as a "side-by-side" on an eMachines ET1641-02w PC; which before had Windows Vista; but was no longer bootable, because the boot sector somehow got trashed. After I installed Ubuntu I can go to Devices/OS and I can access all of my docs, pics, videos, music, etc. on the Windows Vista partition; but I still can't "boot" the Windows partition. I've seen several posts regarding recovering boot sectors using the Boot-repair app; but am wondering if this "boot-repair" is only for the Ubuntu partition. Can I use "boot-repair" to repair the Windows Vista boot sector?

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  • How do I recover a BTRFS partition that will not mount?

    - by Tony
    The installation for 12.04 kept failing, and the solution was to have the installer ignore the btrfs partition that I have previously been using for /home. Now that it's installed, I've been trying to get it to mount the btrfs partition so that I can access my 70GB of files. It won't mount, and btrfsck errors out with the following three lines: parent transid verify failed on 31302336512 wanted 62455 found 62456 parent transid verify failed on 31302336512 wanted 62455 found 62456 parent transid verify failed on 31302336512 wanted 62455 found 62456 Can someone please tell me how to get this partition working? I've read online that I can probably recover the data using btrfs-restore, but I can't find that program anywhere.

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  • Convert this SQL Query into LINQ (OVER (PARTITION BY Date))

    - by user1106649
    Here's the query i'm trying to convert into Linq: SELECT R.Code, R.FlightNumber, S.[Date], S.Station, R.Liters, SUM(R.Liters) OVER (PARTITION BY Year([Date]), Month([Date]), Day([Date])) AS Total_Liters FROM S INNER JOIN R ON S.ID = R.SID WHERE (R.Code = 'AC') AND FlightNumber = '124' GROUP BY Station, Code, FlightNumber, [Date], Liter ORDER BY R.FlightNumber, [Date] Thanks for any help.

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  • Ubuntu 9.10 Server (minimal virtual machine) partitioning

    - by John
    I am setting up a generic Ubuntu server and am trying to figure out the (best) way to partition the machine. Again, this is just a generic one: The default drive is 20GB. Some guides show: Separate /home, /usr, /var and /tmp partitions Another one suggested something like this: / 4GB /boot 512MB /tmp 1GB /home 5GB /usr 5GB /var 5GB What is the best way to accomplish this?

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