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  • How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?

    - by Stu Thompson
    Prelude: I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS. About 18 months ago I moved our servers from a premium hosting centric vendor to a barebones rack pusher in a tier IV data center. (Literally across the street.) This ment doing much more ourselves--things like networking, storage and monitoring. As part the big move, to replace our leased direct attached storage from the hosting company, I built a 9TB two-node NAS based on SuperMicro chassises, 3ware RAID cards, Ubuntu 10.04, two dozen SATA disks, DRBD and . It's all lovingly documented in three blog posts: Building up & testing a new 9TB SATA RAID10 NFSv4 NAS: Part I, Part II and Part III. We also setup a Cacit monitoring system. Recently we've been adding more and more data points, like SMART values. I could not have done all this without the awesome boffins at ServerFault. It's been a fun and educational experience. My boss is happy (we saved bucket loads of $$$), our customers are happy (storage costs are down), I'm happy (fun, fun, fun). Until yesterday. Outage & Recovery: Some time after lunch we started getting reports of sluggish performance from our application, an on-demand streaming media CMS. About the same time our Cacti monitoring system sent a blizzard of emails. One of the more telling alerts was a graph of iostat await. Performance became so degraded that Pingdom began sending "server down" notifications. The overall load was moderate, there was not traffic spike. After logging onto the application servers, NFS clients of the NAS, I confirmed that just about everything was experiencing highly intermittent and insanely long IO wait times. And once I hopped onto the primary NAS node itself, the same delays were evident when trying to navigate the problem array's file system. Time to fail over, that went well. Within 20 minuts everything was confirmed to be back up and running perfectly. Post-Mortem: After any and all system failures I perform a post-mortem to determine the cause of the failure. First thing I did was ssh back into the box and start reviewing logs. It was offline, completely. Time for a trip to the data center. Hardware reset, backup an and running. In /var/syslog I found this scary looking entry: Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_00], 6 Currently unreadable (pending) sectors Nov 15 06:49:44 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_07], SMART Prefailure Attribute: 1 Raw_Read_Error_Rate changed from 171 to 170 Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 16 Currently unreadable (pending) sectors Nov 15 06:49:45 umbilo smartd[2827]: Device: /dev/twa0 [3ware_disk_10], 4 Offline uncorrectable sectors Nov 15 06:49:45 umbilo smartd[2827]: Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error Nov 15 06:49:45 umbilo smartd[2827]: # 1 Short offline Completed: read failure 90% 6576 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 2 Short offline Completed: read failure 90% 6087 3421766910 Nov 15 06:49:45 umbilo smartd[2827]: # 3 Short offline Completed: read failure 10% 5901 656821791 Nov 15 06:49:45 umbilo smartd[2827]: # 4 Short offline Completed: read failure 90% 5818 651637856 Nov 15 06:49:45 umbilo smartd[2827]: So I went to check the Cacti graphs for the disks in the array. Here we see that, yes, disk 7 is slipping away just like syslog says it is. But we also see that disk 8's SMART Read Erros are fluctuating. There are no messages about disk 8 in syslog. More interesting is that the fluctuating values for disk 8 directly correlate to the high IO wait times! My interpretation is that: Disk 8 is experiencing an odd hardware fault that results in intermittent long operation times. Somehow this fault condition on the disk is locking up the entire array Maybe there is a more accurate or correct description, but the net result has been that the one disk is impacting the performance of the whole array. The Question(s) How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt? Am I being naïve to think that the RAID card should have dealt with this? How can I prevent a single misbehaving disk from impacting the entire array? Am I missing something?

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  • Referencing file on disk from NSManagedObject

    - by Kamchatka
    Hello, What would be the best way to name a file associated to a NSManagedObject. The NSManagedObject will hold the URL to this file. But I need to create a unique filename for my file. Is there some kind of autoincrement id that I could use? Should I use mktemp (but it's not a temporary file) or try to convert the NSManagedObjectId to a filename? but I fear there will be special characters which might cause problem. What would you suggest?

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  • How to check if something is stored in CoreData

    - by Terrel Gibson
    Hi I want to be able to tore some information in core data and but i am unsure of how to check if the file was saved properly. I tried using NSLog but it returns null when its called. I have a dictionary which has a uniqueID and a title which I want to save. I pass this in along with the context of the database. I then sort the database to check if it has any duplicates or not, if not then I add the file. +(VacationPhoto*) photoWithFlickrInfo: (NSDictionary*) flickrInfo inManagedObjectContext: (NSManagedObjectContext*) context{ //returns the dictionary NSLog(@"Photo To Store =%@", flickrInfo); VacationPhoto * photo = nil; NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"VacationPhoto"]; request.predicate = [NSPredicate predicateWithFormat:@"uniqueID = %@", [flickrInfo objectForKey:FLICKR_PHOTO_ID]]; NSSortDescriptor * descriptor = [NSSortDescriptor sortDescriptorWithKey:@"title" ascending:YES]; request.sortDescriptors = [NSArray arrayWithObject:descriptor]; NSError *error = nil; NSArray *matches = [context executeFetchRequest:request error:&error]; if (!matches || [matches count] > 1) { // handle error } else if ( [matches count] == 0){ photo.title = [flickrInfo objectForKey:FLICKR_PHOTO_TITLE]; //Returns NULL when called NSLog(@"title = %@", photo.title); photo.uniqueID = [flickrInfo objectForKey:FLICKR_PHOTO_ID]; //Returns NULL when called NSLog(@"ID = %@", photo.uniqueID); } else { //If photo already exists this is called photo = [matches lastObject]; } return photo; }

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  • While saving a PNG image using NSData writetofile saves corrupted data on the iphone disk

    - by jAmi
    I have a number of images (PNG,GIF and JPG) in my Application Resource Bundle. I want some images to be saved in my Documents Directory so i use : imgPath=[documentsDirectoryPath stringByAppendingPathComponent:@"myImage.png"]; if (![fileMgr fileExistsAtPath:imgPath]) { [[fileMgr contentsAtPath:[[NSBundle mainBundle] pathForResource:@"myImage"ofType:@"png"]] writeToFile:imgPath atomically:NO]; } This saves an Image file on my desired Path but this file has an Extra 300 bytes (of maybe junk data) in it which results in a corrupted image... Am i doing something wrong here? This works in the simulator but on the real device the image has some extra 300 bytes. Also a GIF image gets copied nicely and works but this problem occurs for PNG image.

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  • Has anybody used the WB B-tree library?

    - by Chris B
    I stumbled across the WB on-disk B-tree library: http://people.csail.mit.edu/jaffer/WB It seems like it could be useful for my purposes (swapping data to disk during very large statistical calculations that do not fit in memory), but I was wondering how stable it is. Reading the manual, it seems worringly 'researchy' - there are sections labelled [NOT IMPLEMENTED] etc. But maybe the manual is just out-of-date. So, is this library useable? Am I better off looking at Tokyo Cabinet, MemcacheDB, etc.? By the way I am working in Java.

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  • Is unnecessary error handling recommended in business logic? eg. Null check/Percentage limit check etc

    - by novice_at_work
    We usually put unnecessary checks in our business logic to avoid failures. Eg. 1. public ObjectABC funcABC(){ ObjectABC obj = new ObjectABC; .......... .......... //its never set to null here. .......... return obj; } ObjectABC o = funABC(); if(o!=null){ //do something } Why do we need this null check if we are sure that it will never be null? Is it a good practice or not? 2. int pplReached = funA(..,..,..); int totalPpl = funB(..,..,..); funA() just puts a few more restriction over result of funB(). Double percentage = (totalPpl==0||totalPpl<pplReached) ? 0.0 : pplReached/totalPpl; Do we again need this check? The questions is: Aren't we swallowing some fundamental issue by putting such checks? Issues which should be shown ideally, are avoided by putting these checks. What is the recommended way?

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  • Check for child duplicates

    - by ebb
    My console app will loop through each User to get their Websites, so that it can take new screenshots of them. However, to prevent taking screenshot of the same website twice I have to check whether there already has been taken screenshot of the website, while looping through another users websites. My current solution is: Database: User |--> ID: 1 |--> FirstName: Joe |--> ID: 2 |--> FirstName: Stranger Websites |--> ID: 1 |--> UserID: 1 |--> URL: http://site.com |--> ID: 2 |--> UserID: 2 |--> URL: http://site.com Console app: static void RenewWebsiteThumbNails() { Console.WriteLine("Starting renewal process..."); using (_repository) { var websitesUpdated = new List<string>(); foreach (var user in _repository.GetAll()) { foreach (var website in user.Websites.Where(website => !websitesUpdated.Contains(website.URL))) { _repository.TakeScreenDumpAndSave(website.URL); websitesUpdated.Add(website.URL); Console.WriteLine(new string('-', 50)); Console.WriteLine("{0} has successfully been renewed", website.URL); } } } } However, it seems wrong to declare a List for such a scenario, just to check whether a specific URL already has been added... any suggestions for an alternative way?

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  • How to open links in new window ONLY IF the check box is checked

    - by Travis
    Here is what i have so far. I have it so they open in new windows, but i want it only if the check box is checked... <!DOCTYPE html> <html> <head> <script> function new() { if ( document.getElementById('checkbox').checked ) window.open( 'y', 'n', 't', 'New Window' ); } else { break; } var OpenNew = document.getElementById('opennew'); OpenNew.addEventListener('click', OpenWin, false ); </script> </head> <body> <p> <form name="test"> <p>Open link in a new window &nbsp; <input type="checkbox" id="checkbox" name="check" /></p> </form> </p> <p> <h2>My favorite Websites to visit</h2> <a href="http://www.youtube.com" target="new" id="y">Youtube</a><br /> <a href="http://www.newegg.com" target="new" id="n">Newegg</a><br /> <a href="http://www.twitch.tv" target="new" id="t">Twitch.tv</a><br /> </p> </body> </html> I am unsure how to actually do the if statement if it is checked then open. It does currently open in a new tab.. i just need it to be only when its checked. Any help with this will be greatly appreciated! Thanks!

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  • Loop to check all 14 days in the pay period

    - by Rachel Ann Arndt
    Name: Calc_Anniversary Input: Pay_Date, Hire_Date, Termination_Date Output: "Y" if is the anniversary of the employee's Hire_Date, "N" if it is not, and "T" if he has been terminated before his anniversary. Description: Create local variables to hold the month and day of the employee's Date_of_Hire, Termination_Date, and of the processing date using the TO_CHAR function. First check to see if he was terminated before his anniversary. The anniversary could be on any day during the pay period, so there will be a loop to check all 14 days in the pay period to see if one was his anniversary. CREATE OR replace FUNCTION Calc_anniversary( incoming_anniversary_date IN VARCHAR2) RETURN BOOLEAN IS hiredate VARCHAR2(20); terminationdate VARCHAR(20); employeeid VARCHAR2(38); paydate NUMBER := 0; BEGIN SELECT Count(arndt_raw_time_sheet_data.pay_date) INTO paydate FROM arndt_raw_time_sheet_data WHERE paydate = incoming_anniversary_date; WHILE paydate <= 14 LOOP SELECT To_char(employee_id, '999'), To_char(hire_date, 'DD-MON'), To_char(termination_date, 'DD-MON') INTO employeeid, hiredate, terminationdate FROM employees, time_sheet WHERE employees.employee_id = time_sheet.employee_id AND paydate = pay_date; IF terminationdate > hiredate THEN RETURN 'T'; ELSE IF To_char(SYSDATE, 'DD-MON') = To_char(hiredate, 'DD-MON')THEN RETURN 'Y'; ELSE RETURN 'N'; END IF; END IF; paydate := paydate + 1; END LOOP; END; Tables I am using CREATE TABLE Employees ( EMPLOYEE_ID INTEGER, FIRST_NAME VARCHAR2(15), LAST_NAME VARCHAR2(25), ADDRESS_LINE_ONE VARCHAR2(35), ADDRESS_LINE_TWO VARCHAR2(35), CITY VARCHAR2(28), STATE CHAR(2), ZIP_CODE CHAR(10), COUNTY VARCHAR2(10), EMAIL VARCHAR2(16), PHONE_NUMBER VARCHAR2(12), SOCIAL_SECURITY_NUMBER VARCHAR2(11), HIRE_DATE DATE, TERMINATION_DATE DATE, DATE_OF_BIRTH DATE, SPOUSE_ID INTEGER, MARITAL_STATUS CHAR(1), ALLOWANCES INTEGER, PERSONAL_TIME_OFF FLOAT, CONSTRAINT pk_employee_id PRIMARY KEY (EMPLOYEE_ID), CONSTRAINT fk_spouse_id FOREIGN KEY (SPOUSE_ID) REFERENCES EMPLOYEES (EMPLOYEE_ID)) / CREATE TABLE Arndt_Raw_Time_Sheet_data ( EMPLOYEE_ID INTEGER, PAY_DATE DATE, HOURS_WORKED FLOAT, SALES_AMOUNT FLOAT, CONSTRAINT pk_employee_id_pay_date_time PRIMARY KEY (EMPLOYEE_ID, PAY_DATE), CONSTRAINT fk_employee_id_time FOREIGN KEY (EMPLOYEE_ID) REFERENCES EMPLOYEES (EMployee_ID)); error FUNCTION Calc_Anniversary compiled Warning: execution completed with warning

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  • Arraylist can't compare objects after they are loaded from disk

    - by Zka
    To make it easy, lets say I have an arraylist allBooks containing class "books" and an arraylist someBooks containing some but not all of the "books". Using contains() method worked fine when I wanted to see if a book from one arraylist was also contained in another. The problem was that this isn't working anymore when I save both of the Arraylists to a .bin file and load them back once the program restarts. Doing the same test as before, the contains() returns false even if the compared objects are the same (have the same info inside). I solved it by overloading the equals method and it works fine, but I want to know why did this happen?

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  • C# arraylist can't compare objects after they are loaded from disk

    - by Zka
    To make it easy, lets say I have an arraylist allBooks containing class "books" and an arraylist someBooks containing some but not all of the "books". Using contains() method worked fine when I wanted to see if a book from one arraylist was also contained in another. The problem was that this isn't working anymore when I save both of the Arraylists to a .bin file and load them back once the program restarts. Doing the same test as before, the contains() returns false even if the compared objects are the same (have the same info inside). I solved it by overloading the equals method and it works fine, but I want to know why did this happen?

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  • Sql Server 2005 Check Constraint not being applied in execution when using variables

    - by DarylS
    Here is some SQL sample code: --Create 2 Sales tables with constraints based on the saledate create table Sales1(SaleDate datetime, Amount money) ALTER TABLE dbo.Sales1 ADD CONSTRAINT CK_Sales1 CHECK (([SaleDate]>='01 May 2010')) GO create table Sales2(SaleDate datetime, Amount money) ALTER TABLE dbo.Sales2 ADD CONSTRAINT CK_Sales2 CHECK (([SaleDate]<'01 May 2010')) GO --Insert some data into Sales1 insert into Sales1 (SaleDate, Amount) values ('02 May 2010', 50) insert into Sales1 (SaleDate, Amount) values ('03 May 2010', 60) GO --Insert some data into Sales2 insert into Sales2 (SaleDate, Amount) values ('30 Mar 2010', 10) insert into Sales2 (SaleDate, Amount) values ('31 Mar 2010', 20) GO --Create a view that combines these 2 tables create VIEW [dbo].[Sales] AS SELECT SaleDate, Amount FROM Sales1 UNION ALL SELECT SaleDate, Amount FROM Sales2 GO --Get the results --Query 1 select * from Sales where SaleDate < '31 Mar 2010' -- if you look at the execution plan this query only looks at Sales2 (Which is good) --Query 2 DECLARE @SaleDate datetime SET @SaleDate = '31 Mar 2010' select * from Sales where SaleDate < @SaleDate -- if you look at the execution plan this query looks at Sales1 and Sales2 (Which is NOT good) Looking at the execution plan you will see that the two queries are differnt. For Query 1 the only table that is accessed is Sales1 (which is good). For Query 2 both tables are accessed (Which is bad). Why are these execution plans different, and how do i get Query 2 to only access the relevant table when variables are used? I have tried to add indexes for the SaleDate column and that does not seem to help.

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  • ASP.Net - How do I allow users to enter html tags in textbox without runtime errors?

    - by Coder
    I have an input textbox on an asp.net page and when a user inputs any tags like break tags or bold an error occurs. I currently am using the following to encode the input: Server.HtmlEncode(mytextbox.Text) However this only encodes characters when they aren't phrased as an html tag, like if the input is "<<<" is there a way for me to allow the user to put the tags in without it leading to a runtime error? Thanks.

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  • NULL pointer dereference in swiotlb_unmap_sg_attrs() on disk IO

    - by Inductiveload
    I'm getting an error I really don't understand when reading or writing files using a PCIe block device driver. I seem to be hitting an issue in swiotlb_unmap_sg_attrs(), which appears to be doing a NULL dereference of the sg pointer, but I don't know where this is coming from, as the only scatterlist I use myself is allocated as part of the device info structure and persists as long as the driver does. There is a stacktrace to go with the problem. It tends to vary a bit in exact details, but it always crashes in swiotlb_unmap_sq_attrs(). I think it's likely I have a locking issue, as I am not sure how to handle the locks around the IO functions. The lock is already held when the request function is called, I release it before the IO functions themselves are called, as they need an (MSI) IRQ to complete. The IRQ handler updates a "status" value, which the IO function is waiting for. When the IO function returns, I then take the lock back up and return to request queue handling. The crash happens in blk_fetch_request() during the following: if (!__blk_end_request(req, res, bytes)){ printk(KERN_ERR "%s next request\n", DRIVER_NAME); req = blk_fetch_request(q); } else { printk(KERN_ERR "%s same request\n", DRIVER_NAME); } where bytes is updated by the request handler to be the total length of IO (summed length of each scatter-gather segment).

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  • Calling a network State check from other activities

    - by Laurent
    I realize this question has been answered before but couldn't find an answer that deals with my specific case. I want to create a class called "InternetConnectionChecks" that will handle checking a network state and http timeouts. I'll call the methods twice in the app (once at the beginning to get data from a server, and once at the end to send user orders to the server). For good form I'd like to put all these methods in a single class rather than copy/paste at different points in my code. To check the network state, I'm using ConnectivityManager; thing is, getSystemService requires a class that extends Activity. package arbuckle.app; import android.app.Activity; import android.app.Service; import android.content.Context; import android.net.ConnectivityManager; import android.net.NetworkInfo; public class InternetConnectionChecks extends Activity { public boolean isNetworkAvailable(){ ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo(); if ((activeNetworkInfo != null)&&(activeNetworkInfo.isConnected())){ return true; }else{ return false; } } } QUESTION: if I call the method isNetworkAvailable from another activity, am I: - going to hit up serious errors. - violating good coding form? *If this isn't the right way to do things, can you point me in the right direction to set up a separate class I can call on to check internet connection? Thanks everyone!

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  • How to check volume is mounted or not using python with a dynamic volume name

    - by SR query
    import subprocess def volumeCheck(volume_name): """This function will check volume name is mounted or not. """ volume_name = raw_input('Enter volume name:') volumeCheck(volume_name) print 'volume_name=',volume_name p = subprocess.Popen(['df', '-h'], stdout=subprocess.PIPE, stderr=subprocess.PIPE) p1, err = p.communicate() pattern = p1 if pattern.find(volume_name): print 'volume found' else: print 'volume not found' While running i always got wrong result "volume found". root@sr-query:/# df -h Filesystem Size Used Avail Use% Mounted on rootfs 938M 473M 418M 54% / /dev/md0 938M 473M 418M 54% / none 250M 4.9M 245M 2% /dev /dev/md2 9.7M 1.2M 8.0M 13% /usr/config /dev/md7 961M 18M 895M 2% /downloads tmpfs 250M 7.9M 242M 4% /var/volatile tmpfs 250M 0 250M 0% /dev/shm tmpfs 250M 0 250M 0% /media/ram **/dev/mapper/vg9-lv9 1016M 65M 901M 7% /VolumeData/sp /dev/mapper/vg10-lv10 1016M 65M 901M 7% /VolumeData/cp** root@sr-query:/# root@sr-query:/# root@sr-query:/# python volume_check.py Enter volume name:raid_10volume volume_name= raid_10volume **volume found** root@sr-query:/# I enterd raid_10volume its not listed here please check the df -h command out put(only 2 volume there sp and cp) , then how it reached else part. what is wrong in my code? Thanks in advance. is there any other way to do this work ! ?

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  • Best data recovery tools?

    - by Nonick
    So due to a recent act of stupidity and bravado, I uttered the words "backups! who needs backups?!" and what followed was the tragic loss of 260gb of data. This scenario in particular is requiring me to recover a repartitioned hard disk, but I was wondering what tools people here use in general to recover lost data. I'm sure everyone has been there, either accidentally rewriting files, resaving an old version, computer crash, hard disk death, user deletes an important document etc. So was thinking it might be an interesting point of discussion as to what you guys use to recover lost data. I appologise if this is considered irrelevant, but considering there has been a few recovery questions, I think this might be interesting.

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  • Prolog, check if term is power of 2

    - by Riku
    i have written following code, which should work with my logic, but it does not. I should check if given term is power of two. For example s(s(s(nul))) should return false, s(s(s(s(nul))) should return true. substractWhileY(X,0,rezult). substractWhileY(s(X),Y,rezult):- Y > 0, number is 1, substractWhileY(X,Y - number, rezult). degreeOftwo(X):- substractWhileY(X,2,rezult), pagalba(X, 2, rezult). calculateAnswer(X, currentCounter, currentValue):- currentCounter is currentCounter * 2, substractWhileY(currentValue, currentCounter , rezult), rezult\= null, calculateAnswer(X, currentCounter , rezult). My idea was to check if given therm is degree of any two and if it is not than it is not the degree of two. With numbers it should work like this. For example i give number 8. First time it checks if 8 - 2 = 0. second time if 8 - 4 = 0. third time if 8 - 8 = 0. so the 8 id power of two. Maybe other solution would work better, so thanks for any help.

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  • zend form check record no exists in database

    - by Yafa Su
    I have a form that check if email exists in the database within 2 tables. I'm using Zend_Validate_Db_NoRecordExists for both validate, but it only check the second one. Any idea why it's not working? class Application_Form_ReferUser extends Zend_Form { public $email, $freeDownload, $buyNow; public function init() { $this->setName('referUser'); $EmailExists = new Zend_Validate_Db_NoRecordExists( array( 'table' => 'referrals', 'field' => 'email' ) ); $EmailExists2 = new Zend_Validate_Db_NoRecordExists( array( 'table' => 'users', 'field' => 'email' ) ); $EmailExists->setMessage('This e-mail is already taken'); $EmailExists2->setMessage('This e-mail is already taken'); $this->email = $this->createElement('text', 'email') ->setLabel('Email') ->addValidator($EmailExists) ->addValidator($EmailExists2) ->addValidator('EmailAddress') ->setRequired(true); $this->freeDownload = $this->createElement('button', 'btn_free_download') ->setLabel('Free Download') ->setAttrib('type', 'submit'); $this->buyNow = $this->createElement('button', 'btn_buy_now') ->setLabel('Buy Now') ->setAttrib('type', 'submit'); $this->addElements(array($this->email, $this->freeDownload, $this->buyNow)); $elementDecorators = array( 'ViewHelper' ); $this->setElementDecorators($elementDecorators); } }

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  • Cant get JavaScipt to check for null objects

    - by CountMurphy
    I really don't know what the issue is here. Far as I can see, the code is simple and should work fine. var Prices=""; for (var PriceCount = 1; PriceCount <= 120; PriceCount++) { var CurrentPrice = "Price" + PriceCount; if (prevDoc.getElementById(CurrentPrice).value != null) { if (Prices == "") { Prices = prevDoc.getElementById(CurrentPrice).value; } else { Prices += "," + prevDoc.getElementById(CurrentPrice).value; } } else { break; } } There could be up to 120 hidden inputs on the form. The moment we check for an input that doesn't exist the loop should break. My test page has two input elements that get pulled. On the third (the null) I get this error in firebug: prevDoc.getElementById(CurrentPrice) is null if (prevDoc.getElementById(CurrentPrice).value != null) { Yes it is null...that's what the check is for ?_? Does any one know what I'm doing wrong? This seems like it should be really straight forward. EDIT: for clarity's sake, prevDoc=window.opener.document

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  • MySQL: LOAD DATA reclaim disk space after delete

    - by Michael
    I have a DB schema composed of MYISAM tables, i am interested to delete old records from time to time from some of the tables. I know that delete does not reclaim the memory space, but as i found in a description of DELETE command, inserts may reuse the space deleted In MyISAM tables, deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions. I am interested if LOAD DATA command also reuses the deleted space? UPDATE I am also interested how the index space reclaimed?

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  • Relating text fields to check boxes in Java

    - by Finzz
    This program requires the user to login and request a database to access. The program then gets a connection object, searches through the database storing the column names into a vector for later use. The problem comes with implementing text fields to allow the user to search for specific values within the database. I can get the check boxes and text fields to appear using a gridlayout and add them to a panel. How do I relate the text fields to their appropriate check box? I've tried adding them to a vector, but then they can't also be added to the panel as well. I've searched for a way to name the text fields as the loop cycles through the column names, but it seems impossible to do without having them declared ahead of time. This can't be done either, as it's impossible to determine the attributes that the user will request. I just need to be able to know the names of the text fields so I can test to see if the user entered information and perform the necessary logic. Let me know if you have to see the rest of the code to give an answer, but hopefully you get the general idea of what I'm trying to accomplish. Picture of UI: try { ResultSet r2 = con.getMetaData().getColumns("", "", rb.getText(), ""); colNames1 = new Vector<String>(); columns1 = new Vector<JCheckBox>(); while (r2.next()) { colNames1.add(r2.getString(4)); JCheckBox cb = new JCheckBox(r2.getString(4)); JTextField tf = new JTextField(10); columns1.add(cb); p3.add(cb); p3.add(tf); } }

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