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• When optimizing database queries, what exactly is the relationship between number of queries and siz

  - by williamjones

  To optimize application speed, everyone always advises to minimize the number of queries an application makes to the database, consolidating them into fewer queries that retrieve more wherever possible. However, this also always comes with the caution that data transferred is still data transferred, and just because you are making fewer queries doesn't make the data transferred free. I'm in a situation where I can over-include on the query in order to cut down the number of queries, and simply remove the unwanted data in the application code. Is there any type of a rule of thumb on how much of a cost there is to each query, to know when to optimize number of queries versus size of queries? I've tried to Google for objective performance analysis data, but surprisingly haven't been able to find anything like that. Clearly this relationship will change for factors such as when the database grows in size, making this somewhat individualized, but surely this is not so individualized that a broad sense of the landscape can't be drawn out? I'm looking for general answers, but for what it's worth, I'm running an application on Heroku.com, which means Ruby on Rails with a Postgres database.

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• Understanding CSRF - Simple Question

  - by byronh

  I know this might make me seem like an idiot, I've read everything there is to read about CSRF and I still don't understand how using a 'challenge token' would add any sort of prevention. Please help me clarify the basic concept, none of the articles and posts here on SO I read seemed to really explicitly state what value you're comparing with what. From OWASP: In general, developers need only generate this token once for the current session. After initial generation of this token, the value is stored in the session and is utilized for each subsequent request until the session expires. If I understand the process correctly, this is what happens. I log in at http://example.com and a session/cookie is created containing this random token. Then, every form includes a hidden input also containing this random value from the session which is compared with the session/cookie upon form submission. But what does that accomplish? Aren't you just taking session data, putting it in the page, and then comparing it with the exact same session data? Seems like circular reasoning. These articles keep talking about following the "same-origin policy" but that makes no sense, because all CSRF attacks ARE of the same origin as the user, just tricking the user into doing actions he/she didn't intend. Is there any alternative other than appending the token to every single URL as a query string? Seems very ugly and impractical, and makes bookmarking harder for the user.

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• Disabling normal link behaviour on click with an if statement in Jquery?

  - by Qwibble

  I've been banging my head with this all day, trying anything and everything I can think of to no gain. I'm no Jquery guru, so am hoping someone here can help me out. What I'm trying to do in pseudo code (concept) seems practical and easy to implement, but obviously not so =D What I have is a navigation sidebar, with sub menu's within some li's, and a link at the head of each li. When a top level link is clicked, I want the jquery to check if the link has a sibling ul. If it does, the link doesn't act like a link, but slides down the sibling sub nav. If there isn't one, the link should act normally. Here's where I'm at currently, what am I doing wrong? $('ul.navigation li a').not('ul.navigation li ul li a').click(function (){ if($(this).parent().contains('ul')){ $('ul.navigation li ul').slideUp(); $(this).siblings('ul').slideDown(); return false; } else{ alert('Link Clicked') // Maybe do some more stuff in here... } }); Any ideas?

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• question regarding templatization of virtual function

  - by jan

  Hi, I am new to this forum and sorry If I am repeating this question. I know that you cannot templatize the virtual function and I do understand the concept behind it. But I still need a way to get across some errors I am getting it. I am able to make my stuff work but it doesn't look to me. Here's the deal, I have class called System, #include "Vector.h" class System { virtual void VectorToLocal(Vector<T>& global_dir,const Vector<T>* global_pos = 0) const = 0; }; class UnresolvedSystem : public System { virtual void VectorToLocal(Vector<T>& global_dir,const Vector<T>* global_pos = 0) const { //do something } }; In Vector.h tenplate<typename T> class Vector { //some functions }; See now I want to templatize VectorToLocal in system.h to take just Vector, but I cannot do it as it is a virtual function. I want a work around. I know I can have VectorToLocal take Vector, Vector etc as arguments. But I do not want to do it. Any help would be really appreciated. Thanks in advance, Jan

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• Reading email address from contacts fails with weird memory issue

  - by CapsicumDreams

  Hi all, I'm stumped. I'm trying to get a list of all the email address a person has. I'm using the ABPeoplePickerNavigationController to select the person, which all seems fine. I'm setting my ABRecordRef personDealingWith; from the person argument to - (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker shouldContinueAfterSelectingPerson:(ABRecordRef)person property:(ABPropertyID)property identifier:(ABMultiValueIdentifier)identifier { and everything seems fine up till this point. The first time the following code executes, all is well. When subsequently run, I can get issues. First, the code: // following line seems to make the difference (issue 1) // NSLog(@"%d", ABMultiValueGetCount(ABRecordCopyValue(personDealingWith, kABPersonEmailProperty))); // construct array of emails ABMultiValueRef multi = ABRecordCopyValue(personDealingWith, kABPersonEmailProperty); CFIndex emailCount = ABMultiValueGetCount(multi); if (emailCount 0) { // collect all emails in array for (CFIndex i = 0; i < emailCount; i++) { CFStringRef emailRef = ABMultiValueCopyValueAtIndex(multi, i); [emailArray addObject:(NSString *)emailRef]; CFRelease(emailRef); } } // following line also matters (issue 2) CFRelease(multi); If compiled as written, the are no errors or static analysis problems. This crashes with a *** -[Not A Type retain]: message sent to deallocated instance 0x4e9dc60 error. But wait, there's more! I can fix it in either of two ways. Firstly, I can uncomment the NSLog at the top of the function. I get a leak from the NSLog's ABRecordCopyValue every time through, but the code seems to run fine. Also, I can comment out the CFRelease(multi); at the end, which does exactly the same thing. Static compilation errors, but running code. So without a leak, this function crashes. To prevent a crash, I need to haemorrhage memory. Neither is a great solution. Can anyone point out what's going on?

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• Pass enum value to method which is called by dynamic object

  - by user329588

  hello. I'm working on program which dynamically(in runtime) loads dlls. For an example: Microsoft.AnalysisServices.dll. In this dll we have this enum: namespace Microsoft.AnalysisServices { [Flags] public enum UpdateOptions { Default = 0, ExpandFull = 1, AlterDependents = 2, } } and we also have this class Cube: namespace Microsoft.AnalysisServices { public sealed class Cube : ... { public Cube(string name); public Cube(string name, string id); .. .. .. } } I dynamically load this dll and create object Cube. Than i call a method Cube.Update(). This method deploy Cube to SQL Analysis server. But if i want to call this method with parameters Cube.Update(UpdateOptions.ExpandFull) i get error, because method doesn't get appropriate parameter. I have already tried this, but doesn't work: dynamic updateOptions = AssemblyLoader.LoadStaticAssembly("Microsoft.AnalysisServices", "Microsoft.AnalysisServices.UpdateOptions");//my class for loading assembly Array s = Enum.GetNames(updateOptions); dynamic myEnumValue = s.GetValue(1);//1 = ExpandFull dynamicCube.Update(myEnumValue);// == Cube.Update(UpdateOptions.ExpandFull) I know that error is in parameter myEnumValue but i don't know how to get dynamically enum type from assembly and pass it to the method. Does anybody know the solution? Thank you very much for answers and help!

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• Turing Machine & Modern Computer

  - by smwikipedia

  I heard a lot that modern computers are based on Turing machine. I'd like to share my understanding and hear your comments. I think the computer is a big general-purpose Turing machine. Each program we write is a small specific-purpose Turing machine. The classical Turing machine do its job based on the input and its current state inside and so do our programs. Let's take a running program (a process) as an example. We know that in the process's address space, there's areas for stack, heap, and code. A classical Turing machine doesn't have the ability to remember many things, so we borrow the concept of stack from the push-down automaton. The heap and stack areas contains the state of our specific-purpose Turing machine (our program). The code area represents the logic of this small Turing machine. And various I/O devices supply input to this Turing machine. The above is my naive understanding about the working paradigm of modern computer. I couln't wait to hear your comments. Thanks very much.

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• PHP OOP: Providing Domain Entities with "Identity"

  - by sunwukung

  Bit of an abstract problem here. I'm experimenting with the Domain Model pattern, and barring my other tussles with dependencies - I need some advice on generating Identity for use in an Identity Map. In most examples for the Data Mapper pattern I've seen (including the one outlined in this book: http://apress.com/book/view/9781590599099) - the user appears to manually set the identity for a given Domain Object using a setter: $UserMapper = new UserMapper; //returns a fully formed user object from record sets $User = $UserMapper->find(1); //returns an empty object with appropriate properties for completion $UserBlank = $UserMapper->get(); $UserBlank->setId(); $UserBlank->setOtherProperties(); Now, I don't know if I'm reading the examples wrong - but in the first $User object, the $id property is retrieved from the data store (I'm assuming $id represents a row id). In the latter case, however, how can you set the $id for an object if it has not yet acquired one from the data store? The problem is generating a valid "identity" for the object so that it can be maintained via an Identity Map - so generating an arbitrary integer doesn't solve it. My current thinking is to nominate different fields for identity (i.e. email) and demanding their presence in generating blank Domain Objects. Alternatively, demanding all objects be fully formed, and using all properties as their identity...hardly efficient. (Or alternatively, dump the Domain Model concept and return to DBAL/DAO/Transaction Scripts...which is seeming increasingly elegant compared to the ORM implementations I've seen...)

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• Encryption puzzle / How to create a ProxyStub for a Remote Assistance ticket

  - by Jon Clegg

  I am trying to create a ticket for Remote Assistance. Part of that requires creating a PassStub parameter. As of the documenation: http://msdn.microsoft.com/en-us/library/cc240115(PROT.10).aspx PassStub: The encrypted novice computer's password string. When the Remote Assistance Connection String is sent as a file over e-mail, to provide additional security, a password is used.<16 In part 16 they detail how to create as PassStub. In Windows XP and Windows Server 2003, when a password is used, it is encrypted using PROV_RSA_FULL predefined Cryptographic provider with MD5 hashing and CALG_RC4, the RC4 stream encryption algorithm. As PassStub looks like this in the file: PassStub="LK#6Lh*gCmNDpj" If you want to generate one yourself run msra.exe in Vista or run the Remote Assistance tool in WinXP. The documentation says this stub is the result of the function CryptEncrypt with the key derived from the password and encrypted with the session id (Those are also in the ticket file). The problem is that CryptEncrypt produces a binary output way larger then the 15 byte PassStub. Also the PassStub isn't encoding in any way I've seen before. Some interesting things about the PassStub encoding. After doing statistical analysis the 3rd char is always a one of: !#$&()+-=@^. Only symbols seen everywhere are: *_ . Otherwise the valid characters are 0-9 a-z A-Z. There are a total of 75 valid characters and they are always 15 bytes. Running msra.exe with the same password always generates a different PassStub, indicating that it is not a direct hash but includes the rasessionid as they say. Some other ideas I've had is that it is not the direct result of CryptEncrypt, but a result of the rasessionid in the MD5 hash. In MS-RA (http://msdn.microsoft.com/en-us/library/cc240013(PROT.10).aspx). The "PassStub Novice" is simply hex encoded, and looks to be the right length. The problem is I have no idea how to go from any hash to way the ProxyStub looks like.

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• About updating a View using in iPhone using Objective C.

  - by Tattat

  I have a scene, called testScene, it works like this: @interface testScene : myScene { IBOutlet UIView *subview; IBOutlet UIView *drawingCanvasView; IBOutlet UIButton *update; } - (void)updateDrawingCanvas: (id) sender; and when the user click the button, update, it will run the updateDrawingCanvas method. So, I have a drawingCanvasView, which gave a drawingCanvas.h, and .m, it like this: #import <UIKit/UIKit.h> @interface DrawingCanvasView : UIView { CGImageRef image; } -(void)setNeedsDisplayInRect:(CGContextRef)context; @end In the DrawingCanvasView, I have a drawRect method like this: CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor); CGContextMoveToPoint(context, 0.0f, 0.0f); CGContextAddLineToPoint(context, 100.0f, 100.0f); CGContextStrokePath(context); And I want the user click the button, and execute this, so I added a new method called setNeedsDisplayInRect: CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor yellowColor].CGColor); CGContextMoveToPoint(context, 0.0f, 0.0f); CGContextAddLineToPoint(context, 200.0f, 200.0f); CGContextStrokePath(context); But I can't called that in my updateDrawingCanvas method, it work like this: - (void)updateDrawingCanvas: (id) sender{ NSLog(@"loaded"); [DrawingCanvasView setNeedsDisplayInRect:UIGraphicsGetCurrentContext()]; } It my logic / concept right? or something I did wrong, thx.

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• Common practice for higher-order-polymorphism in scala

  - by raichoo

  Hi, I'm trying to grasp higher-order-polymophism in scala by implementing a very basic interface that describes a monad but I come across a problem that I don't really understand. I implemented the same with C++ and the code looks like this: #include <iostream> template <typename T> class Value { private: T value; public: Value(const T& t) { this->value = t; } T get() { return this->value; } }; template < template <typename> class Container > class Monad { public: template <typename A> Container<A> pure(const A& a); }; template <template <typename> class Container> template <typename A> Container<A> Monad<Container>::pure(const A& a) { return Container<A>(a); } int main() { Monad<Value> m; std::cout << m.pure(1).get() << std::endl; return 0; } When trying to do the same with scala I fail: class Value[T](val value: T) class Monad[Container[T]] { def pure[A](a: A): Container[A] = Container[A](a) } object Main { def main(args: Array[String]): Unit = { val m = new Monad[Value] m.pure(1) } } The compiler complains about: [raichoo@lain:Scala]:434> scalac highorder.scala highorder.scala:5: error: not found: value Container Container[A](a) ^ one error found What am I doing wrong here? There seems to be a fundamental concept I don't seem to understand about scala typeconstructors. Regards, raichoo

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• Creating foreach loops using Code Igniter controller and view

  - by Tim

  Hello, This is a situation I have found myself in a few times and I just want clear it up once and for all. Best just to show you what I need to do in some example code. My Controller function my_controller() { $id = $this->uri->segment(3); $this->db->from('cue_sheets'); $this->db->where('id', $id); $data['get_cue_sheets'] = $this->db->get(); $this->db->from('clips'); $this->db->where('sheet_id', ' CUE SHEET ID GOES IN HERE ??? '); $data['get_clips'] = $this->db->get(); $this->load->view('show_sheets_and_clips', $data); } My View <?php if($get_cue_sheets->result_array()) { ?> <?php foreach($get_cue_sheets->result_array() as $sheetRow): ?> <h1><?php echo $sheetRow['sheet_name']; ?></h1> <br/> <?php if($get_clips->result_array()) { ?> <ul> <?php foreach($get_clips->result_array() as $clipRow): ?> <li><?php echo $clipRow['clip_name']; ?></li> <?php endforeach; ?> </ul> <?php } else { echo 'No Clips Found'; } ?> <?php endforeach; ?> <?php } ?> The problem I am having is the concept of passing data back to the controller from the view as I am sending the Database Queries off to the view as an array, when I really need to get some more information as to which sheet ID I am looking for to show the relevant clips. I hope this makes sense to someone out there. Thanks, Tim

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• Error in creating trigger using PHP script.. Please help!!!! Geeks

  - by Parth

  I've been successful in creating a simple trigger with a PHP script. The problem comes when I have to use "DELIMITER" in my trigger creating because I have nested if/then statements. For example, the following DOES work: $sql = 'CREATE TRIGGER `database`.`detail` BEFORE INSERT on `database`.`vibez_detail` FOR EACH ROW set @a=new.realtime_value'; $junk = mysqli_query($link, $sql); However, if I need to use "DELIMITER" I get errors galore. Here's what works if I go to the MySQL client at the server: DELIMITER $$; DROP TRIGGER `database`.`detail`$$ CREATE TRIGGER `database`.`detail` BEFORE INSERT on `database`.`vibez_detail` FOR EACH ROW BEGIN set new.data_rate = 69; insert into alarm_trips_parent values (null, new.data_rate, 6969, now()); set @tripped_time = now(); set @tripped:=true; end if; end if; END$$ DELIMITER ;$$ How can I construct the PHP code to get this to work? Seems the mysqli_query($link, $sql) chokes as soon as I put "DELIMITER" in the $sql variable. I get the following error when I attempt to do so: Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DELIMITER //; CREATE TRIGGER `database`.`detail` BEFORE INS' at line 1 Even The concept for using mysqli_multi_query(); didn't worked for me.... :(

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• Help needed in grokking password hashes and salts

  - by javafueled

  I've read a number of SO questions on this topic, but grokking the applied practice of storing a salted hash of a password eludes me. Let's start with some ground rules: a password, "foobar12" (we are not discussing the strength of the password). a language, Java 1.6 for this discussion a database, postgreSQL, MySQL, SQL Server, Oracle Several options are available to storing the password, but I want to think about one (1): Store the password hashed with random salt in the DB, one column Found on SO and elsewhere is the automatic fail of plaintext, MD5/SHA1, and dual-columns. The latter have pros and cons MD5/SHA1 is simple. MessageDigest in Java provides MD5, SHA1 (through SHA512 in modern implementations, certainly 1.6). Additionally, most RDBMSs listed provide methods for MD5 encryption functions on inserts, updates, etc. The problems become evident once one groks "rainbow tables" and MD5 collisions (and I've grokked these concepts). Dual-column solutions rest on the idea that the salt does not need to be secret (grok it). However, a second column introduces a complexity that might not be a luxury if you have a legacy system with one (1) column for the password and the cost of updating the table and the code could be too high. But it is storing the password hashed with a random salt in single DB column that I need to understand better, with practical application. I like this solution for a couple of reasons: a salt is expected and considers legacy boundaries. Here's where I get lost: if the salt is random and hashed with the password, how can the system ever match the password? I have theory on this, and as I type I might be grokking the concept: Given a random salt of 128 bytes and a password of 8 bytes ('foobar12'), it could be programmatically possible to remove the part of the hash that was the salt, by hashing a random 128 byte salt and getting the substring of the original hash that is the hashed password. Then re hashing to match using the hash algorithm...??? So... any takers on helping. :) Am I close?

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• matching an element's class to another element's ID, or *part* of another element's ID

  - by shecky

  hello again Such a simple concept but I'm struggling to express it ... apologies in advance for my verbosity. I have a container div with a class, e.g., ; I want to use that class to do two things: add a class (e.g., 'active') to the nav element whose ID matches the class of div#container (e.g., #nav-primary li# apples) add the same class to another element if part of this element's ID matches the class of #container (e.g., div#secondary-apples) I assume there's an .each() loop to check the primary nav's list items' IDs, and to check the div IDs of the secondary nav ... though the latter needs to have its prefix trimmed ... or should I say more simply if the secondary nav div IDs contain the class of div#container? I've tried a few variations of something like this: <script type="text/javascript"> $(document).ready(function() { $('#nav-primary li').each(function(){ var containerClass = $('#container').attr('class'); var secondaryID = $('#nav-primary li').attr('id'); // something like if ('#nav-primary li id' == (containerClass) { } // or should I first store a variable of the LI's ID and do something like this: if ( secondaryID == containerClass ) { } // and for the trickier part, how do I filter/trim the secondary nav div IDs, something like this: var secondaryNavID = $('#aux-left div[id ... something here to strip the 'secondary-' bit ... ]'); }); // end each }); // end doc.ready.func </script> The markup is, e.g.: ... ... ... ... ... ... ... Many thanks in advance for any suggestions, svs

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• Is there the equivalent of cloud computing for modems?

  - by morpheous

  I asked this question on SF, and someone recommended that I ask it here - (I don't think I have enough points to move a question from SF to SO - and in any case, I don't know how to do it - so here is the question again): I am interested in the concept of PAAS (platform as a service). However, all talk about SAAS/PAAS seems to focus on only the computer itself - not its peripherals. Is it possible to 'outsource' modems as a resource - so that an app running remotely can pump data to a modem in the cloud? As a bit of background to the question, a group of us are thinking of starting a company that offers similar services to companies like twilio etc - but I want to 'outsource' both the computing hardware (thats PAAS - the easy bit) and the modems (thats what I cant seem to find any info on). Does anyone know if modems can be bundled as part of a PAAS service? - alternatively, is there a way that an application running on one computer can communicate (i.e. pump data) to a remote modem residing on another machine?. I assume I can come up with some protocol over UDP or TCP - but there is no point reinventing the wheel - if such a protocol like that already exists (or if it some open source software allows one to do this). Any suggestions on how to solve this problem?

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• Encryption puzzle / How to create a PassStub for a Remote Assistance ticket

  - by Jon Clegg

  I am trying to create a ticket for Remote Assistance. Part of that requires creating a PassStub parameter. As of the documentation: http://msdn.microsoft.com/en-us/library/cc240115(PROT.10).aspx PassStub: The encrypted novice computer's password string. When the Remote Assistance Connection String is sent as a file over e-mail, to provide additional security, a password is used.<16 In part 16 they detail how to create as PassStub. In Windows XP and Windows Server 2003, when a password is used, it is encrypted using PROV_RSA_FULL predefined Cryptographic provider with MD5 hashing and CALG_RC4, the RC4 stream encryption algorithm. As PassStub looks like this in the file: PassStub="LK#6Lh*gCmNDpj" If you want to generate one yourself run msra.exe in Vista or run the Remote Assistance tool in WinXP. The documentation says this stub is the result of the function CryptEncrypt with the key derived from the password and encrypted with the session id (Those are also in the ticket file). The problem is that CryptEncrypt produces a binary output way larger then the 15 byte PassStub. Also the PassStub isn't encoding in any way I've seen before. Some interesting things about the PassStub encoding. After doing statistical analysis the 3rd char is always a one of: !#$&()+-=@^. Only symbols seen everywhere are: *_ . Otherwise the valid characters are 0-9 a-z A-Z. There are a total of 75 valid characters and they are always 15 bytes. Running msra.exe with the same password always generates a different PassStub, indicating that it is not a direct hash but includes the rasessionid as they say. Some other ideas I've had is that it is not the direct result of CryptEncrypt, but a result of the rasessionid in the MD5 hash. In MS-RA (http://msdn.microsoft.com/en-us/library/cc240013(PROT.10).aspx). The "PassStub Novice" is simply hex encoded, and looks to be the right length. The problem is I have no idea how to go from any hash to way the PassStub looks like.

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• How can I work around SQL Server - Inline Table Value Function execution plan variation based on par

  - by Ovidiu Pacurar

  Here is the situation: I have a table value function with a datetime parameter ,lest's say tdf(p_date) , that filters about two million rows selecting those with column date smaller than p_date and computes some aggregate values on other columns. It works great but if p_date is a custom scalar value function (returning the end of day in my case) the execution plan is altered an the query goes from 1 sec to 1 minute execution time. A proof of concept table - 1K products, 2M rows: CREATE TABLE [dbo].[POC]( [Date] [datetime] NOT NULL, [idProduct] [int] NOT NULL, [Quantity] [int] NOT NULL ) ON [PRIMARY] The inline table value function: CREATE FUNCTION tdf (@p_date datetime) RETURNS TABLE AS RETURN ( SELECT idProduct, SUM(Quantity) AS TotalQuantity, max(Date) as LastDate FROM POC WHERE (Date < @p_date) GROUP BY idProduct ) The scalar value function: CREATE FUNCTION [dbo].[EndOfDay] (@date datetime) RETURNS datetime AS BEGIN DECLARE @res datetime SET @res=dateadd(second, -1, dateadd(day, 1, dateadd(ms, -datepart(ms, @date), dateadd(ss, -datepart(ss, @date), dateadd(mi,- datepart(mi,@date), dateadd(hh, -datepart(hh, @date), @date)))))) RETURN @res END Query 1 - Working great SELECT * FROM [dbo].[tdf] (getdate()) The end of execution plan: Stream Aggregate Cost 13% <--- Clustered Index Scan Cost 86% Query 2 - Not so great SELECT * FROM [dbo].[tdf] (dbo.EndOfDay(getdate())) The end of execution plan: Stream Aggregate Cost 4% <--- Filter Cost 12% <--- Clustered Index Scan Cost 86%

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• database schema eligible for delta synchronization

  - by WilliamLou

  it's a question for discussion only. Right now, I need to re-design a mysql database table. Basically, this table contains all the contract records I synchronized from another database. The contract record can be modified, deleted or users can add new contract records via GUI interface. At this stage, the table structure is exactly the same as the Contract info (column: serial number, expiry date etc.). In that case, I can only synchronize the whole table (delete all old records, replace with new ones). If I want to delta(only synchronize with modified, new, deleted records) synchronize the table, how should I change the database schema? here is the method I come up with, but I need your suggestions because I think it's a common scenario in database applications. 1)introduce a sequence number concept/column: for each sequence, mark the new added records, modified records, deleted records with this sequence number. By recording the last synchronized sequence number, only pass those records with higher sequence number; 2) because deleted contracts can be added back, and the original table has primary key constraints, should I create another table for those deleted records? or add a flag column to indicate if this contract has been deleted? I hope I explain my question clearly. Anyway, if you know any articles or your own suggestions about this, please let me know. Thanks!

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• Flexible CMS for non-programmers

  - by Bunkerbewohner

  Hello! I'm looking for a content management system that allows creating single pages out of predefined blocks flexibly. For example I have a "product" block that is used to show producs on a page and it may appear numerous times on one page with different contents. But I also might wanna use it on different pages. Also I have simply generic blocks like multiple column text blocks (1 col, 2 col etc.) where I just want to insert this kind of structure into the page and enter any text. So I'm looking for a cms with someething like a building block / module concept for contents. I'm already searching the web but there are so many CMSs that I can't look into every one. So if anyone knows a solution that might be right for me, please tell me! Technology-wise it just has to run on Linux. If it's OpenSource / free that's great, but I might also pay for it, if it offers the features I want. Thanks for any hints in advance!

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• conceptual question : what do performSelectorOnMainThread do?

  - by hib

  Hello all, I just come across this strange situation . I was using the technique of lazy image loading from apple examples . when I was used the class in my application it gave me topic to learn but don't what was actually happening there . So here goes the scenario : I think everybody has seen the apple lazytableimagesloading . I was reloading my table on finishing the parsing of data : - (void)didFinishParsing:(NSMutableArray *)appList { self.upcomingArray = [NSMutableArray arrayWithArray:loadedApps]; // we are finished with the queue and our ParseOperation [self.upcomingTableView reloadData]; self.queue = nil; // we are finished with the queue and our ParseOperation } but as a result the the connection was not starting and images were not loading . when I completely copy the lazyimageloading and I replaced the above code with the following code it works fine - (void)didFinishParsing:(NSMutableArray *)appList { [self performSelectorOnMainThread:@selector(handleLoadedApps:) withObject:appList waitUntilDone:NO]; self.queue = nil; // we are finished with the queue and our ParseOperation } So I want to know what is the concept behind this . Please let me know if you can not understand the question or details are not enough because I desperately want to know why it is like this ?

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• Where is my python script spending time? Is there "missing time" in my cprofile / pstats trace?

  - by fmark

  I am attempting to profile a long running python script. The script does some spatial analysis on raster GIS data set using the gdal module. The script currently uses three files, the main script which loops over the raster pixels called find_pixel_pairs.py, a simple cache in lrucache.py and some misc classes in utils.py. I have profiled the code on a moderate sized dataset. pstats returns: p.sort_stats('cumulative').print_stats(20) Thu May 6 19:16:50 2010 phes.profile 355483738 function calls in 11644.421 CPU seconds Ordered by: cumulative time List reduced from 86 to 20 due to restriction <20> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.008 0.008 11644.421 11644.421 <string>:1(<module>) 1 11064.926 11064.926 11644.413 11644.413 find_pixel_pairs.py:49(phes) 340135349 544.143 0.000 572.481 0.000 utils.py:173(extent_iterator) 8831020 18.492 0.000 18.492 0.000 {range} 231922 3.414 0.000 8.128 0.000 utils.py:152(get_block_in_bands) 142739 1.303 0.000 4.173 0.000 utils.py:97(search_extent_rect) 745181 1.936 0.000 2.500 0.000 find_pixel_pairs.py:40(is_no_data) 285478 1.801 0.000 2.271 0.000 utils.py:98(intify) 231922 1.198 0.000 2.013 0.000 utils.py:116(block_to_pixel_extent) 695766 1.990 0.000 1.990 0.000 lrucache.py:42(get) 1213166 1.265 0.000 1.265 0.000 {min} 1031737 1.034 0.000 1.034 0.000 {isinstance} 142740 0.563 0.000 0.909 0.000 utils.py:122(find_block_extent) 463844 0.611 0.000 0.611 0.000 utils.py:112(block_to_pixel_coord) 745274 0.565 0.000 0.565 0.000 {method 'append' of 'list' objects} 285478 0.346 0.000 0.346 0.000 {max} 285480 0.346 0.000 0.346 0.000 utils.py:109(pixel_coord_to_block_coord) 324 0.002 0.000 0.188 0.001 utils.py:27(__init__) 324 0.016 0.000 0.186 0.001 gdal.py:848(ReadAsArray) 1 0.000 0.000 0.160 0.160 utils.py:50(__init__) The top two calls contain the main loop - the entire analyis. The remaining calls sum to less than 625 of the 11644 seconds. Where are the remaining 11,000 seconds spent? Is it all within the main loop of find_pixel_pairs.py? If so, can I find out which lines of code are taking most of the time?

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• how do i work bool!

  - by user350217

  HI! im a beginner and im really getting frustrated with this whole concept. i dont understand how to exactly use the bool function. i know what it is but i cantfigure out how to make it work in my program. Im trying to say that if my variable "selection" is any letter beween 'A' and 'I' then it is valid and can continue on to the next function which is called calcExchangeAmt(amtExchanged, selection). if it is false i want it to ask the user if they want to repeat the program and if they agree to repeat i want it to clear the screen and restart to the main function. please help edit my work! this is my bool function: bool isSelectionValid(char selection, char yesNo, double amtExchanged) { bool validData; validData = true; if((selection >= 'a' && selection <= 'i') || (selection >= 'A' && selection <= 'I')) { validData = calcExchangeAmt (amtExchanged, selection); } else(validData == false); { cout<<"Do you wish to continue? (Y for Yes / N for No)"; cin>>yesNo; } do { main(); } while ((yesNo =='y')||(yesNo == 'Y')); { system("cls"); } return 0; } this is the warning that im gettng: warning C4800: 'double' : forcing value to bool 'true' or 'false' (performance warning)

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• An unusual type signature

  - by Travis Brown

  In Monads for natural language semantics, Chung-Chieh Shan shows how monads can be used to give a nicely uniform restatement of the standard accounts of some different kinds of natural language phenomena (interrogatives, focus, intensionality, and quantification). He defines two composition operations, A_M and A'_M, that are useful for this purpose. The first is simply ap. In the powerset monad ap is non-deterministic function application, which is useful for handling the semantics of interrogatives; in the reader monad it corresponds to the usual analysis of extensional composition; etc. This makes sense. The secondary composition operation, however, has a type signature that just looks bizarre to me: (<?>) :: (Monad m) => m (m a -> b) -> m a -> m b (Shan calls it A'_M, but I'll call it <?> here.) The definition is what you'd expect from the types; it corresponds pretty closely to ap: g <?> x = g >>= \h -> return $ h x I think I can understand how this does what it's supposed to in the context of the paper (handle question-taking verbs for interrogatives, serve as intensional composition, etc.). What it does isn't terribly complicated, but it's a bit odd to see it play such a central role here, since it's not an idiom I've seen in Haskell before. Nothing useful comes up on Hoogle for either m (m a -> b) -> m a -> m b or m (a -> b) -> a -> m b. Does this look familiar to anyone from other contexts? Have you ever written this function?

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• how send data record using SendMessage(..) in separate process

  - by XBasic3000

  i use to send a data on two separate process but it fails. it works only under same process... this is concept. //----------------------------------------------------------------------------------- MainApps //----------------------------------------------------------------------------------- Type PMyrec = ^TMyrec; TMyrec = Record name : string; add : string; age : integer; end; :OnButtonSend var aData : PMyrec; begin new(aData); aData.Name := 'MyName'; aData.Add := 'My Address'; aData.Age : 18; SendMessage(FindWindow('SubApps'),WM_MyMessage,0,Integer(@aData)); end; //----------------------------------------------------------------------------------- SubApps //----------------------------------------------------------------------------------- Type PMyrec = ^TMyrec; TMyrec = Record name : string; add : string; age : integer; end; :OnCaptureMessage var aData : PMyrec; begin aData := PMyrec(Msg.LParam); showmessage(aData^.Name); end;

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