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• Modifying existing object attributes in Core Data after the fact

  - by glorifiedHacker

  In a previous question, I was looking for an alternative to modifying how "no date" was being stored in the date attribute of my NSManagedObject subclass. Previously, I had assigned nil to that attribute when a user didn't assign a date. In order to address sorting issues when using NSFetchedResultsController, I have decided to assign [NSDate distantFuture] to the date attribute when a user doesn't assign a date. However, given that this app is already in the wild, I need to update the Core Data store such that any existing nil date values are changed to [NSDate distantFuture]. What is the best way to make this change? The first thing that comes to mind is to iterate through all of the objects in the store in an array and change any nil values that are found. This could be limited to a one-time event by checking against a user defaults key that indicates whether this upgrade has been performed. Is there a way that I can do this with Core Data versioning instead? Or another method that doesn't involve me writing throw-away code?

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• Select all points in a matrix within 30m of another point

  - by pinnacler

  So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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• jquery - array problem help pls.

  - by russp

  Sorry folks, I really need help with posting an array problem. I would imaging it's quite simple, but beyond me. I have this JQuery function (using sortables) $(function() { $("#col1, #col2, #col3, #col4").sortable({ connectWith: '.column', items: '.portlet:not(.ui-state-disabled)', stop : function () { serial_1 = $('#col1').sortable('serialize'); serial_2 = $('#col2').sortable('serialize'); serial_3 = $('#col3').sortable('serialize'); serial_4 = $('#col4').sortable('serialize'); } }); }); Now I can post it to a database like this, and I can loop this ajax through all 4 "serials" $.ajax({ url: "test.php", type: "post", data: serial_1, error: function(){ alert(testit); } }); But that is not what I want to do as it creates 4 rows in the DB table. I want/need to create a single "nested array" from the 4 serials so that it enters the DB as 1 (one) row. My "base" database data looks like this: a:4:{s:4:"col1";a:3:{i:1;s:6:"forums";i:2;s:4:"chat";i:3;s:5:"blogs";}s:4:"col2";a:2:{i:1;s:5:"pages";i:2;s:7:"members";}s:4:"col3";a:2:{i:1;s:9:"galleries";i:2;s:4:"shop";}s:4:"col4";a:1:{i:1;s:4:"news";}} Therefore the JQuery array should "replicate" and create it (obviously will change on sorting) Help please thanks in advance

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• How to color HTML elements based on a user command string

  - by Anonymous the Great

  When you type something like "red:Hi:" it will type "Hi" in red. The following script does not work and I do not know why, (The one who made the sorting PHP function is Graphain, thanks again!) <?php function getit($raw) { # If the value was posted $raw = isset($raw) ? $raw : ""; # Split it based on ':' $parsed = explode(':', $raw); $colorClass = ""; $text = ""; if (count($parsed) >= 2) { $colorClass = $parsed[0]; $text = $parsed[1]; $text = "~~~" . $text . "~~~" . $colorClass; return $text; } } ?> <script type="text/javascript"> function postit() { var preview = document.getElementById("preview").value; var submit = document.getElementById("post").value; var text = <?php getit(submit); ?> var t = text[0]; preview = t; } </script> <textarea id="preview" cols=70 rows=5 readonly>Preview box</textarea> <p> <textarea id="post" cols=70 rows=5/>Submit box</textarea> <p> <input type="button" onclick="postit();" value="Submit"/>

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• ASP.Net MVC: Showing the same data using different layouts...

  - by vdh_ant

  Hi guys I'm wanting to create a page that allows the users to select how they would like to view their data - i.e. summary (which supports grouping), grid (which supports grouping), table (which supports grouping), map, time line, xml, json etc. Now each layout would probably have different use a different view model, which inherit from a common base class/view model. The reason being that each layout needs the object structure that it deals with to be different (some need hierarchical others a flatter structure). Each layout would call the same repository method and each layout would support the same functionality, i.e. searching and filtering (hence these controls would be shared between layouts). The main exception to this would be sorting which only grid and table views would need to support. Now my question is given this what do people think is the best approach. Using DisplayFor to handle the rendering of the different types? Also how do I work this with the actions... I would imagine that I would use the one action, and pass in the layout types, but then how does this support the grouping required for the summary, grid and table views. Do i treat each grouping as just a layout type Also how would this work from a URL point of view - what do people think is the template to support this layout functionality Cheers Anthony

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• TFS query mixing Tasks and Bugs, sorted by Priority

  - by Val

  We're using TFS with MSF for Agile 4.2 on a project, and I have a bunch of work to do, both Tasks and Bugs. Both are prioritized by our managers, and assigned due dates and target releases. I use a Work Item query as my main TODO list, and I want to list all the Work Items assigned to me, in order by due date and priority. Problem: I can't seem to find a way to write a unified query that will list both Tasks and Bugs sorted by date and then priority. The problem is that Tasks and Bugs use different fields for Priority. So, my query currently lists the tasks by Due Date, then by Task Priority, then it lists Bugs by Due Date, then by Priority. So, I see tasks that are due later than bugs: Title Due Date Priority Task Priority task1 4/23/2010 Medium task2 4/23/2010 High task3 4/30/2010 Low task4 4/30/2010 Medium bug1 4/23/2010 1 bug2 4/23/2010 2 What I want: Title Due Date Priority Task Priority task1 4/23/2010 Medium task2 4/23/2010 High bug1 4/23/2010 1 bug2 4/23/2010 2 task3 4/30/2010 Low task4 4/30/2010 Medium I don't care if the bugs come before or after the tasks on the same due date; I just want all the work items grouped together by due date, so I never see Tasks for a later due date before Bugs for an earlier one. Another problem is the sorting on Task Priority -- alpha sort means I can't get them to sort by the meaning of the priority. But that's a minor problem I can live with if I can get the Tasks and Bugs intermingled. Any way to do this in a single query?

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• Reporting Services - can't group by a column called "LanguageId"

  - by marc_s

  Folks, I have a really odd behavior here: I have a SQL Server 2008 Reporting Services report which gets grouped and sorted dynamically. One of the column in my data set which I display is called LanguageId and I was trying to get a grouping going by this LanguageId field. I checked, double-checked and triple-checked the data being returned - it does contain my expected values for LanguageId and everything seems fine and dandy. It just never worked - I didn't get the expected groups, I got things like a specific node actually changing its display value from one ID to another when expanding its subitems, and other really whacky stuff. I discovered that grouping and sorting by LanguageCaption works just fine. It also started working fine after I renamed LanguageId to MyLanguageId. So where on earth is this documented that LanguageId appears to be a system variable / reserved word / keyword of some sort in SQL Server Reporting Services that must be avoided at all costs?? I can't seem to find anything on that topic - even Mr. Google and Mrs. Bing came up empty so far....

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• Breeze Expand not working on WebAPI with EF

  - by Rodney

  I have published a WebAPI service which returns a list of items. I am implementing Breeze and have managed to get it basically working with filtering/sorting. However, the Expand is not working. http://www.ftter.com/desktopmodules/framework/api/dare/dares/?$filter=DareId%20eq%2010&expand%20eq%20ToUser You can see the ToUserId ForeignKey in the response above, but the ToUser properties are NULL (the user definitely exists) You can see the ToUser EF navigation property in the metadata. When I use .Include on the server side I can populate it with EF, but I don't want to do this. [HttpGet] [Queryable(AllowedQueryOptions = AllowedQueryOptions.All)] public HttpResponseMessage Dares() { var response = Request.CreateResponse(HttpStatusCode.OK, (IQueryable<Dare>)contextProvider.Context.Dares); return ControllerUtilities.GetResponseWithCorsHeader(response); } and here is the generated class from my EF model (using Database First) public partial class Dare { public int DareId { get; set; } public int ToUserId { get; set; } public virtual User ToUser { get; set; } }

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• Ideas Related to Subset Sum with 2,3 and more integers

  - by rolandbishop

  I've been struggling with this problem just like everyone else and I'm quite sure there has been more than enough posts to explain this problem. However in terms of understanding it fully, I wanted to share my thoughts and get more efficient solutions from all the great people in here related to Subset Sum problem. I've searched it over the Internet and there is actually a lot sources but I'm really willing to re-implement an algorithm or finding my own in order to understand fully. The key thing I'm struggling with is the efficiency considering the set size will be large. (I do not have a limit, just conceptually large). The two phases I'm trying to implement ideas on is finding two numbers that are equal to given integer T, finding three numbers and eventually K numbers. Some ideas I've though; For the two integer part I'm thing basically sorting the array O(nlogn) and for each element in the array searching for its negative value. (i.e if the array element is 3 searching for -3). Maybe a hash table inclusion could be better, providing a O(1) indexing the element? For the three or more integers I've found an amazing blog post;http://www.skorks.com/2011/02/algorithms-a-dropbox-challenge-and-dynamic-programming/. However even the author itself states that it is not applicable for large numbers. So I was for 2 and 3 and more integers what ideas could be applied for the subset problem. I'm struggling with setting up a dynamic programming method that will be efficient for the large inputs as well.

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• Achieving Thread-Safety

  - by Smasher

  Question How can I make sure my application is thread-safe? Are their any common practices, testing methods, things to avoid, things to look for? Background I'm currently developing a server application that performs a number of background tasks in different threads and communicates with clients using Indy (using another bunch of automatically generated threads for the communication). Since the application should be highly availabe, a program crash is a very bad thing and I want to make sure that the application is thread-safe. No matter what, from time to time I discover a piece of code that throws an exception that never occured before and in most cases I realize that it is some kind of synchronization bug, where I forgot to synchronize my objects properly. Hence my question concerning best practices, testing of thread-safety and things like that. mghie: Thanks for the answer! I should perhaps be a little bit more precise. Just to be clear, I know about the principles of multithreading, I use synchronization (monitors) throughout my program and I know how to differentiate threading problems from other implementation problems. But nevertheless, I keep forgetting to add proper synchronization from time to time. Just to give an example, I used the RTL sort function in my code. Looked something like FKeyList.Sort (CompareKeysFunc); Turns out, that I had to synchronize FKeyList while sorting. It just don't came to my mind when initially writing that simple line of code. It's these thins I wanna talk about. What are the places where one easily forgets to add synchronization code? How do YOU make sure that you added sync code in all important places?

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• Ruby: Why is Array.sort slow for large objects?

  - by David Waller

  A colleague needed to sort an array of ActiveRecord objects in a Rails app. He tried the obvious Array.sort! but it seemed surprisingly slow, taking 32s for an array of 3700 objects. So just in case it was these big fat objects slowing things down, he reimplemented the sort by sorting an array of small objects, then reordering the original array of ActiveRecord objects to match - as shown in the code below. Tada! The sort now takes 700ms. That really surprised me. Does Ruby's sort method end up copying objects about the place rather than just references? He's using Ruby 1.8.6/7. def self.sort_events(events) event_sorters = Array.new(events.length) {|i| EventSorter.new(i, events[i])} event_sorters.sort! event_sorters.collect {|es| events[es.index]} end private # Class used by sort_events class EventSorter attr_reader :sqn attr_reader :time attr_reader :index def initialize(index, event) @index = index @sqn = event.sqn @time = event.time end def <=>(b) @time != b.time ? @time <=> b.time : @sqn <=> b.sqn end end

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• Creating one row of information in excel using a unique value

  - by user1426513

  This is my first post. I am currently working on a project at work which requires that I work with several different worksheets in order to create one mail master worksheet, as it were, in order to do a mail merge. The worksheet contains information regarding different purchases, and each purchaser is identified with their own ID number. Below is an example of what my spreadsheet looks like now (however I do have more columns): ID Salutation Address ID Name Donation ID Name Tickets 9 Mr. John Doe 123 12 Ms. Jane Smith 100.00 12 Ms.Jane Smith 300.00 12 Ms. Jane Smith 456 22 Mr. Mike Man 500.00 84 Ms. Jo Smith 300.00 What I would like to do is somehow sort my data so that everythign with the same unique identifier (ID) lines up on the same row. For example ID 12 Jane Smith - all the information for her will show up under her name matched by her ID number, and ID 22 will match up with 22 etc... When I merged all of my spreadsheets together, I sorted them all by ID number, however my problem is, not everyone who made a donation bought a ticket or some people just bought tickets and nothing us, so sorting doesn't work. Hopefully this makes sense. Thanks in advance.

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• A feeling that I'm not that good developer

  - by Karim

  Hi, Im having a strange feeling, but let me first introduce myself as a software developer. I started to program when I was still a kid, I had about 10 or 11 years. I really enjoy my work and never get bored from it. It's amazing how somebody could be paid for what he really likes to do and would be doing it anyway even for free. WHen I first started to program, I was feeling proud of what I was doing, each application I built was for me a success and after 2-3 year I had a feeling that I'm a coding guru. It was a nice feeling ;-) But the more I was in the field, the more types of software I started to develop I was starting to have a feeling that I'm completely wrong in that I'm guru. I felt that I'm not even a mediocre developer. Each new field I start to work on is giving me this feeling. Like when I once developed a device driver for a client, I saw how much I need to learn about device drivers. When I developed a video filter for an application, I saw how much do I still need to learn about DirectShow, Color Spaces, and all the theory behind that. The worst thing was when I started to learn algorithms. It was several years ago. I knew then the basic structures and algorithms like the sorting, some types of trees, some hashtables, strings etc.. and when I really wanted to learn a group of structures I learned about 5-6 new types and saw that in fact even this small group has several hundred subtypes of structures. It's depressing how little time people have in their lives to learn all this stuff. I'm now a software developer with about 10 years of experience and I still feel that I'm not a proficient developer when I think about things that others do in the industry. Is this normal what I'm experiencing or is it a sign of a destructive excessive ambition? Thanks in advance for any comments.

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• Recursive QuickSort suffering a StackOverflowException -- Need fresh eyes

  - by jon

  I am working on a Recursive QuickSort method implementation in a GenericList Class. I will have a second method that accepts a compareDelegate to compare different types, but for development purposes I'm sorting a GenericList<int I am recieving stackoverflow areas in different places depending on the list size. I've been staring at and tracing through this code for hours and probably just need a fresh pair of (more experienced)eyes. Definitely wanting to learn why it is broken, not just how to fix it. public void QuickSort() { int i, j, lowPos, highPos, pivot; GenericList<T> leftList = new GenericList<T>(); GenericList<T> rightList = new GenericList<T>(); GenericList<T> tempList = new GenericList<T>(); lowPos = 1; highPos = this.Count; if (lowPos < highPos) { pivot = (lowPos + highPos) / 2; for (i = 1; i <= highPos; i++) { if (this[i].CompareTo(this[pivot]) <= 0) leftList.Add(this[i]); else rightList.Add(this[i]); } leftList.QuickSort(); rightList.QuickSort(); for(i=1;i<=leftList.Count;i++) tempList.Add(leftList[i]); for(i=1;i<=rightList.Count;i++) tempList.Add(rightList[i]); this.items = tempList.items; this.count = tempList.count; } }

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• SQL query to translate a list of numbers matched against several ranges, to a list of values

  - by Claes Mogren

  I need to convert a list of numbers that fall within certain ranges into a list of values, ordered by a priority column. The table has the following values: | YEAR | R_MIN | R_MAX | VAL | PRIO | ------------------------------------ 2010 18000 90100 52 6 2010 240000 240099 82 3 2010 250000 259999 50 5 2010 260000 260010 92 1 2010 330000 330010 73 4 2010 330011 370020 50 5 2010 380000 380050 84 2 The ranges will be different for different years. The ranges within one year will never overlap. The input will be a year and a list of numbers that might fall within one these ranges. The list of input number will be small, 1 to 10 numbers. Example of input numbers: (20000, 240004, 375000, 255000) With that input I would like to get a list ordered by the priority column, or a single value: 82 50 52 The only value I'm interested in here is 82, so UNIQUE and MAX_RESULTS=1 would do. It can easily be done with one query per number, and then sorting it in the Java code, but I would prefer to do it in a single SQL query. What SQL query, to be run in an Oracle database, would give me the desired result?

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• What is the complexity of this specialized sort

  - by ADB

  I would like to know the complexity (as in O(...) ) of the following sorting algorithm: there are B barrels that contains a total of N elements, spread unevenly across the barrels. the elements in each barrel are already sorted The sort takes combines all the elements from each barrel in a single sorted list: using an array of size B to store the last sorted element of each barrel (starting at 0) check each barrel (at the last stored index) and find the smallest element copy the element in the final sorted array, increment array counter increment the last sorted element for the barrel we picked from perform those steps N times or in pseudo: for i from 0 to N smallest = MAX_ELEMENT foreach b in B if bIndex[b] < b.length && b[bIndex[b]] < smallest smallest_barrel = b smallest = b[bIndex[b]] result[i] = smallest bIndex[smallest_barrel] += 1 I thought that the complexity would be O(n), but the problem I have with finding the complexity is that if B grows, it has a larger impact than if N grows because it adds another round in the B loop. But maybe that has no effect on the complexity?

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• strcmp() but with 0-9 AFTER A-Z? (C/C++)

  - by Aaron

  For reasons I completely disagree with but "The Powers (of Anti-Usability) That Be" continue to decree despite my objections, I have a sorting routine which does basic strcmp() compares to sort by its name. It works great; it's hard to get that one wrong. However, at the 11th hour, it's been decided that entries which begin with a number should come AFTER entries which begin with a letter, contrary to the ASCII ordering. They cite the EBCDIC standard has numbers following letters so the prior assumption isn't a universal truth, and I have no power to win this argument... but I digress. Therein lies my problem. I've replaced all appropriate references to strcmp with a new function call nonstd_strcmp, and now need to implement the modifications to accomplish the sort change. I've used a FreeBSD source as my base: http://freebsd.active-venture.com/FreeBSD-srctree/newsrc/libkern/strncmp.c.html if (n == 0) return (0); do { if (*s1 != *s2++) return (*(const unsigned char *)s1 - *(const unsigned char *)(s2 - 1)); if (*s1++ == 0) break; } while (--n != 0); return (0); I guess I might need to take some time away to really think about how it should be done, but I'm sure I'm not the only one who's experienced the brain-deadness of just-before-release spec changes.

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• SQLDeveloper using over 100MB of PGA+UGA

  - by Leigh Riffel

  Perhaps this is normal, but in my Oracle 11g database I am seeing programmers using Oracle's SQL Developer regularly consume more than 100MB of combined UGA and PGA memory. I'd like to know if this is normal and what can be done about it. Our database is on the 32 bit version of Windows 2008, so memory limitations are becoming an increasing concern. I am using the following query to show the memory usage: SELECT e.SID, e.username, e.status, b.PGA_MEMORY FROM v$session e LEFT JOIN (select y.SID, y.value pga, TO_CHAR(ROUND(y.value/1024/1024),99999999) || ' MB' PGA_MEMORY from v$sesstat y, v$statname z where y.STATISTIC# = z.STATISTIC# and NAME = 'session pga memory') b ON e.sid=b.sid WHERE (PGA)/1024/1024 > 20 ORDER BY 4 DESC; It seems that the resource usage goes up any time a table is opened in SQLDeveloper, but even when it is closed the memory does not go away. The problem is worse if the table is sorted while it was open as that seems to use even more memory. I understand how this would use memory while it is sorting, and perhaps even while it is still open, but to use memory after it is closed seems wrong to me. Can anyone confirm this? Update: I discovered that my numbers were off due to not understanding that the UGA is stored in the PGA under dedicated server mode. This makes the numbers lower than they were, but the problem still remains that SQL Developer seems to use excessive PGA.

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• Enhancing an 'ORDER BY' clause to judge condition by more than 1 integer

  - by Yvonne

  Hi folks, I have some PHP code which allows me to sort a column into ascending and descending order (upon click of a table row title), which is good. It works perfectly for my D.O.B colum (with date/time field type), but not for a quantity column. For example, I have quantites of 10, 50, 100, 30 and another 100. The order seems to be only appreciating the 1st integer, so my sorting of the column ends up in this order: 10, 100, 100, 30, 50... and 50, 30, 100, 100, 10. This is obviously incorrect as 100 is bigger than 50, therefore both 100 values should appear at the end surely? It seems to me that 100 is only being taken into account as having the '1' value, then it appears before 10 because the system recognises it has another 0. Is this normal to happen? Is there any way I can solve this problem? Thanks for any help. P.S. I can show code if necessary, but would like to know if this is a common issue by default.

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• CMD Prompt > FTP Size Command

  - by Samuel Baldus

  I'm developing a PHP App on IIS 7.5, which uses PHP FTP commands. These all work, apart from ftp_size(). I've tested: cmd.exe > ftp host > username > password > SIZE filename = Invalid Command However, if I access the FTP site through an Internet Browser, the filesize is displayed. Do I need to install FTP Extensions, and if so, which ones and where do I get them? Here is the PHP Code: <?php // FTP Credentials $ftpServer = "www.domain.com"; $ftpUser = "username"; $ftpPass = "password"; // Unlimited Time set_time_limit(0); // Connect to FTP Server $conn = @ftp_connect($ftpServer) or die("Couldn't connect to FTP server"); // Login to FTP Site $login = @ftp_login($conn, $ftpUser, $ftpPass) or die("Login credentials were rejected"); // Set FTP Passive Mode = True ftp_pasv ($conn, true); // Build the file list $ftp_nlist = ftp_nlist($conn, "."); // Alphabetical sorting sort($ftp_nlist); // Display Output foreach ($ftp_nlist as $raw_file) { // Get the last modified time $mod = ftp_mdtm($conn, $raw_file); // Get the file size $size = ftp_size($conn, $raw_file); // Size is not '-1' => file if (!(ftp_size($conn, $raw_file) == -1)) { //output as file echo "Filename: $raw_file<br />"; echo "FileSize: ".number_format($size, '')."Kb</br>"; echo "Last Modified: ".date("d/m/Y H:i", $mod)."</br>"; } } ?>

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• Is it possible in Perl to require a subroutine call is made?

  - by MitchelWB

  I don't know enough about Perl to even know what I'm asking for exactly, but I'm writing a series of subroutines to be available for many individual scripts that all process different incoming flat files. The process is far from perfect, but it's what I've got to deal with and I'm trying to build myself a small library of subs that make it easier for me to manage it all. Each script handles a different incoming flat file with it's own formatting, sorting, grouping and outputting requirements. One common aspect is that we have small text files that house counters that are used to name the output files so that we have no duplicate file names. Because the processing of the data is different for each file, I need to open the file to get my counter value, because this is a common operation, I'd like to put it in a sub to retrieve the counter. But then need to write specific code to process the data. And would like a second sub that allows me to update the counter with the counter once I've processed the data. Is there a way to make the second sub call a requirement if the first one is called? Ideally if it could even be an error that would prevent the script from running at all much like a syntax error. EDIT: Here is a little [ugly and simplified] psuedo-code to give a better feel for what the current process is: require "importLibrary.plx"; #open data source file open DataIn, $filename; #call getCounterInfo from importLibrary.plx to get the counter value from counter file $counter = &getCounterInfo($counterFileName); while (<DataIn>) { #Process data based on unique formatting and requirements #output to task files based on requirements and name files using the $counter #increment $counter } #update counter file with new value of $counter &updateCounterInfo($counter);

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• how does MySQL implement the "group by"?

  - by user188916

  I read from the MySQL Reference Manual and find that when it can take use of index,it just do index scan,other it will create tmp tables and do things like filesort. And I also read from other article that the "Group By" result will sort by group by columns by default,if "order by null" clause added,it won't don filesort. The difference can be found from the "explain ..." clause. so my problem is:what is the difference between "group by" clause that with "order by null" and which doesn't have? I try to use profiling to see what mysql do on the background,and only see result like: result for group clause without order by null: |preparing | 0.000016 | | Creating tmp table | 0.000048 | | executing | 0.000009 | | Copying to tmp table | 0.000109 | **| Sorting result | 0.000023 |** | Sending data | 0.000027 | result for clause with "order by null": preparing | 0.000016 | | Creating tmp table | 0.000052 | | executing | 0.000009 | | Copying to tmp table | 0.000114 | | Sending data | 0.000028 | So I guess what MySQL do when the "order by null" added,it does not use filesort algorithm,maybe when it creates the tmp table,it uses index as well,and then use the index to do group by operation,when completed,it just read result from the table rows and does not sort the result. But my original opinion is that MySQL can use quicksort to sort the items and then do group by,so the result will be sorted as well. Any opinion appreciated,thanks.

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• Is there a reason why SSIS significantly slows down after a few minutes?

  - by Mark

  I'm running a fairly substantial SSIS package against SQL 2008 - and I'm getting the same results both in my dev environment (Win7-x64 + SQL-x64-Developer) and the production environment (Server 2008 x64 + SQL Std x64). The symptom is that initial data loading screams at between 50K - 500K records per second, but after a few minutes the speed drops off dramatically and eventually crawls embarrasingly slowly. The database is in Simple recovery model, the target tables are empty, and all of the prerequisites for minimally logged bulk inserts are being met. The data flow is a simple load from a RAW input file to a schema-matched table (i.e. no complex transforms of data, no sorting, no lookups, no SCDs, etc.) The problem has the following qualities and resiliences: Problem persists no matter what the target table is. RAM usage is lowish (45%) - there's plenty of spare RAM available for SSIS buffers or SQL Server to use. Perfmon shows buffers are not spooling, disk response times are normal, disk availability is high. CPU usage is low (hovers around 25% shared between sqlserver.exe and DtsDebugHost.exe) Disk activity primarily on TempDB.mdf, but I/O is very low (< 600 Kb/s) OLE DB destination and SQL Server Destination both exhibit this problem. To sum it up, I expect either disk, CPU or RAM to be exhausted before the package slows down, but instead its as if the SSIS package is taking an afternoon nap. SQL server remains responsive to other queries, and I can't find any performance counters or logged events that betray the cause of the problem. I'll gratefully reward any reasonable answers / suggestions.

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• How to use MySQL geospatial extensions with spherical geometries

  - by Joshua

  Hi Everyone, I would like to store thousands of latitude/longitude points in a MySQL db. I was successful at setting up the tables and adding the data using the geospatial extensions where the column 'coord' is a Point(lat, lng). Problem: I want to quickly find the 'N' closest entries to latitude 'X' degrees and longitude 'Y' degrees. Since the Distance() function has not yet been implemented, I used GLength() function to calculate the distance between (X,Y) and each of the entries, sorting by ascending distance, and limiting to 'N' results. The problem is that this is not calculating shortest distance with spherical geometry. Which means if Y = 179.9 degrees, the list of closest entries will only include longitudes of starting at 179.9 and decreasing even though closer entries exist with longitudes increasing from -179.9. How does one typically handle the discontinuity in longitude when working with spherical geometries in databases? There has to be an easy solution to this, but I must just be searching for the wrong thing because I have not found anything helpful. Should I just forget the GLength() function and create my own function for calculating angular separation? If I do this, will it still be fast and take advantage of the geospatial extensions? Thanks! josh UPDATE: This is exactly what I am describing above. However, it is only for SQL Server. Apparently SQL Server has a Geometry and Geography datatypes. The geography does exactly what I need. Is there something similar in MySQL?

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• OrderBy Linq.Expression as parameter = (Of Func(Of T,IComparable)) to perform LinqToEntity is not working

  - by NicoJuicy

  I'd like to get this working: Call: (Count & Page are used for pagination, so Count = 20 and Page = 1 for example, for the first 20 values). Sorting should be by name LeverancierService.GetLeveranciers(Function(el) el.Name, Count, Page) Equivalent in c#: LeverancierService.GetLeveranciers(el= el.Name, Count, Page) Method that gives an error (parameters shown above): Public Overridable Function GetAllPaged(orderby As Expression(Of Func(Of T, IComparable)), ByVal Count As Integer, ByVal Page As Integer) As IEnumerable(Of T) Return dbset.OrderBy(orderby).Skip((Page - 1) * Count).Take(Count).ToList() End Function Already tried changing it to this, but it gives the same error: Public Overridable Function GetAllPaged(Of TOrderBy)(orderby As Expression(Of Func(Of T, TOrderBy)), ByVal Count As Integer, ByVal Page As Integer) As IEnumerable(Of T) Return dbset.OrderBy(orderby).Skip((Page - 1) * Count).Take(Count).ToList() End Function Error: Unable to cast the type 'System.String' to type 'System.IComparable'. LINQ to Entities only supports casting Entity Data Model primitive types. Any idea how to do this? Extra info: I'm in a DDD-layered application, so the parameter should stay the same as the called method is an overridden interface (eg. if i change this, i have to do this for 200 times or so, because it's in VB.Net and not in C# (= 1 change) ) I know there is a way to change the expression to a string and then use DLinq (= Dynamic Linq), but that's not how it should be.

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