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  • hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException

    - by user121196
    when saving an object to database using hibernate, sometimes it fails because certain fields of the object exceed the maximum varchar length defined in the database. There force I am using the following approach: 1. attempt to save 2. if getting an DataException, then I truncate the fields in the object to the max length specified in the db definition, then try to save again. However, in the second save after truncation. I'm getting the following exception: hibernate: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails here's the relevant code, what's wrong? public static void saveLenientObject(Object obj){ try { save2(rec); } catch (org.hibernate.exception.DataException e) { // TODO Auto-generated catch block e.printStackTrace(); saveLenientObject(rec, e); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } private static void saveLenientObject(Object rec, DataException e) { Util.truncateObject(rec); System.out.println("after truncation "); save2(rec); } public static void save2(Object obj) throws Exception{ try{ beginTransaction(); getSession().save(obj); commitTransaction(); }catch(Exception e){ e.printStackTrace(); rollbackTransaction(); //closeSession(); throw e; }finally{ closeSession(); } }

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  • Function to even out multiple arrays

    - by Moak
    Assume I have a function evenOut($array, $limit){ //returns exactly $limit items } and this data $animals = array(); $animals['barn'] = array_fill(0,20, 'b'); $animals['forest'] = array_fill(0,20, 'f'); $animals['house'] = array_fill(0,20, 'h'); $animals['mountain'] = array_fill(0,20, 'm'); I want to return a maximum of 10 animals, however they should be spread out evenly among the locations they come from. so if i did evenOut($animals,8); i'd get 2 of each('b','b','f','f','h','h','m','m',) evenOut($animals,2); should return ('b','f') if I have this data $animals = array(); $animals['barn'] = array_fill(0,1, 'b'); $animals['forest'] = array_fill(0,3, 'f'); $animals['house'] = array_fill(0,8, 'h'); $animals['mountain'] = array_fill(0,1, 'm'); evenOut($animals,8); expected result would be ('b','f','f','f','h','h','h','m',) evenOut($animals,10); expected result would be ('b','f','f','f','h','h','h','h','h','m',) $animals = array(); $animals['barn'] = array_fill(0,0, 'b'); $animals['forest'] = array_fill(0,3, 'f'); evenOut($animals,10); expected result would be ('f','f','f') I'm not sure how I should approach this, I am hoping there is a simple way

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  • A data structure based on the R-Tree: creating new child nodes when a node is full, but what if I ha

    - by Tom
    I realize my title is not very clear, but I am having trouble thinking of a better one. If anyone wants to correct it, please do. I'm developing a data structure for my 2 dimensional game with an infinite universe. The data structure is based on a simple (!) node/leaf system, like the R-Tree. This is the basic concept: you set howmany childs you want a node (a container) to have maximum. If you want to add a leaf, but the node the leaf should be in is full, then it will create a new set of nodes within this node and move all current leafs to their new (more exact) node. This way, very populated areas will have a lot more subdivisions than a very big but rarely visited area. This works for normal objects. The only problem arises when I have more than maxChildsPerNode objects with the exact same X,Y location: because the node is full, it will create more exact subnodes, but the old leafs will all be put in the exact same node again because they have the exact same position -- resulting in an infinite loop of creating more nodes and more nodes. So, what should I do when I want to add more leafs than maxChildsPerNode with the exact same position to my tree? PS. if I failed to explain my problem, please tell me, so I can try to improve the explanation.

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  • drawing graphs in php

    - by user434885
    i am using php to generate graphs from arrays. I wish to create multiple graphs on the same page as i need to design a summary report from answers extracted from a database. Currently i am using this code and am only able to get one single graph. what additions to the code do i need to make to get multiple graphs? <?php function draw_graph($values) { // Get the total number of columns we are going to plot $columns = count($values); // Get the height and width of the final image $width = 300; $height = 200; // Set the amount of space between each column $padding = 5; // Get the width of 1 column $column_width = $width / $columns ; // Generate the image variables $im = imagecreate($width,$height); $gray = imagecolorallocate ($im,0xcc,0xcc,0xcc); $gray_lite = imagecolorallocate ($im,0xee,0xee,0xee); $gray_dark = imagecolorallocate ($im,0x7f,0x7f,0x7f); $white = imagecolorallocate ($im,0xff,0xff,0xff); // Fill in the background of the image imagefilledrectangle($im,0,0,$width,$height,$white); $maxv = 0; // Calculate the maximum value we are going to plot for($i=0;$i<$columns;$i++)$maxv = max($values[$i],$maxv); // Now plot each column for($i=0;$i<$columns;$i++) { $column_height = ($height / 100) * (( $values[$i] / $maxv) *100); $x1 = $i*$column_width; $y1 = $height-$column_height; $x2 = (($i+1)*$column_width)-$padding; $y2 = $height; imagefilledrectangle($im,$x1,$y1,$x2,$y2,$gray_dark); } header ("Content-type: image/png"); imagepng($im); imagedestroy($im); } $values = array("23","32","35","57","12"); $values2 = array("123","232","335","157","102"); draw_graph($values2); draw_graph($values);//no output is coming draw_graph($values2);//no output is coming draw_graph($values);//no output is coming ?>

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  • Generating all possible subsets of a given QuerySet in Django

    - by Glen
    This is just an example, but given the following model: class Foo(models.model): bar = models.IntegerField() def __str__(self): return str(self.bar) def __unicode__(self): return str(self.bar) And the following QuerySet object: foobar = Foo.objects.filter(bar__lt=20).distinct() (meaning, a set of unique Foo models with bar <= 20), how can I generate all possible subsets of foobar? Ideally, I'd like to further limit the subsets so that, for each subset x of foobar, the sum of all f.bar in x (where f is a model of type Foo) is between some maximum and minimum value. So, for example, given the following instance of foobar: >> print foobar [<Foo: 5>, <Foo: 10>, <Foo: 15>] And min=5, max=25, I'd like to build an object (preferably a QuerySet, but possibly a list) that looks like this: [[<Foo: 5>], [<Foo: 10>], [<Foo: 15>], [<Foo: 5>, <Foo: 10>], [<Foo: 5>, <Foo: 15>], [<Foo: 10>, <Foo: 15>]] I've experimented with itertools but it doesn't seem particularly well-suited to my needs. I think this could be accomplished with a complex QuerySet but I'm not sure how to start.

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  • MySQL: Limit rows linked to each joined row

    - by SolidSnakeGTI
    Hello, Specifications: MySQL 4.1+ I've certain situation that requires certain result set from MySQL query, let's see the current query first & then ask my question: SELECT thread.dateline AS tdateline, post.dateline AS pdateline, MIN(post.dateline) FROM thread AS thread LEFT JOIN post AS post ON(thread.threadid = post.threadid) LEFT JOIN forum AS forum ON(thread.forumid = forum.forumid) WHERE post.postid != thread.firstpostid AND thread.open = 1 AND thread.visible = 1 AND thread.replycount >= 1 AND post.visible = 1 AND (forum.options & 1) AND (forum.options & 2) AND (forum.options & 4) AND forum.forumid IN(1,2,3) GROUP BY post.threadid ORDER BY tdateline DESC, pdateline ASC As you can see, mainly I need to select dateline of threads from 'thread' table, in addition to dateline of the second post of each thread, that's all under the conditions you see in the WHERE CLAUSE. Since each thread has many posts, and I need only one result per thread, I've used GROUP BY CLAUSE for that purpose. This query will return only one post's dateline with it's related unique thread. My questions are: How to limit returned threads per each forum!? Suppose I need only 5 threads -as a maximum- to be returned for each forum declared in the WHERE CLAUSE 'forum.forumid IN(1,2,3)', how can this be achieved. Is there any recommendations for optimizing this query (of course after solving the first point)? Notes: I prefer not to use sub-queries, but if it's the only solution available I'll accept it. Double queries not recommended. I'm sure there's a smart solution for this situation. Appreciated advice in advance :)

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  • 32-bit JVM on 64-bit Windows crashes on launch with -Xmx1300m and plenty of free memory

    - by Konrad Garus
    I'm struggling with Java heap space settings. The default Java on Windows is the 32-bit client regardless of OS version (that's what Oracle recommends to all users). It appears to set max heap size to 256 MB by default, and that is too little for me. I use a custom launcher to start the application. I would like it to use more memory on computers with plenty RAM, and default to -Xmx512m on those with less RAM. As far as I'm aware, the only way is the static -Xmx setting (that has to be set on launch). I have a user who has 8 GB RAM, 64-bit Windows and 32-bit Java 7. Maximum memory visible to the JVM is 4G (as returned by querying OperatingSystemMXBean). I understand why, no issue. For some reason my application is unable to start for this user with -Xmx1300m, even though he has 2.3G free memory. He closed some applications (having 5G free memory), and still it would not launch. The error reported to me was: error occured during init of vm could not reserve enough space for object heap What's going on? Could it be that the 32-bit JVM is only able to address the "first" 4G of memory and has to have a 1300M block available within those first 4 gigabytes? How can I solve this problem, except for asking everyone to install 64-bit Java (what is unlikely to be acceptable)?

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  • Page URL and database organization.

    - by shurik2533
    I want that its name would be the page address. For example, if page has heading "Some Page", than its address should be http://somesite/some_page/. "some_page"-name generated by system automatically. "some_page" - is the unique identifier of page. The problem in that the user in the future can enter a name which already exists that will cause an error. It is necessary to find an optimum variant of the decision of a problem for great volumes of the data. I have solved a problem as follows: The page identifier in a database is the name of page and a suffix which is by default equal to zero. At page addition there is a check on existence. If such page does not exist, the suffix is equal 0 and its name is "some_page", if page is exist, than - search for the maximum number of a suffix and suffix=suffix+1 and page name become "some_page_1". For this I create in a database the compound key from fields "suffix" and "pageName": Table Pages suffix|pageName |pageTitle 0 |some_page |Some Page 1 |some_page |Some Page 0 |other_page|Other Page Addition of pages occurs through stored procedure: CREATE PROCEDURE addPage (pageNameVal VARCHAR(100), pageTitleVal VARCHAR(100)) BEGIN DECLARE v INT DEFAULT 0; SELECT MAX(suffix) FROM pages WHERE pageName=pageNameVal INTO v; IF v >= 0 THEN SET v = v + 1; ELSE SET v = 0; END IF; INSERT INTO pages (suffix, pageName) VALUES (pageNameVal, v, pageTitleVal); END; Whether there are more the best decisions?

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  • python recursive iteration exceeding limit for tree implementation

    - by user3698027
    I'm implementing a tree dynamically in python. I have defined a class like this... class nodeobject(): def __init__(self,presentnode=None,parent=None): self.currentNode = presentnode self.parentNode = parent self.childs = [] I have a function which gets possible childs for every node from a pool def findchildren(node, childs): # No need to write the whole function on how it gets childs Now I have a recursive function that starts with the head node (no parent) and moves down the chain recursively for every node (base case being the last node having no children) def tree(dad,children): for child in children: childobject = nodeobject(child,dad) dad.childs.append(childobject) newchilds = findchildren(child, children) if len(newchilds) == 0: lastchild = nodeobject(newchilds,childobject) childobject.childs.append(lastchild) loopchild = copy.deepcopy(lastchild) while loopchild.parentNode != None: print "last child" else: tree(childobject,newchilds) The tree formation works for certain number of inputs only. Once the pool gets bigger, it results into "MAXIMUM RECURSION DEPTH EXCEEDED" I have tried setting the recursion limit with set.recursionlimit() and it doesn't work. THe program crashes. I want to implement a stack for recursion, can someone please help, I have gone no where even after trying for a long time ?? Also, is there any other way to fix this other than stack ?

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  • t-sql help with recursive sort of query

    - by stackoverflowuser
    Hi Based on the following table ID Path --------------------------------------- 1 \\Root 2 \\Root\Node0 3 \\Root\Node0\Node1 4 \\Root\Node0\Node2 5 \\Root\Node3 6 \\Root\Node3\Node4 7 \\Root\Node5 ... N \\Root\Node5\Node6\Node7\Node8\Node9\Node10 so on... There are around 1000 rows in this table. I want to display individual node in seperate columns. Maximum columns to be displayed 5 (i.e. node till 5 level deep). So the output will look as below ID Path Level 0 Level 1 Level 2 Level 3 Level 4 Level 5 ---------------------------------------------------------------------------------------- 1 \\Root Root Null Null Null Null Null 2 \\Root\Node0 Root Node 0 Null Null Null Null 3 \\Root\Node0\Node1 Root Node 0 Node 1 Null Null Null 4 \\Root\Node0\Node2 Root Node 0 Node 2 Null Null Null 5 \\Root\Node3 Root Node 3 Null Null Null Null 6 \\Root\Node3\Node4 Root Node 3 Node 4 Null Null Null 7 \\Root\Node5 Root Node 5 Null Null Null Null ... N (see in above table) Root Node 5 Node 6 Node 7 Node 8 Node 9 The only way i can think of is to open a cursor, loop through each row and perform string split, just fetch the first 5 nodes and then insert into a temp table. Pls. suggest. Thanks

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  • C++ and its type system: How to deal with data with multiple types?

    - by sub
    "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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  • How to get the real, actual duration of an MP3 file (VBR or CBR) server-side

    - by Cummander Checkov
    I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only. When testing this locally, i noticed that ffmpeg printed two extra lines in green. Command used: ffmpeg -i song_9747c077aef8.mp3 ffmpeg says: [mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510 [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate After a nice, warm google session, i found some posts on this, but no solution was found. I then tried to increase the maximum duration: ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3 After this, ffmpeg returned only the second line: [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that here the duration is correct. After more research i stumbled over mp3info - which i installed and used. mp3info -p "%S" song_9747c077aef8.mp3 mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations. I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value. Now i ran out of options. If somebody knows how to get around this, any hints, tips, guides or corrections are welcome! Thank You!

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  • HTML Table: How to resize data cells when already specified "colspan"?

    - by Jenny
    I have tabular data to display, which has a meaning to both rows and columns. Columns are time blocks, rows are days. A particular datacell is confined to a single day, but can be in multiple time block. To show this, I am using the colspan tag. <div id = "GuideTable"> <table> <tr> <td colspan = 3> </td></tr></table> </div> Or Whatever. I'm trying to apply CSS formating to the entire table, and for changing colors, etc, things are fine, but wanting to have a consistent width is where I am running into problems. Right now, each data cell's width seems tied to the maximum width in its column (everything auto lines up). Some columns are itty bitty, others are huge. I'm trying to make columns consistently sized (even if that means every column is as big as the biggest column needs to be), but setting an individual datacells width (either via css or in the tag itself) is getting me nowhere. I'm thinking maybe the colspan tag is overriding my manual width? If that's the case, how can I change the width of a column as a whole, especially since they aren't explicitly defined? (CAN you explicitly define columns?) Examples of the CSS I'm using: #GuideTable td{ background:#ffffff; border-style: solid; border-width: 1px; width: 100px; }

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  • [PHP, CSS, & ?] fixed width div, resizing text on the fly based on length

    - by Andrew Heath
    Let's say you've got a simple fixed-width layout that pulls a title from a MySQL database. CSS: #wrapper { width: 800px; } h1 { width: 100%; } HTML: <html> <body> <div id="wrapper"> <h1> $titleString </h1> </div> </body> </html> But the catch is, the length of the title string pulled from your MySQL database varies wildly. Sometimes it might be 10 characters, sometimes it might be 80. It's possible to establish a min & max character count. How, if at all possible, do I get the text-size of my <h1>$titleString</h1> to enlarge/decrease on-the-fly such that the string is only ever on one line and best fit to that line length? I've seen a lot of questions about resizing the div - but in my case the div must always be 100% (800px) and I want to best-fit the title. Obviously a maximum text-size value would have to be set so 5 character strings don't become gargantuan. Does anyone have a suggestion? I'm only using PHP/MySQL/CSS on this page at the moment, but incorporation of another language is fine if it means I can solve the problem. The only thing I can think of is a bruteforce approach whereby through trial and error I establish acceptable string character count ranges matched with CSS em sizes, but that'd be a pretty ugly implementation from the code side.

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  • merging two tables, while applying aggregates on the duplicates (max,min and sum)

    - by cloudraven
    I have a table (let's call it log) with a few millions of records. Among the fields I have Id, Count, FirstHit, LastHit. Id - The record id Count - number of times this Id has been reported FirstHit - earliest timestamp with which this Id was reported LastHit - latest timestamp with which this Id was reported This table only has one record for any given Id Everyday I get into another table (let's call it feed) with around half a million records with these fields among many others: Id Timestamp - Entry date and time. This table can have many records for the same id What I want to do is to update log in the following way. Count - log count value, plus the count() of records for that id found in feed FirstHit - the earliest of the current value in log or the minimum value in feed for that id LastHit - the latest of the current value in log or the maximum value in feed for that id. It should be noticed that many of the ids in feed are already in log. The simple thing that worked is to create a temporary table and insert into it the union of both as in Select Id, Min(Timestamp) As FirstHit, MAX(Timestamp) as LastHit, Count(*) as Count FROM feed GROUP BY Id UNION ALL Select Id, FirstHit,LastHit,Count FROM log; From that temporary table I do a select that aggregates Min(firsthit), max(lasthit) and sum(Count) Select Id, Min(FirstHit),Max(LastHit),Sum(Count) FROM @temp GROUP BY Id; and that gives me the end result. I could then delete everything from log and replace it with everything with temp, or craft an update for the common records and insert the new ones. However, I think both are highly inefficient. Is there a more efficient way of doing this. Perhaps doing the update in place in the log table?

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  • c++ expected constant expression

    - by cpp
    #include <iostream> #include <fstream> #include <cmath> #include <math.h> #include <iomanip> using std::ifstream; using namespace std; int main (void) { int count=0; float sum=0; float maximum=-1000000; float sumOfX; float sumOfY; int size; int negativeY=0; int positiveX=0; int negativeX=0; ifstream points; //the points to be imported from file //points.open( "data.dat"); //points>>size; //cout<<size<<endl; size=100; float x[size][2]; while (count<size) { points>>(x[count][0]); //cout<<"x= "<<(x[count][0])<<" ";//read in x value points>>(x[count][1]); //cout<<"y= "<<(x[count][1])<<endl;//read in y value count++; } This program is giving me expected constant expression error on the line where I declare float x[size][2]. why?

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  • Is there a quality, file-size, or other benefit to JPEG sizes being multiples of 8px or 16px?

    - by davebug
    The JPEG compression encoding process splits a given image into blocks of 8x8 pixels, working with these blocks in future lossy and lossless compressions. [source] It is also mentioned that if the image is a multiple 1MCU block (defined as a Minimum Coded Unit, 'usually 16 pixels in both directions') that lossless alterations to a JPEG can be performed. [source] I am working with product images and would like to know both if, and how much benefit can be derived from using multiples of 16 in my final image size (say, using an image with size 480px by 360px) vs. a non-multiple of 16 (such as 484x362). In this example I am not interested in further alterations, editing, or recompression of the final image. To try to get closer to a specific answer where I know there must be largely generalities: Given a 480x360 image that is 64k and saved at maximum quality in Photoshop [example]: Can I expect any quality loss from an image that is 484x362 What amount of file size addition can I expect (for this example, the additional space would be white pixels) Are there any other disadvantages to growing larger than the 8px grid? I know it's arbitrary to use that specific example, but it would still be helpful (for me and potentially any others pondering an image size) to understand what level of compromise I'd be dealing with in breaking the non-8px grid. The key issue here is a debate I've had is whether 8-pixel divisible images are higher quality than images that are not divisible by 8-pixels.

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  • Javascript Regex: Testing string for intelligent query

    - by Shyam
    Hi, I have a string that holds user input. This string can contain various types of data, like: a six digit id a zipcode that contains out of 4 digits and two alphanumeric characters a name (characters only) As I am using this string to search through a database, the query type is determined on the type of search, which i want to handle serverside using JavaScript (yes, I am using JavaScript serverside). Searching on StackOverflow, brought me some interesting information, like the .test-method, which seems perfect for my needs. The test-method returns either true or false based on the evaluation on the string using a regex object. I am using this page as a reference: http://www.javascriptkit.com/jsref/regexp.shtml So I am trying to determine the zipcode, by using the following very noobish regex. var r = /[A-Za-z]{2,2}/ As far I can understand, this should limit the amount of occurrences of alphanumeric characters to a maximum of two. See beneath the output of my JavaScript console. > var r = /[A-Za-z]{2,2}/ > var x = "2233AL" > r.test(x) true > var x = "2233A" > r.test(x) false > var x = "2233ALL" > r.test(x) true /* i want this to be false */ > A little help would be really appreciated!

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  • How does an ASP.NET programmer go from working on/developing existing sites, to creating one from sc

    - by SLC
    I've been an ASP.NET developer for some time, always working on existing ASP.NET pages, modifying functionality, adding features, tweaking things etc. but have never built a site up from scratch. I've read books on ASP.NET, and they generally talk you through the various features of ASP.NET with a mock up site, but it's always very basic and they jump straight in. The time has come however, to write a site from scratch for a client. I've never done this before. There are design considerations, but like a lot of ASP.NET sites, the basic idea is, you have a site, where users can log in, and save some information like their name and password and address. The site has some functionality, but that's the basic design of a majority of (business-related) asp.net websites I would wager. I know how to program in ASP.NET already on an existing site, but I don't know how to design my own properly that meets the criteria above. I guess the main worry is security. I don't know the best way to handle a simple log-in system that stores user information like their name and password. I understand there are a few approaches to this, but the catch with this project is that it has to be absolutely bulletproof. Maximum security. All those good practices for security, it needs to have them all. I'm not asking what they are, but I am asking where to begin. What should be the first steps after I do File New Project ? Where can I look for information about setting up a secure ASP.NET website? I'll figure out the content and page layout later, it's the framework that is the big thing. Any and all advice would be welcome. I really want to get my first from-scratch project right from the beginning. Just to confuse things, it's possible I will be using MVC, I am not sure if this has any impact.

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  • Why use shorter VARCHAR(n) fields?

    - by chryss
    It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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  • Limiting object allocation over multiple threads

    - by John
    I have an application which retrieves and caches the results of a clients query. The client then requests different chunks of data and the application sends the relevant results and removes them from the cache. A new requirement for this application is that there needs to be a run-time configurable maximum number of results which may be cached. I've taken the naive approach and implemented this by using a counter under a lock which is incremented every time a result is cached and decremented whenever a result is removed from the cache. Unfortunately, this has drastically reduced the applications performance when processing a large number of concurrent requests. I have tried both a critical section lock and spin-lock; the performance improves a bit with a spin-lock, but is still unacceptably slow. Is there a better way to solve this problem which may improve performance? Right now I have a thread pool that services requests and each request is tied to a Request object which stores that cached results for that particular request. Here is a simplified pseudo code version of my current implementation: void ResultCallback( Result result, Request *request ) { lock totalResultsCached lock cachedLimit if( totalResultsCached + 1 > cachedLimit ) { unlock cachedLimit unlock totalResultsCached //cancel the request return; } ++totalResultsCached; unlock cachedLimit unlock totalResultsCached request.add(result) } void SendResults( int resultsToSend, Request *request ) { while ( resultsToSend > 0 ) { send(request.remove()) lock totalResultsCached --totalResultsCached unlock totalResultsCached --resultsToSend; } }

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  • Ordering z-indexes in an array

    - by Tom Gullen
    I have an array which looks something along the lines of resourceData[0][0] = "pic1.jpg"; resourceData[0][1] = 5; resourceData[1][0] = "pic2.jpg"; resourceData[1][1] = 2; resourceData[2][0] = "pic3.jpg"; resourceData[2][1] = 900; resourceData[3][0] = "pic4.jpg"; resourceData[3][1] = 1; The numeric represents the z-index of the image. Minimum z-index value is 1. Maximum (not really important) is 2000. I have all the rendering and setting z-indexes done fine. My question is, I want to have four functions: // Brings image to z front function bringToFront(resourceIndex) { // Set z-index to max + 1 resourceData[resourceIndex][1] = getBiggestZindex() + 1; // Change CSS property of image to bring to front $('#imgD' + resourceIndex).css("z-index", resourceData[resourceIndex][1]); } function bringUpOne(resourceIndex) { } function bringDownOne(resourceIndex) { } // Send to back z function sendToBack(resourceIndex) { } So given then index [3] (900 z): If we send it to the back, it will take the value 1, and [3] will have to go to 2, but that conflicts with [1] who has a 2 z-index so they need to go to three etc. Is there an easy programatical way of doing this because as soon as I start doing this it's going to get messy. It's important that the indexes of the array don't change. We can't sort the array unfortunately due to design. Update Thanks for answers, I'll post the functions here once they are written incase anyone comes across this in the future (note this code has zindex listed in [6]) // Send to back z function sendToBack(resourceIndex) { resourceData[resourceIndex][6] = 1; $('#imgD' + resourceIndex).css("z-index", 1); for (i = 0; i < resourceData.length; i++) { if (i != resourceIndex) { resourceData[i][6]++; $('#imgD' + i).css("z-index", resourceData[i][6]); } } }

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  • How to easily apply a function to a collection in C++

    - by Jesse Beder
    I'm storing images as arrays, templated based on the type of their elements, like Image<unsigned> or Image<float>, etc. Frequently, I need to perform operations on these images; for example, I might need to add two images, or square an image (elementwise), and so on. All of the operations are elementwise. I'd like get as close as possible to writing things like: float Add(float a, float b) { return a+b; } Image<float> result = Add(img1, img2); and even better, things like complex ComplexCombine(float a, float b) { return complex(a, b); } Image<complex> result = ComplexCombine(img1, img2); or struct FindMax { unsigned currentMax; FindMax(): currentMax(0) {} void operator(unsigned a) { if(a > currentMax) currentMax = a; } }; FindMax findMax; findMax(img); findMax.currentMax; // now contains the maximum value of 'img' Now, I obviously can't exactly do that; I've written something so that I can call: Image<float> result = Apply(img1, img2, Add); but I can't seem to figure out a generic way for it to detect the return type of the function/function object passed, so my ComplexCombine example above is out; also, I have to write a new one for each number of arguments I'd like to pass (which seems inevitable). Any thoughts on how to achieve this (with as little boilerplate code as possible)?

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  • UITableViewCell: how to verify the kind of accessoryType in all cells?

    - by R31n4ld0_
    Hello, Guys. I have a UITableView in that some cells are marked with UITableViewCellAccessoryCheckmark at the initialization of the view. When the user selects another row, I have to check if the maximum number of selected rows was achieved before. To do that, I used the code bellow: - (NSInteger)tableView:(UITableView *)tableView numberOfSelectedRowsInSection:(NSInteger)section{ NSInteger numberOfRows = [self tableView:tableView numberOfRowsInSection:section]; NSInteger numberOfSelectedRows = 0; for (int i = 0; i < numberOfRows; i++) { UITableViewCell *otherCell = [tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:section]]; if (otherCell.accessoryType == UITableViewCellAccessoryCheckmark) { numberOfSelectedRows++; } } return numberOfSelectedRows; } If my number of rows is, as example, 20, the variable numberOfRows is setted correctly with 20. Lets say that 13 rows already are marked with UITableViewCellAccessoryCheckmark. So, numberOfSelectedRows should be 13 after the loop, but only the marked and VISIBLE cells are considered. So, if I have 9 cells showed and 7 are marked, the numberOfSelectedRows returns 7 instead of 13 (but the for iterate 20 times, as expected). Is this a correct behavior of UITableView or it is a bug of iPhone simulator? Thanks in advance.

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  • Iterative Reduction to Null Matrix

    - by user1459032
    Here's the problem: I'm given a matrix like Input: 1 1 1 1 1 1 1 1 1 At each step, I need to find a "second" matrix of 1's and 0's with no two 1's on the same row or column. Then, I'll subtract the second matrix from the original matrix. I will repeat the process until I get a matrix with all 0's. Furthermore, I need to take the least possible number of steps. I need to print all the "second" matrices in O(n) time. In the above example I can get to the null matrix in 3 steps by subtracting these three matrices in order: Expected output: 1 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 1 0 0 1 0 0 0 1 1 0 0 I have coded an attempt, in which I am finding the first maximum value and creating the second matrices based on the index of that value. But for the above input I am getting 4 output matrices, which is wrong: My output: 1 0 0 0 1 0 0 0 1 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 My solution works for most of the test cases but fails for the one given above. Can someone give me some pointers on how to proceed, or find an algorithm that guarantees optimality? Test case that works: Input: 0 2 1 0 0 0 3 0 0 Output 0 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0

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