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• Multilevel nested product categories display with asp.net and sql server?

  - by Kunal

  I have a product category table with the following fields: cat_id (PK) Cat_name Cat_desc Parent_Cat_Id Now when a user wants to add a product he should be able to select multiple categories from a listbox(multiselection enabaled). But to let the user know the hierarchy of the categories, I need to display them in the following style: parent category 1 parent category 1-sub category 1 parent category 1-sub category 1-sub-sub category 1 parent category 1-sub category 1-sub-sub category 2 parent category 1-sub category 2 Parent category 2 ... I know that to achieve this I need to use recursive programming. But how can we do it via stored procedures? That would be much more efficient, right? Thanks in advance for your kind help.

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• What's the official Microsoft way to track counts of dynamic controls to be reconstructed upon Postback?

  - by John K

  When creating dynamic controls based on a data source of arbitrary and changing size, what is the official way to track exactly how many controls need to be rebuilt into the page's control collection after a Postback operation (i.e. on the server side during the ASP.NET page event lifecycle) specifically the point at which dynamic controls are supposed to be rebuilt? Where is the arity stored for retrieval and reconstruction usage? By "official" I mean the Microsoft way of doing it. There exist hacks like Session storage, etc but I want to know the bonafide or at least Microsoft-recommended way. I've been unable to find a documentation page stating this information. Usually code samples work with a set of dynamic controls of known numbers. It's as if doing otherwise would be tougher. Update: I'm not inquiring about user controls or static expression of declarative controls, but instead about dynamically injecting controls completely from code-behind, whether they be mine, 3rd-party or built-in ASP.NET controls.

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• How to implement a good system for login/out into a webapp

  - by Brandon Wang

  I am one of the developers at PassPad, a secure password generator and username storage system. We're still working on it, but I have a few questions on the best way to implement a secure login/out system. Right now, what we plan on doing is to have the login system save a cookie with the username and a session key, and that's all that serves as authentication. The server verifies the two to match. Upon login/out a new key is created. This is a security-related webapp and while we don't actually store any information that might make the user queasy, because it is security-oriented it makes it a necessity for us to at least appear secure in a way that the user would be happy with. Is there a better way to implement a login/out system in PHP? Preferably it won't take too much coding time or server resources. Is there anything else I need to implement, like brute-force protection, etc? How would I go about that?

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• Any tips of how to handle hierarchical trees in relational model?

  - by George

  Hello all. I have a tree structure that can be n-levels deep, without restriction. That means that each node can have another n nodes. What is the best way to retrieve a tree like that without issuing thousands of queries to the database? I looked at a few other models, like flat table model, Preorder Tree Traversal Algorithm, and so. Do you guys have any tips or suggestions of how to implement a efficient tree model? My objective in the real end is to have one or two queries that would spit the whole tree for me. With enough processing i can display the tree in dot net, but that would be in client machine, so, not much of a big deal. Thanks for the attention

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• Recursive function causing a stack overflow

  - by dbyrne

  I am trying to write a simple sieve function to calculate prime numbers in clojure. I've seen this question about writing an efficient sieve function, but I am not to that point yet. Right now I am just trying to write a very simple (and slow) sieve. Here is what I have come up with: (defn sieve [potentials primes] (if-let [p (first potentials)] (recur (filter #(not= (mod % p) 0) potentials) (conj primes p)) primes)) For small ranges it works fine, but causes a stack overflow for large ranges: user=> (sieve (range 2 30) []) [2 3 5 7 11 13 17 19 23 29] user=> (sieve (range 2 15000) []) java.lang.StackOverflowError (NO_SOURCE_FILE:0) I thought that by using recur this would be a non-stack-consuming looping construct? What am I missing?

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• The sieve of Eratosthenes in F#

  - by IVlad

  I am interested in an implementation of the sieve of eratosthenes in purely functional F#. I am interested in an implementation of the actual sieve, not the naive functional implementation that isn't really the sieve, so not something like this: let rec PseudoSieve list = match list with | hd::tl -> hd :: (PseudoSieve <| List.filter (fun x -> x % hd <> 0) tl) | [] -> [] The second link above briefly describes an algorithm that would require the use of a multimap, which isn't available in F# as far as I know. The Haskell implementation given uses a map that supports an insertWith method, which I haven't seen available in the F# functional map. Does anyone know a way to translate the given Haskell map code to F#, or perhaps knows of alternative implementation methods or sieving algorithms that are as efficient and better suited for a functional implementation or F#?

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• Will being self-taught limit me?

  - by Isaiah

  I'm 21 and am pretty efficient in html/css, python, and javascript. I also know my way around lisp languages and enjoy programing in them. My problem is that I'm extremely self-taught and not quite confident that I could land a job programing, but I really need a job soon as I've just become a father. I haven't even created a resume yet because I'm not really sure what to put on it except my lone experience. So I wanted to ask, will being primarily self-taught with some experience on small projects I've done for a few clients limit me too much? I mean I know I need some kind of education so I've enrolled part time in a community college to work on a degree in computer science, but it's years till then. And if it will limit me a lot, what kind of skills would be good to work on to make my chances any better? Thank You

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• Why Switch/Case and not If/Else If?

  - by OB OB

  This question in mainly pointed at C/C++, but I guess other languages are relevant as well. I can't understand why is switch/case still being used instead of if/else if. It seems to me much like using goto's, and results in the same sort of messy code, while the same results could be acheived with if/else if's in a much more organized manner. Still, I see these blocks around quite often. A common place to find them is near a message-loop (WndProc...), whereas these are among the places when they raise the heaviest havoc: variables are shared along the entire block, even when not propriate (and can't be initialized inside it). Extra attention has to be put on not dropping break's, and so on... Personally, I avoid using them, and I wonder wether I'm missing something? Are they more efficient than if/else's? Are they carried on by tradition?

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• Make xargs execute the command once for each line of input

  - by Readonly

  How can I make xargs execute the command exactly once for each line of input given? It's default behavior is to chunk the lines and execute the command once, passing multiple lines to each instance. From http://en.wikipedia.org/wiki/Xargs: find /path -type f -print0 | xargs -0 rm In this example, find feeds the input of xargs with a long list of file names. xargs then splits this list into sublists and calls rm once for every sublist. This is more efficient than this functionally equivalent version: find /path -type f -exec rm '{}' \; I know that find has the "exec" flag. I am just quoting an illustrative example from another resource.

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

  - by Steve Eisner

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

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• Fastest way to put contents of Set<String> to a single String with words separated by a whitespace?

  - by Lars Andren

  I have a few Set<String>s and want to transform each of these into a single String where each element of the original Set is separated by a whitespace " ". A naive first approach is doing it like this Set<String> set_1; Set<String> set_2; StringBuilder builder = new StringBuilder(); for (String str : set_1) { builder.append(str).append(" "); } this.string_1 = builder.toString(); builder = new StringBuilder(); for (String str : set_2) { builder.append(str).append(" "); } this.string_2 = builder.toString(); Can anyone think of a faster, prettier or more efficient way to do this?

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• SQL latest/top items in category

  - by drozzy

  What is a scalable way to select latest 10 items from each category. I have a schema list this: item category updated so I want to select 10 last update items from each category. The current solution I can come up with is to query for categories first and then issue some sort of union query: query = none for cat in categories: query += select top 10 from table where category=cat order by updated I am not sure how efficient this will be for bigger databases (1 million rows). If there is a way to do this in one go - that would be nice. Any help appreciated.

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• How do I use Eval() to reference values in a SortedDictionary in an asp Repeater?

  - by MatthewMartin

  I thought I was clever to switch from the memory intensive DataView to SortedDictionary as a memory efficient sortable data structure. Now I have no idea how get the key and value out of the datasource in the <%# or Eval() expressions. SortedDictionary<int, string> data = RetrieveNames(); rCurrentTeam.DataSource = data; rCurrentTeam.DataBind(); <asp:Repeater ID="rNames" runat="server"> <ItemTemplate> <asp:Label ID="lblName" runat="server" Text='<%# Eval("what?") %>' /> </ItemTemplate> </asp:Repeater> Any suggestions?

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• What is the technological basis for Azure DocumentDB?

  - by user1703840

  Microsoft announced the availability of Azure DocumentDB as follows... A fully-managed, highly-scalable, NoSQL document database service. - Rich query over a schema-free JSON data model - Transactional execution of JavaScript logic - Scalable storage and throughput - Tunable consistency - Rapid development with familiar technologies - Blazingly fast and write optimized database service I really like the "transactional execution of JavaScript logic". Sounds like an approach similar to that of PostgreSQL NoSQL. Anyone know what is the technological basis for the Azure DocumentDB service? SQL Server?

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• Searching with Linq

  - by Phil

  I have a collection of objects, each with an int Frame property. Given an int, I want to find the object in the collection that has the closest Frame. Here is what I'm doing so far: public static void Search(int frameNumber) { var differences = (from rec in _records select new { FrameDiff = Math.Abs(rec.Frame - frameNumber), Record = rec }).OrderBy(x => x.FrameDiff); var closestRecord = differences.FirstOrDefault().Record; //continue work... } This is great and everything, except there are 200,000 items in my collection and I call this method very frequently. Is there a relatively easy, more efficient way to do this?

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• Flex / ZendAMF / PHP app, corrupted data with some linux clients problem

  - by Laurent Jégou

  Hello, i'm buiding a survey web application, using Flex for the front-end (nice forms), and a MySQL database for the storage, linked by PHP with the help of ZendAMF. I largely borrowed from this nice tutorial by Alan Gruskoff : http://digitalshowcase.biz/wordpress/?page_id=26 (The only one tutorial i've found to work with the last version of Flex). The app seems to works nicely in my tests, except on certain linux boxes : the data is somehow corrupted : there is no error message, no glitch, but the response of the forms are not what the user selected. I tried to reproduce the error on a fresh installed ubuntu VM, but it works fine. I've asked friends for some tests, and several linux users showed the same problem, on ubuntu and suse machines, all freshly updated and functionnal. The application was targeted to be the survey tool for my doctoral thesis, so i'm quite desperate here, and before i'm dumping it to start anew with php only, i'm asking here in case someone can help, thanks :-) Please excuse my english, by the way. LJ.

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• MySqli Prepared Statment Fetch Row

  - by pws5068

  I'm looking for an efficient way to select a specific row with a php prepared statement. $iDB = new mysqliDB(); $stmt = $iDB->prepare($sql); $stmt->bind_param('s',$searhStr); $stmt->execute(); $stmt->store_result(); $stmt->bind_result($objID,$typeID,$year,$updated); // Now jump to row $rowNumber echo("Obj ID = {$objID}"); Any suggestions? Thanks!

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• Put an object in Handler message

  - by Tsimmi

  Hi! I need to download an image from the internet, in a different thread, and then send that image object in the handler message, to the UI thread. I already have this: ... Message msg = Message.obtain(); Bundle b = new Bundle(); b.putParcelable("MyObject", (Parcelable) object); msg.setData(b); handler.sendMessage(msg); And when I receive this message, I want to extract the object: ... public void handleMessage(Message msg) { super.handleMessage(msg); MyObject objectRcvd = (MyObject) msg.getData().getParcelable("IpTile"); addToCache(ipTile); mapView.invalidate(); } But this is giving me: ...java.lang.ClassCastException... Can anyone help? And by the way, is this the most efficient way to pass an object to the UI Thread? Thank you all!

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• How do I get the position of a result in the list after an order_by?

  - by Bob Bob

  I'm trying to find an efficient way to find the rank of an object in the database related to it's score. My naive solution looks like this: rank = 0 for q in Model.objects.all().order_by('score'): if q.name == 'searching_for_this' return rank rank += 1 It should be possible to get the database to do the filtering, using order_by: Model.objects.all().order_by('score').filter(name='searching_for_this') But there doesn't seem to be a way to retrieve the index for the order_by step after the filter. Is there a better way to do this? (Using python/django and/or raw SQL.) My next thought is to pre-compute ranks on insert but that seems messy.

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• Best data-structure to use for two ended sorted list

  - by fmark

  I need a collection data-structure that can do the following: Be sorted Allow me to quickly pop values off the front and back of the list Remain sorted after I insert a new value Allow a user-specified comparison function, as I will be storing tuples and want to sort on a particular value Thread-safety is not required Optionally allow efficient haskey() lookups (I'm happy to maintain a separate hash-table for this though) My thoughts at this stage are that I need a priority queue and a hash table, although I don't know if I can quickly pop values off both ends of a priority queue. I'm interested in performance for a moderate number of items (I would estimate less than 200,000). Another possibility is simply maintaining an OrderedDictionary and doing an insertion sort it every-time I add more data to it. Furthermore, are there any particular implementations in Python. I would really like to avoid writing this code myself.

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• posmax: like argmax but gives the position(s) of the element x for which f[x] is maximal

  - by dreeves

  Mathematica has a built-in function ArgMax for functions over infinite domains, based on the standard mathematical definition. The analog for finite domains is a handy utility function. Given a function and a list (call it the domain of the function), return the element(s) of the list that maximize the function. Here's an example of finite argmax in action: http://stackoverflow.com/questions/471029/canonicalize-nfl-team-names/472213#472213 And here's my implementation of it (along with argmin for good measure): (* argmax[f, domain] returns the element of domain for which f of that element is maximal -- breaks ties in favor of first occurrence. *) SetAttributes[{argmax, argmin}, HoldFirst]; argmax[f_, dom_List] := Fold[If[f[#1]>=f[#2], #1, #2]&, First[dom], Rest[dom]] argmin[f_, dom_List] := argmax[-f[#]&, dom] First, is that the most efficient way to implement argmax? What if you want the list of all maximal elements instead of just the first one? Second, how about the related function posmax that, instead of returning the maximal element(s), returns the position(s) of the maximal elements?

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• Perform Grouping of Resultset in Code

  - by NinjaBomb

  Stackoverflowers, I have a resultset from a SQL query in the form of: Category Column2 Column3 A 2 3.50 A 3 2 B 3 2 B 1 5 ... I need to group the resultset based on the Category column and sum the values for Column2 and Column3. I have to do it in code because I cannot perform the grouping in the SQL query that gets the data due to the complexity of the query (long story). This grouped data will then be displayed in a table. I have it working for specific set of values in the Category column, but I would like a solution that would handle any possible values that appear in the Category column. I know there has to be a straightforward, efficient way to do it but I cannot wrap my head around it right now. How would you accomplish it?

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• NoSQL and meteorological data

  - by christian studer

  So there's this new cool thing, these NoSQL-databases. And so there's my data: Rows of rows of rows of meteorological data: Values, representing certain measurements at a certain station (Identified by a WMO number, not coordinates), at a certain time. Not every station measures every parameter, not every parameter is measured all the time. I store this data (30 years worth of hourly values, resulting in ~1 billion values) currently in MySQL. The continous growth and the forseeable addition of even more data give me a little headache. Reading about the document based NoSQL systems which seem to scale rather easily, I was wondering if NoSQL is a viable data storage concept for meteorological data too. Do you have any experience with this?

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• Efficiency of Java code with primitive types

  - by super89

  Hello! I want to ask which piece of code is more efficient in Java? Code 1: void f() { for(int i = 0 ; i < 99999;i++) { for(int j = 0 ; j < 99999;j++) { //Some operations } } } Code 2: void f() { int i,j; for(i = 0 ; i < 99999;i++) { for(j = 0 ; j < 99999;j++) { //Some operations } } } My teacher said that second is better, but I can't agree that opinion.

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• php - comparing timestamp dates to make sure user is of minimum age

  - by Micheal Ken

  When a user signs up the system has to check that they are old enough to do so, in this example they have to be atleast 8 years old $minAge = strtotime(date("d")."-".date("m")."-".(date("Y")-8)); $dob = strtotime($day."-".$month."-".$year); $minAge = 01-03-2004, $dob = 01-02-2011 I basically need to make sure this person was born before 2004 but I want to know whether I have to convert the timestamps to do a comparison or whether there is a more efficient way. Any help is appreciated, thank you

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