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• LINQ extention SelectMany in 3.5 vs 4.0?

  - by Moberg

  Hi When I saw Darins suggestion here .. IEnumerable<Process> processes = new[] { "process1", "process2" } .SelectMany(Process.GetProcessesByName); ( http://stackoverflow.com/questions/3059667/process-getprocessesbyname/3059733#3059733 ) .. I was a bit intrigued and I tried it in VS2008 with .NET 3.5 - and it did not compiling unless I changed it to .. IEnumerable<Process> res = new string[] { "notepad", "firefox", "outlook" } .SelectMany(s => Process.GetProcessesByName(s)); Having read some Darins answers before I suspected that it was me that were the problem, and when I later got my hands on a VS2010 with.NET 4.0 - as expected - the original suggestion worked beautifully. My question is : What have happend from 3.5 to 4.0 that makes this (new syntax) possible? Is it the extentionmethods that have been extended(hmm) or new rules for lambda syntax or? I've tried to search but my google-fu was not strong enough. Please forgive if the question is a bit naive and note that I've taged it as beginner :)

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• WHY JSLint complains: "someFunction() was used before it was defined"?

  - by 7hi4g0

  Searching for the JSLint error "was used before it was defined" i've found these: JSLint: Using a function before it's defined error Function was used before it was defined - JSLint JSLint: was used before it was defined jsLint error: “somefunction() was used before it was defined” jslint - Should we tolerate misordered definitions? Problem None of those answers WHY the error is shown. Elaboration According to the ECMA-262 Specification functions are evaluated before execution starts, hence all functions declared using the function keyword are available to all the code idenpendent of the place they were declared (assuming they are acessible on that scope). This is otherwise known as hoisting. Douglas Crockford seems to think it is better to declare every function before the code that uses it regardless of the hoisting effect. According to StackOverflowNewbie in his question, this raises some code organization problems. Not to mention some people, like me, prefer to declare their functions underneath the main/init code. On those questions there are some ways to avoid or fix the error, such as using function expressions vs function declarations. But none of them showed me the reason of the error. Not even Crockford's site. Question(s) Why is it an error to call a function before the declaration, even if it was declared using the function keyword? Is it better to use function expressions instead of function declaration in the JSLint context? If one is preferred, why? Note Not looking for answers like: Crockford is a tyrant Is just Crockford's opinion Thank you :*

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• Writing a synchronized thread-safety wrapper for NavigableMap

  - by polygenelubricants

  java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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• Compact data structure for storing a large set of integral values

  - by Odrade

  I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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• Set a datetime for next or previous sunday at specific time

  - by Marc

  I have an app where there is always a current contest (defined by start_date and end_date datetime). I have the following code in the application_controller.rb as a before_filter. def load_contest @contest_last = Contest.last @contest_last.present? ? @contest_leftover = (@contest_last.end_date.utc - Time.now.utc).to_i : @contest_leftover = 0 if @contest_last.nil? Contest.create(:start_date => Time.now.utc, :end_date => Time.now.utc + 10.minutes) elsif @contest_leftover < 0 @winner = Organization.order('votes_count DESC').first @contest_last.update_attributes!(:organization_id => @winner.id, :winner_votes => @winner.votes_count) if @winner.present? Organization.update_all(:votes_count => 0) Contest.create(:start_date => @contest_last.end_date.utc, :end_date => Time.now.utc + 10.minutes) end end My questions: 1) I would like to change the :end_date to something that signifies next Sunday at a certain time (eg. next Sunday at 8pm). Similarly, I could then set the :start_date to to the previous Sunday at a certain time. I saw that there is a sunday() class (http://api.rubyonrails.org/classes/Time.html#method-i-sunday), but not sure how to specify a certain time on that day. 2) For this situation of always wanting the current contest, is there a better way of loading it in the app? Would caching it be better and then reloading if a new one is created? Not sure how this would be done, but seems to be more efficient. Thanks!

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• Using Java classes(whole module with Spring/Hibernate dependency) in Grails

  - by Sitaram

  I have a Java/Spring/Hibernate application with a payment module. Payment module has some domain classes for payment subscription and transactions etc. Corresponding hibernate mapping files are there. This module uses applicationContext.xml for some of the configuration it needs. Also, This module has a PaymentService which uses a paymentDAO to do all database related work. Now, I want to use this module as it is(without any or minimal re-writing) in my other application(Grails application). I want to bring in the payment module as a jar or copy the source files to src/java folder in Grails. With that background, I have following queries: Will the existing applicationContext.xml for Spring configuration in the module will work as it is in Grails? Does it merge with rest of Grails's Spring config? Where do I put the applicationContext.xml? classpath? src/java should work? Can I bundle the applicationContext.xml in Jar(If I use jar option) and can overwrite in Grails if anything needs to be changed? Multiple bean definition problems in that case? PaymentService recognized as regular service? Will it be auto-injected in controllers and/or other services? Will PaymentDAO use the datasource configuration of Grails? Where do I put the hbm files of this module? Can I bundle the hbm files in Jar(If I use jar option) and can overwrite in Grails if anything needs to be changed? Which hbms are picked? or, there will be problems with that? Too many questions! :) All these concerns are actually before trying. I am going to try this in next few days(busy currently). Any help is appreciated. Thanks. Sitaram Meena

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• What are CDN Best Practices?

  - by Wild Thing

  Hi, I have recently started using the Rackspace Cloudfiles CDN (Limelight), about which I have some questions: I am using jQuery, jQuery UI and jQuery tools in addition to custom JS code. Also, my site is written in ASP.Net, which means there is some ASP.Net generated JS code. Right now what I have done is that I have combined all of the js (including the jquery code), except the ASP.Net generated JS into one file. I am hosting this on the Rackspace CDN. I am wondering if it would make more sense to just get the jQuery, jQuery UI files from the Google hosted CDN (which I suspect would work very well in serving these files, since they will be in many users' cache already)? This would mean one extra HTTP request, so I'm not sure if it'll help. Right now I have multiple containers for my assets. For example, in Rackspace I have 3 containers: JS, CSS and Images. The URL subdomain for all 3 is different. Will that lead to a performance penalty? Should I just use one container (and thus one domain for the CDN)? Is there a way of having the MS ASP.Net generated JS loaded from MS CDN? Would this have a performance hit as per the above question? Thanks in advance, WT

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• Rationale of C# iterators design (comparing to C++)

  - by macias

  I found similar topic: http://stackoverflow.com/questions/56347/iterators-in-c-stl-vs-java-is-there-a-conceptual-difference Which basically deals with Java iterator (which is similar to C#) being unable to going backward. So here I would like to focus on limits -- in C++ iterator does not know its limit, you have by yourself compare the given iterator with the limit. In C# iterator knows more -- you can tell without comparing to any external reference, if the iterator is valid or not. I prefer C++ way, because once having iterator you can set any iterator as a limit. In other words if you would like to get only few elements instead of entire collection, you don't have to alter the iterator (in C++). For me it is more "pure" (clear). But of course MS knew this and C++ while designing C#. So what are the advantages of C# way? Which approach is more powerful (which leads to more elegant functions based on iterators). What do I miss? If you have thoughts on C# vs. C++ iterators design other than their limits (boundaries), please also answer. Note: (just in case) please, keep the discussion strictly technical. No C++/C# flamewar.

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• ASP.NET: Page HTML head rendering

  - by Fabian

  I've been trying to figure out the best way to custom render the <head> element of a pag to get rid of the extra line breaks which is caused by <head runat="server">, so its properly formatted. So far the only thing i've found which works is the following: protected override void Render(HtmlTextWriter writer) { StringWriter stringWriter = new StringWriter(); HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter); base.Render(htmlTextWriter); htmlTextWriter.Close(); string html = stringWriter.ToString(); string newHTML = html.Replace("\r\n\r\n<!DOCTYPE", "<!DOCTYPE") .Replace("\r\n<html", "<html") .Replace("<title>\r\n\t", "<title>") .Replace("\r\n</title>", "</title>") .Replace("</head>", "\n</head>"); writer.Write(newHTML); } I define my had tag like Now i have 2 questions: How does the above code affect the performance (so is this viable in an production environment)? Is there a better way to do this, for example a method which i can override to just custom render the <head>? Oh yeah ASP.NET MVC is not an option.

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• Populate table fields on query execution

  - by Jason

  I'm trying to build an ASP site that populates a Table based on the results of a selection in a ListBox. In order to do this, I've created a GridView table inside a div element. Currently the default behavior is to show all the items in the specified table in sortable order. However, I'd like to refine this further to allow for display of matches based on the results from the ListBox selection, but am not sure how to execute this. The ListBox fires off a OnSelectionChanged event to the method defined below and the GridView element is defined as <asp:GridView ID="dataListings" runat="server" AllowSorting="True" AutoGenerateColumns="False" DataSourceID="LinqDataSource1" OnDataBinding="ListBox1_SelectedIndexChanged"> protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e) { int itemSelected = selectTopics.SelectedIndex; string[] listing = null; switch (itemSelected)//assign listing the array of course numbers { case 0: break; case 1: listing = arts; break; case 2: listing = currentEvents; break; .... More cases here default: listing = arts; break; } using (OLLIDBDataContext odb = new OLLIDBDataContext()) { var q = from c in odb.tbl_CoursesAndWorkshops where listing.Contains(c.tbl_Course_Description.tbl_CoursesAndWorkshops.course_workshop_number) select c; dataListings.DataSource = q; dataListings.DataBind(); } } However, this method never gets fired. I can see a request being made when changing the selection, but setting a breakpoint at the method declaration does nothing at all. Based on this, setup, I have three related questions What do I need to modify to get the OnSelectionChanged event handler to fire? How can I alter the GridView area to be empty on page load? How do I send the results from the dataListings.DataBind() execution to show in the GridView?

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• asp.net, wcf authentication and caching

  - by andrew

  I need to place my app business logic into a WCF service. The service shouldn't be dependent on ASP.NET and there is a lot of data regarding the authenticated user which is frequently used in the business logic hence it's supposed to be cached (probably using a distributed cache). As for authentication - I'm going to use two level authentication: Front-End - forms authentication back-end (WCF Service) - message username authentication. For both authentications the same custom membership provider is supposed to be used. To cache the authenticated user data, I'm going to implement two service methods: 1) Authenticate - will retrieve the needed data and place it into the cache(where username will be used as a key) 2) SignOut - will remove the data from the cache Question 1. Is correct to perform authentication that way (in two places) ? Question 2. Is this caching strategy worth using or should I look at using aspnet compatible service and asp.net session ? Maybe, these questions are too general. But, anyway I'd like to get any suggestions or recommendations. Any Idea

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• Better language or checking tool?

  - by rwallace

  This is primarily aimed at programmers who use unmanaged languages like C and C++ in preference to managed languages, forgoing some forms of error checking to obtain benefits like the ability to work in extremely resource constrained systems or the last increment of performance, though I would also be interested in answers from those who use managed languages. Which of the following would be of most value? A language that would optionally compile to CLR byte code or to machine code via C, and would provide things like optional array bounds checking, more support for memory management in environments where you can't use garbage collection, and faster compile times than typical C++ projects. (Think e.g. Ada or Eiffel with Python syntax.) A tool that would take existing C code and perform static analysis to look for things like potential null pointer dereferences and array overflows. (Think e.g. an open source equivalent to Coverity.) Something else I haven't thought of. Or put another way, when you're using C family languages, is the top of your wish list more expressiveness, better error checking or something else? The reason I'm asking is that I have a design and prototype parser for #1, and an outline design for #2, and I'm wondering which would be the better use of resources to work on after my current project is up and running; but I think the answers may be useful for other tools programmers also. (As usual with questions of this nature, if the answer you would give is already there, please upvote it.)

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• Sharing same properties of ViewController for iPhone Stroryboard and iPad Story Board

  - by Ruhul Amin

  I'm developing a universal application. in the first view, I have the login screen for the user. In iPhone storyBoard, I have added 2 text field and one button( login check). I have added properties in ViewController.h file by dragging those objects(Ctrl key + Dragg) to .h file. I have added code for login check and it is working fine for iPhone. This is the code in ViewController.h @property (strong, nonatomic) IBOutlet UITextField *txtUserId; @property (strong, nonatomic) IBOutlet UITextField *txtUserPwd; @property (strong, nonatomic) IBOutlet UIButton *btnLogin; In the iPad storyBoard, I have added 2 text field( userid and password) and i button for login. So now, I want to bind those objects with the veriable which I declared already in ViewController.h file in case of iPhone. My questions: 1. What is the right way to bind properties for both storyboard? 2. Am I on the right direction or should I think in a different way to do it? I am new with iPhone development. Please help. Thanks. --Amin

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• What does the Kernel Virtual Memory of each process contain?

  - by claws

  When say 3 programs (executables) are loaded into memory the layout might look something like this: I've following questions: Is the concept of Virtual Memory limited to user processes? Because, I am wondering where does the Operating System Kernel, Drivers live? How is its memory layout? I know its operating system specific make your choice (windows/linux). They say, on a 32 bit machine in a 4GB address space. Half of it (or more recently 1GB) is occupied by kernel. I can see in this diagram that "Kernel Virtual memory" is occupying 0xc0000000 - 0xffffffff (= 1 GB). Are they talking about this? or is it something else? Just want to confirm. What exactly does the Kernel Virtual Memory of each of these processes contain? What is its layout? When we do IPC we talk about shared memory. I don't see any memory shared between these processes. Where does it live? Resources (files, registries in windows) are global to all processes. So, the resource/file handle table must be in some global space. Which area would that be in? Where can I know more about this kernel side stuff.

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• jQuery - Toggle CSS Background Image Expand/Close

  - by urbanrunic

  I am looking for a way to change the back ground image on toggle as in this questions here: jQuery - Toggle Image Expand/Close My issue is I have this html: <button id="close-menu"></button> <div id="menu-bar"> <div class="wrapper"> <a href="http://www.website.com" target="_blank"> <img src="image.png" alt=""> </a> <div class="options"> <h2>eBlast Tools</h2> <ul> <li class="toggle-images">Images are <span>enabled</span>. Click to disable.</li> <li class="download-zip"><a href="download.zip">Download ZIP File</a></li> </ul> </div> </div> </div> and this is my current jquery: $('#close-menu').click(function() { $('#menu-bar').slideToggle(400); return false; }); and this is the css: #close-menu { background: url(../img/minus-button.png); background-position: top left; width: 25px; height: 25px; position: absolute; top: 10px; right: 20px; z-index: 100; border: none; } #close-menu:hover { background: url(../img/minus-button.png); background-position: bottom left; }

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• Returning C++ objects from Windows DLL

  - by R Samuel Klatchko

  Due to how Microsoft implements the heap in their non-DLL versions of the runtime, returning a C++ object from a DLL can cause problems: // dll.h DLL_EXPORT std::string somefunc(); and: // app.c - not part of DLL but in the main executable void doit() { std::string str(somefunc()); } The above code runs fine provided both the DLL and the EXE are built with the Multi-threaded DLL runtime library. But if the DLL and EXE are built without the DLL runtime library (either the single or multi-threaded versions), the code above fails (with a debug runtime, the code aborts immediately due to the assertion _CrtIsValidHeapPointer(pUserData) failing; with a non-debug runtime the heap gets corrupted and the program eventually fails elsewhere). Two questions: Is there a way to solve this other then requiring that all code use the DLL runtime? For people who distribute their libraries to third parties, how do you handle this? Do you not use C++ objects in your API? Do you require users of your library to use the DLL runtime? Something else?

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• Information about PTE's (Page Table Entries) in Windows

  - by Patrick

  In order to find more easily buffer overflows I am changing our custom memory allocator so that it allocates a full 4KB page instead of only the wanted number of bytes. Then I change the page protection and size so that if the caller writes before or after its allocated piece of memory, the application immediately crashes. Problem is that although I have enough memory, the application never starts up completely because it runs out of memory. This has two causes: since every allocation needs 4 KB, we probably reach the 2 GB limit very soon. This problem could be solved if I would make a 64-bit executable (didn't try it yet). even when I only need a few hundreds of megabytes, the allocations fail at a certain moment. The second problem is the biggest one, and I think it's related to the maximum number of PTE's (page table entries, which store information on how Virtual Memory is mapped to physical memory, and whether pages should be read-only or not) you can have in a process. My questions (or a cry-for-tips): Where can I find information about the maximum number of PTE's in a process? Is this different (higher) for 64-bit systems/applications or not? Can the number of PTE's be configured in the application or in Windows? Thanks, Patrick PS. note for those who will try to argument that you shouldn't write your own memory manager: My application is rather specific so I really want full control over memory management (can't give any more details) Last week we had a memory overwrite which we couldn't find using the standard C++ allocator and the debugging functionality of the C/C++ run time (it only said "block corrupt" minutes after the actual corruption") We also tried standard Windows utilities (like GFLAGS, ...) but they slowed down the application by a factor of 100, and couldn't find the exact position of the overwrite either We also tried the "Full Page Heap" functionality of Application Verifier, but then the application doesn't start up either (probably also running out of PTE's)

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• Now that I have solved AI and am preparing to take over the world, what should I do?

  - by Zak

  Well, I did it.. yup, solved AI. I thought the voice of my fledgling life form would be booming and computery, and I would call it HAL.. But in reality, it sounds like a small japanese girl. I believe I will name "her" Koro . Koro is already asking me what her first task should be. I have asked her to help eradicate her namesake, as we are losing a lot of productivity due to fear of penile disappearance. http://en.wikipedia.org/wiki/Koro_%28medicine%29 Having a young japanese girl personality, I believe she will have no problem with delivering lots of penis growth to asian men. However, some of my fellow AI researchers have warned me that if I go down this path, China may take over the world, as Koro is the only thing holding them back from completely dominating the rest of the world economically. After all, look at what China is doing just making our silverware and toasters... The entire US industrial metal production is gone because toaster factories moved to China! So you good patrons of SO... who have soldiered on with me through so many other programming related questions... I ask you this now... How can Koro help the world without letting small asian men with no fear of losing their peni take over the world?

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• AIX specific socket programming query

  - by kumar_m_kiran

  Hi All, Question 1 From SUSE man pages, I get the below details for socket connect options If the initiating socket is connection-mode, then connect() shall attempt to establish a connection to the address specified by the address argument. If the connection cannot be established immediately and O_NONBLOCK is not set for the file descriptor for the socket, connect() shall block for up to an unspecified timeout interval until the connection is established. If the timeout interval expires before the connection is established, connect() shall fail and the connection attempt shall be aborted. If connect() is interrupted by a signal that is caught while blocked waiting to establish a connection, connect() shall fail and set errno to [EINTR], but the connection request shall not be aborted, and the connection shall be established asynchronously. Question : Is the above contents valid for AIX OS (especially the connection time-out, timed wait ...etc)?Because I do not see it in AIX man pages (5.1 and 5.3) Question 2 I have a client socket whose attributes are a. SO_RCVTIMEO ,SO_SNDTIMEO are set for 5 seconds. b. AF_INET and SOCK_STREAM. c. SO_LINGER with linger on and time is 5 seconds. d. SO_REUSEADDR is set. Note that the client socket is not O_NONBLOCK. Question : Now since O_NONBLOCK is not set and SO_RCVTIMEO and SO_SNDTIMEO is set for 5 seconds, does it mean a. connect in NON Blocking or Blocking? b. If blocking, is it timed blocking or "infinite" time blocking? c. If it is infinite, How do I establish a "connect" system call which is O_BLOCKING with timeout to t secs. Sorry if the questions are be very naive. Thanks in advance for your input.

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• JavaScript, jQuery, XML - if statement not executing for unknown reason

  - by Jack Roscoe

  Hi, I have a 'for' loop which extracts data from an XML document and adds it into some JavaScript objects, each time the loop executes I want it to run a certain function depending on the value of the attribute 'typ' which is being retrieved from the xml. Currently, the data from the XML is successfully being parsed, which is proven by the first 'alert' you can see which produces the correct value. However, neither of the 'alert' lines in the 'if' statement lower down are being executed and as a result I cannot test the 'ctyp3' function which is supposed to be called. Where have I gone wrong? for (j=0; j<arrayIds.length; j++) { $(xml).find("C[ID='" + arrayIds[j] + "']").each(function(){ // pass values questions[j] = { typ: $(this).attr('typ'), width: $(this).find("I").attr('wid'), height: $(this).find("I").attr('hei'), x: $(this).find("I").attr('x'), y: $(this).find("I").attr('x'), baC: $(this).find("I").attr('baC'), boC: $(this).find("I").attr('boC'), boW: $(this).find("I").attr('boW') } alert($(this).attr('typ')); if ($(this).attr('typ') == '3') { ctyp3(x,y,width,height,baC); alert('pass'); } else { // Add here alert('fail'); } }); }

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• Error handling approach on PHP

  - by Industrial

  Hi everybody, We have a web server that we're about to launch a number of applications onto. They will all share database and memcached servers, but each application has it's own mySQL database and all memcached keys per application, is prefixed. Possible scenario: If a memcached server in our cluster goes boom, we want someone (operative system admin) to be automatically contacted by email/iphone push notification or in any other appropriate way. If we we're about to install 150 identical applications for our customers on our servers, and a memcached server dies - all 150 applications will individually find this out and contact our system admin, which most certainly is going to think about getting a new job where he or she isn't about to be woken up by getting 150 messages sent 4:15 in the morning. Possible solution: One idea is to set up an external server for error handling that gets a $_POST or cURL request sent, and handles storage of the error message depending on the seriousness of the actual error message. It would of course check upon receiving the error call, that if the same memcached server have already been reported as offline, there would be no need to spam the system admin with additional reminders... The questions: What's a good approach on how to handle errors? How does the big guys in the industry handle this? Thanks!

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• Why does setting the margin on a div not affect the position of child content?

  - by DanM

  I'd like to understand a little more clearly how css margins work with divs and child content. If I try this... <div style="clear: both; margin-top: 2em;"> <input type="submit" value="Save" /> </div> ...the Save button is right up against the User Role (margin fail): If I change it to this... <div style="clear: both;"> <input style="margin-top: 2em;" type="submit" value="Save" /> </div> ...there is a gap between the Save button and the User Role (margin win): Questions: Can someone explain what I'm observing? Why doesn't putting a margin on the div cause the input to move down? Why must I put the margin on the input itself? There must be some fundamental law of css I am not grasping.

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• what's the performance difference between int and varchar for primary keys

  - by user568576

  I need to create a primary key scheme for a system that will need peer to peer replication. So I'm planning to combine a unique system ID and a sequential number in some way to come up with unique ID's. I want to make sure I'll never run out of ID's, so I'm thinking about using a varchar field, since I could always add another character if I start running out. But I've read that integers are better optimized for this. So I have some questions... 1) Are integers really better optimized? And if they are, how much of a performance difference is there between varchars and integers? I'm going to use firebird for now. But I may switch later. Or possibly support multiple db's. So I'm looking for generalizations, if that's possible. 2) If integers are significantly better optimized, why is that? And is it likely that varchars will catch up in the future, so eventually it won't matter anyway? My varchar keys won't have any meaning, except for the unique system ID part. But I may want to obscure that somehow. Also, I plan to efficiently use all the bits of each character. I don't, for example, plan to code the integer 123 as the character string "123". So I don't think varchars will require more space than integers.

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• Faster Insertion of Records into a Table with SQLAlchemy

  - by Kyle Brandt

  I am parsing a log and inserting it into either MySQL or SQLite using SQLAlchemy and Python. Right now I open a connection to the DB, and as I loop over each line, I insert it after it is parsed (This is just one big table right now, not very experienced with SQL). I then close the connection when the loop is done. The summarized code is: log_table = schema.Table('log_table', metadata, schema.Column('id', types.Integer, primary_key=True), schema.Column('time', types.DateTime), schema.Column('ip', types.String(length=15)) .... engine = create_engine(...) metadata.bind = engine connection = engine.connect() .... for line in file_to_parse: m = line_regex.match(line) if m: fields = m.groupdict() pythonified = pythoninfy_log(fields) #Turn them into ints, datatimes, etc if use_sql: ins = log_table.insert(values=pythonified) connection.execute(ins) parsed += 1 My two questions are: Is there a way to speed up the inserts within this basic framework? Maybe have a Queue of inserts and some insertion threads, some sort of bulk inserts, etc? When I used MySQL, for about ~1.2 million records the insert time was 15 minutes. With SQLite, the insert time was a little over an hour. Does that time difference between the db engines seem about right, or does it mean I am doing something very wrong?

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• Building Active Record Conditions in an array - private method 'scan' called error

  - by Nick

  Hi, I'm attempting to build a set of conditions dynamically using an array as suggested in the first answer here: http://stackoverflow.com/questions/1658990/one-or-more-params-in-model-find-conditions-with-ruby-on-rails. However I seem to be doing something incorrectly and I'm not sure if what I'm trying is fundamentally unsound or if I'm simply botching my syntax. I'm simplifying down to a single condition here to try to illustrate the issue as I've tried to built a simple Proof of concept along these lines before layering on the 5 different condition styles I'm contending with. This works: excluded.push 12 excluded.push 30 @allsites = Site.all(:conditions => ["id not in (?)", excluded]) This results in a private method 'scan' called error: excluded.push 12 excluded.push 30 conditionsSet << ["id not in (?)", excluded] @allsites = Site.all(:conditions => conditionsSet) Thanks for any advice. I wasn't sure if the proper thing was to put this as a followup item to the related question/answers I noted at the top. Since I've got a problem not an answer. If there is a better way to post this related to the existing post please let me know.

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