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  • How to Determine The Module a Particular Exception Class is Defined In

    - by doug
    Note: i edited my Q (in the title) so that it better reflects what i actually want to know. In the original title and in the text of my Q, i referred to the source of the thrown exception; what i meant, and what i should have referred to, as pointed out in one of the high-strung but otherwise helpful response below, is the module that the exception class is defined in. This is evidenced by the fact that, again, as pointed out in one of the answers below the answer to the original Q is that the exceptions were thrown from calls to cursor.execute and cursor.next, respectively--which of course, isn't the information you need to write the try/except block. For instance (the Q has nothing specifically to do with SQLite or the PySQLite module): from pysqlite2 import dbapi2 as SQ try: cursor.execute('CREATE TABLE pname (id INTEGER PRIMARY KEY, name VARCHARS(50)') except SQ.OperationalError: print("{0}, {1}".format("table already exists", "... 'CREATE' ignored")) # cursor.execute('SELECT * FROM pname') while 1: try: print(cursor.next()) except StopIteration: break # i let both snippets error out to see the exception thrown, then coded the try/finally blocks--but that didn't tell me anything about which module the exception class is defined. In my example, there's only a single imported module, but where there are many more, i am interested to know how an experienced pythonista identifies the exception source (search-the-docs-till-i-happen-to-find-it is my current method). [And yes i am aware there's a nearly identical question on SO--but for C# rather than python, plus if you read the author's edited version, you'll see he's got a different problem in mind.]

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  • Database structure - is mySQL the right choice?

    - by Industrial
    Hi everyone, We are currently planning the database structure of a quite complex e-commerce web app that has flexibility as it's main cornerstone. Our app features a large amount of data (products) and we have run into a slight headache trying to keep performance high without compromizing normalization rules in the database, or leaving our highly beloved flexibility concept behind when integrating product options (also widely known as product attributes or parameters). Based on various references and sources available, we have made up lists on pros and cons of all major and well known database patterns to solve this. After comparing these, we have come up with two final alternatives: EAV (Entity-attribute-value model) : Pros: Database is used for all sorting. Cons: All related queries will include a number of joins between multiple tables in order to complete the collection of data. SLOB (Serialized LOB, also known as Facade?) : Pros: Very flexible. Keeping the number of necessary joins low compared to a EAV design pattern. Easy to update/add/remove data from each product. Cons: All sorting will be done by the application instead of the database. Will use lots of performance (memory?) when big datasets is processed by a large number of users. Our main questions: Which pattern/structure would you use, or maybe even a different solution? Is there better databases besides mySQL available nowadays to accomplish what we want? Thanks a lot! Reference: http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters

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  • Progress Bar design patterns?

    - by shoosh
    The application I'm writing performs a length algorithm which usually takes a few minutes to finish. During this time I'd like to show the user a progress bar which indicates how much of the algorithm is done as precisely as possible. The algorithm is divided into several steps, each with its own typical timing. For instance- initialization (500 milli-sec) reading inputs (5 sec) step 1 (30 sec) step 2 (3 minutes) writing outputs (7 sec) shutting down (10 milli-sec) Each step can report its progress quite easily by setting the range its working on, say [0 to 150] and then reporting the value it completed in its main loop. What I currently have set up is a scheme of nested progress monitors which form a sort of implicit tree of progress reporting. All progress monitors inherit from an interface IProgressMonitor: class IProgressMonitor { public: void setRange(int from, int to) = 0; void setValue(int v) = 0; }; The root of the tree is the ProgressMonitor which is connected to the actual GUI interface: class GUIBarProgressMonitor : public IProgressMonitor { GUIBarProgressMonitor(ProgressBarWidget *); }; Any other node in the tree are monitors which take control of a piece of the parent progress: class SubProgressMonitor : public IProgressMonitor { SubProgressMonitor(IProgressMonitor *parent, int parentFrom, int parentLength) ... }; A SubProgressMonitor takes control of the range [parentFrom, parentFrom+parentLength] of its parent. With this scheme I am able to statically divide the top level progress according to the expected relative portion of each step in the global timing. Each step can then be further subdivided into pieces etc' The main disadvantage of this is that the division is static and it gets painful to make changes according to variables which are discovered at run time. So the question: are there any known design patterns for progress monitoring which solve this issue?

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  • Converting from CVS to SVN to Hg, does 'hg convert' require pointing to an SVN checkout or just a re

    - by Terry
    As part of migrating full CVS history to Hg, I've used cvs2svn to create an SVN repo in a local directory. It's first level directory structure is: 2010-04-21 09:39 AM <DIR> . 2010-04-21 09:39 AM <DIR> .. 2010-04-21 09:39 AM <DIR> locks 2010-04-21 09:39 AM <DIR> hooks 2010-04-21 09:39 AM <DIR> conf 2010-04-21 09:39 AM 229 README.txt 2010-04-21 11:45 AM <DIR> db 2010-04-21 09:39 AM 2 format 2 File(s) 231 bytes After setting up hg and the convert extension and attempting the convert, I get the following on convert: C:\>hg convert file://localhost/Users/terry/Desktop/repoSVN assuming destination repoSVN-hg initializing destination repoSVN-hg repository file://localhost/Users/terry/Desktop/repoSVN does not look like a CVS checkout file://localhost/Users/terry/Desktop/repoSVN does not look like a Git repo file://localhost/Users/terry/Desktop/repoSVN does not look like a Subversion repo file://localhost/Users/terry/Desktop/repoSVN is not a local Mercurial repo file://localhost/Users/terry/Desktop/repoSVN does not look like a darcs repo file://localhost/Users/terry/Desktop/repoSVN does not look like a monotone repo file://localhost/Users/terry/Desktop/repoSVN does not look like a GNU Arch repo file://localhost/Users/terry/Desktop/repoSVN does not look like a Bazaar repo file://localhost/Users/terry/Desktop/repoSVN does not look like a P4 repo abort: file://localhost/Users/terry/Desktop/repoSVN: missing or unsupported repository I have TortoiseHg installed. For info, hg version reports: Mercurial Distributed SCM (version 1.4.3) This version of Mercurial seems to have some svn bindings if library.zip in the install is to be believed. Do I need to do a checkout and point hg convert to it for this to work properly?

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  • How to add and remove nested model fields dynamically using Haml and Formtastic

    - by Brightbyte8
    We've all seen the brilliant complex forms railscast where Ryan Bates explains how to dynamically add or remove nested objects within the parent object form using Javascript. Has anyone got any ideas about how these methods need to be modified so as to work with Haml Formtastic? To add some context here's a simplified version of the problem I'm currently facing: # Teacher form (which has nested subject forms) [from my application] - semantic_form_for(@teacher) do |form| - form.inputs do = form.input :first_name = form.input :surname = form.input :city = render 'subject_fields', :form => form = link_to_add_fields "Add Subject", form, :subjects # Individual Subject form partial [from my application] - form.fields_for :subjects do |ff| #subject_field = ff.input :name = ff.input :exam = ff.input :level = ff.hidden_field :_destroy = link_to_remove_fields "Remove Subject", ff # Application Helper (straight from Railscasts) def link_to_remove_fields(name, f) f.hidden_field(:_destroy) + link_to_function(name, "remove_fields(this)") end def link_to_add_fields(name, f, association) new_object = f.object.class.reflect_on_association(association).klass.new fields = f.fields_for(association, new_object, :child_index => "new_#{association}") do |builder| render(association.to_s.singularize + "_fields", :f => builder) end link_to_function(name, h("add_fields(this, \"#{association}\", \"#{escape_javascript(fields)} \")")) end #Application.js (straight from Railscasts) function remove_fields(link) { $(link).previous("input[type=hidden]").value = "1"; $(link).up(".fields").hide(); } function add_fields(link, association, content) { var new_id = new Date().getTime(); var regexp = new RegExp("new_" + association, "g") $(link).up().insert({ before: content.replace(regexp, new_id) }); } The problem with implementation seems to be with the javascript methods - the DOM tree of a Formtastic form differs greatly from a regular rails form. I've seen this question asked online a few times but haven't come across an answer yet - now you know that help will be appreciated by more than just me! Jack

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  • method for specialized pathfinding?

    - by rlbond
    I am working on a roguelike in my (very little) free time. Each level will basically be a few rectangular rooms connected together by paths. I want the paths between rooms to be natural-looking and windy, however. For example, I would not consider the following natural-looking: B X X X XX XX XX AXX I really want something more like this: B X XXXX X X X X AXXXXXXXX These paths must satisfy a few properties: I must be able to specify an area inside which they are bounded, I must be able to parameterize how windy and lengthy they are, The lines should not look like they started at one path and ended at the other. For example, the first example above looks as if it started at A and ended at B, because it basically changed directions repeatedly until it lined up with B and then just went straight there. I was hoping to use A*, but honestly I have no idea what my heuristic would be. I have also considered using a genetic algorithm, but I don't know how practical that method might end up. My question is, what is a good way to get the results I want? Please do not just specify a method like "A*" or "Dijkstra's algorithm," because I also need help with a good heuristic.

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  • Handling mach exceptions in 64bit OS X application

    - by Brad S
    I have been able to register my own mach port to capture mach exceptions in my applications and it works beautifully when I target 32 bit. However when I target 64 bit, my exception handler catch_exception_raise() gets called but the array of exception codes that is passed to the handler are 32 bits wide. This is expected in a 32 bit build but not in 64 bit. In the case where I catch EXC_BAD_ACCESS the first code is the error number and the second code should be the address of the fault. Since the second code is 32 bits wide the high 32 bits of the 64 bit fault address is truncated. I found a flag in <mach/exception_types.h> I can pass in task_set_exception_ports() called MACH_EXCEPTION_CODES which from looking at the Darwin sources appears to control the size of the codes passed to the handler. It looks like it is meant to be ored with the behavior passed in to task_set_exception_ports(). However when I do this and trigger an exception, my mach port gets notified, I call exc_server() but my handler never gets called, and when the reply message is sent back to the kernel I get the default exception behavior. I am targeting the 10.6 SDK. I really wish apple would document this stuff better. Any one have any ideas?

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  • finding "line-breaks" in textarea that is word-wrapping ARABIC text

    - by Irfan jamal
    I have a string of text that I display in a textarea (right-to-left orientation). The user can resize the textarea dynamically (I use jquery for this) and the text will wrap as necessary. When the user hits submit, I will take that text and create an image using PHP, BUT before submitting I would like to know where the "line-breaks" or rather "word-wraps" occur. Everywhere I have looked so far only shows me how to process line-breaks on the php side. I want to make it clear that there ARE NO LINE-BREAKS. What I have is one LONG string that will be word-wrapped in different ways based on the width of the textarea set by the user. I can't use "columns" or any other standard width representation because I have a very complex arabic font that is actually composed of glyphs (characters) of numerous different widths. If anyone knows of a way of accessing where the word wraps occur (either in a textarea or a div if need-be), I'd really like to know. My only other solution is to actually store (in my DB) the width of every single character (somewhat tedious since there are over 200 characters in 600 different fonts, for a total of...some huge number). My hopes aren't high, but I thought I would ask. Thanks i. jamal

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  • django-mptt: how to successfully move nodes around

    - by Parand
    django-mptt seems determined to drive me out of my mind. I'm trying to do something relatively simple: I'm going to delete a node, and need to do something reasonable with the node's children. Namely, I'd like to move them up one level so they're children of their current parent's parent. That is, if the tree looks like: Root | Grandpa | Father | | C1 C2 I'm going to delete Father, and would like C1 and C2 to be children of Grandpa. Here's the code I'm using: class Node(models.Model): first_name = models.CharField(max_length=80, blank=True) parent = models.ForeignKey('self', null=True, blank=True, related_name='children') def reparent_children(self, parent): print "Reparenting" for child in self.get_children(): print "Working on", child.first_name, "to parent", parent.email parent = Node.objects.get(id=parent.id) child.move_to(parent, 'last-child') child.save() So I'd call: father.reparent_children(grandpa) father.parent = None father.save() This works - almost. The children report their parents as Grandpa: c1.parent == grandpa # True Grandpa counts C1 and C2 among its children c1 in grandpa.children.all() # True However, Root disowns these kids. c1.get_root() == father # c1's root is father, instead of Root c1 in root.get_descendants() # False How do I get the children to move and their root not get corrupted?

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  • using ghostscript in server mode to convert pdfs to pngs

    - by emh
    while i am able to convert a specific page of a PDF to a PNG like so: gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -dGraphicsAlphaBits=4 -sOutputFile=gymnastics-20.png -dFirstPage=20 -dLastPage=20 gymnastics.pdf i am wondering if i can somehow use ghostscript's JOBSERVER mode to process several conversions without having to incur the cost of starting up ghostscript each time. from: http://pages.cs.wisc.edu/~ghost/doc/svn/Use.htm -dJOBSERVER Define \004 (^D) to start a new encapsulated job used for compatibility with Adobe PS Interpreters that ordinarily run under a job server. The -dNOOUTERSAVE switch is ignored if -dJOBSERVER is specified since job servers always execute the input PostScript under a save level, although the exitserver operator can be used to escape from the encapsulated job and execute as if the -dNOOUTERSAVE was specified. This also requires that the input be from stdin, otherwise an error will result (Error: /invalidrestore in --restore--). Example usage is: gs ... -dJOBSERVER - < inputfile.ps -or- cat inputfile.ps | gs ... -dJOBSERVER - Note: The ^D does not result in an end-of-file action on stdin as it may on some PostScript printers that rely on TBCP (Tagged Binary Communication Protocol) to cause an out-of-band ^D to signal EOF in a stream input data. This means that direct file actions on stdin such as flushfile and closefile will affect processing of data beyond the ^D in the stream. the idea is to run ghostscript in-process. the script would receive a request for a particular page of a pdf and would use ghostscript to generate the specified image. i'd rather not start up a new ghostscript process every time.

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  • Does RabbitMq do round-robin from the exchange to the queues

    - by Lancelot
    Hi, I am currently evaluating message queue systems and RabbitMq seems like a good candidate, so I'm digging a little more into it. To give a little context I'm looking to have something like one exchange load balancing the message publishing to multiple queues. I don't want to replicate the messages, so a fanout exchange is not an option. Also the reason I'm thinking of having multiple queues vs one queue handling the round-robin w/ the consumers, is that I don't want our single point of failure to be at the queue level. Sounds like I could add some logic on the publisher side to simulate that behavior by editing the routing key and having the appropriate bindings in place. But that's kind of a passive approach that wouldn't take the pace of the message consumption on each queue into account, potentially leading to fill up one queue if the consumer applications for that queue are dead. I was looking for a more pro-active way from the exchange entity side, that would decide where to send the next message based on each queue size or something of that nature. I read about Alice and the available RESTful APIs but that seems kind of a heavy duty solution to implement fast routing decisions. Anyone knows if round-robin between the exchange the queues is feasible w/ RabbitMQ then? Thanks.

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  • jquery Ajax sortable list stops being sortable when Ajax call updates the list html

    - by Trevor
    Hi, I am using jquery 1.4.2 and trying to achieve the following: 1 - function call that sends a value to a php page to add/remove an item 2 - returns html list of the items 3 - list should still be sortable 4 - save (serialise list) onclick My full WIP is located here [http://www.chittak.co.uk/test4/index_nw3.php][1] I tried to delegate from the level above the UL but I could get this to work $("#construnctionstage").delegate('ul li', 'click', function(){ The initial list is sortable, when you click add/remove the ajax function returns a new list with the a number of items, BUT I am doing something wrong as the alert message continues to work while the list is no longer sortable. $(document).ready(function(){ $('ul').delegate('li', 'click', function(){ alert('You clicked on an li element!'); /*$("#test-list").sortable({ handle : '.handle', update : function () { var order = $('#test-list').sortable('serialize'); $("#info").load("process-sortable.php?"+order); } });*/ }).sortable({ handle : '.handle', update : function () { var order = $('#test-list').sortable('serialize'); $("#info").load("process-sortable.php?"+order); } }); }); <div id="construnctionstage"> <ul id="test-list"> <li id="listItem_1">

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  • Why is "Fixup" needed for Persistence Ignorant POCO's in EF 4?

    - by Eric J.
    One of the much-anticipated features of Entity Framework 4 is the ability to use POCO (Plain Old CLR Objects) in a Persistence Ignorant manner (i.e. they don't "know" that they are being persisted with Entity Framework vs. some other mechanism). I'm trying to wrap my head around why it's necessary to perform association fixups and use FixupCollection in my "plain" business object. That requirement seems to imply that the business object can't be completely ignorant of the persistence mechanism after all (in fact the word "fixup" sounds like something needs to be fixed/altered to work with the chosen persistence mechanism). Specifically I'm referring to the Association Fixup region that's generated by the ADO.NET POCO Entity Generator, e.g.: #region Association Fixup private void FixupImportFile(ImportFile previousValue) { if (previousValue != null && previousValue.Participants.Contains(this)) { previousValue.Participants.Remove(this); } if (ImportFile != null) { if (!ImportFile.Participants.Contains(this)) { ImportFile.Participants.Add(this); } if (ImportFileId != ImportFile.Id) { ImportFileId = ImportFile.Id; } } } #endregion as well as the use of FixupCollection. Other common persistence-ignorant ORMs don't have similar restrictions. Is this due to fundamental design decisions in EF? Is some level of non-ignorance here to stay even in later versions of EF? Is there a clever way to hide this persistence dependency from the POCO developer? How does this work out in practice, end-to-end? For example, I understand support was only recently added for ObservableCollection (which is needed for Silverlight and WPF). Are there gotchas in other software layers from the design requirements of EF-compatible POCO objects?

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  • How should I handle persistence in a Java MUD? OptimisticLockException handling

    - by Chase
    I'm re-implementing a old BBS MUD game in Java with permission from the original developers. Currently I'm using Java EE 6 with EJB Session facades for the game logic and JPA for the persistence. A big reason I picked session beans is JTA. I'm more experienced with web apps in which if you get an OptimisticLockException you just catch it and tell the user their data is stale and they need to re-apply/re-submit. Responding with "try again" all the time in a multi-user game would make for a horrible experience. Given that I'd expect several people to be targeting a single monster during a fight I think the chance of an OptimisticLockException would be high. My view code, the part presenting a telnet CLI, is the EJB client. Should I be catching the PersistenceExceptions and TransactionRolledbackLocalExceptions and just retrying? How do you decide when to stop? Should I switch to pessimistic locking? Is persisting after every user command overkill? Should I be loading the entire world in RAM and dumping the state every couple of minutes? Do I make my session facade a EJB 3.1 singleton which would function as a choke point and therefore eliminating the need to do any type of JPA locking? EJB 3.1 singletons function as a multiple reader/single writer design (you annotate the methods as readers and writers). Basically, what is the best design and java persistence API for highly concurrent data changes in an application where it is not acceptable to present resubmit/retry prompts to the user?

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  • Is there any better IDOMImplementation other than MSXML?

    - by Chau Chee Yang
    There are 3 IDOMImplementation available in Delphi: MSXML Xerces XML ADOM XML v4 MSXML is the default IDOMImplementation. My test is count the time need to load a 10MB xml file. I use a Delphi unit generated from a XSD using XML data binding to load the xml file. This unit has 3 common function: function Getmenubar(Doc: IXMLDocument): IXMLMenubarType; function Loadmenubar(const FileName: WideString): IXMLMenubarType; function Newmenubar: IXMLMenubarType; I learn from the web that some comment that MSXML's overhead is high that it doesn't perform if compare to other XML parser. However, my study shows that MSXML is the best among others. Xerces XML 2nd and ADOM XML v4 the worst: MSXML - 0.6410 seconds Xerces XML - 2.4220 seconds ADOM XML v4 - 67.50 seconds I also come across with OmniXML that claim to have much better performance compare to MSXML but I never success using it with the unit generated by XML data binding. Is there any other vendor that implement IDOMImplementation of Delphi that work much better than MSXML? I am using Delphi 2010 and Windows 7.

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  • Subview of custom NSView is resizing itself to fit within its superview

    - by Jonathan Patt
    I have a custom NSView which contains a subview—for the purposes of solving this issue, the top level view is simply acting as a container and automatically resizes to fit within the window. Its subview draws a rectangle 10 pixels inset from the edge of the window, except for the bottom, which should get clipped by the window until it's resized to show the entire rectangle. It does not, however, behave as I intend, and instead shrinks the height of the rectangle when its superview has a smaller height than it does. How do I avoid this and have it stay at its proper height and instead get clipped when the superview is smaller? The parent view's implementation code is: - (id)initWithFrame:(NSRect)frameRect { self = [super initWithFrame:frameRect]; if (self) { subView = [[SubView alloc] initWithFrame:frameRect]; } return self; } - (void)drawRect:(NSRect)dirtyRect { [[NSColor grayColor] set]; [subView setFrame:NSMakeRect(10, 10, dirtyRect.size.width - 20, 500)]; [self addSubview:subView]; } - (BOOL)isFlipped { return YES; } And the subview is just: - (void)drawRect:(NSRect)dirtyRect { [[NSColor blackColor] set]; [NSBezierPath strokeRect:dirtyRect]; } - (BOOL)isFlipped { return YES; }

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  • Linux Kernel programming: trying to get vm_area_struct->vm_start crashes kernel

    - by confusedKid
    Hi, this is for an assignment at school, where I need to determine the size of the processes on the system using a system call. My code is as follows: ... struct task_struct *p; struct vm_area_struct *v; struct mm_struct *m; read_lock(&tasklist_lock); for_each_process(p) { printk("%ld\n", p->pid); m = p->mm; v = m->mmap; long start = v->vm_start; printk("vm_start is %ld\n", start); } read_unlock(&tasklist_lock); ... When I run a user level program that calls this system call, the output that I get is: 1 vm_start is 134512640 2 EIP: 0073:[<0806e352] CPU: 0 Not tainted ESP: 007b:0f7ecf04 EFLAGS: 00010246 Not tainted EAX: 00000000 EBX: 0fc587c0 ECX: 081fbb58 EDX: 00000000 ESI: bf88efe0 EDI: 0f482284 EBP: 0f7ecf10 DS: 007b ES: 007b 081f9bc0: [<08069ae8] show_regs+0xb4/0xb9 081f9bec: [<080587ac] segv+0x225/0x23d 081f9c8c: [<08058582] segv_handler+0x4f/0x54 081f9cac: [<08067453] sig_handler_common_skas+0xb7/0xd4 081f9cd4: [<08064748] sig_handler+0x34/0x44 081f9cec: [<080648b5] handle_signal+0x4c/0x7a 081f9d0c: [<08066227] hard_handler+0xf/0x14 081f9d1c: [<00776420] 0x776420 Kernel panic - not syncing: Kernel mode fault at addr 0x0, ip 0x806e352 EIP: 0073:[<400ea0f2] CPU: 0 Not tainted ESP: 007b:bf88ef9c EFLAGS: 00000246 Not tainted EAX: ffffffda EBX: 00000000 ECX: bf88efc8 EDX: 080483c8 ESI: 00000000 EDI: bf88efe0 EBP: bf88f038 DS: 007b ES: 007b 081f9b28: [<08069ae8] show_regs+0xb4/0xb9 081f9b54: [<08058a1a] panic_exit+0x25/0x3f 081f9b68: [<08084f54] notifier_call_chain+0x21/0x46 081f9b88: [<08084fef] __atomic_notifier_call_chain+0x17/0x19 081f9ba4: [<08085006] atomic_notifier_call_chain+0x15/0x17 081f9bc0: [<0807039a] panic+0x52/0xd8 081f9be0: [<080587ba] segv+0x233/0x23d 081f9c8c: [<08058582] segv_handler+0x4f/0x54 081f9cac: [<08067453] sig_handler_common_skas+0xb7/0xd4 081f9cd4: [<08064748] sig_handler+0x34/0x44 081f9cec: [<080648b5] handle_signal+0x4c/0x7a 081f9d0c: [<08066227] hard_handler+0xf/0x14 081f9d1c: [<00776420] 0x776420 The first process (pid = 1) gave me the vm_start without any problems, but when I try to access the second process, the kernel crashes. Can anyone tell me what's wrong, and maybe how to fix it as well? Thanks a lot! (sorry for the bad formatting....) edit: This is done in a Fedora 2.6 core in an uml environment.

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  • Nature of Lock is child table while deletion(sql server)

    - by Mubashar Ahmad
    Dear Devs From couple of days i am thinking of a following scenario Consider I have 2 tables with parent child relationship of kind one-to-many. On removal of parent row i have to delete the rows in child those are related to parents. simple right? i have to make a transaction scope to do above operation i can do this as following; (its psuedo code but i am doing this in c# code using odbc connection and database is sql server) begin transaction(read committed) Read all child where child.fk = p1 foreach(child) delete child where child.pk = cx delete parent where parent.pk = p1 commit trans OR begin transaction(read committed) delete all child where child.fk = p1 delete parent where parent.pk = p1 commit trans Now there are couple of questions in my mind Which one of above is better to use specially considering a scenario of real time system where thousands of other operations(select/update/delete/insert) are being performed within a span of seconds. does it ensure that no new child with child.fk = p1 will be added until transaction completes? If yes for 2nd question then how it ensures? do it take the table level locks or what. Is there any kind of Index locking supported by sql server if yes what it does and how it can be used. Regards Mubashar

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  • POSIX AIO Library and Callback Handlers

    - by Charles Salvia
    According to the documentation on aio_read/write, there are basically 2 ways that the AIO library can inform your application that an async file I/O operation has completed. Either 1) you can use a signal, 2) you can use a callback function I think that callback functions are vastly preferable to signals, and would probably be much easier to integrate into higher-level multi-threaded libraries. Unfortunately, the documentation for this functionality is a mess to say the least. Some sources, such as the man page for the sigevent struct, indicate that you need to set the sigev_notify data member in the sigevent struct to SIGEV_CALLBACK and then provide a function handler. Presumably, the handler is invoked in the same thread. Other documentation indicates you need to set sigev_notify to SIGEV_THREAD, which will invoke the callback handler in a newly created thread. In any case, on my Linux system (Ubuntu with a 2.6.28 kernel) SIGEV_CALLBACK doesn't seem to be defined anywhere, but SIGEV_THREAD works as advertised. Unfortunately, creating a new thread to invoke the callback handler seems really inefficient, especially if you need to invoke many handlers. It would be better to use an existing pool of threads, similar to the way most network I/O event demultiplexers work. Some versions of UNIX, such as QNX, include a SIGEV_SIGNAL_THREAD flag, which allows you to invoke handlers using a specified existing thread, but this doesn't seem to be available on Linux, nor does it seem to even be a part of the POSIX standard. So, is it possible to use the POSIX AIO library in a way that invokes user handlers in a pre-allocated background thread/threadpool, rather than creating/destroying a new thread everytime a handler is invoked?

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  • Update PEAR on MAMP MacOsX

    - by Jevgeni Smirnov
    Current I am trying to install phpunit on my mac os x and mamp server: pear config-set auto_discover 1 pear install pear.phpunit.de/PHPUnit Errors which I got during installation: Validation Error: This package.xml requires PEAR version 1.9.4 to parse properly, we are version 1.9.2 pear upgrade pear Nothing to upgrade UPDATE 1 This is my pear config. I assume that I messed up local and mamp installs(I didn't know that mamp also has pear, so I installed local one). I suppose something wrong with bin_dir, php_dir and other paths? Keefir-Samolet-iMac:MAMP jevgenismirnov$ pear config-show Configuration (channel pear.php.net): ===================================== Auto-discover new Channels auto_discover 1 Default Channel default_channel pear.php.net HTTP Proxy Server Address http_proxy PEAR server [DEPRECATED] master_server pear.php.net Default Channel Mirror preferred_mirror pear.php.net Remote Configuration File remote_config PEAR executables directory bin_dir /Users/jevgenismirnov/pear/bin PEAR documentation directory doc_dir /Users/jevgenismirnov/pear/docs PHP extension directory ext_dir /Applications/MAMP/bin/php/php5.3.6/lib/php/extensions/no-debug-non-zts-20090626/ PEAR directory php_dir /Users/jevgenismirnov/pear/share/pear PEAR Installer cache directory cache_dir /var/folders/k7/xpwbcbrs1xs8tlxjk5mvkwrr0000gp/T//pear/cache PEAR configuration file cfg_dir /Users/jevgenismirnov/pear/cfg directory PEAR data directory data_dir /Users/jevgenismirnov/pear/data PEAR Installer download download_dir /tmp/pear/install directory PHP CLI/CGI binary php_bin /Applications/MAMP/bin/php/php5.3.6/bin/php php.ini location php_ini --program-prefix passed to php_prefix PHP's ./configure --program-suffix passed to php_suffix PHP's ./configure PEAR Installer temp directory temp_dir /tmp/pear/install PEAR test directory test_dir /Users/jevgenismirnov/pear/tests PEAR www files directory www_dir /Users/jevgenismirnov/pear/www Cache TimeToLive cache_ttl 3600 Preferred Package State preferred_state stable Unix file mask umask 22 Debug Log Level verbose 1 PEAR password (for password maintainers) Signature Handling Program sig_bin /usr/local/bin/gpg Signature Key Directory sig_keydir /Applications/MAMP/bin/php/php5.3.6/conf/pearkeys Signature Key Id sig_keyid Package Signature Type sig_type gpg PEAR username (for username maintainers) User Configuration File Filename /Users/jevgenismirnov/.pearrc System Configuration File Filename /Applications/MAMP/bin/php/php5.3.6/conf/pear.conf

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  • Child objects in MongoDB

    - by Jeremy B.
    I have been following along with Rob Conery's Linq for MongoDB and have come across a question. In the example he shows how you can easily nest a child object. For my current experiment I have the following structure. class Content { ... Profile Profile { get; set; } } class Profile { ... } This works great when looking at content items. The dilemma I'm facing now is if I want to treat the Profile as an atomic object. As it stands, it appears as if I can not query the Profile object directly but that it comes packaged with Content results. If I want it to be inclusive, but also be able to query on just Profile I feel like my first instinct would be to make Profiles a top level object and then create a foreign key like structure under the Content class to tie the two together. To me it feels like I'm falling back on RDBMS practices and that feels like I'm most likely going against the spirit of Mongo. How would you treat an object you need to act upon independently yet also want as a child object of another object?

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  • How to fix security exception when using recaptcha on MVC site

    - by camainc
    I followed this excellent blog post to implement recaptcha on my MVC site: http://devlicio.us/blogs/derik_whittaker/archive/2008/12/02/using-recaptcha-with-asp-net-mvc.aspx I converted the code to VB, and everything seems to compile ok. However, when the code gets to the place where the recapture is about to be generated, I get a security exception. Here is the function where the exception occurs (on the last line in the function): <Extension()> _ Public Function GenerateCaptcha(ByVal htmlHelper As HtmlHelper) As MvcHtmlString Dim captchaControl As New Recaptcha.RecaptchaControl With captchaControl .ID = "recaptcha" .Theme = "blackglass" .PublicKey = "6Lcv9AsAAAAAALCSZNRfWFmrKjw2AR-yuZAL84Bd" .PrivateKey = "6Lcv9AsAAAAAAHCbRujWcZzrY0z6G_HIMvFyYEPR" End With Dim htmlWriter As New HtmlTextWriter(New IO.StringWriter) captchaControl.RenderControl(htmlWriter) Return MvcHtmlString.Create(htmlWriter.InnerWriter.ToString()) End Function The exception is this: Security Exception Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file. Exception Details: System.Security.SecurityException: Request for the permission of type 'System.Web.AspNetHostingPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. Has anyone else seen this exception, and if so, how did you fix it? Thanks

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  • nHibernate strategies in a web farm

    - by Pete Nelson
    Our current project at work is a new MVC web site that will use a WCF service primarily to access a 3rd party billing system via a web service as well as a small SQL database for user personalization. The WCF service uses nHibernate for the SQL database. We'd like to implement some sort of web farm for load balancing as well as failover and maintenance. I'm trying to decide the best way to handle nHibernate's caching and database concurrency if there are multiple WCF services running. Some scenarios I've been thinking about... 1) Multiple IIS servers, one WCF server. With this setup, the WCF server would be a single point of failure, but there would be no issues with nHibernate caching or database concurrency. 2) Multiple IIS servers, each with it's own WCF service. This removes a single point of failure, but now nHibernate on one machine would not know about database changes done by another machine. Some solutions to number 2 would be to use an IStatelessSession so we're not doing any caching and nHibernate is always fetching directly from the database. This might be the most feasible as our personalization database has very few objects in it. I'm also considering a 2nd-level cache such as memcached or Velocity, but it may be overkill for this system. I'm putting this out there to see if anyone has experience doing this sort of architecture and to get some ideas for a solution. Thanks!

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  • Advice for Future Programmers?

    - by Nate Zaugg
    I have a buddy that is going to be giving some presentations to high-schoolers. Specifically he asked: What would you be looking for if they approached you about work? Perhaps you are in that age group right now. What do you want to know? Perhaps you are just a few years into the workforce. What do you wish someone had told you but never did? Perhaps you have children, relatives or friends in or soon to be in that age group. What are you worried they don't know about? I'm sure there are other perspectives and questions I'm not even thinking about. I'd like to hear what you have to say about it. Here was my list: Don't be afraid to try! Don't let the perception that something is too difficult stop you from experimenting. Curiosity may have killed the cat, but an un-inquisitive person is mostly useless. Stolen from Einstein: You don't really understand something until you can explain it to your grandmother. It's never enough to be smart, you also have to work well with others. Before you can be really smart, you must learn how to learn. There will always be someone smarter than you are -- Become their buddy! Get to know great minds and learn all you can. Some knowledge can only be expressed this way. Communication, Communication, Communication! Projects rarely fail because of technical reasons and the difference between good programmers and outstanding programmers is how well they communicate. A good work ethic never goes unnoticed. Know when to ask for help and when to figure something out for yourself.

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  • Is an LSA MSV1_0 subauthentication package needed for some impersonation use cases?

    - by Chris Sears
    Greetings, I'm working with a vendor who has implemented some code that uses a Windows LSA MSV1_0 subauthentication package (MSDN info if you're interested: http://msdn.microsoft.com/en-us/library/aa374786(VS.85).aspx ) and I'm trying to figure out if it's necessary. As far as I can tell, the subauthentication routine and filter allow for hooking or customizing the standard LSA MSV1_0 logon event processing. The issue is that I don't understand why the vendor's product would need these capabilities. I've asked them and they said they use it to perform impersonation. The product definitely does need to do impersonation, but based on my limited win32 knowledge, they could get the functionality they need using the normal auth APIs (LsaLogonUser, ImpersonateLoggedOnUser, etc) without the subauthentication package. Furthermore, I've worked with a number of similar products that all do impersonation, and this is the only one that's used a subauthentication package. If you're wondering why I would care, a previous version of the product had a bug in the subauthentication package dll that would cause lockups or bluescreens. That makes me rather nervous and has me questioning the use of such a low-level, kernel sensitive interface. I'd like to go back to the vendor and say "There's no way you could need an LSA subauth package for impersonation - take it out", but I'm not sure I understand the use cases and possible limitations of the standard win32 authentication/impersonation APIs well enough to make that claim definitively. So, to the win32 security gurus out there, is there any reason you would need an LSA MSV1_0 subauthentication package if all you were doing is impersonation? Thanks in advance for any thoughts!

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