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• Custom UIView using CALayers disappears after 180º rotation or navigation controller pop

  - by Steve Madsen

  I have a created a custom UIView subclass that is exhibiting some strange behavior. It is a spinning wheel selector, and for performance reasons it is drawn entirely into two CALayer instances. The bottom layer is the wheel itself, which is rotated using setAffineTransform: according to touches. The top layer is eye candy. drawRect: is fairly simple. If the control hasn't been drawn yet (or it's been invalidated), it calls a method that creates the images and assigns them to the layer contents property. - (void) drawRect:(CGRect)rect { if (imageLayer == nil) { [self drawIntoImageLayer]; } [self updateWheelRotation]; } When the view controller using this view first appears, everything is fine. There are two instances where the view completely disappears, however: If the device is rotated a full 180°. After a view controller is popped off the navigation stack and the view becomes visible again. drawRect: is not called either time. Interestingly enough, it IS called after a 90° orientation change, and that causes the view to re-appear. How can I ensure that a custom view using CALayers is redrawn properly in these situations?

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• Bulk Insert of hundreds of millions of records

  - by Dave Jarvis

  What is the fastest way to insert 237 million records into a table that has rules (for distributing the data across 84 child tables)? First I tried inserts. No go. Then I tried inserts with BEGIN/COMMIT. Not nearly fast enough. Next, I tried COPY FROM, but then noticed the documentation states that the rules are ignored. (And it was having difficulties with the column order and date format -- it said that '1984-07-1' was not a valid integer; true, but a bit unexpected.) Some example data: station_id,taken,amount,category_id,flag 1,'1984-07-1',0,4, 1,'1984-07-2',0,4, 1,'1984-07-3',0,4, 1,'1984-07-4',0,4,T Here is the table structure (with one rule included): CREATE TABLE climate.measurement ( id bigserial NOT NULL, station_id integer NOT NULL, taken date NOT NULL, amount numeric(8,2) NOT NULL, category_id smallint NOT NULL, flag character varying(1) NOT NULL DEFAULT ' '::character varying ) WITH ( OIDS=FALSE ); ALTER TABLE climate.measurement OWNER TO postgres; CREATE OR REPLACE RULE i_measurement_01_001 AS ON INSERT TO climate.measurement WHERE date_part('month'::text, new.taken)::integer = 1 AND new.category_id = 1 DO INSTEAD INSERT INTO climate.measurement_01_001 (id, station_id, taken, amount, category_id, flag) VALUES (new.id, new.station_id, new.taken, new.amount, new.category_id, new.flag); I can generate the data into any format. Am looking for something that won't take four days. I originally had the data in MySQL (still do), but am hoping to get a performance increase by switching to PostgreSQL and am eager to use its PL/R extensions for stats. I was also thinking about using: http://pgbulkload.projects.postgresql.org/ Any help, tips, or guidance would be greatly appreciated. Thank you!

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• Mysql Server Optimization

  - by Ish Kumar

  Hi Geeks, We are having serious MySQL(InnoDB) performance issues at a moment when we do: (10-20) insertions on TABLE1 (10-20) updates on TABLE2 Note: Both above operations happens within fraction of a second. And this occurs every few (10-15) minutes. And all online users (approx 400-600) doing read operation on join of TABLE1 & TABLE2 every 1 second. Here is our mysql configuration info: http://docs.google.com/View?id=dfrswh7c_117fmgcmb44 Issues: Lot queries wait and expire later (saw it from phpmyadmin / processes). My poor MySQL server crashes sometimes Questions Q1: Any suggestions to optimize at MySQL level? Q2: I thinking to use persistent connections at application level, is it right? Info Added Later: Database Engine: InnoDB TABLE1 : 400,000 rows (inserting 8,000 daily) & TABLE2: 8,000 rows 1 second query: SELECT b.id, b.user_id, b.description, b.debit, b.created, b.price, u.username, u.email, u.mobile FROM TABLE1 b, TABLE2 u WHERE b.credit = 0 AND b.user_id = u.id AND b.auction_id = "12345" ORDER BY b.id DESC LIMIT 10; // there are few more but they are not so critical. Indexing is good, we are using them wisely. In above query all id's are indexed And TABLE1 has frequent insertions and TABLE2 has frequent updates.

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• How to choose light version of databse system

  - by adopilot

  I am starting one POS (Point of sale) project. Targeting system is going to be written in C# .NET 2 WinForms and as main database server We are going to use MS-SQL Server. As we have a lot of POS devices in chain for one store I will love to have backend local data base system on each POS device. Scenario are following: When main server goes down!! POS application should continue working "off-line" with local database, until connection to main server come up again. Now I am in dilemma which local database is going to be most adoptable for me. Here is some notes for helping me point me in right direction: To be Light "My POS devices art usually old and suffering with performances" To be Free "I have a lot of devices and I do not wont additional cost beside main SQL serer" One day Ill love to try all that port on Mono and Linux OS. Here is what I've researched so far: Simple XML "Light but I am afraid of performance, My main table of items is average of 10K records" SQL-Expres "I am afraid that my POS devices is poor with hardware for SQLExpres, and also hard to install on each device and configure" Less known Advantage Database Server have free distribution of offline ADT system. DBF with extended Library,"Respect for good old DBFs but that era is behind Me with clipper and DBFs" MS Access Sqlite "Mostly like for now, but I am afraid how it is going to pair with MS SQL do they have same Data taypes". I know that in this SO is a lot of subjective data, but at least can someone recommended some others lite database system, or things that I shod most take attention before I choice database.

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• Java SSH2 libraries in depth: Trilead/Ganymed/Orion [/other?]

  - by Bernd Haug

  I have been searching for a pure Java SSH library to use for a project. The single most important needed feature is that it has to be able to work with command-line git, but remote-controlling command-line tools is also important. A pretty common choice, e.g. used in the IntelliJ IDEA git integration (which works very well), seems to be Trilead SSH2. Looking at their website, it's not being maintained any more. Trilead seems to have been a fork of Ganymed SSH2, which was a ETH Zurich project that didn't see releases for a while, but had a recent release by its new owner, Christian Plattner. There is another actively maintained fork from that code base, Orion SSH, that saw an even more recent release, but which seems to get mentioned online much less than the other 2 forks. Has anybody here worked with any of (or, if possible, both) of Ganymed and Orion and could kindly describe the development experience with either/both? Accuracy of documentation [existence of documentation?], stability, buggyness... - all of these would be highly interesting to me. Performance is not so important for my current project. If there is another pure-Java SSH implementation that should be used instead, please feel free to mention it, but please don't just mention a name...describe your judgment from actual experience. Sorry if this question may seem a bit "do my homework"-y, but I've really searched for reviews. Everything out there seems to be either a listing of implementations or short "use this! it's great!" snippets.

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• Can parser combinators be made efficient?

  - by Jon Harrop

  Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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• How to lazy load scripts in YUI that accompany ajax html fragments

  - by Chris Beck

  I have a web app with Tabs for Messages and Contacts (think gmail). Each Tab has a Y.on('click') event listener that retrieves an HTML fragment via Y.io() and renders the fragment via node.setContent(). However, the Contact Tab also requires contact.js to enable an Edit button in the fragment. How do I defer the cost of loading contact.js until the user clicks on the Contacts tab? How should contact.js add it's listener to the Edit button? The Complete function of my Tab's on('click') event could serialize Get.script('contact.js') after Y.io('fragment'). However, for better performance, I would prefer to download the script in parallel to downloading the HTML fragment. In that case, I would need to defer adding an event listener to the Edit button until the Edit button is available. This seems like a common RIA design pattern. What is the best way to implement this with YUI? How should I get the script? How should I defer sections of the script until elements in the fragment are available in the DOM?

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• How/when to hire new programmers, and how to integrate them?

  - by Shaul

  Hiring new programmers, especially in a small company, can often present a Catch-22 situation. We have too much work to do, so we need to hire new programmers. But we can't hire new programmers now, because they will need mentoring and several months of learning curve in your industry/product/environment before they're useful, and none of the programmers has time to be a mentor to a new programmer, because they're all completely swamped with the current work load. That may be a slightly frivolous way of describing the situation, but nevertheless, it's difficult for a small company on a tight budget to justify hiring someone who is not only going to be unproductive for a long time, but will also take away from the performance of the current programmers. How have you dealt with this kind of situation? When is the best time to hire someone? What are the best tasks to assign to a new team member so that they can learn their way around your code base and start getting their hands dirty as quickly as possible? How do you get the new guy useful without bogging your existing programmers down in too much mentoring? Any comments & suggestions you have are much appreciated!

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• When are SQL views appropriate in ASP.net MVC?

  - by sslepian

  I've got a table called Protocol, a table called Eligibility, and a Protocol_Eligibilty table that maps the two together (a many to many relationship). If I wanted to make a perfect copy of an entry in the Protocol table, and create all the needed mappings in the Protocol_Eligibility table, would using an SQL view be helpful, from a performance standpoint? Protocol will have around 1000 rows, Eligibility will have about 200, and I expect each Protocol to map to about 10 Eligibility rows and each Eligibility to map to over 100 rows in Protocol. Here's how I'm doing this with the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility_View where pel.pid == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = (from pel in _documentDataModel.Eligibility where pel.ID == pel_item.eid select pel).First(); newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); } And this is without the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility where pel.Protocol.ID == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { pel_item.EligibilityReference.Load(); newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = pel_item.Eligibility; newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); }

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• spam and dirty words comment post filtering in python (django)

  - by sintaloo

  Hi All, My basic question is how to filter spam and dirty words in a comment post system under python (django). I have a collection of phrases (approximately 3000 phrases) to be filtered. Question (1), are there any existing open source python (or django) package/module/plugin which can handle this job? I knew there was one called Akismet. But from what I understood, it will not solve my problem. Akismet is just a web service and filter the words dictionary defined by Akismet. But I have my own collection of words. Please correct me if I am wrong. Question (2), If there is no such open source package I can use, how to create my own one? The only thing I can think of it's to use regular expression and join all the word phrases with 'or' in a regular expression. but I have 3000 phrases, I think it won't work in term of performance and filter every comment post. any suggestions where should I start from? Thank you very much for your help and time.

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• javascript pausing consistently. How do I find what is causing it to pause?

  - by pedalpete

  I've got a fairly ajax heavy site and I'm trying to tune the performance. I have a function that runs between 20 & 200 times, depending on the user. I'm outputting the time the function takes to execute via console.time in firefox. The function takes about 4-6ms to complete. The strange thing is that on my larger test with 200 or runs through that function, it runs through the first 31, then seems to pause for almost a second before completing the last 170 or so. However, that 'pause' doesn't show up in the console.time logs, and I'm not running any other functions, and the object that gets passed to the function looks the same as all other objects that get passed in. The function is called like this for (var s in thisGroup.events){ showEvent(thisGroup.events[s]) } so, I don't see how or why it would suddenly pause near the beginning. but only pause once and then continue through. The pause ALWAYS happens on the 31st time through the function. I've taken a close look at the 'thisGroup.events[s]' that it is being run through, and it looks like this for #31 "eventId":"5106", "sid":"68", "gid":"29", "uid":"70","type":"event", "startDate":"2010-03-22","startTime":"6:00 PM","endDate":"2010-03-22","endTime":"11:00 PM","durationLength":"5", "durationTime":"5:00", "note":"", "desc":"event" The event immediately after the pause, #32 looks like this "eventId":"5111", "sid":"68", "gid":"29", "uid":"71","type":"event", "startDate":"2010-03-22","startTime":"6:00 PM","endDate":"2010-03-22","endTime":"11:00 PM","durationLength":"5", "durationTime":"5:00", "note":"", "desc":"event" another event that runs through no problem looks like this "eventId":"5113", "sid":"68", "gid":"29", "uid":"72","type":"event", "startDate":"2010-03-22","startTime":"4:30 PM","endDate":"2010-03-22","endTime":"11:00 PM","durationLength":"6.5", "durationTime":"6:30", "note":"", "desc":"event" From the console outputs, it doesn't appear as there is anything hanging or taking up time in the function itself, as the console.time for each event including #31,32 is 4ms. Another strange thing here is that the total time running the for loop across the entire object is coming out as 1014ms which is right for 200 events at 4-6ms each. Any suggestions on how to find this 'pause'? I find it very interesting that it is consistently happening between #31 & #32 only!

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• Threading Practice with Polling.

  - by Stacey

  I have a C# application that has to constantly read from a program; sometimes there is a chance it will not find what it needs, which will throw an exception. This is a limitation of the program it has to read from. This frequently causes the program to lock up as it tries to poll. So I solved it by spawning the 'polling' off into a separate thread. However watching the debugger, the thread is created and destroyed each time. I am uncertain if this is typical or not; but my question is, is this good practice, or am I using the threading for the wrong purpose? ProgramReader { static Thread oThread; public static void Read( Program program ) { // check to see if the program exists if ( false ) oThread = new ThreadStart(program.Poll); if(oThread != null || !oThread.IsAlive ) oThread.Start(); } } This is my general pseudocode. It runs every 10 seconds or so. Is this a huge hit to performance? The operation it performs is relatively small and lightweight; just repetitive.

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• SSIS - Bulk Update at Database Field Level

  - by Adam

  Hello, Here's our mission: Receive files from clients. Each file contains anywhere from 1 to 1,000,000 records. Records are loaded to a staging area and business-rule validation is applied. Valid records are then pumped into an OLTP database in a batch fashion, with the following rules: If record does not exist (we have a key, so this isn't an issue), create it. If record exists, optionally update each database field. The decision is made based on one of 3 factors...I don't believe it's important what those factors are. Our main problem is finding an efficient method of optionally updating the data at a field level. This is applicable across ~12 different database tables, with anywhere from 10 to 150 fields in each table (original DB design leaves much to be desired, but it is what it is). Our first attempt has been to introduce a table that mirrors the staging environment (1 field in staging for each system field) and contains a masking flag. The value of the masking flag represents the 3 factors. We've then put an UPDATE similar to... UPDATE OLTPTable1 SET Field1 = CASE WHEN Mask.Field1 = 0 THEN Staging.Field1 WHEN Mask.Field1 = 1 THEN COALESCE( Staging.Field1 , OLTPTable1.Field1 ) WHEN Mask.Field1 = 2 THEN COALESCE( OLTPTable1.Field1 , Staging.Field1 ) ... As you can imagine, the performance is rather horrendous. Has anyone tackled a similar requirement? We're a MS shop using a Windows Service to launch SSIS packages that handle the data processing. Unfortunately, we're pretty much novices at this stuff.

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• MKL Accelerated Math Libraries for Java...

  - by Kaopua

  I've looked at the related threads on StackOverflow and Googled with not much luck. I'm also very new to Java (I'm coming from a C# and .NET background) so please bear with me. There is so much available in the Java world it's pretty overwhelming. I'm starting on a new Java-on-Linux project that requires some heavy and highly repetitious numerical calculations (i.e. statistics, FFT, Linear Algebra, Matrices, etc.). So maximizing the performance of the mathematical operations is a requirement, as is ensuring the math is correct. So hence I have an interest in finding a Java library that perhaps leverages native acceleration such as MKL, and is proven (so commercial options are definitely a possibility here). In the .NET space there are highly optimized and MKL accelerated commercial Mathematical libraries such as Centerspace NMath and Extreme Optimization. Is there anything comparable in Java? Most of the math libraries I have found for Java either do not seem to be actively maintained (such as Colt) or do not appear to leverage MKL or other native acceleration (such as Apache Commons Math). I have considered trying to leverage MKL directly from Java myself (e.g. JNI), but me being new to Java (let alone interoperating between Java and native libraries) it seemed smarter finding a Java library that has already done this correctly, efficiently, and is proven. Again I apologize if I am mistaken or misguided (even in regarding any libraries I've mentioned) and my ignorance of the Java offerings. It's a whole new world for me coming from the heavily commercialized Microsoft stock so I could easily be mistaken on where to look and regarding the Java libraries I've mentioned. I would greatly appreciate any help or advice.

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• Passing data between ViewControllers versus doing local Fetch in each VC

  - by Tofrizer

  Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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• randomize array using php

  - by Suneth Kalhara

  I need to rendomise the order of follow array using PHP, i tried to use array shuffle and array_random but no luck, can anyone help me please Array ( [0] => Array ( [value] => 4 [label] => GasGas ) [1] => Array ( [value] => 3 [label] => Airoh Helmets ) [2] => Array ( [value] => 12 [label] => XCiting Trials Wear ) [3] => Array ( [value] => 11 [label] => Hebo Trials ) [4] => Array ( [value] => 10 [label] => Jitsie Products ) [5] => Array ( [value] => 9 [label] => Diadora Boots ) [6] => Array ( [value] => 8 [label] => S3 Performance ) [7] => Array ( [value] => 7 [label] => Scorpa ) [8] => Array ( [value] => 6 [label] => Inspired ) [9] => Array ( [value] => 5 [label] => Oset ) )

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• Practical rules for premature optimization

  - by DougW

  It seems that the phrase "Premature Optimization" is the buzz-word of the day. For some reason, iphone programmers in particular seem to think of avoiding premature optimization as a pro-active goal, rather than the natural result of simply avoiding distraction. The problem is, the term is beginning to be applied more and more to cases that are completely inappropriate. For example, I've seen a growing number of people say not to worry about the complexity of an algorithm, because that's premature optimization (eg http://stackoverflow.com/questions/2190275/help-sorting-an-nsarray-across-two-properties-with-nssortdescriptor/2191720#2191720). Frankly, I think this is just laziness, and appalling to disciplined computer science. But it has occurred to me that maybe considering the complexity and performance of algorithms is going the way of assembly loop unrolling, and other optimization techniques that are now considered unnecessary. What do you think? Are we at the point now where deciding between an O(n^n) and O(n!) complexity algorithm is irrelevant? What about O(n) vs O(n*n)? What do you consider "premature optimization"? What practical rules do you use to consciously or unconsciously avoid it? This is a bit vague, but I'm curious to hear other peoples' opinions on the topic.

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• OpenGL equivalent of GDI's HatchBrush or PatternBrush?

  - by Ptah- Opener of the Mouth

  I have a VB6 application (please don't laugh) which does a lot of drawing via BitBlt and the standard VB6 drawing functions. I am running up against performance issues (yes, I do the regular tricks like drawing to memory). So, I decided to investigate other ways of drawing, and have come upon OpenGL. I've been doing some experimenting, and it seems straightforward to do most of what I want; the application mostly only uses very simple drawing -- relatively large 2D rectangles of solid colors and such -- but I haven't been able to find an equivalent to something like a HatchBrush or PatternBrush. More specifically, I want to be able to specify a small monochrome pixel pattern, choose a color, and whenever I draw a polygon (or whatever), instead of it being solid, have it automatically tiled with that pattern, not translated or rotated or skewed or stretched, with the "on" bits of the pattern showing up in the specified color, and the "off" bits of the pattern left displaying whatever had been drawn under the area that I am now drawing on. Obviously I could do all the calculations myself. That is, instead of drawing as a polygon which will somehow automatically be tiled for me, I could calculate all of the lines or pixels or whatever that actually need to be drawn, then draw them as lines or pixels or whatever. But is there an easier way? Like in GDI, where you just say "draw this polygon using this brush"? I am guessing that "textures" might be able to accomplish what I want, but it's not clear to me (I'm totally new to this and the documentation I've found is not entirely obvious); it seems like textures might skew or translate or stretch the pattern, based upon the vertices of the polygon? Whereas I want the pattern tiled. Is there a way to do this, or something like it, other than brute force calculation of exactly the pixels/lines/whatever that need to be drawn? Thanks in advance for any help.

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• Disposing underlying object from finalizer in an immutable object

  - by Juan Luis Soldi

  I'm trying to wrap around Awesomium and make it look to the rest of my code as close as possible to NET's WebBrowser since this is for an existing application that already uses the WebBrowser. In this library, there is a class called JSObject which represents a javascript object. You can get one of this, for instance, by calling the ExecuteJavascriptWithResult method of the WebView class. If you'd call it like myWebView.ExecuteJavascriptWithResult("document", string.Empty).ToObject(), then you'd get a JSObject that represents the document. I'm writing an immutable class (it's only field is a readonly JSObject object) called JSObjectWrap that wraps around JSObject which I want to use as base class for other classes that would emulate .NET classes such as HtmlElement and HtmlDocument. Now, these classes don't implement Dispose, but JSObject does. What I first thought was to call the underlying JSObject's Dispose method in my JSObjectWrap's finalizer (instead of having JSObjectWrap implement Dispose) so that the rest of my code can stay the way it is (instead of having to add using's everywhere and make sure every JSObjectWrap is being properly disposed). But I just realized if more than two JSObjectWrap's have the same underlying JSObject and one of them gets finalized this will mess up the other JSObjectWrap. So now I'm thinking maybe I should keep a static Dictionary of JSObjects and keep count of how many of each of them are being referenced by a JSObjectWrap but this sounds messy and I think could cause major performance issues. Since this sounds to me like a common pattern I wonder if anyone else has a better idea.

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• DataReader-DataSet Hybrid solution

  - by G33kKahuna

  My solution architects and I have exhausted both pure Dataset and Datareader solutions. Basically we have a Microsoft.NET 2.0 windows service application that pulls data based on a query and processes additional tasks per record; almost a poor mans workflow system. The recordsets are broader (in terms of the columns) and deeper (in terms of number of records). We observed that DataSet performs much better in terms of performance but runs into contraints as # of records increase say 100K+ we start seeing System.OutOfMemoryException on a 4G machine with processModel configured to run at memoryLimit set to 85. Since this is a multi-threaded app, there could be multiple threads processing different queries and building different DataSets, so we run into the exception sooner in that case DataReader on the other hand works but is a lot slower and hits other contraints; if there is some sort of disconnect it has to start over again or leaves open connections on the DB side and worst case takes down the service completely etc. So, we decided the best option would be some sort of hybrid solution. I'm open to guidance and suggestions. Are there any hybrid solutions available? Any other suggestions

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• Running an existing LINQ query against a dynamic object (DataTable like)

  - by TomTom

  Hello, I am working on a generic OData provider to go against a custom data provider that we have here. Thsi is fully dynamic in that I query the data provider for the table it knows. I have a basic storage structure in place so far based on the OData sample code. My problem is: OData supports queries and expects me to hand in an IQueryable implementation. On the lowe rside, I dont have any query support. Not a joke - the provider returns tables and the WHERE clause is not supported. Performance is not an issue here - the tables are small. It is ok to sort them in the OData provider. My main problem is this. I submit a SQL statement to get out the data of a table. The result is some sort of ADO.NET data reader here. I need to expose an IQueryable implementation for this data to potentially allow later filtering. Any ide ahow to best touch that? .NET 3.5 only (no 4.0 planned for some time). I was seriously thinking of creating dynamic DTO classes for every table (emitting bytecode) so I can use standard LINQ. Right now I am using a dictionary per entry (not too efficient) but I see no real way to filter / sort based on them.

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• call addsubview again causes slowdown

  - by Tom

  hi guys, i am writing a little music-game for the iphone. I am almost done, this is the only issue which keeps me from rolling it out. any help to solve this is much appreciated. this is what i do: at my appDelegate I add my menu-view-screen to the window. the menu-view-screen acts as a container and controls which view gets presented to the user. means, on the menu-view-screen I got 4 buttons (new game, options, faq, highscore). when the user clicks on a button something as this happens: if (self.gameViewController == nil) { GameViewController *viewController = [[GameViewController alloc] initWithNibName:@"GameViewController" bundle:nil]; self.gameViewController = viewController; [viewController release]; } [self.view addSubview:self.gameViewController.view]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleSwitchViewNotificationFromGameView:) name:@"SwitchView" object:gameViewController]; when the user returns to the menu, this piece of code gets executed: [[NSNotificationCenter defaultCenter] removeObserver:self]; [self.gameViewController viewWillDisappear:YES]; [self.gameViewController.view removeFromSuperview]; this works fine for all screens but not for the gamescreen(well this is the only one with heaps of user-interaction) means the responsiveness of the iphone(when playing tones) gets really slow. The performance is fine when I display the gameview for the first time. it starts getting slower as soon as I add it to the menu-views-container-subviews again (addsubview) (basically open up a new game) any ideas what causes(or to get around) this? thanks heaps Best regards Tom

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• Help on understanding multiple columns on an index?

  - by Xaisoft

  Assume I have a table called "table" and I have 3 columns, a, b, and c. What does it mean to have a non-clustered index on columns a,b? Is a nonclustered index on columns a,b the same as a nonclustered index on columns b,a? (Note the order). Also, Is a nonclustered index on column a the same as a nonclustered index on a,c? I was looking at the website sqlserver performance and they had these dmv scripts where it would tell you if you had overlapping indexes and I believe it was saying that having an index on a is the same as a,b, so it is redundant. Is this true about indexes? One last question is why is the clustered index put on the primary key. Most of the time the primary key is not queried against, so shouldn't the clustered index be on the most queried column. I am probably missing something here like having it on the primary key speeds up joins? Great explanations. Should I turn this into a wiki and change the title index explanation?

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• Which apache worker to use with passenger and how?

  - by Millisami

  I've this config in my apache2.conf <IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 150 MaxRequestsPerChild 0 </IfModule> # worker MPM # StartServers: initial number of server processes to start # MaxClients: maximum number of simultaneous client connections # MinSpareThreads: minimum number of worker threads which are kept spare # MaxSpareThreads: maximum number of worker threads which are kept spare # ThreadsPerChild: constant number of worker threads in each server process # MaxRequestsPerChild: maximum number of requests a server process serves <IfModule mpm_worker_module> StartServers 2 MaxClients 15 MinSpareThreads 4 MaxSpareThreads 5 ThreadsPerChild 15 MaxRequestsPerChild 50000 </IfModule> Now I'm confused here. Which module gets loaded on which conditions? The phusion guys have suggested to use the worker module. Since both are present in apache conf file, do I have to comment the mpm_prefork_module or leave it as it is? Following is my passenger conf file for apache: LoadModule passenger_module /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4/ext/apache2/mod_passenger.so PassengerRoot /usr/lib/ruby/gems/1.8/gems/passenger-2.2.4 PassengerRuby /usr/bin/ruby1.8 PassengerMaxPoolSize 3 PassengerPoolIdleTime 999999 RailsFrameworkSpawnerIdleTime 0 RailsAppSpawnerIdleTime 0 I'm running just a single Rails 2.3.2 app on 256MB slice at slicehost. I'm not quite satisfied with the performance yet. Are the settings above are any good??

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• Interface for reading variable length files with header and footer.

  - by John S

  I could use some hints or tips for a decent interface for reading file of special characteristics. The files in question has a header (~120 bytes), a body (1 byte - 3gb) and a footer (4 bytes). The header contains information about the body and the footer is only a simple CRC32-value of the body. I use Java so my idea was to extend the "InputStream" class and add a constructor such as "public MyInStream( InputStream in)" where I immediately read the header and the direct the overridden read()'s the body. Problem is, I can't give the user of the class the CRC32-value until the whole body has been read. Because the file can be 3gb large, putting it all in memory is a be an idea. Reading it all in to a temporary file is going to be a performance hit if there are many small files. I don't know how large the file is because the InputStream doesn't have to be a file, it could be a socket. Looking at it again, maybe extending InputStream is a bad idea. Thank you for reading the confused thoughts of a tired programmer. :)

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