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  • ROW_NUMBER() VS. DISTINCT

    - by ramadan2050
    Dear All, I have a problem with ROW_NUMBER() , if i used it with DISTINCT in the following Query I have 2 scenarios: 1- run this query direct : give me for example 400 record as a result 2- uncomment a line which start with [--Uncomment1--] : give me 700 record as a result it duplicated some records not all the records what I want is to solve this problem or to find any way to show a row counter beside each row, to make a [where rownumber between 1 and 30] --Uncomment2-- if I put the whole query in a table, and then filter it , it is work but it still so slow waiting for any feedback and I will appreciate that Thanks in advance SELECT * FROM (SELECT Distinct CRSTask.ID AS TaskID, CRSTask.WFLTaskID, --Uncomment1-- ROW_NUMBER() OVER (ORDER By CRSTask.CreateDate asc ) AS RowNum , CRSTask.WFLStatus AS Task_WFLStatus, CRSTask.Name AS StepName, CRSTask.ModifiedDate AS Task_ModifyDate, CRSTask.SendingDate AS Task_SendingDate, CRSTask.ReceiveDate AS Task_ReceiveDate, CRSTask.CreateDate AS Task_CreateDate, CRS_Task_Recipient_Vw.Task_CurrentSenderName, CRS_Task_Recipient_Vw.Task_SenderName, CRS_INFO.ID AS CRS_ID, CRS_INFO.ReferenceNumber, CRS_INFO.CRSBeneficiaries, CRS_INFO.BarCodeNumber, ISNULL(dbo.CRS_FNC_GetTaskReceiver(CRSTask.ID), '') + ' ' + ISNULL (CRS_Organization.ArName, '') AS OrgName, CRS_Info.IncidentID, COALESCE(CRS_Subject.ArSubject, '??? ????') AS ArSubject, COALESCE(CRS_INFO.Subject, 'Blank Subject') AS CRS_Subject, CRS_INFO.Mode, CRS_Task_Recipient_Vw.ReceiverID, CRS_Task_Recipient_Vw.ReceiverType, CRS_Task_Recipient_Vw.CC, Temp_Portal_Users_View.ID AS CRS_LockedByID, Temp_Portal_Users_View.ArabicName AS CRS_LockedByName, CRSDraft.ID AS DraftID, CRSDraft.Type AS DraftType, CASE WHEN CRS_Folder = 1 THEN Task_SenderName WHEN CRS_Folder = 2 THEN Task_SenderName WHEN CRS_Folder = 3 THEN Task_CurrentSenderName END AS SenderName, CRS_Task_Folder_Vw.CRS_Folder, CRS_INFO.Status, CRS_INFO.CRS_Type, CRS_Type.arName AS CRS_Type_Name FROM CRS_Task_Folder_Vw LEFT OUTER JOIN CRSTask ON CRSTask.ID = CRS_Task_Folder_Vw.TaskID LEFT OUTER JOIN CRS_INFO ON CRS_INFO.ID = CRSTask.CRSID LEFT OUTER JOIN CRS_Subject ON COALESCE( SUBSTRING( CRS_INFO.Subject, CHARINDEX('_', CRS_INFO.Subject) + 1, LEN(CRS_INFO.Subject) ), 'Blank Subject' ) = CRS_Subject.ID LEFT OUTER JOIN CRSInfoAttribute ON CRS_INFO.ID = CRSInfoAttribute.ID LEFT OUTER JOIN CRS_Organization ON CRS_Organization.ID = CRSInfoAttribute.SourceID LEFT OUTER JOIN CRS_Type ON CRS_INFO.CRS_Type = CRS_Type.ID LEFT OUTER JOIN CRS_Way ON CRS_INFO.CRS_Send_Way = CRS_Way.ID LEFT OUTER JOIN CRS_Priority ON CRS_INFO.CRS_Priority_ID = CRS_Priority.ID LEFT OUTER JOIN CRS_SecurityLevel ON CRS_INFO.SecurityLevelID = CRS_SecurityLevel.ID LEFT OUTER JOIN Portal_Users_View ON Portal_Users_View.ID = CRS_INFO.CRS_Initiator LEFT OUTER JOIN AD_DOC_TBL ON CRS_INFO.DocumentID = AD_DOC_TBL.ID LEFT OUTER JOIN CRSTask AS Temp_CRSTask ON CRSTask.ParentTask = Temp_CRSTask.ID LEFT OUTER JOIN Portal_Users_View AS Temp_Portal_Users_View ON Temp_Portal_Users_View.ID = AD_DOC_TBL.Lock_User_ID LEFT OUTER JOIN Portal_Users_View AS Temp1_Portal_Users_View ON Temp1_Portal_Users_View.ID = CRS_INFO.ClosedBy LEFT OUTER JOIN CRSDraft ON CRSTask.ID = CRSDraft.TaskID LEFT OUTER JOIN CRS_Task_Recipient_Vw ON CRSTask.ID = CRS_Task_Recipient_Vw.TaskID --LEFT OUTER JOIN CRSTaskReceiverUsers ON CRSTask.ID = CRSTaskReceiverUsers.CRSTaskID AND CRS_Task_Recipient_Vw.ReceiverID = CRSTaskReceiverUsers.ReceiverID LEFT OUTER JOIN CRSTaskReceiverUserProfile ON CRSTask.ID = CRSTaskReceiverUserProfile.TaskID WHERE Crs_Info.SUBJECT <> 'Blank Subject' AND (CRS_INFO.Subject NOT LIKE '%null%') AND CRS_Info.IsDeleted <> 1 /* AND CRSTask.WFLStatus <> 6 AND CRSTask.WFLStatus <> 8 */ AND ( ( CRS_Task_Recipient_Vw.ReceiverID IN (1, 29) AND CRS_Task_Recipient_Vw.ReceiverType IN (1, 3, 4) ) ) AND 1 = 1 )Codes --Uncomment2-- WHERE Codes.RowNum BETWEEN 1 AND 30 ORDER BY Codes.Task_CreateDate ASC

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  • How to optimize my PostgreSQL DB for prefix search?

    - by asmaier
    I have a table called "nodes" with roughly 1.7 million rows in my PostgreSQL db =#\d nodes Table "public.nodes" Column | Type | Modifiers --------+------------------------+----------- id | integer | not null title | character varying(256) | score | double precision | Indexes: "nodes_pkey" PRIMARY KEY, btree (id) I want to use information from that table for autocompletion of a search field, showing the user a list of the ten titles having the highest score fitting to his input. So I used this query (here searching for all titles starting with "s") =# explain analyze select title,score from nodes where title ilike 's%' order by score desc; QUERY PLAN ----------------------------------------------------------------------------------------------------------------------- Sort (cost=64177.92..64581.38 rows=161385 width=25) (actual time=4930.334..5047.321 rows=161264 loops=1) Sort Key: score Sort Method: external merge Disk: 5712kB -> Seq Scan on nodes (cost=0.00..46630.50 rows=161385 width=25) (actual time=0.611..4464.413 rows=161264 loops=1) Filter: ((title)::text ~~* 's%'::text) Total runtime: 5260.791 ms (6 rows) This was much to slow for using it with autocomplete. With some information from Using PostgreSQL in Web 2.0 Applications I was able to improve that with a special index =# create index title_idx on nodes using btree(lower(title) text_pattern_ops); =# explain analyze select title,score from nodes where lower(title) like lower('s%') order by score desc limit 10; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------ Limit (cost=18122.41..18122.43 rows=10 width=25) (actual time=1324.703..1324.708 rows=10 loops=1) -> Sort (cost=18122.41..18144.60 rows=8876 width=25) (actual time=1324.700..1324.702 rows=10 loops=1) Sort Key: score Sort Method: top-N heapsort Memory: 17kB -> Bitmap Heap Scan on nodes (cost=243.53..17930.60 rows=8876 width=25) (actual time=96.124..1227.203 rows=161264 loops=1) Filter: (lower((title)::text) ~~ 's%'::text) -> Bitmap Index Scan on title_idx (cost=0.00..241.31 rows=8876 width=0) (actual time=90.059..90.059 rows=161264 loops=1) Index Cond: ((lower((title)::text) ~>=~ 's'::text) AND (lower((title)::text) ~<~ 't'::text)) Total runtime: 1325.085 ms (9 rows) So this gave me a speedup of factor 4. But can this be further improved? What if I want to use '%s%' instead of 's%'? Do I have any chance of getting a decent performance with PostgreSQL in that case, too? Or should I better try a different solution (Lucene?, Sphinx?) for implementing my autocomplete feature?

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  • How to salvage SQL server 2008 query from KILLED/ROLLBACK state?

    - by littlegreen
    I have a stored procedure that inserts batches of millions of rows, emerging from a certain query, into an SQL database. It has one parameter selecting the batch; when this parameter is omitted, it will gather a list of batches and recursively call itself, in order to iterate over batches. In (pseudo-)code, it looks something like this: CREATE PROCEDURE spProcedure AS BEGIN IF @code = 0 BEGIN ... WHILE @@Fetch_Status=0 BEGIN EXEC spProcedure @code FETCH NEXT ... INTO @code END END ELSE BEGIN -- Disable indexes ... INSERT INTO table SELECT (...) -- Enable indexes ... Now it can happen that this procedure is slow, for whatever reason: it can't get a lock, one of the indexes it uses is misdefined or disabled. In that case, I want to be able kill the procedure, truncate and recreate the resulting table, and try again. However, when I try and kill the procedure, the process frequently oozes into a KILLED/ROLLBACK state from which there seems to be no return. From Google I have learned to do an sp_lock, find the spid, and then kill it with KILL <spid>. But when I try to kill it, it tells me SPID 75: transaction rollback in progress. Estimated rollback completion: 0%. Estimated time remaining: 554 seconds. I did find a forum message hinting that another spid should be killed before the other one can start a rollback. But that didn't work for me either, plus I do not understand, why that would be the case... could it be because I am recursively calling my own stored procedure? (But it should be having the same spid, right?) In any case, my process is just sitting there, being dead, not responding to kills, and locking the table. This is very frustrating, as I want to go on developing my queries, not waiting hours on my server sitting dead while pretending to be finishing a supposed rollback. Is there some way in which I can tell the server not to store any rollback information for my query? Or not to allow any other queries to interfere with the rollback, so that it will not take so long? Or how to rewrite my query in a better way, or how kill the process successfully without restarting the server?

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  • Optimizing Haskell code

    - by Masse
    I'm trying to learn Haskell and after an article in reddit about Markov text chains, I decided to implement Markov text generation first in Python and now in Haskell. However I noticed that my python implementation is way faster than the Haskell version, even Haskell is compiled to native code. I am wondering what I should do to make the Haskell code run faster and for now I believe it's so much slower because of using Data.Map instead of hashmaps, but I'm not sure I'll post the Python code and Haskell as well. With the same data, Python takes around 3 seconds and Haskell is closer to 16 seconds. It comes without saying that I'll take any constructive criticism :). import random import re import cPickle class Markov: def __init__(self, filenames): self.filenames = filenames self.cache = self.train(self.readfiles()) picklefd = open("dump", "w") cPickle.dump(self.cache, picklefd) picklefd.close() def train(self, text): splitted = re.findall(r"(\w+|[.!?',])", text) print "Total of %d splitted words" % (len(splitted)) cache = {} for i in xrange(len(splitted)-2): pair = (splitted[i], splitted[i+1]) followup = splitted[i+2] if pair in cache: if followup not in cache[pair]: cache[pair][followup] = 1 else: cache[pair][followup] += 1 else: cache[pair] = {followup: 1} return cache def readfiles(self): data = "" for filename in self.filenames: fd = open(filename) data += fd.read() fd.close() return data def concat(self, words): sentence = "" for word in words: if word in "'\",?!:;.": sentence = sentence[0:-1] + word + " " else: sentence += word + " " return sentence def pickword(self, words): temp = [(k, words[k]) for k in words] results = [] for (word, n) in temp: results.append(word) if n > 1: for i in xrange(n-1): results.append(word) return random.choice(results) def gentext(self, words): allwords = [k for k in self.cache] (first, second) = random.choice(filter(lambda (a,b): a.istitle(), [k for k in self.cache])) sentence = [first, second] while len(sentence) < words or sentence[-1] is not ".": current = (sentence[-2], sentence[-1]) if current in self.cache: followup = self.pickword(self.cache[current]) sentence.append(followup) else: print "Wasn't able to. Breaking" break print self.concat(sentence) Markov(["76.txt"]) -- module Markov ( train , fox ) where import Debug.Trace import qualified Data.Map as M import qualified System.Random as R import qualified Data.ByteString.Char8 as B type Database = M.Map (B.ByteString, B.ByteString) (M.Map B.ByteString Int) train :: [B.ByteString] -> Database train (x:y:[]) = M.empty train (x:y:z:xs) = let l = train (y:z:xs) in M.insertWith' (\new old -> M.insertWith' (+) z 1 old) (x, y) (M.singleton z 1) `seq` l main = do contents <- B.readFile "76.txt" print $ train $ B.words contents fox="The quick brown fox jumps over the brown fox who is slow jumps over the brown fox who is dead."

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  • Multiline editable textarea in SVG

    - by Timo
    I'm trying to implement multiline editable textfield in SVG. I have the following code in http://jsfiddle.net/ca4d3/ : <svg width="1000" height="1000" overflow="scroll"> <g transform="rotate(5)"> <rect width="300" height="400" fill="#22DD22" fill-opacity="0.5"/> </g> <foreignObject x="10" y="10" overflow="visible" width="10000" height="10000" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"> <p style="display:table-cell;padding:10px;border:1px solid red; background-color:white;opacity:0.5;font-family:Verdana; font-size:20px;white-space: pre; word-wrap: normal; overflow: visible; overflow-y: visible; overflow-x:visible;" contentEditable="true" xmlns="http://www.w3.org/1999/xhtml"> Write here some text. Be smart and select some word. If you wanna be really COOL, paste here something cool! </p> </foreignObject> </svg> In newest Chrome, Safari and Firefox the code works in some way, but in Opera and IE 9 not. The goal is that: 0) Works in newest Chrome, Safari, Firefox, Opera and IE and if ever possible in some pads. 1) White-spaces are preserved and text wraps only on newline char (works in Chrome, Safari and Firefox, but not in Opera and IE 9 *). 2) The textfield is editable (in the same reliable and stabile way as textareas and contenteditable p elements in html) and height and width is expanded to fit text (works in Chrome, Safari and Firefox, but not in Opera and IE 9 *). 3) Texfield can be transformed (rotated, skewed, translated) while maintaining text editability (Tested rotation, but not work in any browser *). EDIT: Foreignobject rotation works on Firefox 15.0.1, but not in Safari 5.1.7 (6534.57.2), Chrome 22.0.1229.79, Opera 12.02, IE 9. Tested on Mac OS X 10.6.8. 4) Textfield can be clipped and masked while not necessarily maintaining text editability (not yet tested). *) using above code These all can be achieved using Flash, but Flash has so severe problems that it is not suitable for my purposes (after every little change in code, all have to be compiled again using Flex, which is slow, font size has limits, tracking technique is pixeloriented, not relative to em size etc.) and there still are differences across platforms. And I want to give a try to SVG! GUESTION: Can I achieve my goals 0-4 with current SVG support in browsers? Is coming SVG 2.0 for some help in this case? EDIT: Changed display:table to display:table-cell (and added new jsfiddle), because display:table made the field to loses focus when pressed arrow-up on first text row.

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  • counter and displaylist AS3

    - by VideoDnd
    How can I connect my counter to my display list?I've got a counter and a displaylist working, but I need help with everything in between. Try to explain I finished a Snowflake tutorial. The snowballs are children that are called to the stage. When connected to a dynamic variable, they move around and look like snow. I want my counter to move numbers around. I've got a counter, and I've got a 'for loop' to add children to the stage. link to file http://sandboxfun.weebly.com/ actionscript-3 //DISPLAYLIST "puts stuff on stage" for (var i:int = 0; i < 9; i++) { var t:MovieClip = new Tee(); t.x = 105 + i * 111; addChild(t);100 } //ARRAY //var o:Object = new Object(); <br> //var TeeProps:Dictionary= new Dictionary(true); <br> //var Tees:Array = new Array(); <br> //TeeProps[t] = o; <br> //addChild(t); <br> //Tees.push(t); <br> //} <br> //COUNTER drop in "mytext" text field to see it work var timer:Timer = new Timer(10); var count:int = 0; //start at -1 if you want the first decimal to be 0 var fcount:int = 100; timer.addEventListener(TimerEvent.TIMER, incrementCounter); timer.start(); function incrementCounter(event:TimerEvent) { count++; fcount=int(count*count/1000);//starts out slow... then speeds up // mytext.text = formatCount(fcount); } function formatCount(i:int):String { var fraction:int = i % 100; var whole:int = i / 100; return ("0000000" + whole).substr(-7, 7) + "." + (fraction < 10 ? "0" + fraction : fraction); } I'm rebuilding a earlier version for learning purposes.

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  • Running out of memory with UIImage creation on an offscreen Bitmap Context by NSOperation

    - by sigsegv
    I have an app with multiple UIView subclasses that acts as pages for a UIScrollView. UIViews are moved back and forth to provide a seamless experience to the user. Since the content of the views is rather slow to draw, it's rendered on a single shared CGBitmapContext guarded by locks by NSOperation subclasses - executed one at once in an NSOperationQueue - wrapped up in an UIImage and then used by the main thread to update the content of the views. -(void)main { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc]init]; if([self isCancelled]) { return; } if(nil == data) { return; } // Buffer is the shared instance of a CG Bitmap Context wrapper class // data is a dictionary CGImageRef img = [buffer imageCreateWithData:data]; UIImage * image = [[UIImage alloc]initWithCGImage:img]; CGImageRelease(img); if([self isCancelled]) { [image release]; return; } NSDictionary * result = [[NSDictionary alloc]initWithObjectsAndKeys:image,@"image",id,@"id",nil]; // target is the instance of the UIView subclass that will use // the image [target performSelectorOnMainThread:@selector(updateContentWithData:) withObject:result waitUntilDone:NO]; [result release]; [image release]; [pool release]; } The updateContentWithData: of the UIView subclass performed on the main thread is just as simple -(void)updateContentWithData:(NSDictionary *)someData { NSDictionary * data = [someData retain]; if([[data valueForKey:@"id"]isEqualToString:[self pendingRequestId]]) { UIImage * image = [data valueForKey:@"image"]; [self setCurrentImage:image]; [self setNeedsDisplay]; } // If the image has not been retained, it should be released together // with the dictionary retaining it [data release]; } The drawLayer:inContext: method of the subclass will just get the CGImage from the UIImage and use it to update the backing layer or part of it. No retain or release is involved in the process. The problem is that after a while I run out of memory. The number of the UIViews is static. CGImageRef and UIImage are created, retained and released correctly (or so it seems to me). Instruments does not show any leaks, just the free memory available dip constantly, rise a few times, and then dip even lower until the application is terminated. The app cycles through about 2-300 of the aforementioned pages before that, but I would expect to have the memory usage reach a more or less stable level of used memory after a bunch of pages have been already skimmed at fast speed or, since the images are up to 3MB in size, deplete way earlier. Any suggestion will be greatly appreciated.

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  • Why is cell phone software still so primitive?

    - by Tomislav Nakic-Alfirevic
    I don't do mobile development, but it strikes me as odd that features like this aren't available by default on most phones: full text search: searches all address book contents, messages, anything else being a plus better call management: e.g. a rotating audio call log, meaning you always have the last N calls recorded for your listening pleasure later (your little girl just said her first "da-da" while you were on a business trip, you had a telephone job interview, you received complex instructions to do something etc.) bluetooth remote control (like e.g. anyRemote, but available by default on a bluetooth phone) no multitasking capabilities worth mentioning and in general no e.g. weekly software updates, making the phone much more usable (even if it had to be done over USB, rather than over the network). I'm sure I was dumbfounded by the lack or design of other features as well, but they don't come to mind right now. To clarify, I'm not talking about smartphones here: my plain, 2-year old phone has a CPU an order of magnitude faster than my first PC, about as much storage space and it's ridiculous how bad (slow, unwieldy) the software is and it's not one phone or one manufacturer. What keeps the (to me) obvious software functionality vacuum on a capable hardware platform from being filled up? Edit: I believe a clarification on the multitasking point might be beneficial. I'll use my phone as an example, although the point is much more general. The phone can multitask and in fact does: you can listen to music and do something else at the same time. On the other hand, the way the software has been designed makes multitasking next to useless. (Ditto with the external touch screen: it can take touch commands, but only one application makes use of it, and only with 3 commands.) To take the multitasking example to the extreme, if I plug my phone into my laptop and it registers as an external disk, it doesn't allow any kind of operation: messages, calling, calendar, everything out of reach, although I can receive a call. No "battery life" issue there: it's charging while connected. BTW, another example of design below the current state of the art: I don't see a phone on the horizon which will remember where in an audio or video file you were when you stopped listening/watching it last time (podcasts are a good use case). Simplistic rewind/fast forward functionality only aggravates the problem.

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  • Not able to delete list which dynamically created with jquery.

    - by shin
    I have two html here. The first one is dynamically generated by php and second one is just html to test. I also have the following jquery. When I click a cross with class delete in the second ones(plain html), it works nicely. However when I click a cross in the first ones, it does not work. It redirect me to the home page with # at the end. I am hoping someone point out what I am doing wrong. Thank in advance. HTML First part (dyanmicall generated) <ul style="display: block;" id="message"> <li class="41"> <span class="user"><strong>shin</strong></span> <span class="msg"> delete this as well</span> <span class="date">2010-01-15 07:47:31</span> <a href="#" id="41" class="delete">x</a> <div class="clear"></div></li> <li class="40"> <span class="user"><strong>shin</strong></span> <span class="msg"> delete me as well</span> <span class="date">2010-01-14 16:01:44</span> <a href="#" id="40" class="delete">x</a> <div class="clear"></div></li> ... ...</ul> Second part which is plain html <ul id="another"> <li><a href="#">you can't delete me</a></li> <li><a href="#" class="delete">delete this</a></li> <li><a href="#" class="delete">delete this</a></li> </ul> Here is jquery $(".delete").click(function(event) { event.preventDefault(); loading.fadeIn(); var commentContainer = $(this).parent(); var id = $(this).attr("id"); // var string = 'id='+ id ; $.ajax({ type: "POST", url: "index.php/admin/messages/changestatus/"+id, // data: string, cache: false, success: function(){ commentContainer.slideUp('slow', function() {$(this).remove();}); loading.fadeOut(); } }); return false; }); I am using CodeIgniter by the way.

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  • Visual Studio soft-crashing when encountering XAML Errors in initialize.

    - by Aren
    I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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  • Performance Optimization for Matrix Rotation

    - by Summer_More_More_Tea
    Hello everyone: I'm now trapped by a performance optimization lab in the book "Computer System from a Programmer's Perspective" described as following: In a N*N matrix M, where N is multiple of 32, the rotate operation can be represented as: Transpose: interchange elements M(i,j) and M(j,i) Exchange rows: Row i is exchanged with row N-1-i A example for matrix rotation(N is 3 instead of 32 for simplicity): ------- ------- |1|2|3| |3|6|9| ------- ------- |4|5|6| after rotate is |2|5|8| ------- ------- |7|8|9| |1|4|7| ------- ------- A naive implementation is: #define RIDX(i,j,n) ((i)*(n)+(j)) void naive_rotate(int dim, pixel *src, pixel *dst) { int i, j; for (i = 0; i < dim; i++) for (j = 0; j < dim; j++) dst[RIDX(dim-1-j, i, dim)] = src[RIDX(i, j, dim)]; } I come up with an idea by inner-loop-unroll. The result is: Code Version Speed Up original 1x unrolled by 2 1.33x unrolled by 4 1.33x unrolled by 8 1.55x unrolled by 16 1.67x unrolled by 32 1.61x I also get a code snippet from pastebin.com that seems can solve this problem: void rotate(int dim, pixel *src, pixel *dst) { int stride = 32; int count = dim >> 5; src += dim - 1; int a1 = count; do { int a2 = dim; do { int a3 = stride; do { *dst++ = *src; src += dim; } while(--a3); src -= dim * stride + 1; dst += dim - stride; } while(--a2); src += dim * (stride + 1); dst -= dim * dim - stride; } while(--a1); } After carefully read the code, I think main idea of this solution is treat 32 rows as a data zone, and perform the rotating operation respectively. Speed up of this version is 1.85x, overwhelming all the loop-unroll version. Here are the questions: In the inner-loop-unroll version, why does increment slow down if the unrolling factor increase, especially change the unrolling factor from 8 to 16, which does not effect the same when switch from 4 to 8? Does the result have some relationship with depth of the CPU pipeline? If the answer is yes, could the degrade of increment reflect pipeline length? What is the probable reason for the optimization of data-zone version? It seems that there is no too much essential difference from the original naive version. EDIT: My test environment is Intel Centrino Duo processor and the verion of gcc is 4.4 Any advice will be highly appreciated! Kind regards!

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  • Optimizing jQuery for Tabs

    - by jpdbaugh
    I am in the process of developing a widget. The widget has three tabs that are implemented in the following way. <div id="widget"> <ul id="tabs"> <li><a href="http...">One</a></li> <li><a href="http...">Two</a></li> <li><a href="http...">Three</a></li> </ul> <div id="tab_container"> <div id="tab_content"> //Tab Content goes here... </div> </div> </div> // The active class is initialized when the document loads $("#tabs li a").click(function() { $("#tabs li.active").removeClass("active"); $("#tab_content").load($(this).attr('href')); $(this).parent().addClass("active"); return false; }); The problem I am having is that the jquery code that have written is very slow. If the user changes tabs quickly the widget gets behing and bogged down. This causes the tabs to to not align with the data being displayed and just general lag. I believe that this is because the tab is being changed before $.load() is finished. I have tried to implement the following: ("#tabs li a").click(function() { $("#tabs li.active").removeClass("active"); $("#tab_content").load($(this).attr('href'), function (){ $(this).parent().addClass("active"); }); return false; }); It is my understanding that the callback function within in the load function does not execute until the load function is completed. I think this would solve my problem, however I can not come up with a way to select the correct tab that was clicked within the callback function. If this is not the way to do this then what is the best way implement these tabs so that they would stop loading an old request and load the newest tab selection by the user? Thanks

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  • JQuery fadeIn after src changed but fadeIn on the previous src anyway !

    - by Anna
    Hello ! I have a jquery bug and I've been looking for hours now, I can't figure out what's wrong... I have this code : $(document).ready(function(){ $('#ulPhotos a').click(function() { var newSrc= $(this).find('img').attr('src').split("/"); bigPictureName = 'big'+newSrc[2]; $('#pho').hide(); $('#imageBig').attr("src", "images/photos/"+bigPictureName); $('#pho').fadeIn('slow'); var alt = $(this).find('img').attr('alt'); $('#legend').html(alt); }); }); and this in html : <ul id="ulPhotos"> <li><a href="#centre"><img src="images/photos/09.jpg" title="La Reine de la Nuit au Comedia" alt="<em>La Reine de la Nuit</em> au Comedia"/></a> <a href="#centre"><img src="images/photos/03.jpg" title="Manuelita, La Périchole à l&rsquo;Opéra Comique" alt="Manuelita, <em>La Périchole</em> à l&#8217;Opéra Comique" /></a></li> <li><a href="#centre" ><img src="images/photos/12.png" title="" alt="Marion Baglan Carnac Ré" /></a> and this in for bigImage : </div> <div id="pho" a name="centre"> <p id="legend"> La Reine de la Nuit</p> <img src="images/photos/big09.jpg" alt="Marion Baglan" id="imageBig"/> </div> It simply changes the source of my img in a div named pho... but sometimes when the new image is too heavy, the fadeIn executes on the previous src !! so we see the fadeIn first on the previous image, and then, the right picture appears without fadeIn.... am I missing something? ps : the page is here http://www.marion-baglan.net/photos.htm#centre if you click fast you can see it... and when I try to put some bigger photos, it's very obvious...

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  • do I need to close an audio Clip?

    - by Michael
    have an application that processes real-time data and is supposed to beep when a certain event occurs. The triggering event can occur multiple times per second, and if the beep is already playing when another event triggers the code is just supposed to ignore it (as opposed to interrupting the current beep and starting a new one). Here is the basic code: Clip clickClip public void prepareProcess() { super.prepareProcess(); clickClip = null; try { clipFile = new File("C:/WINDOWS/Media/CHIMES.wav"); ais = AudioSystem.getAudioInputStream(clipFile); clickClip = AudioSystem.getClip(); clickClip.open(ais); fileIsLoaded = true; } catch (Exception ex) { clickClip = null; fileIsLoaded = false; } } public void playSound() { if (fileIsLoaded) { if ((clickClip==null) || (!clickClip.isRunning())) { try { clickClip.setFramePosition(0); clickClip.start(); } catch (Exception ex) { System.out.println("Cannot play click noise"); ex.printStackTrace(); } } } The prepareProcess method gets run once in the beginning, and the playSound method is called every time a triggering event occurs. My question is: do I need to close the clickClip object? I know I could add an actionListener to monitor for a Stop event, but since the event occurs so frequently I'm worried the extra processing is going to slow down the real-time data collection. The code seems to run fine, but my worry is memory leaks. The code above is based on an example I found while searching the net, but the example used an actionListener to close the Clip specifically "to eliminate memory leaks that would occur when the stop method wasn't implemented". My program is intended to run for hours so any memory leaks I have will cause problems. I'll be honest: I have no idea how to verify whether or not I've got a problem. I'm using Netbeans, and running the memory profiler just gave me a huge list of things that I don't know how to read. This is supposed to be the simple part of the program, and I'm spending hours on it. Any help would be greatly appreciated! Michael

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  • How to do a search from a list with non-prefix keywords[Solved]

    - by aNui
    The Problem is Solved. Thanks for every answers. First of all, sorry if my english or my post got any mistakes. I am programming a program to search the name from the list and I need to find them even if the keyword is not in front of the names (that's what I mean non-prefix) e.g. if I my list is the music instruments and I type "guit" to the search textbox. It should find the names "Guitar, Guitarrón, Acoustic Guitar, Bass Guitar, ..." or something like this Longdo Dictionary's search suggestion. here is my simple and stupid algorithm (that's all I can do) const int SEARCHROWLIMIT = 30; private string[] DoSearch(string Input, string[] ListToSearch) { List<string> FoundNames = new List<string>(); int max = 0; bool over = false; for (int k = 0; !over; k++) { foreach (string item in ListToSearch) { max = (max > item.Length) ? max : item.Length; if (k > item.Length) continue; if (k >= max) { over = true; break; } if (!Input.Equals("Search") && item.Substring(k, item.Length - k).StartsWith(Input, StringComparison.OrdinalIgnoreCase)) { bool exist = false; int i = 0; while (!exist && i < FoundNames.Count) { if (item.Equals(FoundNames[i])) { exist = true; break; } i++; } if (!exist && FoundNames.Count < SEARCHROWLIMIT) FoundNames.Add(item); else if (FoundNames.Count >= SEARCHROWLIMIT) over = true; } } } return FoundNames.ToArray(); } I think this algorithm is too slow for a large number of names and after several trial-and-error, I decided to add SEARCHROWLIMIT to breaks the operation And I also think there're some readymade methods that can do that. And another problem is I need to search music instruments by a category like strings, percussions, ... and by the country of origins. So I need to search them with filter by type and country. please help me. P.S. Me and my friends are just student from Thailand and developing the project to compete in Microsoft Imagine Cup 2010 and please become fan on our facebook page [KRATIB][3]. And we're so sorry we don't have much information in English but you can talk to us in English.

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  • show/hide html table columns using css

    - by Art Peterson
    I want to display a basic html table with controls to toggle showing/hiding of additional columns: <table id="mytable"> <tr> <th>Column 1</th> <th class="col1">1a</th> <th class="col1">1b</th> <th>Column 2</th> <th class="col2">2a</th> <th class="col2">2b</th> </tr> <tr> <td>100</td> <td class="col1">40</td> <td class="col1">60</td> <td>200</td> <td class="col2">110</td> <td class="col2">90</td> </tr> </table> So Column 1 and Column 2 will be the only columns displayed by default - but when you click on the Column 1 I want 1a and 1b to toggle, and same with Column 2 with 2a and 2b. I may end up with more columns and lots of rows - so any javascript looping approaches have been too slow to work with when I tested. The only approach that seems to be fast enough is to set up some css like this: table.hide1 .col1 { display: none; } table.hide2 .col2 { display: none; } table.hide3 .col3 { display: none; } table.show1 .col1 { display: table-cell; } table.show2 .col2 { display: table-cell; } table.show3 .col3 { display: table-cell; } And then set up onClick function calls on the table header cells that will trigger a toggle - and determine which css class to set "mytable" to that will create the toggle effect that I'm looking for. Is there an easy way to set this up so that the code can work for n # of columns?

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  • Optimize date query for large child tables: GiST or GIN?

    - by Dave Jarvis
    Problem 72 child tables, each having a year index and a station index, are defined as follows: CREATE TABLE climate.measurement_12_013 ( -- Inherited from table climate.measurement_12_013: id bigint NOT NULL DEFAULT nextval('climate.measurement_id_seq'::regclass), -- Inherited from table climate.measurement_12_013: station_id integer NOT NULL, -- Inherited from table climate.measurement_12_013: taken date NOT NULL, -- Inherited from table climate.measurement_12_013: amount numeric(8,2) NOT NULL, -- Inherited from table climate.measurement_12_013: category_id smallint NOT NULL, -- Inherited from table climate.measurement_12_013: flag character varying(1) NOT NULL DEFAULT ' '::character varying, CONSTRAINT measurement_12_013_category_id_check CHECK (category_id = 7), CONSTRAINT measurement_12_013_taken_check CHECK (date_part('month'::text, taken)::integer = 12) ) INHERITS (climate.measurement) CREATE INDEX measurement_12_013_s_idx ON climate.measurement_12_013 USING btree (station_id); CREATE INDEX measurement_12_013_y_idx ON climate.measurement_12_013 USING btree (date_part('year'::text, taken)); (Foreign key constraints to be added later.) The following query runs abysmally slow due to a full table scan: SELECT count(1) AS measurements, avg(m.amount) AS amount FROM climate.measurement m WHERE m.station_id IN ( SELECT s.id FROM climate.station s, climate.city c WHERE -- For one city ... -- c.id = 5182 AND -- Where stations are within an elevation range ... -- s.elevation BETWEEN 0 AND 3000 AND 6371.009 * SQRT( POW(RADIANS(c.latitude_decimal - s.latitude_decimal), 2) + (COS(RADIANS(c.latitude_decimal + s.latitude_decimal) / 2) * POW(RADIANS(c.longitude_decimal - s.longitude_decimal), 2)) ) <= 50 ) AND -- -- Begin extracting the data from the database. -- -- The data before 1900 is shaky; insufficient after 2009. -- extract( YEAR FROM m.taken ) BETWEEN 1900 AND 2009 AND -- Whittled down by category ... -- m.category_id = 1 AND m.taken BETWEEN -- Start date. (extract( YEAR FROM m.taken )||'-01-01')::date AND -- End date. Calculated by checking to see if the end date wraps -- into the next year. If it does, then add 1 to the current year. -- (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date GROUP BY extract( YEAR FROM m.taken ) The sluggishness comes from this part of the query: m.taken BETWEEN /* Start date. */ (extract( YEAR FROM m.taken )||'-01-01')::date AND /* End date. Calculated by checking to see if the end date wraps into the next year. If it does, then add 1 to the current year. */ (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date The HashAggregate from the plan shows a cost of 10006220141.11, which is, I suspect, on the astronomically huge side. There is a full table scan on the measurement table (itself having neither data nor indexes) being performed. The table aggregates 237 million rows from its child tables. Question What is the proper way to index the dates to avoid full table scans? Options I have considered: GIN GiST Rewrite the WHERE clause Separate year_taken, month_taken, and day_taken columns to the tables What are your thoughts? Thank you!

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  • Dynamic data-entry value store

    - by simendsjo
    I'm creating a data-entry application where users are allowed to create the entry schema. My first version of this just created a single table per entry schema with each entry spanning a single or multiple columns (for complex types) with the appropriate data type. This allowed for "fast" querying (on small datasets as I didn't index all columns) and simple synchronization where the data-entry was distributed on several databases. I'm not quite happy with this solution though; the only positive thing is the simplicity... I can only store a fixed number of columns. I need to create indexes on all columns. I need to recreate the table on schema changes. Some of my key design criterias are: Very fast querying (Using a simple domain specific query language) Writes doesn't have to be fast Many concurrent users Schemas will change often Schemas might contain many thousand columns The data-entries might be distributed and needs syncronization. Preferable MySQL and SQLite - Databases like DB2 and Oracle is out of the question. Using .Net/Mono I've been thinking of a couple of possible designs, but none of them seems like a good choice. Solution 1: Union like table containing a Type column and one nullable column per type. This avoids joins, but will definitly use a lot of space. Solution 2: Key/value store. All values are stored as string and converted when needed. Also use a lot of space, and of course, I hate having to convert everything to string. Solution 3: Use an xml database or store values as xml. Without any experience I would think this is quite slow (at least for the relational model unless there is some very good xpath support). I also would like to avoid an xml database as other parts of the application fits better as a relational model, and being able to join the data is helpful. I cannot help to think that someone has solved (some of) this already, but I'm unable to find anything. Not quite sure what to search for either... I know market research is doing something like this for their questionnaires, but there are few open source implementations, and the ones I've found doesn't quite fit the bill. PSPP has much of the logic I'm thinking of; primitive column types, many columns, many rows, fast querying and merging. Too bad it doesn't work against a database.. And of course... I don't need 99% of the provided functionality, but a lot of stuff not included. I'm not sure this is the right place to ask such a design related question, but I hope someone here has some tips, know of any existing work, or can point me to a better place to ask such a question. Thanks in advance!

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  • Retrieve names of running processes

    - by Dave DeLong
    Hi everyone, First off, I know that similar questions have been asked, but the answers provided haven't been very helpful so far (they all recommend one of the following options). I have a user application that needs to determine if a particular process is running. Here's what I know about the process: The name The user (root) It should already be running, since it's a LaunchDaemon, which means Its parent process should be launchd (pid 1) I've tried several ways to get this, but none have worked so far. Here's what I've tried: Running ps and parsing the output. This works, but it's slow (fork/exec is expensive), and I'd like this to be as fast as possible. Using the GetBSDProcessList function listed here. This also works, but the way in which they say to retrieve the process name (accessing kp_proc.p_comm from each kinfo_proc structure) is flawed. The resulting char* only contains the first 16 characters of the process name, which can be seen in the definition of the kp_proc structure: #define MAXCOMLEN 16 //defined in param.h struct extern_proc { //defined in proc.h ...snip... char p_comm[MAXCOMLEN+1]; ...snip... }; Using libProc.h to retrieve process information: pid_t pids[1024]; int numberOfProcesses = proc_listpids(PROC_ALL_PIDS, 0, NULL, 0); proc_listpids(PROC_ALL_PIDS, 0, pids, sizeof(pids)); for (int i = 0; i < numberOfProcesses; ++i) { if (pids[i] == 0) { continue; } char name[1024]; proc_name(pids[i], name, sizeof(name)); printf("Found process: %s\n", name); } This works, except it has the same flaw as GetBSDProcessList. Only the first portion of the process name is returned. Using the ProcessManager function in Carbon: ProcessSerialNumber psn; psn.lowLongOfPSN = kNoProcess; psn.highLongOfPSN = 0; while (GetNextProcess(&psn) == noErr) { CFStringRef procName = NULL; if (CopyProcessName(&psn, &procName) == noErr) { NSLog(@"Found process: %@", (NSString *)procName); } CFRelease(procName); } This does not work. It only returns process that are registered with the WindowServer (or something like that). In other words, it only returns apps with UIs, and only for the current user. I can't use -[NSWorkspace launchedApplications], since this must be 10.5-compatible. In addition, this only returns information about applications that appear in the Dock for the current user. I know that it's possible to retrieve the name of running processes (since ps can do it), but the question is "Can I do it without forking and exec'ing ps?". Any suggestions?

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  • transforming binary data using ssis and sql server 2008

    - by Rick
    Hello All - I have a task to import/transform and extract zipped binary files that contain both text data as well as embeded binary data. Within the data is data that is relational in nature and needs to be processed into a defined database structure. Currently I have a C# single threaded app that essentially grabs all the files from the directory (currently there is 13K files of varying sizes) and extracts the data on a single thread line by line inserts to the database. As you could imagine this is a very slow process and unacceptable. There are several different parsing routines used depending on the header record in the file. There are potentially upto a million rows per file when all the data is extracted to the row level of detail. Follow on task is to parse those rows into their appropriate tables based on is content. i.e. the textual content has to be parsed further into "buckets" of like data in the database. That about sums up the big picture. Now for the problem task list. How do i iterate through a packet of data using SSIS? In the app the file is decompressed and then is parsed using streams data type and byte arrays and is routed to the required parsing routine based on the header data of each packet. There is bit swapping involved as well. Should i wrap up the app code into a script task(s) and let it do the custom processing? The data is seperated by year and the sql server tables is partitioned by year as well. I need to be able to "catch" bad file data as well and process by hand most likely. Should i simply load the zipped file to sql as a blob and parse the file with T-SQL? Would that be multi threaded if done that way? Not sure how to do the parsing in tsql that is involved here. Which do you think would be faster? Potentially the data that is currently processed via files could come to us via a socket. Can SSIS collect that data in real time? How would i go about setting that up? Processing these new files from the directorys will become a daily task. I can manage the data once i get it to sql server. Getting it there in a timely fashion seems to be the long pole in the tent for me. I would appreciate any comments or suggestions from the group. Rick

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  • SQL efficiency argument, add a column or solvable by query?

    - by theTurk
    I am a recent college graduate and a new hire for software development. Things have been a little slow lately so I was given a db task. My db skills are limited to pet projects with Rails and Django. So, I was a little surprised with my latest task. I have been asked by my manager to subclass Person with a 'Parent' table and add a reference to their custodian in the Person table. This is to facilitate going from Parent to Form when the custodian, not the Parent, is the FormContact. Here is a simplified, mock structure of a sql-db I am working with. I would have drawn the relationship tables if I had access to Visio. We have a table 'Person' and we have a table 'Form'. There is a table, 'FormContact', that relates a Person to a Form, not all Persons are related to a Form. There is a relationship table for Person to Person relationships (Employer, Parent, etc.) I've asked, "Why this couldn't be handled by a query?" Response, Inefficient. (Really!?!) So, I ask, "Why not have a reference to the Form? That would be more efficient since you wouldn't be querying the FormContacts table with the reference from child/custodian." Response, this would essentially make the Parent is a FormContact. (Fair enough.) I went ahead an wrote a query to get from non-FormContact Parent to Form, and tested on the production server. The response time was instantaneous. *SOME_VALUE* is the Parent's fk ID. SELECT FormID FROM FormContact WHERE FormContact.ContactID IN (SELECT SourceContactID FROM ContactRelationship WHERE (ContactRelationship.RelatedContactID = *SOME_VALUE*) AND (ContactRelationship.Relationship = 'Parent')); If I am right, "This is an unnecessary change." What should I do, defend my position or should I concede to the managers request? If I am wrong. What is my error? Is there a better solution than the manager's?

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  • jQuery: List expands on page load

    - by Hasanah
    I've been looking for something very simple: How to make a side navigation expand with animation on page load, but all the tutorial websites I usually go to don't seem to have it. The closest I could find is this jQuery sample: http://codeblitz.wordpress.com/2009/04/15/jquery-animated-collapsible-list/ I've managed to strip down the list like so: <script type="text/javascript" src="jquery-1.3.2.min.js"></script> <script type="text/javascript"> $(function(){ $('li') .css('pointer','default') .css('list-style','none'); $('li:has(ul)') .click(function(event){ if (this == event.target) { $(this).css('list-style', (!$(this).children().is(':hidden')) ? 'none' : 'none'); $(this).children().toggle('slow'); } return false; }) .css({cursor:'pointer', 'list-style':'none'}) .children().hide(); $('li:not(:has(ul))').css({cursor:'default', 'list-style':'none'}); }); <body> <fieldset> <legend>Collapsable List Demo</legend> <ul> <li>A - F</li> <li>G - M <ul> <li>George Kent Technology Centre</li> <li>Hampshire Park</li> <li>George Kent Technology Centre</li> <li>Hampshire Park</li> </ul> </li> <li> N - R </li> <li>S - Z</li> </ul> </fieldset> My question is: Is there any way to make this list expand on page load instead of on click? I also don't need it to collapse at all; basically I need only the animating expansion. Thank you for your time and advice. :)

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  • Given a trace of packets, how would you group them into flows?

    - by zxcvbnm
    I've tried it these ways so far: 1) Make a hash with the source IP/port and destination IP/port as keys. Each position in the hash is a list of packets. The hash is then saved in a file, with each flow separated by some special characters/line. Problem: Not enough memory for large traces. 2) Make a hash with the same key as above, but only keep in memory the file handles. Each packet is then put into the hash[key] that points to the right file. Problems: Too many flows/files (~200k) and it might run out of memory as well. 3) Hash the source IP/port and destination IP/port, then put the info inside a file. The difference between 2 and 3 is that here the files are opened and closed for each operation, so I don't have to worry about running out of memory because I opened too many at the same time. Problems: WAY too slow, same number of files as 2 so also impractical. 4) Make a hash of the source IP/port pairs and then iterate over the whole trace for each flow. Take the packets that are part of that flow and place them into the output file. Problem: Suppose I have a 60 MB trace that has 200k flows. This way, I would process, say, a 60 MB file 200k times. Maybe removing the packets as I iterate would make it not so painful, but so far I'm not sure this would be a good solution. 5) Split them by IP source/destination and then create a single file for each one, separating the flows by special characters. Still too many files (+50k). Right now I'm using Ruby to do it, which might've been a bad idea, I guess. Currently I've filtered the traces with tshark so that they only have relevant info, so I can't really make them any smaller. I thought about loading everything in memory as described in 1) using C#/Java/C++, but I was wondering if there wouldn't be a better approach here, especially since I might also run out of memory later on even with a more efficient language if I have to use larger traces. In summary, the problem I'm facing is that I either have too many files or that I run out of memory. I've also tried searching for some tool to filter the info, but I don't think there is one. The ones I've found only return some statistics and wouldn't scan for every flow as I need.

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  • Designing a database file format

    - by RoliSoft
    I would like to design my own database engine for educational purposes, for the time being. Designing a binary file format is not hard nor the question, I've done it in the past, but while designing a database file format, I have come across a very important question: How to handle the deletion of an item? So far, I've thought of the following two options: Each item will have a "deleted" bit which is set to 1 upon deletion. Pro: relatively fast. Con: potentially sensitive data will remain in the file. 0x00 out the whole item upon deletion. Pro: potentially sensitive data will be removed from the file. Con: relatively slow. Recreating the whole database. Pro: no empty blocks which makes the follow-up question void. Con: it's a really good idea to overwrite the whole 4 GB database file because a user corrected a typo. I will sell this method to Twitter ASAP! Now let's say you already have a few empty blocks in your database (deleted items). The follow-up question is how to handle the insertion of a new item? Append the item to the end of the file. Pro: fastest possible. Con: file will get huge because of all the empty blocks that remain because deleted items aren't actually deleted. Search for an empty block exactly the size of the one you're inserting. Pro: may get rid of some blocks. Con: you may end up scanning the whole file at each insert only to find out it's very unlikely to come across a perfectly fitting empty block. Find the first empty block which is equal or larger than the item you're inserting. Pro: you probably won't end up scanning the whole file, as you will find an empty block somewhere mid-way; this will keep the file size relatively low. Con: there will still be lots of leftover 0x00 bytes at the end of items which were inserted into bigger empty blocks than they are. Rigth now, I think the first deletion method and the last insertion method are probably the "best" mix, but they would still have their own small issues. Alternatively, the first insertion method and scheduled full database recreation. (Probably not a good idea when working with really large databases. Also, each small update in that method will clone the whole item to the end of the file, thus accelerating file growth at a potentially insane rate.) Unless there is a way of deleting/inserting blocks from/to the middle of the file in a file-system approved way, what's the best way to do this? More importantly, how do databases currently used in production usually handle this?

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  • J2ME/Java: Referencing StringBuffer through Threads

    - by Jemuel Dalino
    This question might be long, but I want to provide much information. Overview: I'm creating a Stock Quotes Ticker app for Blackberry. But I'm having problems with my StringBuffer that contains an individual Stock information. Process: My app connects to our server via SocketConnection. The server sends out a formatted set of strings that contains the latest Stock trade. So whenever a new trade happens, the server will send out an individual Stock Quote of that trade. Through an InputStream I am able to read that information and place each character in a StringBuffer that is referenced by Threads. By parsing based on char3 I am able to determine a set of stock quote/information. char1 - to separate data char3 - means end of a stock quote/information sample stock quote format sent out by our server: stock_quote_name(char 1)some_data(char1)some_data(char1)(char3) My app then parses that stock quote to compare certain data and formats it how it will look like when displayed in the screen. When trades happen gradually(slow) the app works perfectly. However.. Problem: When trades happen too quickly and almost at the same time, My app is not able to handle the information sent efficiently. The StringBuffer has its contents combined with the next trade. Meaning Two stock information in one StringBuffer. field should be: Stock_quote_name some_data some_data sample of what's happening: Stock_quote_name some_data some_dataStock_quote_name some_data some_data here's my code for this part: while (-1 != (data = is.read())) { sb.append((char)data); while(3 != (data = is.read())) { sb.append((char)data); } UiApplication.getUiApplication().invokeLater(new Runnable() { public void run() { try { synchronized(UiApplication.getEventLock()) { SetStringBuffer(sb); DisplayStringBuffer(); RefreshStringBuffer(); } } catch (Exception e) { System.out.println("Error in setting stringbuffer: " + e.toString()); } } }); } public synchronized void DisplayStringBuffer() { try { //parse sb - string buffer ...... } catch(Exception ex) { System.out.println("error in DisplayStringBuffer(): " + ex.toString()); } } public synchronized void SetStringBuffer(StringBuffer dataBuffer) { this.sb =dataBuffer; System.out.println(sb); } public synchronized void RefreshStringBuffer() { this.sb.delete(0, this.sb.length()); } From what I can see, when trades happen very fast, The StringBuffer is not refreshed immediately and still has the contents of the previous trade, when i try to put new data. My Question is: Do you guys have any suggestion on how i can put data into the StringBuffer, without the next information being appended to the first content

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