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  • Can a T-SQL variable represent an entire row?

    - by elbillaf
    I'm coding for MS SQL Server 10. I have two databases that contain dozens of tables. Each table in one database contains a table with the same name in the other database. Tables with the same name have identical format (fields and data types). The contents of the two tables are similar but not identical. I need to update one based on changes made to the other, but only under certain circumstances. I think I want to use a cursor for this, but I can't find a good example to go by. So far, the MSDN examples are reading one field at a time into a variable. I do need to be able to read /modify two fields which are identical in each table, but I gotta believe there's something less tedious than declaring variables for every field of every table. I would like to be able to FETCH an entire row, check a couple of fields and then make a decision of whether I want to write the entire row to the other table after changing two fields - but do I have to declare variables for EVERY field I want to fetch / write? There's no way to just FETCH an entire row and write an entire row?

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  • Objective C iPhone performance issue

    - by Asad Khan
    Ok guys I am developing an iPhone app I have a Model class which follows a Singleton design pattern. Now I have an NSArray in it which is initialized to around some 1000 NSStrings in the init method. Now I need to use this data in some view controller. so I import Model.h, I create an array of NSString objects in view controller & set the data to it. But now the problem is that now I have 2000 NSStrings currently allocated, which I believe is not a good thing on iPhone due to memory considerations. releasing model object wont help because I've overrided release method to release nothing according to the pattern & I cannot change the design now because now a lot of code works on the assumption of model being a singleton. & in future maybe the initial NSStrings may grow to 2000 or even more & then I'll have 4000 NSStrings allocated at one time .... I am a little confused on how to go about it any suggestions

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  • SELECT SQL Variable - should i avoid using this syntax and always use SET?

    - by Sholom
    Hi All, This may look like a duplicate to here, but it's not. I am trying to get a best practice, not a technical answer (which i already (think) i know). New to SQL Server and trying to form good habits. I found a great explanation of the functional differences between SET @var = and SELECT @var = here: http://vyaskn.tripod.com/differences_between_set_and_select.htm To summarize what each has that the other hasn't (see source for examples): SET: ANSI and portable, recommended by Microsoft. SET @var = (SELECT column_name FROM table_name) fails when the select returns more then one value, eliminating the possibility of unpredictable results. SET @var = (SELECT column_name FROM table_name) will set @var to NULL if that's what SELECT column_name FROM table_name returned, thus never leaving @var at it's prior value. SELECT: Multiple variables can be set in one statement Can return multiple system variables set by the prior DML statement SELECT @var = column_name FROM table_name would set @var to (according to my testing) the last value returned by the select. This could be a feature or a bug. Behavior can be changed with SELECT @j = (SELECT column_name FROM table_name) syntax. Speed. Setting multiple variables with a single SELECT statement as opposed to multiple SET/SELECT statements is much quicker. He has a sample test to prove his point. If you could design a test to prove the otherwise, bring it on! So, what do i do? (Almost) always use SET @var =, using SELECT @var = is messy coding and not standard. OR Use SELECT @var = freely, it could accomplish more for me, unless the code is likely to be ported to another environment. Thanks

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  • How to close and open access to SQL Server 2008 in Windows application?

    - by hgulyan
    Hi, I have a MS Access 97 application (but the question is general) working directly with SQL Server 2008 (without application server or anything). Numbers of users can be up to 1000. Windows Authentication is used. The question is: How to handle modes, so some users will be allowed to work in read-only mode some users won't have access to db for some time My versions: Using a table with a mode id for every group of users, that will work the same way. On Form Load application will query that table for mode id. Using trigger on the tables, that must work according to that mode. The trigger will query mode value and doesn't work if access is closed or it's in read-only mode I know these are not the best solutions, that's why I'm asking for your advice. There's one more point. If the mode is changed to "access-is-closed" for a group of users, that group must not be able to query to DB starting that moment. With first solution I wrote it won't work, because user can be in application at that moment and no form load event will work. How can I do this? Is there any optimal solution? Thank you. Any help would be appreciated.

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  • SQL Server Compact Edition 3.5 performance

    - by Wili
    I am using SQL Server CE 3.5 SP1 in one of my client applications. When a user loads the program and starts using it, performance is fine. If the user lets the program sit idle for a while, it takes a considerable amount of time (10 or more seconds) for the program to respond. Every time the user asks for a new screen, a call is made to the SQL CE database to get the data for that screen. It seems like the hard drive may be going to sleep and then when the database is accessed, the hard drive has to wake back up. Is it possible to load the entire database into memory and work from that? Are there any other suggestions on how to increase performance?

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  • Strange performance behaviour

    - by plastilino
    I'm puzzled with this. In my machine Direct calculation: 375 ms Method calculation: 3594 ms, about TEN times SLOWER If I place the method calulation BEFORE the direct calculation, both times are SIMILAR. Woud you check it in your machine? class Test { static long COUNT = 50000 * 10000; private static long BEFORE; /*--------METHOD---------*/ public static final double hypotenuse(double a, double b) { return Math.sqrt(a * a + b * b); } /*--------TIMER---------*/ public static void getTime(String text) { if (BEFORE == 0) { BEFORE = System.currentTimeMillis(); return; } long now = System.currentTimeMillis(); long elapsed = (now - BEFORE); BEFORE = System.currentTimeMillis(); if (text.equals("")) { return; } String message = "\r\n" + text + "\r\n" + "Elapsed time: " + elapsed + " ms"; System.out.println(message); } public static void main(String[] args) { double a = 0.2223221101; double b = 122333.167; getTime(""); /*--------DIRECT CALCULATION---------*/ for (int i = 1; i < COUNT; i++) { Math.sqrt(a * a + b * b); } getTime("Direct: "); /*--------METHOD---------*/ for (int k = 1; k < COUNT; k++) { hypotenuse(a, b); } getTime("Method: "); } }

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  • C++ application as a service with high performance

    - by sand
    I need to provide a C++ application as a service. Client of the service and the service can be on the same machine or distributed on different machines based on the load. This application takes a ~2KB string as input and returns almost similar size of string after some processing. Turnaround time for the client should be really quick. What is the best mechanism to implement this?

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  • HTML 5 performance on Firefox ?

    - by asksuperuser
    I tried this sample here: http://9elements.com/io/projects/html5/canvas/ After a few minutes, Firefox slows down so much I can't even popup any menu. When I closed the tab, Firefox comes back to normal again. So is HTML 5 really a good choice now ?

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  • C++ Performance/memory optimization guidelines

    - by ML
    Hi All, Does anyone have a resource for C++ memory optimization guidelines? Best practices, tuning, etc? As an example: Class xxx { public: xxx(); virtual ~xxx(); protected: private: }; Would there be ANY benefit on the compiler or memory allocation to get rid of protected and private since there there are no items that are protected and private in this class?

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  • Improve disk read performance (multiple files) with threading

    - by pablo
    I need to find a method to read a big number of small files (about 300k files) as fast as possible. Reading them sequentially using FileStream and reading the entire file in a single call takes between 170 and 208 seconds (you know, you re-run, disk cache plays its role and time varies). Then I tried using PInvoke with CreateFile/ReadFile and using FILE_FLAG_SEQUENTIAL_SCAN, but I didn't appreciate any changes. I tried with several threads (divide the big set in chunks and have every thread reading its part) and this way I was able to improve speed just a little bit (not even a 5% with every new thread up to 4). Any ideas on how to find the most effective way to do this?

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  • Performance of Serialized Objects in C++

    - by jm1234567890
    Hi Everyone, I'm wondering if there is a fast way to dump an STL set to disk and then read it back later. The internal structure of a set is a binary tree, so if I serialize it naively, when I read it back the program will have to go though the process of inserting each element again. I think this is slow even if it is read back in correct order, correct me if I am wrong. Is there a way to "dump" the memory containing the set into disk and then read it back later? That is, keep everything in binary format, thus avoiding the re-insertion. Do the boost serialization tools do this? Thanks! EDIT: oh I should probably read, http://www.parashift.com/c++-faq-lite/serialization.html I will read it now... no it doesn't really help

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  • Run SQL Scripts from C# application across domains

    - by Saravanan AR
    To run sql script files from my C# application, I referred this. http://social.msdn.microsoft.com/Forums/en/adodotnetdataproviders/thread/43e8bc3a-1132-453b-b950-09427e970f31 it works perfectly when my machine and DB server are in the same domain. my problem now is, i'm executing this console application from a machine (name: X, user id: abc, domain D1). the SQL server is in another machine (name: Y, domain: D2). I use VPN to connect to machine Y with user id 'abc' and work on SQL in remote desktop. how can i run sql scripts across domains? I use this in a custom activity in my TFS build template as the last step to run the scripts in the target database which is in domain D2. i'm getting this error: "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)" is it possible to connect to the DB using the admin user ID of machine Y in domain D2?

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  • Python performance profiling (file close)

    - by user1853986
    First of all thanks for your attention. My question is how to reduce the execution time of my code. Here is the relevant code. The below code is called in iteration from the main. def call_prism(prism_input_file,random_length): prism_output_file = "path.txt" cmd = "prism %s -simpath %d %s" % (prism_input_file,random_length,prism_output_file) p = os.popen(cmd) p.close() return prism_output_file def main(prism_input_file, number_of_strings): ... for n in range(number_of_strings): prism_output_file = call_prism(prism_input_file,z[n]) ... return I used statistics from the "profile statistics browser" when I profiled my code. The "file close" system command took the maximum time (14.546 seconds). The call_prism routine is called 10 times. But the number_of_strings is usually in thousands, so, my program takes lot of time to complete. Let me know if you need more information. By the way I tried with subprocess, too. Thanks.

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  • postgres min function performance

    - by wutzebaer
    hi i need the lowest value for runnerId this query: SELECT "runnerId" FROM betlog WHERE "marketId" = '107416794' ; takes 80ms (1968 result rows) this SELECT min("runnerId") FROM betlog WHERE "marketId" = '107416794' ; takes 1600ms is there a faster way to find the minimum, or should i calc the min in my java programm? "Result (cost=100.88..100.89 rows=1 width=0)" " InitPlan 1 (returns $0)" " -> Limit (cost=0.00..100.88 rows=1 width=9)" " -> Index Scan using runneridindex on betlog (cost=0.00..410066.33 rows=4065 width=9)" " Index Cond: ("runnerId" IS NOT NULL)" " Filter: ("marketId" = 107416794::bigint)" CREATE INDEX marketidindex ON betlog USING btree ("marketId" COLLATE pg_catalog."default"); another idea SELECT "runnerId" FROM betlog WHERE "marketId" = '107416794' ORDER BY "runnerId" LIMIT 1 >1600ms SELECT "runnerId" FROM betlog WHERE "marketId" = '107416794' ORDER BY "runnerId" >>100ms how can a limit slow the query down?

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  • Objective-C vs JavaScript loop performance

    - by micadelli
    I have a PhoneGap mobile application that I need to generate an array of match combinations. In JavaScript side, the code hanged pretty soon when the array of which the combinations are generated from got a bit bigger. So, I thought I'll make a plugin to generate the combinations, passing the array of javascript objects to native side and loop it there. To my surprise the following codes executes in 150 ms (JavaScript) whereas in native side (Objective-C) it takes ~1000 ms. Does anyone know any tips for speeding up those executing times? When players exceeds 10, i.e. the length of the array of teams equals 252 it really gets slow. Those execution times mentioned above are for 10 players / 252 teams. Here's the JavaScript code: for (i = 0; i < GAME.teams.length; i += 1) { for (j = i + 1; j < GAME.teams.length; j += 1) { t1 = GAME.teams[i]; t2 = GAME.teams[j]; if ((t1.mask & t2.mask) === 0) { GAME.matches.push({ Team1: t1, Team2: t2 }); } } } ... and here's the native code: NSArray *teams = [[NSArray alloc] initWithArray: [options objectForKey:@"teams"]]; NSMutableArray *t = [[NSMutableArray alloc] init]; int mask_t1; int mask_t2; for (NSInteger i = 0; i < [teams count]; i++) { for (NSInteger j = i + 1; j < [teams count]; j++) { mask_t1 = [[[teams objectAtIndex:i] objectForKey:@"mask"] intValue]; mask_t2 = [[[teams objectAtIndex:j] objectForKey:@"mask"] intValue]; if ((mask_t1 & mask_t2) == 0) { [t insertObject:[teams objectAtIndex:i] atIndex:0]; [t insertObject:[teams objectAtIndex:j] atIndex:1]; /* NSArray *newCombination = [[NSArray alloc] initWithObjects: [teams objectAtIndex:i], [teams objectAtIndex:j], nil]; */ [combinations addObject:t]; } } } ... the array in question (GAME.teams) looks like this: { count = 2; full = 1; list = ( { index = 0; mask = 1; name = A; score = 0; }, { index = 1; mask = 2; name = B; score = 0; } ); mask = 3; name = A; }, { count = 2; full = 1; list = ( { index = 0; mask = 1; name = A; score = 0; }, { index = 2; mask = 4; name = C; score = 0; } ); mask = 5; name = A; },

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  • C# Performance on Errors

    - by pm_2
    It would appear that catching an error is slower that performing a check prior to the error (for example a TryParse). The related questions that prompt this observation are here and here. Can anyone tell me why this is so - why is it more costly to catch an error that to perform one or many checks of the data to prevent the error?

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  • How can I improve the performance of this algorithm

    - by Justin
    // Checks whether the array contains two elements whose sum is s. // Input: A list of numbers and an integer s // Output: return True if the answer is yes, else return False public static boolean calvalue (int[] numbers, int s){ for (int i=0; i< numbers.length; i++){ for (int j=i+1; j<numbers.length;j++){ if (numbers[i] < s){ if (numbers[i]+numbers[j] == s){ return true; } } } } return false; }

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  • PHP array performance

    - by dfo
    Hi, this is my first question on Stackoverflow, please bear with me. I'm testing an algorithm for 2d bin packing and I've chosen PHP to mock it up as it's my bread-and-butter language nowadays. As you can see on http://themworks.com/pack_v0.2/oopack.php?ol=1 it works pretty well, but you need to wait around 10-20 seconds for 100 rectangles to pack. For some hard to handle sets it would hit the php's 30s runtime limit. I did some profiling and it shows that most of the time my script goes through different parts of a small 2d array with 0's and 1's in it. It either checks if certain cell equals to 0/1 or sets it to 0/1. It can do such operations million times and each times it takes few microseconds. I guess I could use an array of booleans in a statically typed language and things would be faster. Or even make an array of 1 bit values. I'm thinking of converting the whole thing to some compiled language. Is PHP just not good for it? If I do need to convert it to let's say C++, how good are the automatic converters? My script is just a lot of for loops with basic arrays and objects manipulations. Thank you! Edit. This function gets called more than any other. It reads few properties of a very simple object, and goes through a very small part of a smallish array to check if there's any element not equal to 0. function fits($bin, $file, $x, $y) { $flag = true; $xw = $x + $file->get_width();; $yh = $y + $file->get_height(); for ($i = $x; $i < $xw; $i++) { for ($j = $y; $j < $yh; $j++) { if ($bin[$i][$j] !== 0) { $flag = false; break; } } if (!$flag) break; } return $flag; }

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  • C/C++ variable length automatic array performance

    - by aaa
    hello. Is there significant cpu/memory overhead associated with using automatic arrays with g++/Intel on 64-bit x86 linux platform? int function(int N) { double array[N]; overhead compared to allocating array before hand (assuming function is called multiple times) overhead compared to using new overhead compared to using malloc range of N maybe from 1kb to 16kb roughly, stack overrun is not a problem Thank you

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  • Which should I use? (performance)

    - by Yim
    I want to know a simple thing: when setting up a style that is inherited by all its children, is it recommended most specific? (even if you don't care others having this style) Structure: html body parent_content wrapper p I don't care having parent_content or wrapper having the style I do care changing the html or body style (or all p) So what should I use? #parent_content{ color:#555; } #parent_content p{ color:#555; } #wrapper{ color:#555; } ... Also, some links to tutorials about this would be great

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