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  • Boost::Asio : io_service.run() vs poll() or how do I integrate boost::asio in mainloop

    - by user300713
    Hi, I am currently trying to use boost::asio for some simple tcp networking for the first time, and I allready came across something I am not really sure how to deal with. As far as I understand io_service.run() method is basically a loop which runs until there is nothing more left to do, which means it will run until I release my little server object. Since I allready got some sort of mainloop set up, I would rather like tp update the networking loop manually from there just for the sake of simplicity, and I think io_service.poll() would do what I want, sort of like this: void myApplication::update() { myIoService.poll(); //do other stuff } This seems to work, but I am still wondering if there is a drawback from this method since that does not seem to be the common way to deal with boost::asios io services. Is this a valid approach or should I rather use io_service.run() in a non blocking extra thread?

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  • SQL Server stored procedures - update column based on variable name..?

    - by ClarkeyBoy
    Hi, I have a data driven site with many stored procedures. What I want to eventually be able to do is to say something like: For Each @variable in sproc inputs UPDATE @TableName SET @variable.toString = @variable Next I would like it to be able to accept any number of arguments. It will basically loop through all of the inputs and update the column with the name of the variable with the value of the variable - for example column "Name" would be updated with the value of @Name. I would like to basically have one stored procedure for updating and one for creating. However to do this I will need to be able to convert the actual name of a variable, not the value, to a string. Question 1: Is it possible to do this in T-SQL, and if so how? Question 2: Are there any major drawbacks to using something like this (like performance or CPU usage)? I know if a value is not valid then it will only prevent the update involving that variable and any subsequent ones, but all the data is validated in the vb.net code anyway so will always be valid on submitting to the database, and I will ensure that only variables where the column exists are able to be submitted. Many thanks in advance, Regards, Richard Clarke Edit: I know about using SQL strings and the risk of SQL injection attacks - I studied this a bit in my dissertation a few weeks ago. Basically the website uses an object oriented architecture. There are many classes - for example Product - which have many "Attributes" (I created my own class called Attribute, which has properties such as DataField, Name and Value where DataField is used to get or update data, Name is displayed on the administration frontend when creating or updating a Product and the Value, which may be displayed on the customer frontend, is set by the administrator. DataField is the field I will be using in the "UPDATE Blah SET @Field = @Value". I know this is probably confusing but its really complicated to explain - I have a really good understanding of the entire system in my head but I cant put it into words easily. Basically the structure is set up such that no user will be able to change the value of DataField or Name, but they can change Value. I think if I were to use dynamic parameterised SQL strings there will therefore be no risk of SQL injection attacks. I mean basically loop through all the attributes so that it ends up like: UPDATE Products SET [Name] = '@Name', Description = '@Description', Display = @Display Then loop through all the attributes again and add the parameter values - this will have the same effect as using stored procedures, right?? I dont mind adding to the page load time since this is mainly going to affect the administration frontend, and will marginly affect the customer frontend.

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  • effective retrieve for a voting system in PHP and MySQL

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date | vote_type Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • How to "kill" background worker completely?

    - by Ken Hung
    Hi All, I am writing a windows application that runs a sequence of digital IO actions repeatedly. This sequence of actions starts when the user click a "START" button, and it is done by a background worker in backgroundWorker1_DoWork(). However, there are occasions when I get the "This backgroundworker is currently busy......." error message. I am thinking of implementing the following in the code, by using a while loop to "kill" the background worker before starting another sequence of action: if (backgroundWorker1.IsBusy == true) { backgroundWorker1.CancelAsync(); while (backgroundWorker1.IsBusy == true) { backgroundWorker1.CancelAsync(); } backgroundWorker1.Dispose(); } backgroundWorker1.RunWorkerAsync(); I think my main concern is, will the backgroundWorker1 be "killed" eventually? If it will, will it take a long time to complete it? Will this coding get me into an infinite loop?

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  • Slow SelectSingleNode

    - by Simon
    I have a simple structured XML file like this: <ttest ID="ttest00001", NickName="map00001"/> <ttest ID="ttest00002", NickName="map00002"/> <ttest ID="ttest00003", NickName="map00003"/> <ttest ID="ttest00004", NickName="map00004"/> ..... This xml file can be around 2.5MB. In my source code I will have a loop to get nicknames In each loop, I have something like this: nickNameLoopNum = MyXmlDoc.SelectSingleNode("//ttest[@ID=' + testloopNum + "']").Attributes["NickName"].Value This single line will cost me 30 to 40 millisecond. I searched some old articles (dated back to 2002) saying, use some sort of compiled "xpath" can help the situation, but that was 5 years ago. I wonder is there a mordern practice to make it faster? (I'm using .NET 3.5)

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  • asp.net mvc viewdata

    - by mazhar kaunain baig
    <% foreach (var Lang in ((IEnumerable<Egovt.Models.Language>)ViewData["Languages"])) { %> <div id="tabs-<%=Html.Encode(Lang.int_LangId) %>"> <% foreach (var OrganizationMeta in ((IEnumerable<Egovt.Models.OrganizationMeta>)ViewData["OrganizationMeta"])) { %> <% if (OrganizationMeta.vcr_DateType == "text") { %> <%=Server.HtmlDecode(OrganizationMeta.vcr_MetaValue)%><br /> <a href="#"></a> <% } else if (OrganizationMeta.vcr_DateType == "file") { %> <img alt="Image" src="../../Content/Logo/dd.gif" /> <% } %> <% } %> </div> <% } %> I want to base my second loop on the basis of first loop on the langid field, there are many ways but what you guys will use

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  • Triggering shouldStartLoadWithRequest with multiple window.location.href calls

    - by AlBeebe
    Im trying to pass multiple things from a webpage inside a UIWebView back to my iPhone app via the shouldStartLoadWithRequest method of the UIWebView. Basically my webpage calls window.location.href = "command://foo=bar" and i am able to intercept that in my app no problem. Now if i create a loop and do multiple window.location.href calls at once, then shouldStartLoadWithRequest only appears to get called on once and the call it gets is the very last firing of window.location.href at the end of the loop. The same thing happens with the webview for Android, only the last window.location.href gets processed.

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  • effective retrieve for a voting system in PHP

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • realtime diagnostics

    - by Ion Todirel
    I have an application which has a loop, part of a "Scheduler", which runs at all time and is the heart of the application. Pretty much like a game loop, just that my application is a WPF application and it's not a game. Naturally the application does logging at many points, but the Scheduler does some sensitive monitoring, and sometimes it's impossible just from the logs to tell what may have gotten wrong (and by wrong I don't mean exceptions) or the current status. Because Scheduler's inner loop runs at short intervals, you can't do file I/O-based logging (or using the Event Viewer) in there. First, you need to watch it in real-time, and secondly the log file would grow in size very fast. So I was thinking of ways to show this data to the user in the realtime, some things I considered: Display the data in realtime in the UI Use AllocConsole/WriteConsole to display this information in a console Use a different console application which would display this information, communicate between the Scheduler and the console app using pipes or other IPC techniques Use Windows' Performance Monitor and somehow feed it with this information ETW Displaying in the UI would have its issues. First it doesn't integrate with the UI I had in mind for my application, and I don't want to complicate the UI just for this. This diagnostics would only happen rarely. Secondly, there is going to be some non-trivial data protection, as the Scheduler has it's own thread. A separate console window would work probably, but I'm still worried if it's not too much threshold. Allocating my own console, as this is a windows app, would probably be better than a different console application (3), as I don't need to worry about IPC communication, and non-blocking communication. However a user could close the console I allocated, and it would be problematic in that case. With a separate process you don't have to worry about it. Assuming there is an API for Performance Monitor, it wouldn't be integrated too well with my app or apparent to the users. Using ETW also doesn't solve anything, just a random idea, I still need to display this information somehow. What others think, would there be other ways I missed?

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  • Imagemagick - File Naming

    - by Josh Crowder
    I am using the convert command to convert a pdf to multiple pngs, I need the naming conventions to be slide-##.png at the moment they come out like slide-1.png but because there is 20+ slides when I loop through them to add them into the model the order comes up wrong, so it looks like slide-1.png slide-10.png slide-11.png and so on, how can I force convert to use double numbers like 01 02 03 and so forth or is there a better way to loop through them, this is the code I have at the moment def convert_keynote_to_slides system('convert -size 640x300 ' + keynote.queued_for_write[:original].path + ' ~/rails/arcticfox/public/system/keynotes/slides/'+File.basename( self.keynote_file_name )+'0%d.png') slide_basename = File.basename( self.keynote_file_name ) files = Dir.entries('/Users/joshcrowder/rails/arcticfox/public/system/keynotes/slides') for file in files #puts file if file.include?(slide_basename +'-') self.slides.build("slide" => "#{file}") if file.include?(slide_basename) end end

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  • Does .NET Regex support global matching?

    - by Dave
    I haven't been able to find anything online regarding this. There's RegexOptions, but it doesn't have Global as one of its options. The inline modifiers list also doesn't mention global matching. In a nutshell, I've got a regex to parse something like --arga= "arg1" --argb ="arg2" into separate argument name/value pairs using this regex: --(\\w+)\\s*=\\s*\"(\\w+)\"\\s* but the .NET Regex class doesn't do it globally (iteratively). So in order for me to get this to work, I'd have to do a match, then remove this from the argument string, and loop over and over again until I've exhausted all of the arguments. It would be nicer to run the regex once, and then loop over the match groups to get the name value pairs. Is this possible? What am I missing?

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  • CSV string handling

    - by Christian Hagelid
    Typical way of creating a CSV string (pseudocode): create a CSV container object (like a StringBuilder in C#) Loop through the strings you want to add appending a comma after each one After the loop, remove that last superfluous comma. Code sample: public string ReturnAsCSV(ContactList contactList) { StringBuilder sb = new StringBuilder(); foreach (Contact c in contactList) { sb.Append(c.Name + ","); } sb.Remove(sb.Length - 1, 1); //sb.Replace(",", "", sb.Length - 1, 1) return sb.ToString(); } I feel that there should be an easier / cleaner / more efficient way of removing that last comma. Any ideas? Update I like the idea of adding the comma by checking if the container is empty, but doesn't that mean more processing as it needs to check the length of the string on each occurrence?

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  • Tuple struct constructor complains about private fields

    - by Grubermensch
    I am working on a basic shell interpreter to familiarize myself with Rust. While working on the table for storing suspended jobs in the shell, I have gotten stuck at the following compiler error message: tsh.rs:8:18: 8:31 error: cannot invoke tuple struct constructor with private fields tsh.rs:8 let mut jobs = job::JobsList(vec![]); ^~~~~~~~~~~~~ It's unclear to me what is being seen as private here. As you can see below, both of the structs are tagged with pub in my module file. So, what's the secret sauce? tsh.rs use std::io; mod job; fn main() { // Initialize jobs list let mut jobs = job::JobsList(vec![]); loop { /*** Shell runtime loop ***/ } } job.rs use std::fmt; pub struct Job { jid: int, pid: int, cmd: String } impl fmt::Show for Job { /*** Formatter ***/ } pub struct JobsList(Vec<Job>); impl fmt::Show for JobsList { /*** Formatter ***/ }

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  • Bit manipulation, permutate bits

    - by triktae
    Hi. I am trying to make a loop that loops through all different integers where exactly 10 of the last 40 bits are set high, the rest set low. The reason is that I have a map with 40 different values, and I want to sum all different ways ten of these values can be multiplied. (This is just out of curiosity, so it's really the "bitmanip"-loop that is of interest, not the sum as such.) If I were to do this with e.g. 2 out of 4 bits, it would be easy to set all manually, 0011 = 7, 0101 = 5, 1001 = 9, 0110 = 6, 1010 = 10, 1100 = 12, but with 10 out of 40 I can't seem to find a method to generate these effectively. I tried, starting with 1023 ( = 1111111111 in binary), finding a good way to manipulate this, but with no success. I've been trying to do this in C++, but it's really the general method(if any) that is of interest. I did some googling, but with little success, if anyone has a good link, that would of course be appreciated too. :)

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  • Trying to drop all tables from my schema with no rows?

    - by Vineet
    I am trying to drop all tables in schema with no rows,but when i am executing this code i am getting an error THis is the code: create or replace procedure tester IS v_count NUMBER; CURSOR emp_cur IS select table_name from user_tables; BEGIN FOR emp_rec_cur IN emp_cur LOOP EXECUTE IMMEDIATE 'select count(*) from '|| emp_rec_cur.table_name INTO v_count ; IF v_count =0 THEN EXECUTE IMMEDIATE 'DROP TABLE '|| emp_rec_cur.table_name; END IF; END LOOP; END tester; ERROR at line 1: ORA-29913: error in executing ODCIEXTTABLEOPEN callout ORA-29400: data cartridge error KUP-00554: error encountered while parsing access parameters KUP-01005: syntax error: found "identifier": expecting one of: "badfile, byteordermark, characterset, data, delimited, discardfile, exit, fields, fixed, load, logfile, nodiscardfile, nobadfile, nologfile, date_cache, processing, readsize, string, skip, variable" KUP-01008: the bad identifier was: DELIMETED KUP-01007: at line 1 column 9 ORA-06512: at "SYS.ORACLE_LOADER", line 14 ORA-06512: at line 1 ORA-06512: at "SCOTT.TESTER", line 9 ORA-06512: at line 1

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  • NHybernate, the Parallel Framework, and SQL Server

    - by andy
    hey guys, we have a loop that: 1.Loops over several thousand xml files. Altogether we're parsing millions of "user" nodes. 2.In each iteration we parse a "user" xml, do custom deserialization 3.finally, in each iteration, we send our object to nhibernate for saving. We use: .SaveOrUpdateAndFlush(user); This is a lengthy process, and we thought it would be a perfect candidate for testing out the .NET 4.0 Parallel libraries. So we wrapped the loop in a: Parallel.ForEach(); After doing this, we start getting "random" Timeout Exceptions from SQL Server, and finally, after leaving it running all night, OutOfMemory unhandled exceptions. I haven't done deep debugging on this yet, but what do you guys think. Is this simply a limitation of SQL Server, or could it be our NHibernate setup, or what? cheers andy

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  • Create Oracle Cursor

    - by Mohammad
    Hi, I create a cursor like this: SQL> CREATE OR REPLACE PROCEDURE Update_STUD_FinAid ( AIDY_CODE IN VARCHAR2 ) IS 2 CURSOR PublicationC IS 3 SELECT SGBSTDN_USER_ID from SGBSTDN 4 WHERE SGBSTDN_TERM_CODE_EFF ='201030'; 5 BEGIN 6 close PublicationC; 7 8 OPEN PublicationC; 9 10 FOR PublicationR IN PublicationC 11 LOOP 12 DBMS_OUTPUT.PUT_LINE( PublicationR.SGBSTDN_USER_ID ); 13 END LOOP; 14 15 close PublicationC; 16 17 END; 18 / Procedure created. And then when I run the Procedure then I get this error: ERROR at line 1: ORA-06512: at line 2 Please advise. Thanks

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  • SharpSSH gets stuck in an infinite stream read in C# SSH app

    - by Ric Coles
    Afternoon all, I'm having a small problem with the SharpSSH library for .Net (see http://www.tamirgal.com/blog/page/SharpSSH.aspx) SshStream ssh = new SshStream("some ip address", "some username", "some password"); ssh.Prompt = "\n"; ssh.RemoveTerminalEmulationCharacters = true; ssh.Write("ssh some ip address"); // Don't care about this response ssh.ReadResponse(); ssh.Write("lss /mnt/sata[1-4]"); // Don't care about this response (for now) ssh.ReadResponse(); // while the stream can be read while (ssh.CanRead) { Console.WriteLine(ssh.ReadResponse()); } ssh.Close(); As you can see, it's fairly straight forward. However, when the while-loop gets stepped into, it won't break out of the loop when everything has been printed to the console and there is nothing else to read. Is there anyway I can manually force it to break when there is nothing else to be read? Cheers, Ric

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  • Qt: Writing plugins for other applications

    - by Rasmus Faber
    I am writing a plugin for another application. I want to support the plugin on multiple platforms, so I am strongly considering using Qt. The plugin needs to be able to show some basic GUI. The plugin interface does not in any way handle GUI - it is just a simple DLL/shared library specified with a C-header file. Can I use Qt inside such a shared library? The calling application might or might not be using Qt itself. Any hints on what to do? Do I need to run a QApplication event-loop in a separate thread? Or can I just call the event-loop myself while waiting for input? (I only need modal dialogs).

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  • How to program a real-time accurate audio sequencer on the iphone?

    - by Walchy
    Hi... I want to program a simple audio sequencer on the iphone but I can't get accurate timing. The last days I tried all possible audio techniques on the iphone, starting from AudioServicesPlaySystemSound and AVAudioPlayer and OpenAL to AudioQueues. In my last attempt I tried the CocosDenshion sound engine which uses openAL and allows to load sounds into multiple buffers and then play them whenever needed. Here is the basic code: init: int channelGroups[1]; channelGroups[0] = 8; soundEngine = [[CDSoundEngine alloc] init:channelGroups channelGroupTotal:1]; int i=0; for(NSString *soundName in [NSArray arrayWithObjects:@"base1", @"snare1", @"hihat1", @"dit", @"snare", nil]) { [soundEngine loadBuffer:i fileName:soundName fileType:@"wav"]; i++; } [NSTimer scheduledTimerWithTimeInterval:0.14 target:self selector:@selector(drumLoop:) userInfo:nil repeats:YES]; In the initialisation I create the sound engine, load some sounds to different buffers and then establish the sequencer loop with NSTimer. audio loop: - (void)drumLoop:(NSTimer *)timer { for(int track=0; track<4; track++) { unsigned char note=pattern[track][step]; if(note) [soundEngine playSound:note-1 channelGroupId:0 pitch:1.0f pan:.5 gain:1.0 loop:NO]; } if(++step>=16) step=0; } Thats it and it works as it should BUT the timing is shaky and instable. As soon as something else happens (i.g. drawing in a view) it goes out of sync. As I understand the sound engine and openAL the buffers are loaded (in the init code) and then are ready to start immediately with alSourcePlay(source); - so the problem may be with NSTimer? Now there are dozens of sound sequencer apps in the appstore and they have accurate timing. I.g. "idrum" has a perfect stable beat even in 180 bpm when zooming and drawing is done. So there must be a solution. Does anybody has any idea? Thanks for any help in advance! Best regards, Walchy

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  • appending to cursor in oracle

    - by Omnipresent
    I asked a question yesterday which got answers but didnt answer the main point. I wanted to reduce amount of time it took to do a MINUS operation. Now, I'm thinking about doing MINUS operation in blocks of 5000, appending each iterations results to the cursor and finally returning the cursor. I have following: V_CNT NUMBER :=0; V_INTERVAL NUMBER := 5000; begin select count(1) into v_cnt from TABLE_1 while (v_cnt > 0) loop open cv_1 for SELECT A.HEAD,A.EFFECTIVE_DATE, FROM TABLE_1 A WHERE A.TYPE_OF_ACTION='6' AND A.EFFECTIVE_DATE >= ADD_MONTHS(SYSDATE,-15) AND A.ROWNUM <= V_INTERVAL MINUS SELECT B.head,B.EFFECTIVE_DATE, FROM TABLE_2 B AND B.ROWNUM <= V_INTERVAL V_CNT := V_CNT - V_INTERVAL; END LOOP; end; However, as you see...in each iteration the cursor is overwritten. How can I change the code so that in each iteration it appends to cv_1 cursor rather than overwriting?

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  • Concatenation with Zero is not occurring properly in code?

    - by Vineet
    I was trying to reverse a number in PL/SQL. It's working fine, but when my number contains any 0, the output is unexpected. For example: 1234 output 4321 1000 output 1 1203 ouput 3021 10001 output 1 DECLARE r number(9); num number(9):=&p_num; BEGIN WHILE num>=1 LOOP IF mod(num,10)=0 THEN -- extracting last digit of a number . r:=r||0; --if end digit is 0 then concat r with 0 ELSE r:=r||mod(num,10);--if mod is not 0 then it would be last digit. END IF; num:=trunc(num/10);--Removing last digit from number END LOOP; dbms_output.put_line(r); END;

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  • Looping through JSON arrays

    - by George
    I'm trying to pull the field names in the header of some JSON output. The following is a sample of the JSON header info: {"HEADER":{"company":{"label":"Company Name"},"streetaddress":{"label":"Street Address"},"ceo":{"label":"CEO Name","fields":{"firstname":{"label":"First Name"},"lastname":{"label":"Last Name"}}} I'm able to loop through the header and output the field and label (i.e. company and Company Name) using the following code: obj = JSON.parse(jsonResponse); for (var key in obj.HEADER) { response.write ( obj.HEADER[key].label ); response.write ( key ); } but can't figure out how to loop through and output the sub array of fields (i.e. firstname and First Name). Any ideas?

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  • using joins or multiple queries in php/mysql

    - by askkirati
    Here i need help with joins. I have two tables say articles and users. while displaying articles i need to display also the user info like username, etc. So will it be better if i just use joins to join the articles and user tables to fetch the user info while displaying articles like below. SELECT a.*,u.username,u.id FROM articles a JOIN users u ON u.id=a.user_id OR can this one in php. First i get the articles with below sql SELECT * FROM articles Then after i get the articles array i loop though it and get the user info inside each loop like below SELECT username, id FROM users WHERE id='".$articles->user_id."'; Which is better can i have explanation on why too. Thank you for any reply or views

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  • One large file or multiple small files?

    - by Dan
    I have an application (currently written in Python as we iron out the specifics but eventually it will be written in C) that makes use of individual records stored in plain text files. We can't use a database and new records will need to be manually added regularly. My question is this: would it be faster to have a single file (500k-1Mb) and have my application open, loop through, find and close a file OR would it be faster to have the records separated and named using some appropriate convention so that the application could simply loop over filenames to find the data it needs? I know my question is quite general so direction to any good articles on the topic are as appreciated as much as suggestions. Thanks very much in advance for your time, Dan

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