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  • Improve Log Exceptions

    - by Jaider
    I am planning to use log4net in a new web project. In my experience, I see how big the log table can get, also I notice that errors or exceptions are repeated. For instance, I just query a log table that have more than 132.000 records, and I using distinct and found that only 2.500 records are unique (~2%), the others (~98%) are just duplicates. so, I came up with this idea to improve logging. Having a couple of new columns: counter and updated_dt, that are updated every time try to insert same record. If want to track the user that cause the exception, need to create a user_log or log_user table, to map N-N relationship. Create this model may made the system slow and inefficient trying to compare all these long text... Here the trick, we should also has a hash column of binary of 16 or 32, that hash the message and the exception, and configure an index on it. We can use HASHBYTES to help us. I am not an expert in DB, but I think that will made the faster way to locate a similar record. And because hashing doesn't guarantee uniqueness, will help to locale those similar record much faster and later compare by message or exception directly to make sure that are unique. This is a theoretical/practical solution, but will it work or bring more complexity? what aspects I am leaving out or what other considerations need to have? the trigger will do the job of insert or update, but is the trigger the best way to do it?

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  • ASP .NET page runs slow in production

    - by Brandi
    I have created an ASP .NET page that works flawlessly and quickly from Visual Studio. It does a very large database read from a database on our network to load a gridview inside of an update panel. It displays progress in an Ajax modalpopupextender. Of course I don't expect it to be instant what with the large db reads, but it takes on the order of seconds, not on the order of minutes. This is all working great until I put it up on the server - it is very, VERY slow when I access it via the internet - takes several minutes to load the database information into the gridview. I'm baffled why it would not perform the exact same as it had from Visual Studio. (It is in release mode and I have taken off the debug flag) I have since been trying things like eliminating unneeded update panels and throwing out the ajax tool. Nothing has made it any faster on production. It is not the database as far as I know, since it has been consistently fast from my computer (from visual studio) and consistently slow from the server. I am wondering, where do I look next? Has anyone else had this problem before? Could this be caused by update panels or Ajax modalpopupextenders in different parts of the application? Why would the live behaviour differ so much from the localhost behaviour? Both the server with the ASP .NET page and the server with the database are servers on our network. I'm using Visual Studio 2008. Thank you in advance for any insight or advice.

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  • FOSS ASP.Net Session Replication Solution?

    - by jsight
    I've been searching (with little success) for a free/opensource session clustering and replication solution for asp.net. I've run across the usual suspects (indexus sharedcache, memcached), however, each has some limitations. Indexus - Very immature, stubbed session interface implementation. Its otherwise a great caching solution, though. Memcached - Little replication/failover support without going to a db backend. Several SF.Net projects - All aborted in the early stages... nothing that appears to have any traction, and one which seems to have gone all commercial. Microsoft Velocity - Not OSS, but seems nice. Unfortunately, I didn't see where CTP1 supported failover, and there is no clear roadmap for this one. I fear that this one could fall off into the ether like many other MS dev projects. I am fairly used to the Java world where it is kind of taken for granted that many solutions to problems such as this will be available from the FOSS world. Are there any suitable alternatives available on the .Net world?

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  • SQL Server compare table entries for update

    - by Dave
    I have a trade table with several million rows. Each row represents the version of a trade. If I'm given a possibly new trade I compare it to the latest version in the trade table. If it has changed I add a new version, otherwise I do nothing. In order to compare the 2 trades I read the version from the trade table into my application. This doesn't work well when I'm given 10s of thousands of possibly new trades. Even batching reads to read in a 1000 trades at once and compare them the whole process can take several minutes. All the time is spent in the DB. I'm trying to find a way to compare the possibly new trades to the ones in the trade table without so much I/O. What I've come up with so far is adding a hash column to each row in the trade table. The hash is of all the trade fields. Then when I'm given possibly new trades I compute their hash, put the values into a temporary table, then find ones that are different. This feels very hacky. Is there a better way of doing it? Thanks

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  • POSTmethod and PHP- login verification

    - by Neethusha
    I wrote a code for login verification..I got output with GET. But i need output with POST since it is more secure.pls let me know if there is any error in my code. javascript code: var xml; function verifyusernamepasswd(pass) { //pass is password that will be passed as parameter xml=new XMLHttpRequest(); var url="http://localhost/loginvalidate.php"; var para="q="+username+"&p="+pass;//username is global xml.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); xml.setRequestHeader("Content-length", para.length); xml.setRequestHeader("Connection", "close"); xml.open("POST",url,true); xml.onreadystatechange=statechanged1; xml.send(para); } function statechanged1() { if(xml.readyState==4) alert(xml.responseText); } php code: <?php $username=$_POST["q"]; $password=$_POST["p"]; $con=mysql_connect("localhost","root","blaze"); if(!$con) { die('Could not connect: '.mysql.error()); } mysql_select_db("BLAZE",$con) or die("No such Db"); $result=mysql_query("SELECT Passwword FROM USERTABLE WHERE Userhandle='$username'"); if($result==null) echo "false"; else if($result!=null) { $row=mysql_fetch_array($result); if((strcmp($row['Passwword'],$password)==0)) echo "true"; else echo "false"; } ?> the verification does not return anything, cos my alert is not displayed at all...pls tell me whats wrong....

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  • EF Many-to-many dbset.Include in DAL on GenericRepository

    - by Bryant
    I can't get the QueryObjectGraph to add INCLUDE child tables if my life depended on it...what am I missing? Stuck for third day on something that should be simple :-/ DAL: public abstract class RepositoryBase<T> where T : class { private MyLPL2Context dataContext; private readonly IDbSet<T> dbset; protected RepositoryBase(IDatabaseFactory databaseFactory) { DatabaseFactory = databaseFactory; dbset = DataContext.Set<T>(); DataContext.Configuration.LazyLoadingEnabled = true; } protected IDatabaseFactory DatabaseFactory { get; private set; } protected MyLPL2Context DataContext { get { return dataContext ?? (dataContext = DatabaseFactory.Get()); } } public IQueryable<T> QueryObjectGraph(Expression<Func<T, bool>> filter, params string[] children) { foreach (var child in children) { dbset.Include(child); } return dbset.Where(filter); } ... DAL repositories public interface IBreed_TranslatedSqlRepository : ISqlRepository<Breed_Translated> { } public class Breed_TranslatedSqlRepository : RepositoryBase<Breed_Translated>, IBreed_TranslatedSqlRepository { public Breed_TranslatedSqlRepository(IDatabaseFactory databaseFactory) : base(databaseFactory) {} } BLL Repo: public IQueryable<Breed_Translated> QueryObjectGraph(Expression<Func<Breed_Translated, bool>> filter, params string[] children) { return _r.QueryObjectGraph(filter, children); } Controller: var breeds1 = _breedTranslatedRepository .QueryObjectGraph(b => b.Culture == culture, new string[] { "AnimalType_Breed" }) .ToList(); I can't get to Breed.AnimalType_Breed.AnimalTypeId ..I can drill as far as Breed.AnimalType_Breed then the intelisense expects an expression? Cues if any, DB Tables: bold is many-to-many Breed, Breed_Translated, AnimalType_Breed, AnimalType, ...

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  • Android Maven and Refresh Problem

    - by antonio Musella
    Hi all, i've a strange problem with maven and android I've 3 maven project and 2 normal java maven project divided in this manner : normal project : model project ... packaged as jar ... contains java Pojo Bean and Interface. Dao Project ... packaged as jar ... contains Db Logic - Depend on model Project Android Application Maven project ContentProvider ... packaged as apk ... contains ContentProviders only. Depends on Dao Project Editors ... packaged as apk ... contains only Editor, Depends on Dao project MainApp ... packaged as apk ... contains MyApp, Depends on DAO ... The Problem is that if i modify DAO Project , Then do a maven clean and maven install of all apk project, then run as Android Application within Eclipse, i don't see updated app on my Emulator. Nicely if i shut down my ubuntu workstation and restart it i can see The updated app on my Emulator. Do you know a solution for this issue ? thanks and regards

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  • collection_select not working as expected

    - by kgb
    First time I've come to use collection_select in a project and I've hit a wall with it. A Profile has_one Team, Team has_many Profile. In my view for editing profiles I have this. <td><%= f.collection_select(:team_id, @team, :id, :title) %></td> Which populates the drop down with titles of teams as expected. The couple of examples I have read seem to use it in a very similar way. I can't figure out when the profile is saved why it isn't populating the team_id field in my DB. In the development log the team_id is being passed. Processing ProfilesController#update (for 127.0.0.1 at 2010-03-28 22:49:16) [PUT] Parameters: {"commit"=>"Update", "profile"=>{"dob(1i)"=>"2010", "second_name"=>"", "dob(2i)"=>"3", "role"=>"", "dob(3i)"=>"28", "project"=>"", "specialties"=>"", "about"=>"", "team_id"=>"1", "status"=>"", "first_name"=>""}, "authenticity_token"=>"sdTiFPGj9JCO3OEge5EGNGxZbQSsq9ME5LP342EBjyc=", "id"=>"3"} The update controller is the standard scaffold one, this has worked fine for all other additions to the profile model I'd made previously. Am I missing something obvious?

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  • How do I tweak columns in a Flat File Destination in SSIS?

    - by theog
    I have an OLE DB Data source and a Flat File Destination in the Data Flow of my SSIS Project. The goal is simply to pump data into a text file, and it does that. Where I'm having problems is with the formatting. I need to be able to rtrim() a couple of columns to remove trailing spaces, and I have a couple more that need their leading zeros preserved. The current process is losing all the leading zeros. The rtrim() can be done by simple truncation and ignoring the truncation errors, but that's very inelegant and error prone. I'd like to find a better way, like actually doing the rtrim() function where needed. Exploring similar SSIS questions & answers on SO, the thing to do seems to be "Use a Script Task", but that's ususally just thrown out there with no details, and it's not at all an intuitive thing to set up. I don't see how to use scripting to do what I need. Do I use a Script Task on the Control Flow, or a Script Component in the Data Flow? Can I do rtrim() and pad strings where needed in a script? Anybody got an example of doing this or similar things? Many thanks in advance.

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  • How to Update with LINQ?

    - by DaveDev
    currently, I'm doing an update similar to as follows, because I can't see a better way of doing it. I've tried suggestions that I've read in blogs but none work, such as http://msdn.microsoft.com/en-us/library/bb425822.aspx and http://weblogs.asp.net/scottgu/archive/2007/05/19/using-linq-to-sql-part-1.aspx Maybe these do work and I'm missing some point. Has anyone else had luck with them? // please note this isn't the actual code. // I've modified it to clarify the point I wanted to make // and also I didn't want to post our code here! public bool UpdateMyStuff(int myId, List<int> funds) { // get MyTypes that correspond to the ID I want to update IQueryable<MyType> myTypes = database.MyTypes.Where(xx => xx.MyType_MyId == myId); // delete them from the database foreach (db.MyType mt in myTypes) { database.MyTypes.DeleteOnSubmit(mt); } database.SubmitChanges(); // create a new row for each item I wanted to update, and insert it foreach (int fund in funds) { database.MyType mt = new database.MyType { MyType_MyId = myId, fund_id = fund }; database.MyTypes.InsertOnSubmit(mt); } // try to commit the insert try { database.SubmitChanges(); return true; } catch (Exception) { return false; throw; } } Unfortunately, there isn't a database.MyTypes.Update() method so I don't know a better way to do it. Can sombody suggest what I could do? Thanks. ..as a side note, why isn't there an Update() method?

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  • Should I Use Anchor, Button Or Form Submit For "Follow" Feature In Rails

    - by James
    I am developing an application in Rails 3 using a nosql database. I am trying to add a "Follow" feature similar to twitter or github. In terms of markup, I have determined that there are three ways to do this. 1) Use a regular anchor. (Github Uses This Method) <a href="/users/follow?target=Joe">Follow</a> 2) Use a button. (Twitter Uses This Method) <button href="/friendships/create/">Follow</button> 3) Use a form with a submit button. (Has some advantages for me, but I haven't see anyone do it yet.) <form method="post" id="connection_new" class="connection_new" action="/users/follow"> <input type="hidden" value="60d7b563355243796dd8496e17d36329" name="target" id="target"> <input type="submit" value="Follow" name="commit" id="connection_submit"> </form> Since I want to store the user_id in the database and not the username, options 1 and 2 will force me to do a database query to get the actual user_id, whereas option 3 will allow me to store the user_id in a hidden form field so that I don't have to do any database lookups. I can just get the id from the params hash on form submission. I have successfully got each of these methods working, but I would like to know what is the best way to do this. Which way is more semantic, secure, better for spiders, etc...? Is there a reason both twitter and github don't use forms to do this? Any guidance would be appreciated. I am leaning towards using the form method since then I don't have to query the db to get the id of the user, but I am worried that there must be a reason the big guys are just using anchors or buttons for this. I am a newb so go easy on me if I am totally missing something. Thanks!

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  • most efficient method of turning multiple 1D arrays into columns of a 2D array

    - by Ty W
    As I was writing a for loop earlier today, I thought that there must be a neater way of doing this... so I figured I'd ask. I looked briefly for a duplicate question but didn't see anything obvious. The Problem: Given N arrays of length M, turn them into a M-row by N-column 2D array Example: $id = [1,5,2,8,6] $name = [a,b,c,d,e] $result = [[1,a], [5,b], [2,c], [8,d], [6,e]] My Solution: Pretty straight forward and probably not optimal, but it does work: <?php // $row is returned from a DB query // $row['<var>'] is a comma separated string of values $categories = array(); $ids = explode(",", $row['ids']); $names = explode(",", $row['names']); $titles = explode(",", $row['titles']); for($i = 0; $i < count($ids); $i++) { $categories[] = array("id" => $ids[$i], "name" => $names[$i], "title" => $titles[$i]); } ?> note: I didn't put the name = value bit in the spec, but it'd be awesome if there was some way to keep that as well.

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  • how to synchronize database table and directory with php

    - by twmulloy
    hello, I have a directory with files and a database table with what should be the same files. I would like to be able to synchronize the database table with the directory. What would be the most efficient way to do this? or would I realistically only be able to do this in a brute manner? Here's my approach: 1. retrieve all of the files in the directory as array 2. retrieve all of the filenames in the database table as array 3. loop through the file values in the directory array and use in_array() on the database table array to verify the filename is in that array, and if not then start building an array to insert the missing filenames. run db query to add each missing file row to database table 4. loop through directory array and use in_array() on the directory array and anything not found in the directory array will just be deleted from the table. Is there a better way to go about this? or something better for this in php than in_array()?

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  • Nhibernate - getting single column from other table

    - by Muhammad Akhtar
    I have following tables Employee: ID,CompanyID,Name //CompanyID is foriegn key of Company Table Company: CompanyID, Name I want to map this to the following class: public class Employee { public virtual Int ID { get; set; } public virtual Int CompanyID { get; set; } public virtual string Name { get; set; } public virtual string CompanyName { get; set; } protected Employee() { } } here is my xml class <class name="Employee" table="Employee" lazy="true"> <id name="Id" type="Int32" column="Id"> <generator class="native" /> </id> <property name="CompanyID" column="CompanyID" type="Int32" not-null="false"/> <property name="Name" column="Name" type="String" length="100" not-null="false"/> What I need to add in xml class to map CompanyName in my result? here is my code... public ArrayList getTest() { ISession session = NHibernateHelper.GetCurrentSession(); string query = "select Employee.*,(Company.Name)CompanyName from Employee inner join Employee on Employee.CompanyID = Company.CompanyID"; ArrayList document = (ArrayList)session.CreateSQLQuery(query, "Employee", typeof(Document)).List(); return document; } but in the returned result, I am getting CompanyName is null is result set and other columns are fine. Note:In DB, tables don't physical relation Please suggest my solution ------ Thanks

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  • C# algorithm for figuring out different possible combinations...

    - by ttomsen
    I have 10 boxes, each box can hold one item from a group/type of items, each 'group' type only fits in one of the 10 box types. The pool can have n number of items. The groups have completely distinct items. Each item has a price, i want an algorithm that will generate all the different possibilities, so i can figure out different price points. so a smaller picture of the problem BOX A - can have item 1,2,3,4 in it BOX B - can have item 6,7,8,9,10,11,12 BOX C - can have item 13,15,16,20,21 The items are stored in a db, they have a column which denotes which box they can go in. All box types are stored in an array, and I can put the items in a generic list. Anyone see a straightforward way to do this. I have tried doing 10 nested foreach's to see if i could find a simpler way. The nested loops will take MANY hours to run. the nested for each's basically pull all combinations, then calculate a rank for each combination, and store the top 10 ranked combination of items for output

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  • Hibernate 3.5.0 causes extreme performance problems

    - by user303396
    I've recently updated from hibernate 3.3.1.GA to hibernate 3.5.0 and I'm having a lot of performance issues. As a test, I added around 8000 entities to my DB (which in turn cause other entities to be saved). These entities are saved in batches of 20 so that the transactions aren't too large for performance reasons. When using hibernate 3.3.1.GA all 8000 entities get saved in about 3 minutes. When using hibernate 3.5.0 it starts out slower than with hibernate 3.3.1. But it gets slower and slower. At around 4,000 entities, it sometimes takes 5 minutes just to save a batch of 20. If I then go to a mysql console and manually type in an insert statement from the mysql general query log, half of them run perfect in 0.00 seconds. And half of them take a long time (maybe 40 seconds) or timeout with "ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction" from MySQL. Has something changed in hibernate's transaction management in version 3.5.0 that I should be aware of? The ONLY thing I changed to experience these unusable performance issues is replace the following hibernate 3.3.1.GA jar files: com.springsource.org.hibernate-3.3.1.GA.jar, com.springsource.org.hibernate.annotations-3.4.0.GA.jar, com.springsource.org.hibernate.annotations.common-3.3.0.ga.jar, com.springsource.javassist-3.3.0.ga.jar with the new hibernate 3.5.0 release hibernate3.jar and javassist-3.9.0.GA.jar. Thanks.

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  • How do I make JPA POJO classes + Netbeans forms play well together?

    - by Zak
    I started using netbeans to design forms to edit the instances of various classes I have made in a small app I am writing. Basically, the app starts, an initial set of objects is selected from the DB and presented in a list, then an item in the list can be selected for editing. When the editor comes up it has form fields for many of the data fields in the class. The problem I run into is that I have to create a controller that maps each of the data elements to the correct form element, and create an inordinate number of small conversion mapping lines of code to convert numbers into strings and set the correct element in a dropdown, then another inordinate amount of code to go back and update the underlying object with all the values from the form when the save button is clicked. My question is; is there a more directly way to make the editing of the form directly modify the contents of my class instance? I would like to be able to have a default mapping "controller" that I can configure, then override the getter/setter for a particular field if needed. Ideally, there would be standard field validation for things like phone numbers, integers, floats, zip codes, etc... I'm not averse to writing this myself, I would just like to see if it is already out there and use the right tool for the right job.

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  • How can I make this LinqToSQL query work? (SqlExecption)

    - by kversch
    The following code gives me an SqlException: OO theCourse = subject.Course; var students = dc.studentsCourses.Where(x = x.course == theCourse).Select(x = x.student); "Invalid object name 'dbo.studentsCourses'." I tried the following code instead but I also get an Exception. My original question was asked on Aardvark and can be read bellow: var allStudents = from s in dc.students select s; List thestudents = new List(); foreach (student s in allStudents) { if (s.courses.Contains(theCourse)) { thestudents.Add(s); } } I did a right click, "run custom tool" on my dbml and checked my names of my tables and entities. The project compiles but I get an Exception at runtime on this line: "if (s.courses.Contains(theCourse))" Any ideas? Original question on Aardvark: How do I do a LinqToSQL query that gives me this: I want to select all students that attended a certain lesson. The lesson is from a certain course. So select the course the lesson is from. Now select all the students that are following that course. There is a many-to-many relationship between the students and the courses table in my DB. I already extended my LINQ entities to be able to select student.Courses and course.Students using this method: http://www.codeproject.com/KB/linq/linq-to-sql-many-to-many.aspx

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  • problems with retrieving data that was saved outside of a grails webflow

    - by callie16
    Hi, this is actually connected to an earlier question of mine here. Anyway, I have 3 domains that look like this: class A { ... static hasMany = [ b : B ] ... } class B { ... static belongsTo = [ a : A ] static hasMany = [ c : C ] ... } class C { ... static belongsTo = [ b : B ] ... } In my GSP page, I call an action in the Controller via a remote function in a javascript block (I'm using Dojo so I'm passing data to be saved this way... it's not a form per se so I use JSON for now to pass the data to the Controller). Let's say, I'm calling something like this: def someAction = { def jsonArr = [parse the JSON here] def tmpA = A.get(params.id) ... def tmpB = new B() b.someParam = jsonArr.someParam ... def tmpC = new C() tmpC.cParam = jsonArr.cParam tmpB.addToC(tmpC) tmpB.save(flush: true) //this may or may not be here but I'm adding it for the sake of completeness tmpA.addToB(tmpB) tmpA.save(flush: true) // NOTE: If I check here via println or whatnot, tmpA has a tmpB which has a tmpC... in other words, the data got saved. It's also in the DB. redirect(action: 'order' ...) } Then comes the fun part. Here's the webflow sample: def orderFlow = { ... someStateIShouldEndUpIn { on("next") { // or on previous... doesn't matter def anId = params.id def currA = A.get(anId) // this does NOT return a null value def testB = currA.b // this DOES return a null value }.to("somePage") ... } ... } Any ideas on why this happens? Moreover, when I dump the data of currA, b=null... instead of b=[] or b=[contents of tmpB]. Any help would be seriously appreciated... been at this for a couple of days now... Thanks!

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  • Blackberry Asynchronous HTTP Requests - How?

    - by Kai
    The app I'm working on has a self contained database. The only time I need HTTP request is when the user first loads the app. I do this by calling a class that verifies whether or not a local DB exists and, if not, create one with the following request: HttpRequest data = new HttpRequest("http://www.somedomain.com/xml", "GET", this); data.start(); This xml returns a list of content, all of which have images that I want to fetch AFTER the original request is complete and stored. So something like this won't work: HttpRequest data = new HttpRequest("http://www.somedomain.com/xml", "GET", this); data.start(); HttpRequest images = new HttpRequest("http://www.somedomain.com/xmlImages", "GET", this); images.start(); Since it will not treat this like an asynchronous request. I have not found much information on adding callbacks to httpRequest, or any other method I could use to ensure operation 2 does not execute until operation 1 is complete. Any help would be appreciated. Thanks

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  • Node & Redis: Crucial Design Issues in Production Mode

    - by Ali
    This question is a hybrid one, being both technical and system design related. I'm developing the backend of an application that will handle approx. 4K request per second. We are using Node.js being super fast and in terms of our database struction we are using MongoDB, with Redis being a layer between Node and MongoDB handling volatile operations. I'm quite stressed because we are expecting concurrent requests that we need to handle carefully and we are quite close to launch. However I do not believe I've applied the correct approach on redis. I have a class Student, and they constantly change stages(such as 'active', 'doing homework','in lesson' etc. Thus I created a Redis DB for each state. (1 for being 'active', 2 for being 'doing homework'). Above I have the structure of the 'active' students table; xa5p - JSON stringified object #1 pQrW - JSON stringified object #2 active_student_table - {{studentId:'xa5p'}, {studentId:'pQrW'}} Since there is no 'select all keys method' in Redis, I've been suggested to use a set such that when I run command 'smembers' I receive the keys and later on do 'get' for each id in order to find a specific user (lets say that age older than 15). I've been also suggested that in fact I used never use keys in production mode. My question is, no matter how 'conceptual' it is, what specific things I should avoid doing in Node & Redis in production stage?. Are they any issues related to my design? Students must be objects and I sure can list them in a list but I haven't done yet. Is it that crucial in production stage?

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  • If we make a number every millisecond, how much data would we have in a day?

    - by Roger Travis
    I'm a bit confused here... I'm being offered to get into a project, where would be an array of certain sensors, that would give off reading every millisecond ( yes, 1000 reading in a second ). Reading would be a 3 or 4 digit number, for example like 818 or 1529. This reading need to be stored in a database on a server and accessed remotely. I never worked with such big amounts of data, what do you think, how much in terms of MBs reading from one sensor for a day would be?... 4(digits)x1000x60x60x24 ... = 345600000 bits ... right ? about 42 MB per day... doesn't seem too bad, right? therefor a DB of, say, 1 GB, would hold 23 days of info from 1 sensor, correct? I understand that MySQL & PHP probably would not be able to handle it... what would you suggest, maybe some aps? azure? oracle? ... Thansk!

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  • Django: Paginator + raw SQL query

    - by Silver Light
    Hello! I'm using Django Paginator everywhere on my website and even wrote a special template tag, to make it more convenient. But now I got to a state, where I need to make a complex custom raw SQL query, that without a LIMIT will return about 100K records. How can I use Django Pagintor with custom query? Simplified example of my problem: My model: class PersonManager(models.Manager): def complicated_list(self): from django.db import connection #Real query is much more complex cursor.execute("""SELECT * FROM `myapp_person`"""); result_list = [] for row in cursor.fetchall(): result_list.append(row[0]); return result_list class Person(models.Model): name = models.CharField(max_length=255); surname = models.CharField(max_length=255); age = models.IntegerField(); objects = PersonManager(); The way I use pagintation with Django ORM: all_objects = Person.objects.all(); paginator = Paginator(all_objects, 10); try: page = int(request.GET.get('page', '1')) except ValueError: page = 1 try: persons = paginator.page(page) except (EmptyPage, InvalidPage): persons = paginator.page(paginator.num_pages) This way, Django get very smart, and adds LIMIT to a query when executing it. But when I use custom manager: all_objects = Person.objects.complicated_list(); all data is selected, and only then python list is sliced, which is VERY slow. How can I make my custom manager behave similar like built in one?

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  • EF 4.0 Code only assocation from abstract to derived

    - by Jeroen
    Using EF 4.0 Code only i want to make an assocation between an abstract and normal class. I have class 'Item', 'ContentBase' and 'Test'. 'ContentBase' is abstract and 'Test' derives from it. 'ContentBase' has a property 'Item' that links to an instance of 'Item'. So that 'Test.Item' or any class that derives from 'ContentBase' has an 'Item' navigation property. In my DB every record for Test has a matching record for Item. public class Item { public int Id { get; set;} } public abstract class ContentBase { public int ContentId { get; set;} public int Id { get; set;} public Item Item { get; set;} } public class Test : ContentBase { public string Name { get; set;} } now some init code public void SomeInitFunction() { var itemConfig = new EntityConfiguration<Item>(); itemConfig.HasKey(p => p.Id); itemConfig.Property(p => p.Id).IsIdentity(); this.ContextBuilder.Configurations.Add(itemConfig); var testConfig = new EntityConfiguration<Test>(); testConfig.HasKey(p => p.ContentId); testConfig.Property(p => p.ContentId).IsIdentity(); // the problem testConfig.Relationship(p => p.Item).HasConstraint((p, q) => p.Id == q.Id); this.ContextBuilder.Configurations.Add(testConfig); } This gives an error: A key is registered for the derived type 'Test'. Keys must be registered for the root type 'ContentBase'. anyway i try i get an error. What am i a doing wrong?

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  • Mysql - Operand should contain 1 column(s) : What's wrong with the query...?

    - by SpikETidE
    Hi everybody.... I am trying to query a database to find the following If a customer searches for a hotel in a city between dates A and B, find and return the hotels in which rooms are free between the two dates. There will be more than one room in each room type(i.e. 5 Rooms in type A, 10 rooms in Type B etc) and we have to query the db to find only those hotels in which there is atleast one room free in atleast one type. This is my table structure.... **Structure for table 'reservations'** reservation_id hotel_id room_id customer_id payment_id no_of_rooms check_in_date check_out_date reservation_date **Structure for table 'hotels'** hotel_id hotel_name hotel_description hotel_address hotel_location hotel_country hotel_city hotel_type hotel_stars hotel_image hotel_deleted **Structure for table 'rooms'** room_id hotel_id room_name max_persons total_rooms room_price room_image agent_commision room_facilities service_tax vat city_tax room_description room_deleted And this is my query $city_search = '15'; $check_in_date = '29-03-2010'; $check_out_date = '31-03-2010'; $dateFormat_check_in = "DATE_FORMAT('$reservations.check_in_date','%d-%m-%Y')"; $dateFormat_check_out = "DATE_FORMAT('$reservations.check_out_date','%d-%m-%Y')"; $dateCheck = "$dateFormat_check_in >= '$check_in_date' AND $dateFormat_check_out <= '$check_out_date'"; $query = "SELECT $rooms.room_id, $rooms.room_name, $rooms.max_persons, $rooms.room_price, $hotels.hotel_id, $hotels.hotel_name, $hotels.hotel_stars, $hotels.hotel_type FROM $hotels,$rooms,$reservations WHERE $hotels.hotel_city = '$city_search' AND $hotels.hotel_id = $rooms.hotel_id AND $hotels.hotel_deleted = '0' AND $rooms.room_deleted = '0' AND $rooms.total_rooms - (SELECT SUM($reservations.no_of_rooms) as tot, $rooms.room_id as id FROM $reservations,$rooms WHERE $dateCheck GROUP BY $reservations.room_id) > '0'"; The number of rooms already reserved in each room type in each hotel will be stored in the reservations table... The query returns the error : Operand should contain 1 column(s) I tried running the sub-query alone but i don't get any result... And i have lost quite some amount of hair trying to de-bug this query from yesterday... What's wrong with this...? Or is there a better way to do what i mentioned above...? Thanks for your time...

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