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  • Design suggestion for expression tree evaluation with time-series data

    - by Lirik
    I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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  • Lucene and Special Characters

    - by Brandon
    I am using Lucene.Net 2.0 to index some fields from a database table. One of the fields is a 'Name' field which allows special characters. When I perform a search, it does not find my document that contains a term with special characters. I index my field as such: Directory DALDirectory = FSDirectory.GetDirectory(@"C:\Indexes\Name", false); Analyzer analyzer = new StandardAnalyzer(); IndexWriter indexWriter = new IndexWriter(DALDirectory, analyzer, true, IndexWriter.MaxFieldLength.UNLIMITED); Document doc = new Document(); doc.Add(new Field("Name", "Test (Test)", Field.Store.YES, Field.Index.TOKENIZED)); indexWriter.AddDocument(doc); indexWriter.Optimize(); indexWriter.Close(); And I search doing the following: value = value.Trim().ToLower(); value = QueryParser.Escape(value); Query searchQuery = new TermQuery(new Term(field, value)); Searcher searcher = new IndexSearcher(DALDirectory); TopDocCollector collector = new TopDocCollector(searcher.MaxDoc()); searcher.Search(searchQuery, collector); ScoreDoc[] hits = collector.TopDocs().scoreDocs; If I perform a search for field as 'Name' and value as 'Test', it finds the document. If I perform the same search as 'Name' and value as 'Test (Test)', then it does not find the document. Even more strange, if I remove the QueryParser.Escape line do a search for a GUID (which, of course, contains hyphens) it finds documents where the GUID value matches, but performing the same search with the value as 'Test (Test)' still yields no results. I am unsure what I am doing wrong. I am using the QueryParser.Escape method to escape the special characters and am storing the field and searching by the Lucene.Net's examples. Any thoughts?

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  • code igniter codeigniter question, making anchor load page containing data from referenced row in DB

    - by thrice801
    Hi, Im trying to learn the code igniter library and object oriented php in general and have a question. Ok so Ive gotten as far as making a page which loads all of the rows from my database and in there, Im echoing an anchor tag which is a link to the following structure. [code]echo anchor("videos/video/$row-video_id", $row-video_title);[/code] So, I have a class called Videos which extends the controller, within that class there is index and video, which is being called correctly (when you click on the video title, it sends you to videos/video/5 for example, 5 being the primary key of the table im working with. So basically all Im trying to do is pass that 5 back to the controller, and then have the particular video page output the particular rows data from the videos table. My function in my controller for video looks like this - [code] function video() { $data['main_content'] = 'video'; $data['video_title'] = 'test'; $this-load-view('includes/template', $data); } [/code] So ya, basically test should be instead of test, a returned value of a query which says get in the table "videos", the row with the video_id of "5", and make $data['video_title'] = value of video_title in database... Should have this figured out by now but dont, any help would be appreciated!

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  • I am using relational division with EAV, but I need to find results in EAV that have some of the cat

    - by NewToDB
    I have two tables: CREATE TABLE EAV ( subscriber_id INT(1) NOT NULL DEFAULT '0', attribute_id CHAR(62) NOT NULL DEFAULT '', attribute_value CHAR(62) NOT NULL DEFAULT '', PRIMARY KEY (subscriber_id,attribute_id) ) INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (1,'color','red') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (1,'size','xl') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (1,'garment','shirt') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (2,'color','red') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (2,'size','xl') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (2,'garment','pants') INSERT INTO EAV (subscriber_id, attribute_id, attribute_value) VALUES (3,'garment','pants') CREATE TABLE CRITERIA ( attribute_id CHAR(62) NOT NULL DEFAULT '', attribute_value CHAR(62) NOT NULL DEFAULT '' ) INSERT INTO CRITERIA (attribute_id, attribute_value) VALUES ('color', 'red') INSERT INTO CRITERIA (attribute_id, attribute_value) VALUES ('size', 'xl') To find all subscribers in the EAV that match my criteria, I use relational division: SELECT DISTINCT(subscriber_id) FROM EAV WHERE subscriber_id IN (SELECT E.subscriber_id FROM EAV AS E JOIN CRITERIA AS CR ON E.attribute_id = CR.attribute_id AND E.attribute_value = CR.attribute_value GROUP BY E.subscriber_id HAVING COUNT() = (SELECT COUNT() FROM CRITERIA)) This gives me an unique list of subscribers who have all the criteria. So that means I get back subscriber 1 and 2 since they are looking for the color red and size xl, and that's exactly my criteria. But what if I want to extend this so that I also get subscriber 3 since this subscriber didn't specifically say what color or size they want (ie. there is no entry for attribute 'color' or 'size' in the EAV table for subscriber 3). Given my current design, is there a way I can extend my query to include subscribers that have zero or more of the attributes defined, and if they do have the attribute defined, then it must match the criteria? Or is there a better way to design the table to aid in querying?

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  • High performance text file parsing in .net

    - by diamandiev
    Here is the situation: I am making a small prog to parse server log files. I tested it with a log file with several thousand requests (between 10000 - 20000 don't know exactly) What i have to do is to load the log text files into memory so that i can query them. This is taking the most resources. The methods that take the most cpu time are those (worst culprits first): string.split - splits the line values into a array of values string.contains - checking if the user agent contains a specific agent string. (determine browser ID) string.tolower - various purposes streamreader.readline - to read the log file line by line. string.startswith - determine if line is a column definition line or a line with values there were some others that i was able to replace. For example the dictionary getter was taking lots of resources too. Which i had not expected since its a dictionary and should have its keys indexed. I replaced it with a multidimensional array and saved some cpu time. Now i am running on a fast dual core and the total time it takes to load the file i mentioned is about 1 sec. Now this is really bad. Imagine a site that has tens of thousands of visits a day. It's going to take minutes to load the log file. So what are my alternatives? If any, cause i think this is just a .net limitation and i can't do much about it.

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  • Capturing time intervals when somebody was online? How would you impement this feature?

    - by Kirzilla
    Hello, Our aim is to build timelines saying about periods of time when user was online. (It really doesn't matter what user we are talking about and where he was online) To get information about onliners we can call API method, someservice.com/api/?call=whoIsOnline whoIsOnline method will give us a list of users currently online. But there is no API method to get information about who IS NOT online. So, we should build our timelines using information we got from whoIsOnline. Of course there will be a measurement error (we can't track information in realtime). Let's suppose that we will call whoIsOnline method every 2 minutes (yes, we will run our script by cron every 2 minutes). For example, calling whoIsOnline at 08:00 will return Peter_id Michal_id Andy_id calling whoIsOnline at 08:02 will return Michael_id Andy_id George_id As you can see, Peter has gone offline, but we have new onliner - George. Available instruments are Db(MySQL) / text files / key-value storage (Redis/memcache); feel free to choose any of them (or even all of them). So, we have to get information like this George_id was online... 12 May: 08:02-08:30, 12:40-12:46, 20:14-22:36 11 May: 09:10-12:30, 21:45-23:00 10 May: was not online And now question... How would you store information to implement such timelines? How would you query/calculate information about periods of time when user was online? Additional information.. You cannot update information about offline users, only users who are "currently" online. Solution should be flexible: timeline information could be represented relating to any timezone. We should keep information only for last 7 days. Every user seen online is automatically getting his own identifier in our database. Uff.. it was really hard for me to write it because my English is pretty bad, but I hope my question will be clear for you. Thank you.

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  • Issue Querying LDAP DirectoryEntry in ASP.NET

    - by davemackey
    I have users login to my application via Active Directory and then pull from their AD information to garner information about that user like so: Dim ID as FormsIdentity = DirectCast(User.Identity, FormsIdentity) Dim ticket as FormsAuthenticationTicket = ID.Ticket Dim adDirectory as New DirectoryEntry("LDAP://DC=my,DC=domain,DC=com") Dim adTicketID as String = ticket.Name.Substring(0, 5) Session("people_id") = adDirectory.Children.Find("CN=" & adTicketID).Properties("employeeID").Value Session("person_name") = adDirectory.Children.Find("CN=" & adTicketID).Properties("displayName").Value Now, I want to be able to impersonate other users...so that I can "test" the application as them, so I added a textbox and a button to the page and when the button is clicked the text is assigned to a session variable like so: Session("impersonate_user") = TextBox1.Text When the page reloads I check to see if Session("impersonate_user") has a value other than "" and then attempt to query Active Directory using this session variable like so: If CStr(Session("impersonate_user")) <> "" Then Dim adDirectory as New DirectoryEntry(LDAP://DC=my,DC=domain,DC=com") Dim adTicketID as String = CStr(Session("impersonate_user")) Session("people_id") = adDirectory.Children.Find("CN=" & adTicketID).Properties("employeeID").Value Session("person_name")= adDirectory.Children.Find("CN=" & adTicketID).Properties("displayName").Value Else [use the actual ticket.name to get this info.] End If But this doesn't work. Instead, it throws an error on the first Session line stating, "DirectoryServicesCOMException was unhandled by user code There is no such object on the server." Why? I know I'm giving it a valid username! Is something strange happening in the casting of the session? The code is essentially the same between each method except that in one method rather than pulling from ticket.Name I pull from a session variable for the login I'll be looking up with AD.

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  • Web Hosting URL Length Limit?

    - by Isaac Waller
    Hello, I am designing a web application which is a tie in to my iPhone application. It sends massively large URLs to the web server (15000 about.) I was using NearlyFreeSpeech.net, but they only support URLS up to 2000 characters. I was wondering if anybody knows of web hosting that will support really large URLs? Thanks, Isaac Edit: My program needs to open a picture in Safari. I could do this 2 ways: send it base64 encoded in the URL and just echo the query parameters. first POST it to the server in my application, then the server would send back a unique ID after storing the photo in a database, which I would append to a URL which I would open in Safari which retrieved the photo from the database and delete it from the database. You see, I am lazy, and I know Mobile Safari can support URI's up to 80 000 characters, so I think this is a OK way to do it. If there is something really wrong with this, please tell me. Edit: I ended up doing it the proper POST way. Thanks.

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  • Zend: Fetching row from session db table after generating session id

    - by Nux
    Hi, I'm trying to update the session table used by Zend_Session_SaveHandler_DbTable directly after authenticating the user and writing the session to the DB. But I can neither update nor fetch the newly inserted row, even though the session id I use to check (Zend_Session::getId()) is valid and the row is indeed inserted into the table. Upon fetching all session ids (on the same request) the one I newly inserted is missing from the results. It does appear in the results if I fetch it with something else. I've checked whether it is a problem with transactions and that does not seem to be the problem - there is no active transaction when I'm fetching the results. I've also tried fetching a few seconds after writing using sleep(), which doesn't help. $auth->getStorage()->write($ident); //sleep(1) $update = $this->db->update('session', array('uid' => $ident->user_id), 'id='.$this->db->quote(Zend_Session::getId())); $qload = 'SELECT id FROM session'; $load = $this->db->fetchAll($qload); echo $qload; print_r($load); $update fails. $load doesn't contain the row that was written with $auth-getStorage()-write($identity). $qload does contain the correct query - copying it to somewhere else leads to the expected result, that is the inserted row is included in the results. Database used is MySQL - InnoDB. If someone knows how to directly fix this (i.e. on the same request, not doing something like updating after redirecting to another page) without modifying Zend_Session_SaveHandler_DbTable: Thank you very much!

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  • Catching 'Last Record' in Coldfusion for IE javascript bug

    - by Simon Hume
    I'm using ColdFusion to pull UK postcodes into an array for display on a Google Map. This happens dynamically from a SQL database, so the numbers can range from 1 to 100+ the script works great, however, in IE (groan) it decides to display one point way off line, over in California somewhere. I fixed this issue in a previous webapp, this was due to the comma between each array item still being present at the end. Works fine in Firefox, Safari etc, but not IE. But, that one was using a set 10 records, so was easy to fix. I just need a little if statement to wrap around my comma to hide it when it hits the last record. I can't seem to get it right. Any tips/suggestions? here is the line of code in question: var address = [<cfloop query="getApplicant"><cfif getApplicant.dbHomePostCode GT ""><cfoutput>'#getApplicant.dbHomePostCode#',</cfoutput></cfif> </cfloop>]; Hopefully someone can help with this rather simple request. I'm just having a bad day at the office!

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  • Detecting a Dispose() from an exception inside using block

    - by Augusto Radtke
    I have the following code in my application: using (var database = new Database()) { var poll = // Some database query code. foreach (Question question in poll.Questions) { foreach (Answer answer in question.Answers) { database.Remove(answer); } // This is a sample line that simulate an error. throw new Exception("deu pau"); database.Remove(question); } database.Remove(poll); } This code triggers the Database class Dispose() method as usual, and this method automatically commits the transaction to the database, but this leaves my database in an inconsistent state as the answers are erased but the question and the poll are not. There is any way that I can detect in the Dispose() method that it being called because of an exception instead of regular end of the closing block, so I can automate the rollback? I don´t want to manually add a try ... catch block, my objective is to use the using block as a logical safe transaction manager, so it commits to the database if the execution was clean or rollbacks if any exception occured. Do you have some thoughts on that?

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  • Full Text Search in SQL Server 2008 shows wrong display_item for Thai language

    - by ensecoz
    I am working with SQL Server 2008. My task is to investigate the issue where FTS cannot find the right result for Thai. First, I have the table which enables the FTS on the column 'ItemName' which is nvarchar. The Catalog is created with the Thai Language. Note that the Thai language is one of the languages that doesn't separate the word by spaces, so '????' '???' '????' are written like this in a sentence: '???????????' In the table, there are many rows that include the word (????); for example row#1 (ItemName: '???????????') On the webpage, I try to search for '????' but SQL Server cannot find it. So I try to investigate it by trying the following query in SQL Server: select * from sys.dm_fts_parser(N'"???????????"', 1054, 0, 0) ...to see how the words are broken. The first one is the text to be broken. The second parameter is to specify that we're using Thai (WorkBreaker, so on). Here is the result: row#1 (display_item: '????', source_item: '???????????') row#2 (display_item: '????', source_item: '???????????') row#3 (display_item: '??', source_item: '???????????') Notice that the first and second row display the wrong display_item '?' in the '????' isn't even Thai characters. '?' in '????' is not a Thai character either. So the question is where did those alien characters come from? I guess this why I cannot search for '????' because the word breaker is broken and keeping the wrong character in the indexes. Please help!

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  • How do I improve this design for dealing with intersecting date ranges and resolving date range conf

    - by derdo
    I am working on some code that deals with date ranges. I have pricing activities that have a starting-date and an end-date to set a certain price for that range. There are multiple pricing activities with intersecting date ranges. What I ultimately need is the ability to query valid prices for a date range. I pass in (jan1,jan31) and I get back a list that says jan1--jan10 $4 , jan11--jan19 $3 jan20--jan31 $4. There are priorities between pricing activities. Some type of pricing activities have high priority, so they override other pricing activities and for certain type of pricing activities lowest price wins etc. I currently have a class that holds these pricing activities and keeps a resolved pricing calendar. As I add new pricing activities I update the resolved calendar. As I write more tests/code, it started to get very complicated with all the different cases (pricing activities intersecting in different ways). I am ending up with very complicated code where I am resolving a newly added pricing activity. See AddPricingActivity() method below. Can anybody think of a simpler way to deal with this? Could there be similar code somewhere out there? Public class PricingActivity() { DateTime startDate; DateTime endDate; Double price; Public bool StartsBeforeEndsAfter (PricingActivity pAct) { // pAct covers this pricing activity } Public bool StartsMiddleEndsAfter (PricingActivity pAct){ // early part of pAct Itersects with later part of this pricing activity } //more similar methods to cover all the combinations of intersecting } Public Class PricingActivityList() { List<PricingActivity> activities; SortedDictionary<Date, PricingActivity> resolvedPricingCalendar; Public void AddPricingActivity(PricingActivity pAct) { //update the resolvedCalendar //go over each activity and find intersecting ones //update the resolved calendar correctly //depending on the type of the intersection //this part is getting out of hand….. } }

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  • .NET - getting form field key/value pairs?

    - by AverageJoe719
    Hi there, I've got a form with textboxes and I want to run some server side validation code on the values after the form is submitted. I was planning to grab all the textbox controls on the page and adding them to a list, then running a for each loop that says for each control in the list query the database where fieldValidation.Name = Control.Name. This would return to me an object and an associated function where i coudl then input the Control.Value and actually perform the validation. My friend told me building the list is not necessary because all languages have a way to get key/value pairs from forms (he doesn't know .NET so coudln't help me). I may be searching the wrong term here but I have not been able to find a result, or maybe I misunderstood my friend. Is there some kind of dictionary or key/value pair automatically generated upon form submissions that contains the value that was submitted and...I guess also the control? Or am I just misunderstanding him. If he was just saying populate a key/value pair based on the form submissions, how does that help me in this situation over a list that contains the control? Thanks =)

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  • Java JSP/Servlet: controller servlet throwing the famous stack overflow

    - by NoozNooz42
    I've read several docs and I don't get it: I know I'm doing something wrong but I don't understand what. I've got a website that is entirely dynamically generated: there's hardly any static content at all. So, trying to understand JSP/Servlet, I've written my own "front controller" intercepting every single query, it looks like this: <servlet-mapping> <servlet-name>defaultservlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> Basically I want any user request, like: example.org example.org/bar example.org/foo.html to all go through a default servlet which I've written. The servlet then examines the URI and find to which .jsp the request must be dispatched, and then does, after having set all the attributes correctly, a: RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/jsp/index.jsp"); dispatcher.forward(req, resp); When I'm using a url-pattern (in web.xml) like, say, *.html, everything works fine. But when I change it to /* (to really intercept everything), I enter an endless loop and it ends up with a... StackOverflow :) When the request is dispatched, is the URI ".../WEB-INF/jsp/index.jsp" itself matched by the web.xml filter /* that I set? How should I do if I want to intercept everything using a /* url-pattern and yet be able to dispatch/forward/? I'm not asking about specs/Javadocs here: I'm really confused about the bigger picture and I'd need some explanation as to what could be going on. Am I not supposed to intercept really everything? If I can intercept everything, what should I be aware of regarding forwarding/dispatching?

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  • Table valued function only returns CLR error

    - by Anthony
    I have read-only access to a database that was set up for a third-party, closed-source app. Once group of (hopefully) useful table functions only returns the error: Failed to initialize the Common Language Runtime (CLR) v2.0.50727 with HRESULT 0x80131522. You need to restart SQL server to use CLR integration features. (severity 16) But in theory, the third-party app should be able to use the function (either directly or indirectly), so I'm convinced I'm not setting things up right. I'm very new to SQL Server, so I could be missing something obvious. Or I could be missing something really slight, I have no idea. Here is an example of a query that returns the above error: SELECT * FROM dbo.UncompressDataDateRange(4,'Apr 24 2010 12:00AM','Apr 30 2010 12:00AM') Where the function takes three parameters: The Data Set (int) -- basically the data has 6 classifications, and the giant table this should be pulling from has a column to indicate which is which. startDate (smalldatetime) endDate (smalldatetime) There are other, similar functions that expand on the same idea, all returning the same error. Quick Note: I'm not sure if this is relevant, but I was able to connect to the database via SQL Studio (but without the privs to script the functions as code), and a checked the dependency for the above sample function. It turns out that it is a dependent of a view that I have gotten to work, and that view is dependent of the larger, much-hairier data-table. This makes me think I should somehow be pointing the function at the results of the view, but I'm not seeing any documentation that shows how that is done.

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  • org.hibernate.NonUniqueObjectException Within GWT application using hibernate through gilead

    - by molleman
    Hello Guys, i am working on a project for college that uses GWT,Hibernate and Gilead. Basically for the moment users should be able to add friends and remove them. also a user can see if his or her friends are online or not. my trouble is that when i add a friend that is already related to another friend i get this error org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.example.client.YFUser#4] i have a service class public class TestServiceImpl extends PersistentRemoteService implements TestService { this is my service class for my gwt application. my toruble is here with my implmentation class of my serivce in this method that is called when a user presses add friend button on the client-side public void addYFUserFriend(String userName){ //this retrieves the current user YFUser user = (YFUser)getSession().getAttribute(SESSION_USER); Session session = com.example.server.HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); YFUser friend = (YFUser) session.createQuery("select u FROM YFUser u where u.username = :username").setParameter("username", userName).uniqueResult(); System.out.println("user " + friend.getUsername() + " Found"); user.getFriends().add(friend); friend.getBefriended().add(user); session.update(user); session.update(friend); session.getTransaction().commit(); } a scenerio : user1 adds user2 as a friend. this works fine. then user3 adds user2 and the exeception is thrown. any ideas why and where my logic is going wrong Ok so i have changed my code, and i have removed all the getCurrentASession() calls and replaced with openSession() call which are closed at the appropiate point, now the error i am getting is com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract void com.example.client.TestService.addYFUserFriend(java.lang.String)' threw an unexpected exception: org.hibernate.NonUniqueResultException: query did not return a unique result: 3

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  • How to make a small engine like Wolfram|Alpha?

    - by Koning WWWWWWWWWWWWWWWWWWWWWWW
    Lets say I have three models/tables: operating_systems, words, and programming_languages: # operating_systems name:string created_by:string family:string Windows Microsoft MS-DOS Mac OS X Apple UNIX Linux Linus Torvalds UNIX UNIX AT&T UNIX # words word:string defenitions:string window (serialized hash of defenitions) hello (serialized hash of defenitions) UNIX (serialized hash of defenitions) # programming_languages name:string created_by:string example_code:text C++ Bjarne Stroustrup #include <iostream> etc... HelloWorld Jeff Skeet h AnotherOne Jon Atwood imports 'SORULEZ.cs' etc... When a user searches hello, the system shows the defenitions of 'hello'. This is relatively easy to implement. However, when a user searches UNIX, the engine must choose: word or operating_system. Also, when a user searches windows (small letter 'w'), the engine chooses word, but should also show Assuming 'windows' is a word. Use as an <a href="etc..">operating system</a> instead. Can anyone point me in the right direction with parsing and choosing the topic of the search query? Thanks. Note: it doesn't need to be able to perform calculations as WA can do.

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  • Design pattern to keep track UITableView rows correspondance to underlying data in constant time.

    - by DenNukem
    When my model changes I want to animate changes in UITableView by inserting/deleting rows. For that I need to know the ordinal of the given row (so I can construct NSIndexPath), which I find hard to do in better-than-linear time. For example, consider that I have a list of addressbook entries which are manualy sorted by the user, i.e. there is no ordering "key" that represents the sort order. There is also a corresponding UITableView that shows one row per addressbook entry. When UITableView queries the datasource I query the NSMUtableArray populated with my entries and return required data in constant time for each row. However, if there is a change in underlying model I am getting a notification "Joe Smith, id#123 has been removed". Now I have a dilemma. A naive approach would be to scan the array, determine the index at which Joe Smith is and then ask UITableView to remove that precise row from the view, also removing it form the array. However, the scan will take linear time to finish. Now I could have an NSDictionary which allows me to find Joe Smith in constant time, but that doesn't do me a lot of good because I still need to find his ordinal index within the array in order to instruct UITableView to remove that row, which is again a linear search. I could further decide to store each object's ordinal inside the object itself to make it constant, but it will become outdated after first such update as all subsequent index values will have changed due to removal of an object. So what is the correct design pattern to accurately reflect model changes in the UITableView in costant (or at least logarithmic) time?

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  • Help converting PHP eregi to preg_match

    - by Jason
    Hi all, I am wondering if someone could please help me convert a piece of PHP code that is now deprecated. Here is the single line I am trying to convert: if(eregi(trim ($request_url_handler[$x]),$this->sys_request_url) && $this->id_found == 0){ It is part of a function that return the configuration settings for a website. Below is the whole function. // GET CORRECT CONFIG FROM DATABASE function get_config($db) { global $tbl_prefix; $db->query("SELECT cid,urls FROM ".$tbl_prefix."sys_config ORDER BY cid"); while($db->next_record()){ $request_url_handler = explode("\n",$db->f("urls")); if(empty($request_url_handler[0])) { $request_url_handler[0] = "@"; $this->id_found = 2; } for($x=0; $x<count($request_url_handler); $x++) { if(empty($request_url_handler[$x])) { $request_url_handler[$x] = "@"; } if(eregi(trim($request_url_handler[$x]),$this->sys_request_url) && $this->id_found == 0) { $this->set_config($db,$db->f("cid")); $this->id_found = 1; } } if($this->id_found == 1) { return($this->sys_config_vars); } } $this->set_config($db,""); return($this->sys_config_vars); } Any help would be great ly appreciated. I only found the the eregi function was deprecated since I updated XAMPP to 1.7.3.

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  • deepcopy and python - tips to avoid using it?

    - by blackkettle
    Hi, I have a very simple python routine that involves cycling through a list of roughly 20,000 latitude,longitude coordinates and calculating the distance of each point to a reference point. def compute_nearest_points( lat, lon, nPoints=5 ): """Find the nearest N points, given the input coordinates.""" points = session.query(PointIndex).all() oldNearest = [] newNearest = [] for n in xrange(nPoints): oldNearest.append(PointDistance(None,None,None,99999.0,99999.0)) newNearest.append(obj2) #This is almost certainly an inappropriate use of deepcopy # but how SHOULD I be doing this?!?! for point in points: distance = compute_spherical_law_of_cosines( lat, lon, point.avg_lat, point.avg_lon ) k = 0 for p in oldNearest: if distance < p.distance: newNearest[k] = PointDistance( point.point, point.kana, point.english, point.avg_lat, point.avg_lon, distance=distance ) break else: newNearest[k] = deepcopy(oldNearest[k]) k += 1 for j in range(k,nPoints-1): newNearest[j+1] = deepcopy(oldNearest[j]) oldNearest = deepcopy(newNearest) #We're done, now print the result for point in oldNearest: print point.station, point.english, point.distance return I initially wrote this in C, using the exact same approach, and it works fine there, and is basically instantaneous for nPoints<=100. So I decided to port it to python because I wanted to use SqlAlchemy to do some other stuff. I first ported it without the deepcopy statements that now pepper the method, and this caused the results to be 'odd', or partially incorrect, because some of the points were just getting copied as references(I guess? I think?) -- but it was still pretty nearly as fast as the C version. Now with the deepcopy calls added, the routine does it's job correctly, but it has incurred an extreme performance penalty, and now takes several seconds to do the same job. This seems like a pretty common job, but I'm clearly not doing it the pythonic way. How should I be doing this so that I still get the correct results but don't have to include deepcopy everywhere?

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  • How to call Postgres function returning SETOF record?

    - by Peter
    I have written the following function: -- Gets stats for all markets CREATE OR REPLACE FUNCTION GetMarketStats ( ) RETURNS SETOF record AS $$ BEGIN SELECT 'R approved offer' AS Metric, SUM(CASE WHEN M.MarketName = 'A+' AND M.Term = 24 THEN LO.Amount ELSE 0 end) AS MarketAPlus24, SUM(CASE WHEN M.MarketName = 'A+' AND M.Term = 36 THEN LO.Amount ELSE 0 end) AS MarketAPlus36, SUM(CASE WHEN M.MarketName = 'A' AND M.Term = 24 THEN LO.Amount ELSE 0 end) AS MarketA24, SUM(CASE WHEN M.MarketName = 'A' AND M.Term = 36 THEN LO.Amount ELSE 0 end) AS MarketA36, SUM(CASE WHEN M.MarketName = 'B' AND M.Term = 24 THEN LO.Amount ELSE 0 end) AS MarketB24, SUM(CASE WHEN M.MarketName = 'B' AND M.Term = 36 THEN LO.Amount ELSE 0 end) AS MarketB36 FROM "Market" M INNER JOIN "Listing" L ON L.MarketID = M.MarketID INNER JOIN "ListingOffer" LO ON L.ListingID = LO.ListingID; END $$ LANGUAGE plpgsql; And when trying to call it like this... select * from GetMarketStats() AS (Metric VARCHAR(50),MarketAPlus24 INT,MarketAPlus36 INT,MarketA24 INT,MarketA36 INT,MarketB24 INT,MarketB36 INT); I get an error: ERROR: query has no destination for result data HINT: If you want to discard the results of a SELECT, use PERFORM instead. CONTEXT: PL/pgSQL function "getmarketstats" line 2 at SQL statement I don't understand this output. I've tried using perform too, but I thought one only had to use that if the function doesn't return anything.

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  • NHibernate: how to handle entity-based validation using session-per-request pattern, without control

    - by Seth Petry-Johnson
    What is the best way to do entity-based validation (each entity class has an IsValid() method that validates its internal members) in ASP.NET MVC, with a "session-per-request" model, where the controller has zero (or limited) knowledge of the ISession? Here's the pattern I'm using: Get an entity by ID, using an IFooRepository that wraps the current NH session. This returns a connected entity instance. Load the entity with potentially invalid data, coming from the form post. Validate the entity by callings its IsValid() method. If valid, call IFooRepository.Save(entity). Otherwise, display error message. The session is currently opened when the request begins and flushed when the request ends. Since my entity is connected to a session, flushing the session attempts to save the changes even if the object is invalid. What's the best way to keep validation logic in the entity class, limit controller knowledge of NH, and avoid saving invalid changes at the end of a request? Option 1: Explicitly evict on validation failure, implicitly flush: if the validation fails, I could manually evict the invalid object in the action method. If successful, I do nothing and the session is automatically flushed. Con: error prone and counter-intuitive ("I didn't call .Save(), why are my invalid changes being saved anyways?") Option 2: Explicitly flush, do nothing by default: By default I can dispose of the session on request end, only flushing if the controller indicates success. I'd probably create a SaveChanges() method in my base controller that sets a flag indicating success, and then query this flag when closing the session at request end. Pro: More intuitive to troubleshoot if dev forgets this step [relative to option 1] Con: I have to call IRepository.Save(entity)' and SaveChanges(). Option 3: Always work with disconnected objects: I could modify my repositories to return disconnected/transient objects, and modify the Repo.Save() method to re-attach them. Pro: Most intuitive, given that controllers don't know about NH. Con: Does this defeat many of the benefits I'd get from NH?

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  • How do I sort an internationalized i18n table with symfony and doctrine?

    - by Maurizio
    I would like to display a list of records from an internationalized table using sfDoctrinePager. Not all the records have been translated to all the languages supported by the application, so I had to implement a fallback mechanism for some fields (by overriding the getFoo() function in the Bar.class.php, as explained in another post here). I have different fallback list for each culture. Everything works fine until when it comes to sorting the records in alphabetical order. I'm sorting the records at the SQL (Dql) level, by adding an -orderBy('t.name') to the query: $q = Doctrine::getTable('Foo') ->createQuery('f') ->leftJoin('f.Translation t') ->orderBy('t.name') But here come the troubles: the list gets not sorted correctly, regardless of the active culture. I get rather better results when I limit the translations to the active culture, like this: ->leftJoin('f.Translation t WITH lang = ?', $request->getParameter('sf_culture'); Then the sorting is correct, as far as all the translations exist for the active culture. If a translation does not exist and I have to take the name from the fallback language, the record will be displayed at the very beginning of the list (I understand this happens because the value for the current culture is null). My question is: is there a best practice for getting internationalized fields (needing fallbacks) sorted correctly with doctrine and sfDoctrinePager? Thank you in advance.

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  • SQL Server Index cost

    - by yellowstar
    I have read that one of the tradeoffs for adding table indexes in SQL Server is the increased cost of insert/update/delete queries to benefit the performance of select queries. I can conceptually understand what happens in the case of an insert because SQL Server has to write entries into each index matching the new rows, but update and delete are a little more murky to me because I can't quite wrap my head around what the database engine has to do. Let's take DELETE as an example and assume I have the following schema (pardon the pseudo-SQL) TABLE Foo col1 int ,col2 int ,col3 int ,col4 int PRIMARY KEY (col1,col2) INDEX IX_1 col3 INCLUDE col4 Now, if I issue the statement DELETE FROM Foo WHERE col1=12 AND col2 > 34 I understand what the engine must do to update the table (or clustered index if you prefer). The index is set up to make it easy to find the range of rows to be removed and do so. However, at this point it also needs to update IX_1 and the query that I gave it gives no obvious efficient way for the database engine to find the rows to update. Is it forced to do a full index scan at this point? Does the engine read the rows from the clustered index first and generate a smarter internal delete against the index? It might help me to wrap my head around this if I understood better what is going on under the hood, but I guess my real question is this. I have a database that is spending a significant amount of time in delete and I'm trying to figure out what I can do about it. When I display the execution plan for the deletion, it just shows an entry for "Clustered Index Delete" on table Foo which lists in the details section the other indices that need to be updated but I don't get any indication of the relative cost of these other indices. Are they all equal in this case? Is there some way that I can estimate the impact of removing one or more of these indices without having to actually try it?

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