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  • Easy way to observe user activity - how improve my database structure.

    - by Thomas
    Welcome, I need some advise to improve perfomence my web application. In the begin I had this structure of database: USER -id (Primary Key) -name -password -email .... PROFILE -user Primary Key, Foreign Key (USER) -birthday -region -photoFile ... PAGES -id (Primary Key) -user Foreign Key(USER) -page -date COMMENTS -id (Primary Key) -user Foreign Key(USER) -page Foreign Key(PAGE) -comment -date FAVOURITES_PAGES -id (Primary Key) -user Foreign Key(USER) -favourite_page Foreign Key(PAGE) -date but now one of the most important page of website is observatory, when everyone can observe activity others users. So I need select all pages, comments and favourites pages some users and display it in one list, sorted by date. For better perfomance (I think) I changed my structure to this: table USER and PROFILE without changes ACTIVITY (additional table- have common fields: user,date) -id (Primary Key) -user Foreign Key(USER) -date -page Foreign Key(PAGE) -comment Foreign Key(COMMENTS) -favourite_page Foreign Key(FAVOURITES_PAGES) PAGES -id (Primary Key) -page COMMENTS -id (Primary Key) -page Foreign Key(PAGE) -comment FAVOURITES_PAGES -id (Primary Key) -favourite_page Foreign Key(PAGE) So now it is very easy get sorted records from all tables. But I have no only foreign key to PAGES, COMMENTS and FAVOURITES_PAGES in ACTIVITY table - there is about ten Foreign Key fields and in one record only one have value, others have None: ACTIVITY id user date page comment ... 1 2 2010-02-23 None 1 2 1 2010-02-21 1 None .... It is corect solution. When I display about 40 records in one page (pagination) I must wait about one secound, but database is almost emty (a few users and about 100 records in others tables). It is depends on amount records per page - I have checked it, but why it takes too long time, becouse of relationships? The website is built in Python/Django. Any advices/opinion?

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  • Simple Select Statement on MySQL Database Hanging

    - by AlishahNovin
    I have a very simple sql select statement on a very large table, that is non-normalized. (Not my design at all, I'm just trying to optimize while simultaneously trying to convince the owners of a redesign) Basically, the statement is like this: SELECT FirstName, LastName, FullName, State FROM Activity Where (FirstName=@name OR LastName=@name OR FullName=@name) AND State=@state; Now, FirstName, LastName, FullName and State are all indexed as BTrees, but without prefix - the whole column is indexed. State column is a 2 letter state code. What I'm finding is this: When @name = 'John Smith', and @state = '%' the search is really fast and yields results immediately. When @name = 'John Smith', and @state = 'FL' the search takes 5 minutes (and usually this means the web service times out...) When I remove the FirstName and LastName comparisons, and only use the FullName and State, both cases above work very quickly. When I replace FirstName, LastName, FullName, and State searches, but use LIKE for each search, it works fast for @name='John Smith%' and @state='%', but slow for @name='John Smith%' and @state='FL' When I search against 'John Sm%' and @state='FL' the search finds results immediately When I search against 'John Smi%' and @state='FL' the search takes 5 minutes. Now, just to reiterate - the table is not normalized. The John Smith appears many many times, as do many other users, because there is no reference to some form of users/people table. I'm not sure how many times a single user may appear, but the table itself has 90 Million records. Again, not my design... What I'm wondering is - though there are many many problems with this design, what is causing this specific problem. My guess is that the index trees are just too large that it just takes a very long time traversing the them. (FirstName, LastName, FullName) Anyway, I appreciate anyone's help with this. Like I said, I'm working on convincing them of a redesign, but in the meantime, if I someone could help me figure out what the exact problem is, that'd be fantastic.

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  • How to add 1 to the value of a column of an existing row in mysql

    - by mithun1538
    Hello everyone, I have a table called pollData. It will always contain only 1 row. It has columns option1, option2, option3, option4, option5 each of type int. In the beginning, these columns have 0 as their value. How do I add 1 to any column, say option2? I mean do i retrieve the value of that column first, perform addition, and store back, or is there any auto increment function?

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  • Best way to retrieve certain field of all documents returned by a lucen search

    - by Philipp
    Hi, I was wondering what the best way is to retrieve a certain field of all documents returned by a Searcher of Lucene. Background: each document has a date field (written on) and I would like to show a timeline of all found documents, so I need to extract the date (day) field of all the documents I find with the search. I currently retrieve every document using Searcher.doc(int, FieldSelector) having the selector only retrieve the certain field. I have indexed 250k documents, the search itself takes no time and returns about 10k document ids. Retrieving those however, takes 20+ seconds. What can I do to speed things up, but still get all the values I need. Thx in advance Philipp

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  • Efficient alternative to merge() when building dataframe from json files with R?

    - by Bryan
    I have written the following code which works, but is painfully slow once I start executing it over thousands of records: require("RJSONIO") people_data <- data.frame(person_id=numeric(0)) json_data <- fromJSON(json_file) n_people <- length(json_data) for(lender in 1:n_people) { person_dataframe <- as.data.frame(t(unlist(json_data[[person]]))) people_data <- merge(people_data, person_dataframe, all=TRUE) } output_file <- paste("people_data",".csv") write.csv(people_data, file=output_file) I am attempting to build a unified data table from a series of json-formated files. The fromJSON() function reads in the data as lists of lists. Each element of the list is a person, which then contains a list of the attributes for that person. For example: [[1]] person_id name gender hair_color [[2]] person_id name location gender height [[...]] structure(list(person_id = "Amy123", name = "Amy", gender = "F", hair_color = "brown"), .Names = c("person_id", "name", "gender", "hair_color")) structure(list(person_id = "matt53", name = "Matt", location = structure(c(47231, "IN"), .Names = c("zip_code", "state")), gender = "M", height = 172), .Names = c("person_id", "name", "location", "gender", "height")) The end result of the code above is matrix where the columns are every person-attribute that appears in the structure above, and the rows are the relevant values for each person. As you can see though, some data is missing for some of the people, so I need to ensure those show up as NA and make sure things end up in the right columns. Further, location itself is a vector with two components: state and zip_code, meaning it needs to be flattened to location.state and location.zip_code before it can be merged with another person record; this is what I use unlist() for. I then keep the running master table in people_data. The above code works, but do you know of a more efficient way to accomplish what I'm trying to do? It appears the merge() is slowing this to a crawl... I have hundreds of files with hundreds of people in each file. Thanks! Bryan

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  • Is there a simple way to convert MySQL data into Title Case?

    - by john.designop.us
    I have a MySQL table where all the data in one column was entered in UPPERCASE, but I need to convert in to Title Case, with recognition of "small words" akin to the Daring Fireball Title Case script. I found this excellent solution for transforming strings to lowercase, but the Title Case function seems to have been left out of my version of MySQL. Is there an elegant way to do this?

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  • Why isnt this returning the new string?

    - by Evan Kimia
    I have a recursive method that reversed a string (HW assignment, has to be recursive). I did it....but its only returning the value of the string after the first pass. By analyzing the output after each pass i can see it does do its job correctly. heres my code, and the output i get below it: String s = "Hello, I love you wont you tell me your name?"; int k=0; public String reverseThisString(String s) { if(k!=s.length()) { String first =s.substring(0,k)+s.charAt(s.length()-1); String end = ""+s.substring(k, s.length()-1); k++; s=first+end; System.out.println(s); this.reverseThisString(s); } return s; } output: ?Hello, I love you wont you tell me your name

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  • mysql error in php

    - by fusion
    i'm trying to run this php code which should display a quote from mysql, but can't figure out where is it going wrong. the result variable is null or empty. can someone help me out. thanks! <?php include 'config.php'; // 'text' is the name of your table that contains // the information you want to pull from $rowcount = mysql_query("select count(*) as rows from quotes"); // Gets the total number of items pulled from database. while ($row = mysql_fetch_assoc($rowcount)) { $max = $row["rows"]; //print_r ($max); } // Selects an item's index at random $rand = rand(1,$max)-1; print_r ($rand); $result = mysql_query("select * from quotes limit $rand, 1") or die ('Error: '.mysql_error()); if (!$result or mysql_num_rows($result)) { echo "Empty"; } else{ while ($row = mysql_fetch_array($result)) { $randomOutput = $row['cQuotes']; echo '<p>' . $randomOutput . '</p>'; } }

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  • stopwatch accuracy

    - by oo
    How accurate is System.Diagnostics.Stopwatch? I am trying to do some metrics for different code paths and I need it to be exact. Should I be using stopwatch or is there another solution that is more accurate. I have been told that sometimes stopwatch gives incorrect information.

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  • Why is numpy's einsum faster than numpy's built in functions?

    - by Ophion
    Lets start with three arrays of dtype=np.double. Timings are performed on a intel CPU using numpy 1.7.1 compiled with icc and linked to intel's mkl. A AMD cpu with numpy 1.6.1 compiled with gcc without mkl was also used to verify the timings. Please note the timings scale nearly linearly with system size and are not due to the small overhead incurred in the numpy functions if statements these difference will show up in microseconds not milliseconds: arr_1D=np.arange(500,dtype=np.double) large_arr_1D=np.arange(100000,dtype=np.double) arr_2D=np.arange(500**2,dtype=np.double).reshape(500,500) arr_3D=np.arange(500**3,dtype=np.double).reshape(500,500,500) First lets look at the np.sum function: np.all(np.sum(arr_3D)==np.einsum('ijk->',arr_3D)) True %timeit np.sum(arr_3D) 10 loops, best of 3: 142 ms per loop %timeit np.einsum('ijk->', arr_3D) 10 loops, best of 3: 70.2 ms per loop Powers: np.allclose(arr_3D*arr_3D*arr_3D,np.einsum('ijk,ijk,ijk->ijk',arr_3D,arr_3D,arr_3D)) True %timeit arr_3D*arr_3D*arr_3D 1 loops, best of 3: 1.32 s per loop %timeit np.einsum('ijk,ijk,ijk->ijk', arr_3D, arr_3D, arr_3D) 1 loops, best of 3: 694 ms per loop Outer product: np.all(np.outer(arr_1D,arr_1D)==np.einsum('i,k->ik',arr_1D,arr_1D)) True %timeit np.outer(arr_1D, arr_1D) 1000 loops, best of 3: 411 us per loop %timeit np.einsum('i,k->ik', arr_1D, arr_1D) 1000 loops, best of 3: 245 us per loop All of the above are twice as fast with np.einsum. These should be apples to apples comparisons as everything is specifically of dtype=np.double. I would expect the speed up in an operation like this: np.allclose(np.sum(arr_2D*arr_3D),np.einsum('ij,oij->',arr_2D,arr_3D)) True %timeit np.sum(arr_2D*arr_3D) 1 loops, best of 3: 813 ms per loop %timeit np.einsum('ij,oij->', arr_2D, arr_3D) 10 loops, best of 3: 85.1 ms per loop Einsum seems to be at least twice as fast for np.inner, np.outer, np.kron, and np.sum regardless of axes selection. The primary exception being np.dot as it calls DGEMM from a BLAS library. So why is np.einsum faster that other numpy functions that are equivalent? The DGEMM case for completeness: np.allclose(np.dot(arr_2D,arr_2D),np.einsum('ij,jk',arr_2D,arr_2D)) True %timeit np.einsum('ij,jk',arr_2D,arr_2D) 10 loops, best of 3: 56.1 ms per loop %timeit np.dot(arr_2D,arr_2D) 100 loops, best of 3: 5.17 ms per loop The leading theory is from @sebergs comment that np.einsum can make use of SSE2, but numpy's ufuncs will not until numpy 1.8 (see the change log). I believe this is the correct answer, but have not been able to confirm it. Some limited proof can be found by changing the dtype of input array and observing speed difference and the fact that not everyone observes the same trends in timings.

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  • LINQ - How to query a range of effective dates that only has start dates

    - by itchi
    I'm using C# 3.5 and EntityFramework. I have a list of items in the database that contain interest rates. Unfortunately this list only contains the Effective Start Date. I need to query this list for all items within a range. However, I can't see a way to do this without querying the database twice. (Although I'm wondering if delayed execution with EntityFramework is making only one call.) Regardless, I'm wondering if I can do this without using my context twice. internal IQueryable<Interest> GetInterests(DateTime startDate, DateTime endDate) { var FirstDate = Context.All().Where(x => x.START_DATE < startDate).Max(x => x.START_DATE); IQueryable<Interest> listOfItems = Context.All().Where(x => x.START_DATE >= FirstDate && x.START_DATE <= endDate); return listOfItems; }

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  • error while loadin applet in web application

    - by pallavi
    I want to run my applet on web application, but i got some error which i mentioned below please help me to get out of this problem ============================================================================================= Java Plug-in 1.7.0 Using JRE version 1.7.0-ea-b116 Java HotSpot(TM) Client VM User home directory = C:\Users\HONEY c: clear console window f: finalize objects on finalization queue g: garbage collect h: display this help message l: dump classloader list m: print memory usage o: trigger logging q: hide console r: reload policy configuration s: dump system and deployment properties t: dump thread list v: dump thread stack x: clear classloader cache 0-5: set trace level to java.lang.RuntimeException: java.lang.NoClassDefFoundError: mp3$1 at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Caused by: java.lang.NoClassDefFoundError: mp3$1 at mp3.(mp3.java:93) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at java.lang.Class.newInstance0(Unknown Source) at java.lang.Class.newInstance(Unknown Source) at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source) at java.awt.event.InvocationEvent.dispatch(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source) Caused by: java.lang.ClassNotFoundException: mp3$1 at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) ... 16 more Caused by: java.io.IOException: open HTTP connection failed:http://viscous10.webng.com/mp3/mp3$1.class at sun.plugin2.applet.Applet2ClassLoader.getBytes(Unknown Source) at sun.plugin2.applet.Applet2ClassLoader.access$000(Unknown Source) at sun.plugin2.applet.Applet2ClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) ... 21 more Exception: java.lang.RuntimeException: java.lang.NoClassDefFoundError: mp3$1 ========================================================================================== but it happens only if i run applet with events and in simple applet i never occurred thanx

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  • Why are my basic Heroku Apps Taking 2 seconds to load?

    - by viatropos
    I have created two very simple heroku apps to test out the service, but it's often taking several seconds to load the page when I first visit them: Cropify - Basic Sinatra App (on github) Textile2HTML - Even more basic Sinatra App (on github) All I did was create a simple sinatra app and deploy it. I haven't done anything to mess with or test the heroku servers. What can I do to improve response time? It's very slow right now and I'm not sure where to start. The code for the projects are on github if that helps. Thanks so much.

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  • Fast modulo 3 or division algorithm?

    - by aaa
    Hello is there a fast algorithm, similar to power of 2, which can be used with 3, i.e. n%3. Perhaps something that uses the fact that if sum of digits is divisible by three, then the number is also divisible. This leads to a next question. What is the fast way to add digits in a number? I.e. 37 - 3 +7 - 10 I am looking for something that does not have conditionals as those tend to inhibit vectorization thanks

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  • Spring 2.5 Hibernate 3.5 NamedQuery

    - by EugeneP
    I do not use HibernateTemplate, but work with getCurrentSession() in my DAO. I would like to know how to declare Hibernate named queries in a beans.xml file (I do not use hbm.xml). And maybe Spring has alternative means to declare Hibernate named queries?

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  • Can MySQL Nested Select return list of results

    - by John
    Hi I want to write a mysql statement which will return a list of results from one table along with a comma separated list of field from another table. I think an example might better explain it Table 1 ======================== id First_Name Surname ---------------------- 1 Joe Bloggs 2 Mike Smith 3 Jane Doe Table 2 ======================== id Person_Id Job_id --------------------- 1 1 1 2 1 2 3 2 2 4 3 3 5 3 4 I want to return a list of people with a comma separated list of job_ids. So my result set would be id First_Name Surname job_id ------------------------------ 1 Joe Bloggs 1,2 2 Mike Smith 2 3 Jane Doe 3,4 I guess the sql would be something like select id, First_Name, Surname, (SELECT job_id FROM Table 2) as job_id from Table 1 but obviously this does not work so need to change the '(SELECT job_id FROM Table 2) as job_id' part. Hope this makes sense Thanks John

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  • Update last child id in parent table using mysql

    - by Sam Saffron
    Given the following tables: Topic id, last_updated_child_id Response id, topic_id, updated_at How do I update the Topic table so the last_updated_child_id is equal to the latest response id (based on date). So for example given: Topic id last_updated_child_id -- ----------------------- 1 null 2 null 3 null Response id topic_id updated_at -- ---- ---- 1 1 2010 2 1 2012 3 1 2011 4 2 2000 I would like to execute an UPDATE statement that would result in the Topic table being: id last_updated_child_id -- ----------------------- 1 2 2 4 3 null Note: I would like to avoid temp tables if possible and am happy for a MySQL specific solution.

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  • Sitecollection Overview Page

    - by ronischuetz
    I have the following situation: MOSS 2007 Server Environment A - Intranet MOSS 2007 Server Environment B - Collaboration Environment (approx. 150 site collections for various issues) Both environments are on different infrastructures but we use the same Active Directory and the same groups. Now we would like to implement the following 2 things: An overview page within the intranet with all available site collections on environment b. An overview page within the intranet with only those site collections the user has access on. now i'm searching for some good ideas what would be the best way to realise something like this. thanks in advance for any response.

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  • Rendering spatial data of GeoQuerySet in a custom view on GeoDjango

    - by dmytro
    Hello. I have just started my first project on GeoDjango. As a matter of fact, with GeoDjango powered Admin application we all have a great possibility to view/edit spatial data, associated with the current object. The problem is that after the objects having been populated I need to render several objects' associated geometry at once on a single map. I might implement it as a model action, redirecting to a custom view. I just don't know, how to include the OpenLayers widget in the view and how to render there my compound geometry from my GeoQuerySet. I would be very thankful for any hint from an experienced GeoDjango programmer.

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  • How to speed up marching cubes?

    - by Dan Vinton
    I'm using this marching cube algorithm to draw 3D isosurfaces (ported into C#, outputting MeshGeomtry3Ds, but otherwise the same). The resulting surfaces look great, but are taking a long time to calculate. Are there any ways to speed up marching cubes? The most obvious one is to simply reduce the spatial sampling rate, but this reduces the quality of the resulting mesh. I'd like to avoid this. I'm considering a two-pass system, where the first pass samples space much more coarsely, eliminating volumes where the field strength is well below my isolevel. Is this wise? What are the pitfalls? Edit: the code has been profiled, and the bulk of CPU time is split between the marching cubes routine itself and the field strength calculation for each grid cell corner. The field calculations are beyond my control, so speeding up the cubes routine is my only option... I'm still drawn to the idea of trying to eliminate dead space, since this would reduce the number of calls to both systems considerably.

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  • T-SQL How To: Compare and List Duplicate Entries in a Table

    - by Dan7el
    SQL Server 2000. Single table has a list of users that includes a unique user ID and a non-unique user name. I want to search the table and list out any users that share the same non-unique user name. For example, my table looks like this: ID User Name Name == ========= ==== 0 parker Peter Parker 1 parker Mary Jane Parker 2 heroman Joseph (Joey) Carter Jones 3 thehulk Bruce Banner What I want to do is do a SELECT and have the result set be: ID User Name Name == ========= ==== 0 parker Peter Parker 1 parker Mary Jane Parker from my table. I'm not a T-SQL guru. I can do the basic joins and such, but I'm thinking there must be an elegant way of doing this. Barring elegance, there must be ANY way of doing this. I appreciate any methods that you can help me with on this topic. Thanks! ---Dan---

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  • SQL Server high CPU and I/O activity database tuning

    - by zapping
    Our application tends to be running very slow recently. On debugging and tracing found out that the process is showing high cpu cycles and SQL Server shows high I/O activity. Can you please guide as to how it can be optimised? The application is now about an year old and the database file sizes are not very big or anything. The database is set to auto shrink. Its running on win2003, SQL Server 2005 and the application is a web application coded in c# i.e vs2005

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  • Is regex too slow? Real life examples where simple non-regex alternative is better

    - by polygenelubricants
    I've seen people here made comments like "regex is too slow!", or "why would you do something so simple using regex!" (and then present a 10+ lines alternative instead), etc. I haven't really used regex in industrial setting, so I'm curious if there are applications where regex is demonstratably just too slow, AND where a simple non-regex alternative exists that performs significantly (maybe even asymptotically!) better. Obviously many highly-specialized string manipulations with sophisticated string algorithms will outperform regex easily, but I'm talking about cases where a simple solution exists and significantly outperforms regex. What counts as simple is subjective, of course, but I think a reasonable standard is that if it uses only String, StringBuilder, etc, then it's probably simple.

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