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  • Optimize slow ranking query

    - by Juan Pablo Califano
    I need to optimize a query for a ranking that is taking forever (the query itself works, but I know it's awful and I've just tried it with a good number of records and it gives a timeout). I'll briefly explain the model. I have 3 tables: player, team and player_team. I have players, that can belong to a team. Obvious as it sounds, players are stored in the player table and teams in team. In my app, each player can switch teams at any time, and a log has to be mantained. However, a player is considered to belong to only one team at a given time. The current team of a player is the last one he's joined. The structure of player and team is not relevant, I think. I have an id column PK in each. In player_team I have: id (PK) player_id (FK -> player.id) team_id (FK -> team.id) Now, each team is assigned a point for each player that has joined. So, now, I want to get a ranking of the first N teams with the biggest number of players. My first idea was to get first the current players from player_team (that is one record top for each player; this record must be the player's current team). I failed to find a simple way to do it (tried GROUP BY player_team.player_id HAVING player_team.id = MAX(player_team.id), but that didn't cut it. I tried a number of querys that didn't work, but managed to get this working. SELECT COUNT(*) AS total, pt.team_id, p.facebook_uid AS owner_uid, t.color FROM player_team pt JOIN player p ON (p.id = pt.player_id) JOIN team t ON (t.id = pt.team_id) WHERE pt.id IN ( SELECT max(J.id) FROM player_team J GROUP BY J.player_id ) GROUP BY pt.team_id ORDER BY total DESC LIMIT 50 As I said, it works but looks very bad and performs worse, so I'm sure there must be a better way to go. Anyone has any ideas for optimizing this? I'm using mysql, by the way. Thanks in advance Adding the explain. (Sorry, not sure how to format it properly) id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY t ALL PRIMARY NULL NULL NULL 5000 Using temporary; Using filesort 1 PRIMARY pt ref FKplayer_pt77082,FKplayer_pt265938,new_index FKplayer_pt77082 4 t.id 30 Using where 1 PRIMARY p eq_ref PRIMARY PRIMARY 4 pt.player_id 1 2 DEPENDENT SUBQUERY J index NULL new_index 8 NULL 150000 Using index

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  • Maven version auto-pom.xml

    - by nkuma001
    Can anyone explain me if the version is specified as auto as mentioned below for the dependecies auto how does it get resolved to the latest from the maven repository? I see that some file when mvn exectutes an temporary file called auto-pom.xml is generated where all the auto is replaced with proper latest revisions from my repository like 1.0-SNAPSHOT

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  • Why One-to-one relationship dosen't work?

    - by eugenn
    I'm trying to create a very simple relationship between two objects. Can anybody explain me why I can't find the Company object via findBy method? class Company { String name String desc City city static constraints = { city(unique: true) } } class City { String name static constraints = { } } class BootStrap { def init = { servletContext -> new City(name: 'Tokyo').save() new City(name: 'New York').save() new Company(name: 'company', city: City.findByName('New York')).save() def c = Company.findByName('company') // Why c=null????! } def destroy = { } }

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  • How to rectify this issues: asp.net PageRequestManagerParserErrorException

    - by sameer
    i have a search panel where on click of search button im getting this exception this is for the first time, subsequent click it result the proper result. Can any one explain how solve the issue. error message: Sys.WebForms.PageRequestManagerParserErrorException: The Message received from the server could not be parsed.Coommon causes for this error are when the response is modified by Calls to Repose.Write(), response filters,HttpModules, or server trace is enabled. Details:Error Parsing near ' | '.

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  • What is mod_php...?

    - by SpikETidE
    Hi everybody... First of all, Pardon this complete n00b question... While going through the zend tutorial here i came across the following statement... Note that the php_flag settings in .htaccess only work if you are using mod_php. Can someone explain what that means...??? Thanks and Regards....

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  • what should be the return type of the hashCode()

    - by subhashis
    The signature of the hashCode() method is public int hashCode(){ return x; } in this case x must be an int(primitive) but plz can anyone explain it to me that the number which the hashCode() returns must be a prime number, even number...etc or there is no specification ? the reason behind i am asking this question is i have seen it in different ids the auto generated code always returns a prime number, so i need to know why? thanks in advance

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  • What will we use Theory Attribute for ?

    - by Sandbox
    I discovered [Theory] and [Datapoint] attributes in NUnit. I am not very sure about how should I use these. I think they can be used for data-driven testing and this has got me interested. There aren't many resources available on the same. Can someone explain to me how to use them or point me to resources? Thanks.

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  • How to display data into datagridview using multi thread?

    - by Mark
    Hi, I have application where I read/receive data all the time (text) and I need to display this data into datagridview, what is the best way to do that in real time, so the data will be changed all the time. I thought about multi threading, if this is a good idea can you guide me with link to explain how to implement it. Thanks

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  • What is Caliburn Validation abstraction

    - by Chen Kinnrot
    Recently I saw this document that specify how great is Caliburn(Not really it compares it to the micro framework, and thats enough). I'm working with Caliburn for more than a year and don't know many things about it. So maybe someone can explain the following(Some of it I can understand but have no iea about the relation to caliburn): Validation abstraction module framework ExpressionTree-Based runtime delegate generation ViewModelFactory ShellFramework I'm working with V1.1 so if something is new in 2.0, just say it belong to the new version I'll learn it probably in the future.

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  • Android Calendar API vs Calendar Provider API

    - by John Roberts
    I'm a little bit confused about the difference between the two. An example of the Calendar API is supposedly located here: http://samples.google-api-java-client.googlecode.com/hg/calendar-android-sample/instructions.html, but the author himself suggests using the Calendar Provider API, details about which are here: http://developer.android.com/guide/topics/providers/calendar-provider.html. Can someone explain to me the difference between the two, and which would be better for me to use for a simple calendar app?

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  • ASP.NET - Update progress while processing data

    - by Danny
    Hope I can explain this correctly. I have a process, that outputs step by step messages (i.e., Processing item 1... Error in item 2 etc etc). I want this to be outputted to the user during the process, and not at the end. I pretty sure i need to do this with threading, but can't find a decent example. Thanks in advanced.

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  • Meaning of message "operations coalesced during safepoint"

    - by elec
    A java app runs with the following flag: -XX:+PrintSafepointStatistics, and then produces the following line on the standard output console: 2 VM operations coalesced during safepoint Anyone cares to explain what this mean ? More generally - is there a Java reference manual somewhere detailling all JVM flags, their use and, most importantly, the expected output, with relevant explanations ?

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  • Why can I set an anonymous enum equal to another in C but not C++?

    - by samoz
    I have the following code snippet: enum { one } x; enum { two } y; x = y; That will compile in C, but in C++, I get the following error: test.c:6: error: cannot convert ‘main()::<anonymous enum>’ to ‘main()::<anonymous enum>’ in assignment Can someone explain to me why this is happening? I would prefer an answer with some specifics about why the compiler behaves this way, rather than just "You can't do that"

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  • Playing a .WAV file in .NET

    - by Mori
    I'm trying to write a SAMPLER program, where each key has a different sound (a WAV file). Can someone explain to me or give me a link to an explanation where i can learn how to play the WAV files? If it matters, I'm working with Microsoft Visual C# and using WinForms.

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  • jQuery noob: change border color of element on hover of another element.

    - by Kyle Sevenoaks
    I'd try to explain what I mean, but there is an easier way: click here for jsfiddle example. Basically I want the border color of the div rfrsh_btn to change when productOptionsMenu is hovered over. I'm using jQuery with the .noConflict var because this site also uses Prototype. jQuery: var $j = jQuery.noConflict(); $j(".productOptionsMenu").hover( function () { $j(#rfrsh_btn).css({"border-color":"#85c222"}); }; ); Thanks :)

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