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  • Processing large recordsets in Rails

    - by japancheese
    Hello, I'm trying to perform a daily operation on a larger than normal dataset (2m+ records). However, Rails seems to take a very long time performing operations on such a dataset. Operations like Dataset.all.each do |data| ... end take a very long time to complete (I assume this is because it can't fit all the items into memory at once, right?). Does anyone have any strategies on how I could handle this situation? I know SQL would probably speed up the process, but I'm looking to use the Rails environment as I can do many more complicated things to the data than I can with just SQL statements.

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  • MySQL multiple dependent subqueries, painfully slow

    - by matt80
    I have a working query that retrieves the data that I need, but unfortunately it is painfully slow (runs over 3 minutes). I have indexes in place, but I think the problem is the multiple dependent subqueries. I've been trying to rewrite the query using joins but I can't seem to get it to work. Any help would be greatly appreciated. The tables: Basically, I have 2 tables. The first (prices) holds the prices of items in a store. Each row is the price of an item that day, and new rows are added every day with an updated price. The second table (watches_US) holds the item information (name, description, etc). CREATE TABLE `prices` ( `prices_id` int(11) NOT NULL auto_increment, `prices_locale` enum('CA','DE','FR','JP','UK','US') NOT NULL default 'US', `prices_watches_ID` char(10) NOT NULL, `prices_date` datetime NOT NULL, `prices_am` varchar(10) default NULL, `prices_new` varchar(10) default NULL, `prices_used` varchar(10) default NULL, PRIMARY KEY (`prices_id`), KEY `prices_am` (`prices_am`), KEY `prices_locale` (`prices_locale`), KEY `prices_watches_ID` (`prices_watches_ID`), KEY `prices_date` (`prices_date`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=61764 ; CREATE TABLE `watches_US` ( `watches_ID` char(10) NOT NULL, `watches_date_added` datetime NOT NULL, `watches_last_update` datetime default NULL, `watches_title` varchar(255) default NULL, `watches_small_image_height` int(11) default NULL, `watches_small_image_width` int(11) default NULL, `watches_description` text, PRIMARY KEY (`watches_ID`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; The query retrieves the last 10 prices changes over a period of 30 hours, ordered by the size of the price change. So I have subqueries to get the newest price, the oldest price within 30 hours, and then to calculate the price change. Here's the query: SELECT watches_US.*, prices.*, watches_US.watches_ID as current_ID, ( SELECT prices_am FROM prices WHERE prices_watches_ID = current_ID AND prices_locale = 'US' ORDER BY prices_date DESC LIMIT 1 ) as new_price, ( SELECT prices_date FROM prices WHERE prices_watches_ID = current_ID AND prices_locale = 'US' ORDER BY prices_date DESC LIMIT 1 ) as new_price_date, ( SELECT prices_am FROM prices WHERE ( prices_watches_ID = current_ID AND prices_locale = 'US') AND ( prices_date >= DATE_SUB(new_price_date,INTERVAL 30 HOUR) ) ORDER BY prices_date ASC LIMIT 1 ) as old_price, ( SELECT ROUND(((new_price - old_price)/old_price)*100,2) ) as percent_change, ( SELECT (new_price - old_price) ) as absolute_change FROM watches_US LEFT OUTER JOIN prices ON prices.prices_watches_ID = watches_US.watches_ID WHERE ( prices_locale = 'US' ) AND ( prices_am IS NOT NULL ) AND ( prices_am != '' ) HAVING ( old_price IS NOT NULL ) AND ( old_price != 0 ) AND ( old_price != '' ) AND ( absolute_change < 0 ) AND ( prices.prices_date = new_price_date ) ORDER BY absolute_change ASC LIMIT 10 How would I rewrite this to use joins instead, or otherwise optimize this so it doesn't take over 3 minutes to get a result? Any help would be greatly appreciated! Thank you kindly.

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  • Multimap Space Issue: Guava

    - by Arpssss
    In my Java code, I am using Guavas Multimap (com.google.common.collect.Multimap) by using this: Multimap< Integer, Integer Index = HashMultimap.create() Here, Multimap key is some portion of URL and value is another portion of URL (converted into integer). Now, I assign my JVM 2560 Mb (2.5 GB) heap space (by using Xmx and Xms). However, it can only store 9 millions of such (key,value) pairs of integers (approx 10 million). But, theoretically (according to memory occupied by int) it should store more. Can anybody help me, 1) Why is this happening (means Multimap is taking lots of space) ? I checked my code with out inserting pairs in Multimap, it takes only 1/2 MB space. 2) Is there any other way or home-baked solution to solve this space issue ? More clearly, how to solve this memory issue ? Thanks in advance and any idea is perfectly OK for me.

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  • Synchronizing MySQL databases

    - by Wasim
    Hi all, I have a maintanance problem synchronizing my MySQL data bases . These are the databases I have : My development DB : Here I make my curret development changes . Staging DB : I need to make all the changes I did in the development on it before using , currently I hold migration scripts for structure and data. Production DB : A production environment . Have to do exacly the same as the staging . My problem , is sync. the structure , and some of the data. This is really a very hard work to maintaine. Is there any technics , tools to do with MySQL . What is replication , is it good for my situation , how to use it . Thanks in advance ...

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  • When is porting data from MySQL to CouchDB NOT advisable? Seeking cautionary tales

    - by dan
    I've dabbled in CouchDB and I have pretty good MySQL experience. I've also created one production application that uses both. I like MySQL but I've run into scaling/concurrency issues with MySQL that CouchDB advertises itself as a general solution for. The problem is that I have MySQL based applications that are pretty huge, and I don't really know whether it would be a good idea or not to try to port them over to a CouchDB datastore. I don't want to put in a lot of time and effort only to find out that my application is really not a good fit for CouchDB. Is there any sort of informed consensus on when porting a MySQL based app to CouchDB is NOT advisable? Any cautionary tales? I think CouchDB is really cool and want to use it more. I'd also like to know ahead of time what specific types of data querying scenarios CouchDB is really not good for, or if CouchDB can really replace MySQL for all the applications I create going forward.

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  • Get information from various sources

    - by Francesc
    Hi. I'm developing an app that has to get some information from various sources (APIs and RSS) and display it to the user in near real-time. What's the best way to get it: 1.Have a cron job to update them all accounts every 12h, and when a user is requesting one, update that account, save it to the DB and show it to the user? 2.Have a cron job to update them all accounts every 6h, and when a user is requesting one, update the account and showing it to the user without saving it to the DB? What's the best way to get it? What's faster? And what's the most scallable?

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  • Can't fill a column of NULLs with actual values by making an association to the proper values in the

    - by UkraineTrain
    I have a table with separate columns for months, days and a varchar column for 6 hour increments for each day ('12AM', '6AM', '12PM', '6PM'). There's also a column that's supposed to have calculated numeric values for each of those 6 hour increments. These calculated values come from some reference table. This reference table contains values for each day for several months broken down by hour where each hour has its own column. So, basically, I have to add the values for each 6 hour increment. I have no idea how to associate the correct values in the reference table to those 6 hour increments. I will really appreciate any help on this.

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  • Any tools or techniques for validating constraints programmatically between databases?

    - by Brandon
    If you had two databases, that had two tables between them that would normally implement a one to one (or many to many) constraint but cannot since they are separate databases, how would you validate this relationship in an application or test? Is there a simple way to do this? For example, a tool or technique that can, given a constraint type, tables and fields, does the validation. I imagine that this isn't the first time this come up so I'm hoping people can share their solution. Thanks.

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  • Amazon S3: allow users to upload on a restricted basis (per bucket maybe)?

    - by Tom
    Hi there, I'm thinking about signing up to the Amazon S3 storage service. What I want to do is create a service where other people can register their own bucket with a certain amount of storage. These users will install my software, which then uploads their files. Of course, the users may only upload what they have paid for. For this to work I would like to create a separate bucket for each customer, each with its own properties. Question 1: is this possible with the API? How? This means that the installed software must have the rights needed to upload to my Amazon S3 account. Question 2: can I create individual authentication IDs for each bucket or customer, so that they can only upload with restrictions I have set? Thanks in advance.

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  • em.createQuery keeps returning null

    - by Developer106
    I have this application which i use JSF 2.0 and EclipseLink, i have entities created for a database made in MySQL, Created these entities using netbeans 7.1.2, it gets created automaticly. Then i use session beans to work with these entities, the thing is the em.createQuery always returns a null, though I checked NamedQueries in the entities and they perfectly match a sample from the entities named queries:- @NamedQueries({ @NamedQuery(name = "Users.findAll", query = "SELECT u FROM Users u"), @NamedQuery(name = "Users.findByUserId", query = "SELECT u FROM Users u WHERE u.userId = :userId"), @NamedQuery(name = "Users.findByUsername", query = "SELECT u FROM Users u WHERE u.username = :username"), @NamedQuery(name = "Users.findByEmail", query = "SELECT u FROM Users u WHERE u.email = :email"), notice how i use this findByEmail query in the session bean :- public Users findByEmail(String email){ em.getTransaction().begin(); String find = "Users.findByEmail"; Query query = em.createNamedQuery(find); query.setParameter("email", email); Users user = (Users) query.getSingleResult(); but it always returns null from this em.createNamedQuery, i tried using .createQuery first but it also was no good. the stacktrace of the exception Caused by: java.lang.NullPointerException at com.readme.entities.sessionBeans.UsersFacade.findByEmail(UsersFacade.java:48) at com.readme.user.signup.SignupBean.checkAvailability(SignupBean.java:137) at com.readme.user.signup.SignupBean.save(SignupBean.java:146) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) What Seems To Be The Problem Here ?

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  • If I take a large datatype. Will it affect performance in sql server

    - by Shantanu Gupta
    If i takes larger datatype where i know i should have taken datatype that was sufficient for possible values that i will insert into a table will affect any performance in sql server in terms of speed or any other way. eg. IsActive (0,1,2,3) not more than 3 in any case. I know i must take tinyint but due to some reasons consider it as compulsion, i am taking every numeric field as bigint and every character field as nVarchar(Max) Please give statistics if possible, to let me try to overcoming that compulsion. I need some solid analysis that can really make someone rethink before taking any datatype.

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  • Select where and where not

    - by Simon
    I have a table containing lessons that I called "cours" (french) and I have several cours inside and I have linked them to students with a table between them to see if they go to the lessons or not. I would like to return data with the SELECT and the data that are NOT select. So, If one student follow 3 courses of 5, I would like to return the 3 courses that he follow and the 2 courses that he doesn't follow. Is there a way to do it ?

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  • Create new table with Wordpress API

    - by Fire G
    I'm trying to create a new plugin to track popular posts based on views and I have everything done and ready to go, but I can't seem to create a new table using the Wordpress API (I can do it with standard PHP or with phpMyAdmin, but I want this plugin to be self-sufficient). I've tried several ways ($wpdb-query, $wpdb-get_results, dbDelta) but none of them will create the new table. function create_table(){ global $wpdb; $tablename = $wpdb->prefix.'popular_by_views'; $ppbv_table = $wpdb->get_results("SHOW TABLES LIKE '".$tablename."'" , ARRAY_N); if(is_null($ppbv_table)){ $create_table_sql = "CREATE TABLE '".$tablename."' ( 'id' BIGINT(50) NOT NULL AUTO_INCREMENT, 'url' VARCHAR(255) NOT NULL, 'views' BIGINT(50) NOT NULL, PRIMARY KEY ('id'), UNIQUE ('id') );"; $wpdb->show_errors(); $wpdb->flush(); if(is_null($wpdb->get_results("SHOW TABLES LIKE '".$tablename."'" , ARRAY_N))) echo 'crap, the SQL failed.'; } else echo 'table already exists, nothing left to do.';}

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  • How to undo SQL changes using installer

    - by Sunil Agarwal
    I have installer to install procedures, scripts, views, etc in SQL server 2005/2008. Now I want to add a condition in the installer like if there is any error while installing, I want to undo all the changes done in SQL server. I tried to store the procedures, views, etc which I am changing while installing and reverting them back if I get any error. But am not able to do it the way I want. Can someone guide me if he had done the same thing? To specify I am using WIX installer. Also if someone has tried SMO, it will be of great help.

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  • how to restore very large .bak file (180 GB) in SQL Server 2008

    - by Umutos
    Hello! I have a verly large .bak file (180 GB) which was stored in Microsoft SQL Server 2008 and I have to restore it. I first installed Microsoft SQL Server 2008 Express and tried to restore it in MS SQL management studio express but it didn't work because there is a size limit. Does anybody know a method how i can restore the file? Its the first time I work with Microsoft SQL and I have no clue what to do. Its really urgend and I would be really helpful for any help! Thanks a lot! Umutos

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  • Fluent nHibernate - How to map a non-key column on a junction table?

    - by The Matt
    Taking an example that is provided on the Fluent nHibernate website, I need to extend it slightly: I need to add a 'Quantity' column to the StoreProduct table. How would I map this using nHibernate? An example mapping is provided for the given scenario above, but I'm not sure how I would get the Quantity column to map to a property on the Product class: public class StoreMap : ClassMap<Store> { public StoreMap() { Id(x => x.Id); Map(x => x.Name); HasMany(x => x.Employee) .Inverse() .Cascade.All(); HasManyToMany(x => x.Products) .Cascade.All() .Table("StoreProduct"); } }

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  • sqlserver how to set job priority

    - by Buzz
    Is there any way to set one job priority higher then other, In my case there are two jobs those are working on same set of tables,first JOB-A which is running every 12 hr and other JOB-B is every 10 minutes , i think at some time when they run simultaneously JOB-B is getting in to deadlock and get failed, i google the topic and found sqlgoverner is helpful in such cases does anyone know how to resolve?

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  • Tablesorter - filter inside input fields and values

    - by Zeracoke
    I have a small quest to accomplish, and I reached a point when nothing works... So the problem is. I have a paged table with a lot of input fields inside the rows with values, and I would like to search inside these values. Let me Show this, I hope that somebody will got the idea what I should do... <script type="text/javascript"> // add parser through the tablesorter addParser method $.tablesorter.addParser({ id: 'inputs', is: function(s) { return false; }, format: function(s, table, cell, cellIndex) { var $c = $(cell); // return 1 for true, 2 for false, so true sorts before false if (!$c.hasClass('updateInput')) { $c .addClass('updateInput') .bind('keyup', function() { $(table).trigger('updateCell', [cell, false]); // false to prevent resort }); } return $c.find('input').val(); }, type: 'text' }); $(function() { $('table').tablesorter({ widgets: ['zebra', 'stickyHeaders', 'resizable', 'filter'], widgetOptions: { stickyHeaders : '', // number or jquery selector targeting the position:fixed element stickyHeaders_offset : 110, // added to table ID, if it exists stickyHeaders_cloneId : '-sticky', // trigger "resize" event on headers stickyHeaders_addResizeEvent : true, // if false and a caption exist, it won't be included in the sticky header stickyHeaders_includeCaption : true, // The zIndex of the stickyHeaders, allows the user to adjust this to their needs stickyHeaders_zIndex : 2, // jQuery selector or object to attach sticky header to stickyHeaders_attachTo : null, // scroll table top into view after filtering stickyHeaders_filteredToTop: true, resizable: true, filter_onlyAvail : 'filter-onlyAvail', filter_childRows : true, filter_startsWith : true, filter_useParsedData : true, filter_defaultAttrib : 'data-value' }, headers: { 1: {sorter: 'inputs', width: '50px'}, 2: {sorter: 'inputs'}, 3: {sorter: 'inputs'}, 4: {sorter: 'inputs'}, 5: {sorter: 'inputs'}, 6: {sorter: 'inputs'}, 7: {sorter: 'inputs', width: '100px'}, 8: {sorter: 'inputs', width: '140px'}, 9: {sorter: 'inputs'}, 10: {sorter: 'inputs'}, 11: {sorter: 'inputs'}, } }); $('table').tablesorterPager({container: $(".pager"), positionFixed: false, size: 50, pageDisplay : $(".pagedisplay"), pageSize : $(".pagesize"), }); $("#table1").tablesorter(options); /* make second table scroll within its wrapper */ options.widgetOptions.stickyHeaders_attachTo = '.wrapper'; // or $('.wrapper') $("#table2").tablesorter(options); }); </script> The structure of the tables: <tr class="odd" style="display: table-row;"> <form action="/self.php" method="POST"> </form><input type="hidden" name="f" value="data"> <td><input type="hidden" name="mod_id" value="741">741</td> <td class="updateInput"><input type="text" name="name" value="Test User Name"></td> <td class="updateInput"><input type="text" name="address" value="2548451 Random address"></td> <td class="updateInput"><input type="email" name="email" value=""></td> <td class="updateInput"><input type="text" name="entitlement" value="none"></td> <td class="updateInput"><input type="text" name="card_number" value="6846416548644352"></td> <td class="updateInput"><input type="checkbox" name="verify" value="1" checked=""></td> <td class="updateInput"><input type="checkbox" name="card_sended" value="1" checked=""></td> <td class="updateInput"><input type="text" name="create_date" value="2014-02-12 21:09:16"></td> <td class="updateInput"><a href="self.php?f=data&amp;del=741">X</a></td> <td class="updateInput"><input type="submit" value="SAVE"></td><td class="updateInput"></td></tr> So the thing is I don't know how to configure the filter to search these values... I already added some options, but none of them are working... Any help would be great!

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  • PHP: Which DB/DB Engine supports search well?

    - by KeyStroke
    Hi, I'm starting a site which relies heavily on search. While it's probably going to search basic meta data in the beginning, it might grow to something bigger in the future. So which DB/DB Engine is best in your opinion when it comes to search performance and future scalability? Appreciate your help

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  • What is the secure way to isolate ftp server users on unix?

    - by djs
    I've read documentation for various ftp daemons and various long threads about the security implications of using a chroot environment for an ftp server when giving users write access. If you read the vsftpd documentation, in particular, it implies that using chroot_local_user is a security hazard, while not using it is not. There seems to be no coverage of the implications of allowing the user access to the entire filesystem (as permitted by their user and group membership), nor to the confusion this can create. So, I'd like to understand what is the correct method to use in practice. Should an ftp server with authenticated write-access users provide a non-chroot environment, a chroot environment, or some other option? Given that Windows ftp daemons don't have the option to use chroot, they need to implement isolation otherwise. Do any unix ftp daemons do something similar?

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