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  • Ruby on Rails: building a model with an attribute not in the database?

    - by randombits
    I have a model that sets one of its attributes based off of a form parameter that a user submits. The model is a child resource to a parent resource Home. A hypothetical example is the following: A class Person has an age attribute. The user submits a birthdate as an HTTP POST parameter and from that, I need to derive the age of the user. So I'd do something like this: @home.people.build(:name => params[:name], :birthdate => params[:birthdate]) Rails would barf on that for obvious reasons, complaining it doesn't know what the attribute birthdate is. What's the proper way of going about this? Is it possible to use the build constructor with the supplied solution so that my foreign key relations are also setup properly? If not, what's a better way to work around this problem?

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  • Is Django's manage.py syncdb or South used to create the test database?

    - by Thierry Lam
    With Django 1.1.1 and South 0.62, running a test from the CLI usually have the following output: Creating table some_model Installing index for my_app.SomeModel model . ----- Ran 1 test in 1s OK After upgrading to South 0.7, the output is invoking South's migration: Creating table some_model Installing index for my_app.SomeModel model Migrating... Running migrations for my_app: - Migrating forwards to 0001_initial > my_app:0001_initial - Loading initial data for my_app Migrated: - my_app . ----- Ran 1 test in 1s OK To create the test DB, has the test always used South migration in the past(before South 0.7) even if the output is not explicitly being shown?

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  • Is saving to database just to get an ID a bad hack?

    - by Narsil
    I hope the title is not too confusing. I am trying to make folders with linq-to-sql objects' IDs. Actually I have to create folders before I should save them. I will use them to keep user uploaded files. As you can see I have to create the folder with the FileID before I can save it there. So I just save a record which will be edited or maybe deleted File newFile = new File(); ...//add some values to fields so they don't throw rule violations db.AddFile(newFile); db.Save(); System.IO.Directory.CreateDirectory("..Uploads/"+newFile.FileId.ToString()); After that I will have to edit some fields and save again. Of course user might stop upload and I would have to delete it. I know I can write a stored procedure to get the next available FileID but some other upload happening at the same time would get the same number. So they would write in same directory which is a thing I don't want. Should I go on with this, would there be some problems? Can you think of a better way?

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  • Designing DAL in .NET to be "data-source independent" and not just "database independent" ?

    - by Munish Goyal
    How to design such flexible DAL (specifically in .NET) ? What interfaces .NET provides and what should be done on my own ? Its a greenfield project starting with SQL Server as data source but in future, parts of it will move to different NoSQL type of datastores. Also, we may need to experiment with lot of different datastores (like some data may have to go with Cassandra, some with RDBMS, some to other DHT etc.) Therefore easily switchable access layer will be needed. All i know right now is the 'data' and 'operations needed on that data'.

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  • KODO: how set up fetch plan for bidirectional relationships?

    - by BestPractices
    Running KODO 4.2 and having an issue inefficient queries being generated by KODO. This happens when fetching an object that contains a collection where that collection has a bidrectional relationship back to the first object. Class Classroom { List<Student> _students; } Class Student { Classroom _classroom; } If we create a fetch plan to get a list of Classrooms and their corresponding Students by setting up the following fetch plan: fetchPlan.addField(Classroom.class,”_students”); This will result in two queries (get the classrooms and then get all students that are in those classrooms), which is what we would expect. However, if we include the reference back to the classroom in our fetch plan in order for the _classroom field to get populated by doing fetchPlan.addField(Student.class, “_classroom”), this will result in X number of additional queries where X is the number of students in each classroom. Can anyone explain how to fix this? KODO already has the original Classroom objects at the point that it's executing the queries to retrieve the Classroom objects and set them in each Student object's _classroom field. So I would expect KODO to simply set those objects in the _classroom field on each Student object accordingly and not go back to the database. Once again, the documentation is sorely lacking with Kodo/JDO/OpenJPA but from what I've read it should be able to do this more efficiently. Note-- EAGER_FETCH.PARALLEL is turned on and I have tried this with caching (query and data caches) turned on and off and there is no difference in the resultant queries.

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  • Inconsistent MySQL COLLATE errors across databases

    - by Teflon Ted
    I have two physically-separate MySQL databases on which I have to run a single query. The query has a section of SQL that looks like this: and foo_table.bar_column like concat('%', rules.pattern, '%') COLLATE utf8_general_ci It runs fine on database A but on database B I get this error: ERROR 1253 (42000): COLLATION 'utf8_general_ci' is not valid for CHARACTER SET 'latin1' If I remove the collation it runs fine on database B but on database A I get this error: ERROR 1267 (HY000): Illegal mix of collations (utf8_general_ci,IMPLICIT) and (utf8_unicode_ci,IMPLICIT) for operation 'like' Is there a version of the query that will run on both databases? Or, is there a configuration I can change on either database to make the query happy in both places? Update: Database A is version 5.1.38, Database B is version 5.1.34

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  • How can I optimize the SELECT statement running on an Oracle database?

    - by Elvis Lou
    I have a SELECT statement in ORACLE: SELECT COUNT(DISTINCT ds1.endpoint_msisdn) multiple30, dss1.service, dss1.endpoint_provisioning_id, dss1.company_scope, Nvl(x.subscription_status, dss1.subscription_status) subscription_status FROM daily_summary ds1 join daily_summary ds2 ON ds1.endpoint_msisdn = ds2.endpoint_msisdn, daily_summary_static dss1, daily_summary_static dss2, (SELECT NULL subscription_status FROM dual UNION ALL SELECT -2 subscription_status FROM dual) x WHERE ds1.summary_ts >= To_date('10-04-2012', 'dd-mm-yyyy') - 30 AND ds1.summary_ts <= To_date('10-04-2012', 'dd-mm-yyyy') AND dss1.last_active >= To_date('10-04-2012', 'dd-mm-yyyy') - 30 AND dss1.last_active <= To_date('10-04-2012', 'dd-mm-yyyy') AND dss2.last_active >= To_date('10-04-2012', 'dd-mm-yyyy') - 30 AND dss2.last_active <= To_date('10-04-2012', 'dd-mm-yyyy') AND dss1.service <> dss2.service AND ( dss1.company_scope = 2 OR dss1.company_scope = 5 ) AND ( dss2.company_scope = 2 OR dss2.company_scope = 5 ) AND dss1.company_scope = dss2.company_scope AND ds1.endpoint_noc_id = dss1.endpoint_noc_id AND ds1.endpoint_host_id = dss1.endpoint_host_id AND ds1.endpoint_instance_id = dss1.endpoint_instance_id AND ds2.endpoint_noc_id = dss2.endpoint_noc_id AND ds2.endpoint_host_id = dss2.endpoint_host_id AND ds2.endpoint_instance_id = dss2.endpoint_instance_id AND dss1.endpoint_provisioning_id = dss2.endpoint_provisioning_id AND Least(1, ds1.total_actions) = 1 AND Least(1, ds2.total_actions) = 1 GROUP BY dss1.service, dss1.endpoint_provisioning_id, dss1.company_scope, Nvl(x.subscription_status, dss1.subscription_status); This query took about 26 minutes to return in my environment, but if I remove the section: dss1.last_active >= to_date('10-04-2012','dd-mm-yyyy') - 30 AND dss1.last_active <= to_date('10-04-2012','dd-mm-yyyy') AND dss2.last_active >= to_date('10-04-2012','dd-mm-yyyy') - 30 AND dss2.last_active <= to_date('10-04-2012','dd-mm-yyyy') AND it only took 20 seconds to run. We have index on the column last_active, I don't know why the section slow down the performance so much? any ideas?

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  • How to store array data in MySQL database using PHP & MySQL?

    - by Cyn
    I'm new to php and mysql and I'm trying to learn how to store the following array data from three different arrays friend[], hair_type[], hair_color[] using MySQL and PHP an example would be nice. Thanks Here is the HTML code. <input type="text" name="friend[]" id="friend[]" /> <select id="hair_type[]" name="hair_type[]"> <option value="Hair Type" selected="selected">Hair Type</option> <option value="Straight">Straight</option> <option value="Curly">Curly</option> <option value="Wavey">Wavey</option> <option value="Bald">Bald</option> </select> <select id="hair_color[]" name="hair_color[]"> <option value="Hair Color" selected="selected">Hair Color</option> <option value="Brown">Brown</option> <option value="Black">Black</option> <option value="Red">Red</option> <option value="Blonde">Blonde</option> </select> <input type="text" name="friend[]" id="friend[]" /> <select id="hair_type[]" name="hair_type[]"> <option value="Hair Type" selected="selected">Hair Type</option> <option value="Straight">Straight</option> <option value="Curly">Curly</option> <option value="Wavey">Wavey</option> <option value="Bald">Bald</option> </select> <select id="hair_color[]" name="hair_color[]"> <option value="Hair Color" selected="selected">Hair Color</option> <option value="Brown">Brown</option> <option value="Black">Black</option> <option value="Red">Red</option> <option value="Blonde">Blonde</option> </select> Here is the MySQL tables below. CREATE TABLE friends_hair ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, hair_id INT UNSIGNED NOT NULL, user_id INT UNSIGNED NOT NULL, PRIMARY KEY (id) ); CREATE TABLE hair_types ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, friend TEXT NOT NULL, hair_type TEXT NOT NULL, hair_color TEXT NOT NULL, PRIMARY KEY (id) );

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  • How to ask database server for current datetime using entity framework?

    - by Levelbit
    I don't want for my current ModifeidDateTime to be machine time already server time. Every time I want to update or add a person to my datebase on SQL Server 2008 I want to fill ModifiedDateTime filed. It's not like I can change update query as with data adapter command when I work with dataset and to define for my ModifiedDateTime filed to be =GetDate(). I created stored function to retutn me a value of GetDate() method, but I have a problem to import procedure which returns values as int, string ... or no value at all, already just entity values as Person for example in my case. Why is that? Anyway, It would be of great help if you can provide me any solution that works to retrieve DateTime value from server.

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  • What's the best way to refactor this Rails controller?

    - by Robert DiNicolas
    I'd like some advice on how to best refactor this controller. The controller builds a page of zones and modules. Page has_many zones, zone has_many modules. So zones are just a cluster of modules wrapped in a container. The problem I'm having is that some modules may have some specific queries that I don't want executed on every page, so I've had to add conditions. The conditions just test if the module is on the page, if it is the query is executed. One of the problems with this is if I add a hundred special module queries, the controller has to iterate through each one. I think I would like to see these module condition moved out of the controller as well as all the additional custom actions. I can keep everything in this one controller, but I plan to have many apps using this controller so it could get messy. class PagesController < ApplicationController # GET /pages/1 # GET /pages/1.xml # Show is the main page rendering action, page routes are aliased in routes.rb def show #-+-+-+-+-Core Page Queries-+-+-+-+- @page = Page.find(params[:id]) @zones = @page.zones.find(:all, :order => 'zones.list_order ASC') @mods = @page.mods.find(:all) @columns = Page.columns # restful params to influence page rendering, see routes.rb @fragment = params[:fragment] # render single module @cluster = params[:cluster] # render single zone @head = params[:head] # render html, body and head #-+-+-+-+-Page Level Json Conversions-+-+-+-+- @metas = @page.metas ? ActiveSupport::JSON.decode(@page.metas) : nil @javascripts = @page.javascripts ? ActiveSupport::JSON.decode(@page.javascripts) : nil #-+-+-+-+-Module Specific Queries-+-+-+-+- # would like to refactor this process @mods.each do |mod| # Reps Module Custom Queries if mod.name == "reps" @reps = User.find(:all, :joins => :roles, :conditions => { :roles => { :name => 'rep' } }) end # Listing-poc Module Custom Queries if mod.name == "listing-poc" limit = params[:limit].to_i < 1 ? 10 : params[:limit] PropertyEntry.update_from_listing(mod.service_url) @properties = PropertyEntry.all(:limit => limit, :order => "city desc") end # Talents-index Module Custom Queries if mod.name == "talents-index" @talent = params[:type] @reps = User.find(:all, :joins => :talents, :conditions => { :talents => { :name => @talent } }) end end respond_to do |format| format.html # show.html.erb format.xml { render :xml => @page.to_xml( :include => { :zones => { :include => :mods } } ) } format.json { render :json => @page.to_json } format.css # show.css.erb, CSS dependency manager template end end # for property listing ajax request def update_properties limit = params[:limit].to_i < 1 ? 10 : params[:limit] offset = params[:offset] @properties = PropertyEntry.all(:limit => limit, :offset => offset, :order => "city desc") #render :nothing => true end end So imagine a site with a hundred modules and scores of additional controller actions. I think most would agree that it would be much cleaner if I could move that code out and refactor it to behave more like a configuration.

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  • MySQL app with Cassandra in mind

    - by SODA
    I am planning to make a web app which will eventually use Cassandra. But now that I don't have it and don't have server(s) to run it from, I'd like to start by using MySQL. The question is, is it possible to structure data and queries in such a way that it would be fairly easy to later port it to Cassandra? Main idea, I guess, would be writing MySQL queries that would be possible to change to same Cassandra queries. Maybe you have a better suggestion?

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  • How do I request a single random row from a force.com database in SOQL?

    - by Ollie C
    Total row-count is in the range 10k-100k rows. Can I use RAND() on force.com? Unfortunately although all the rows have a unique numeric identifier, there are many gaps, and I'd often want to select a random row from a filtered subset anyway. I suspect there's no particularly efficient way to do this, but is it possible at all? Ultimately all I want to do is to extract one row from a table (or a subset based on specific filter criteria) at random. If force.com doesn't let me select a random row, then can I query the rows to select from, and assign sequential IDs to all the rows, say 1-1,035, and then select a random number in that range locally, say 349, and then get row 349?

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  • How to map combinations of things to a relational database?

    - by Space_C0wb0y
    I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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  • What exactly is Arel in Rails 3.0?

    - by Will
    I understand that it is a replacement for ActiveRecord and that it uses objects instead of queries. But... why is this better? will objects/queries be "easier" to create? will it lead to more efficient SQL queries? will it be compatible with all major DB's? - I assume it will. will it be easier/harder to use with stored procedures?

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  • How to secure the communication between an MSSQL database and a c# administrative tool?

    - by citronas
    How can I secure the communication between a C# programm running locally on my computer and a MSSQL Server in a hosted environment? I have an asp.net application that is secured by SSL encryption. So using the asp.net from an open wlan connection is no problem. How can I achieve the same kind of encryption for my administrative tool? Would it be best to write a service? But how would that connection to the service be secured?

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  • Postgresql count+sort performance

    - by invictus
    I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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