The answer is simple: from the database.

By the way - when you [take a look into the source code of db:* tasks][1] you can see that migration tasks calls schema:dump after the run

    desc &quot;Migrate the database (options: VERSION=x, VERBOSE=false).&quot;
    task :migrate =&gt; :environment do
      ActiveRecord::Migration.verbose = ENV[&quot;VERBOSE&quot;] ? ENV[&quot;VERBOSE&quot;] == &quot;true&quot; : true
      ActiveRecord::Migrator.migrate(&quot;db/migrate/&quot;, ENV[&quot;VERSION&quot;] ? ENV[&quot;VERSION&quot;].to_i : nil)
      Rake::Task[&quot;db:schema:dump&quot;].invoke if ActiveRecord::Base.schema_format == :ruby
    end

So the migration works in the way that it change the database and __then__ generate schema.rb file. 


  [1]: https://github.com/rails/rails/blob/master/activerecord/lib/active_record/railties/databases.rake

I am using a ALAsset Framework for accessing the files in the device&#39;s photo gallery.
  
So far I am able to access the thumbnail and display it.  
I want to display the actual image in an image view but I am unable to figure out how to do this.  

I tried using the URLs field in the ALAsset object but was unsuccessful.
  
Anybody knows how this can be done?  

Here&#39;s some code where I was able to access the thumbnail and place it in a table cell:  

    - (UITableViewCell *)tableView:(UITableView *)tableView 
             cellForRowAtIndexPath:(NSIndexPath *)indexPath {

 
      static NSString *CellIdentifier = @&quot;Cell&quot;;
 
      UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
      if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
      }
      //here &#39;asset&#39; represents the ALAsset object
 

      asset = [assets objectAtIndex:indexPath.row];
           //i am accessing the thumbnail here
      [cell.imageView setImage:[UIImage imageWithCGImage:[asset thumbnail]]];
      [cell.textLabel setText:[NSString stringWithFormat:@&quot;Photo %d&quot;, indexPath.row+1]];
 
      return cell;
    }


display image from URL retrieved from ALAsset in iPhone

I&#39;ve had been told that since .net linq is so slow we shouldn&#39;t use it and was wondering anyone else has come up with the same conclusion, and example is:

Took 1443ms to do 1000000000 compares non-LINQ.  
Took 4944ms to do 1000000000 compares with LINQ.  
(243% slower)

the non-LINQ code:

    for (int i = 0; i &lt; 10000; i++)
    {
        foreach (MyLinqTestClass1 item in lst1) //100000 items in the list
        {
            if (item.Name == &quot;9999&quot;)
            {
                isInGroup = true;
                break;
            }
        }
    }
Took 1443ms to do 1000000000 compares non-LINQ.


LINQ code:      

    for (int i = 0; i &lt; 10000; i++)  
        isInGroup = lst1.Cast&lt;MyLinqTestClass1&gt;().Any(item =&gt; item.Name == &quot;9999&quot;);  


Took 4944ms to do 1000000000 compares with LINQ.

I guess its possible to optimize the LINQ code but the thought was that its easily to get really slow LINQ code and given that it shouldn&#39;t be used. Given that LINQ is slow then it would also follow that PLINQ is slow and NHibernate LINQ would be slow so any kind on LINQ statement should not be used. 

Has anyone else found that LINQ is so slow that they wished they had never used it, or am I making a too general conclusion based on benchmarks like this?

Should LINQ be avoided because it&#39;s slow?

Does

    rake db:schema:dump

recreate `schema.rb` from migrations or the database itself?


Does rake db:schema:dump recreate schema.rb from migrations or the database itself?

Does
<pre><code class="hljs language-lua">rake db:schema:dump
</code></pre>
recreate <code>schema.rb</code> from migrations or the database itself?

Hi (huge Rails newbie here), I have the following models:

    class Shop &lt; ActiveRecord::Base
      belongs_to :user
      validates_uniqueness_of :title, :user_id, :message =&gt; &quot;is already being used&quot;
    end

and

    class User &lt; ActiveRecord::Base
      has_one :shop, :dependent =&gt; :destroy
    end

When I&#39;m about to create a new shop, I get the following error:

    private method `create&#39; called for nil:NilClass

This is my controller:

    @user = current_user
    @shop = @user.shop.create(params[:shop])

I&#39;ve tried different variations by reading guides and tutorials here and there, but I&#39;m more confused than before and can&#39;t get it to work. Any help would be greatly appreciated.

Rails: create on has_one association

I have a rails app and I want to render an action without using my application layout (which has page header / footer stuff in it).

How could I go about doing this?

Ruby on Rails - How do I render an action without the application layout?

On my development machine, I use port 10524. So I start my server this way :

    rails s -p 10524
Is there a way to change the default port to 10524 so I wouldn&#39;t have to append the port each time I start the server?

How to change Rails 3 server default port in develoment?

This seems like a noob question, but the simple answer is eluding me. I need to call `link_to` in an `ActionController` method to spit out an HTML link.  `ActionView::Helpers::UrlHelper.link_to` calls `url_for`, but this calls the AV module&#39;s version instead of the controller&#39;s. I managed to coerce this into doing what I intended by putting

      #FIXME there must be a better way to mixin link_to
      alias_method :self_url_for, :url_for
      include ActionView::Helpers::UrlHelper
      alias_method :url_for, :self_url_for

in the controller.  But, I&#39;m still not sure why it works exactly. Could someone please explain the method scope and hiding that&#39;s happening here?  What&#39;s a better way to mix in `link_to` (or generally, to include only some methods from a module) so I can call it in the controller (generating a flash string with a link is the use case.)

Please, no lectures about MVC--if anything, `link_to` should be in a module separate from `url_for`.  Judging from the amount of noise on this, lots of people run into this seemingly trivial snag and end up wasting an hour doing it the &quot;Rails way&quot; when really what is wanted is a one minute hack to make my app work now.  Is there a &quot;Rails way&quot; to do this with helpers perhaps? Or a better ruby way?



How to mixin and call link_to from controller in Rails?

I have namespace in my routes.rb

      namespace :businesses do
        resources :registration
      end

My controller is in a subdirectory businesses/registration_controller.

    def new
      @business = Business.new
    end

In my view, I want to do this `form_for @business do |f| ...` but I am getting the following error:

`No route matches {:controller=&gt;&quot;businesses&quot;, :action=&gt;&quot;create&quot;}`

Restarted the server and I&#39;m also getting this:

`undefined method `businesses_path&#39; for #&lt;#&lt;Class:0x10339df38&gt;:0x10339bb20&gt;`


Here are my rake routes:



                       home_index GET    /home/index(.:format)                       {:action=&gt;&quot;index&quot;, :controller=&gt;&quot;home&quot;}
                 new_user_session GET    /users/sign_in(.:format)                    {:action=&gt;&quot;new&quot;, :controller=&gt;&quot;devise/sessions&quot;}
                     user_session POST   /users/sign_in(.:format)                    {:action=&gt;&quot;create&quot;, :controller=&gt;&quot;devise/sessions&quot;}
             destroy_user_session GET    /users/sign_out(.:format)                   {:action=&gt;&quot;destroy&quot;, :controller=&gt;&quot;devise/sessions&quot;}
                    user_password POST   /users/password(.:format)                   {:action=&gt;&quot;create&quot;, :controller=&gt;&quot;devise/passwords&quot;}
                new_user_password GET    /users/password/new(.:format)               {:action=&gt;&quot;new&quot;, :controller=&gt;&quot;devise/passwords&quot;}
               edit_user_password GET    /users/password/edit(.:format)              {:action=&gt;&quot;edit&quot;, :controller=&gt;&quot;devise/passwords&quot;}
                    user_password PUT    /users/password(.:format)                   {:action=&gt;&quot;update&quot;, :controller=&gt;&quot;devise/passwords&quot;}
         cancel_user_registration GET    /users/cancel(.:format)                     {:action=&gt;&quot;cancel&quot;, :controller=&gt;&quot;devise/registrations&quot;}
                user_registration POST   /users(.:format)                            {:action=&gt;&quot;create&quot;, :controller=&gt;&quot;devise/registrations&quot;}
            new_user_registration GET    /users/sign_up(.:format)                    {:action=&gt;&quot;new&quot;, :controller=&gt;&quot;devise/registrations&quot;}
           edit_user_registration GET    /users/edit(.:format)                       {:action=&gt;&quot;edit&quot;, :controller=&gt;&quot;devise/registrations&quot;}
                user_registration PUT    /users(.:format)                            {:action=&gt;&quot;update&quot;, :controller=&gt;&quot;devise/registrations&quot;}
                user_registration DELETE /users(.:format)                            {:action=&gt;&quot;destroy&quot;, :controller=&gt;&quot;devise/registrations&quot;}
                            users GET    /users(.:format)                            {:action=&gt;&quot;index&quot;, :controller=&gt;&quot;users&quot;}
                            users POST   /users(.:format)                            {:action=&gt;&quot;create&quot;, :controller=&gt;&quot;users&quot;}
                         new_user GET    /users/new(.:format)                        {:action=&gt;&quot;new&quot;, :controller=&gt;&quot;users&quot;}
                        edit_user GET    /users/:id/edit(.:format)                   {:action=&gt;&quot;edit&quot;, :controller=&gt;&quot;users&quot;}
                             user GET    /users/:id(.:format)                        {:action=&gt;&quot;show&quot;, :controller=&gt;&quot;users&quot;}
                             user PUT    /users/:id(.:format)                        {:action=&gt;&quot;update&quot;, :controller=&gt;&quot;users&quot;}
                             user DELETE /users/:id(.:format)                        {:action=&gt;&quot;destroy&quot;, :controller=&gt;&quot;users&quot;}
       full_tree_admin_categories GET    /admin/categories/full_tree(.:format)       {:action=&gt;&quot;full_tree&quot;, :controller=&gt;&quot;admin/categories&quot;}
                 admin_categories GET    /admin/categories(.:format)                 {:action=&gt;&quot;index&quot;, :controller=&gt;&quot;admin/categories&quot;}
                 admin_categories POST   /admin/categories(.:format)                 {:action=&gt;&quot;create&quot;, :controller=&gt;&quot;admin/categories&quot;}
               new_admin_category GET    /admin/categories/new(.:format)             {:action=&gt;&quot;new&quot;, :controller=&gt;&quot;admin/categories&quot;}
              edit_admin_category GET    /admin/categories/:id/edit(.:format)        {:action=&gt;&quot;edit&quot;, :controller=&gt;&quot;admin/categories&quot;}
                   admin_category GET    /admin/categories/:id(.:format)             {:action=&gt;&quot;show&quot;, :controller=&gt;&quot;admin/categories&quot;}
                   admin_category PUT    /admin/categories/:id(.:format)             {:action=&gt;&quot;update&quot;, :controller=&gt;&quot;admin/categories&quot;}
                   admin_category DELETE /admin/categories/:id(.:format)             {:action=&gt;&quot;destroy&quot;, :controller=&gt;&quot;admin/categories&quot;}
    businesses_registration_index GET    /businesses/registration(.:format)          {:action=&gt;&quot;index&quot;, :controller=&gt;&quot;businesses/registration&quot;}
    businesses_registration_index POST   /businesses/registration(.:format)          {:action=&gt;&quot;create&quot;, :controller=&gt;&quot;businesses/registration&quot;}
      new_businesses_registration GET    /businesses/registration/new(.:format)      {:action=&gt;&quot;new&quot;, :controller=&gt;&quot;businesses/registration&quot;}
     edit_businesses_registration GET    /businesses/registration/:id/edit(.:format) {:action=&gt;&quot;edit&quot;, :controller=&gt;&quot;businesses/registration&quot;}
          businesses_registration GET    /businesses/registration/:id(.:format)      {:action=&gt;&quot;show&quot;, :controller=&gt;&quot;businesses/registration&quot;}
          businesses_registration PUT    /businesses/registration/:id(.:format)      {:action=&gt;&quot;update&quot;, :controller=&gt;&quot;businesses/registration&quot;}
          businesses_registration DELETE /businesses/registration/:id(.:format)      {:action=&gt;&quot;destroy&quot;, :controller=&gt;&quot;businesses/registration&quot;}
                             root        /(.:format)                                 {:action=&gt;&quot;index&quot;, :controller=&gt;&quot;home&quot;}



Rails Routes Namespaces and form_for

Is there a way to set the schema for a query so that in the rest of the query I can refer to tables just by their name without prepending them with a schema name?

For instance, I would like to do something like this:

    Use [schemaName]
    select * from [tableName]

as opposed to this:

    select * from [schemaName].[tableName]

set default schema for a sql query

Is there a query that can be run in mysql that shows all tables and their default collation?  Even better if there was on that could show all collations on all columns of all tables.

Query to show all tables and their collation

Is there a schema validation language for YAML? I&#39;ve googled but couldn&#39;t find anything useful.

Something like XSD format, using the language itself to describe the schema, would be the best choice in my case. 

YAML Schema Validation?

I need to write an **sql script** that creates both a **new database *AND* a new schema** in the database I just created.

How can I do it? Can I somehow change the current database to the new one? Or can I somehow specify the database for CREATE SCHEMA?

I&#39;m using PostgreSQL 9.0

PostgreSQL: Create schema in specific database

I used to think schema were the &quot;upper wrapper&quot; object before the database itself.
I mean `DB.schema.&lt;what_ever_object_name_under_schema&gt;`.

Well, the catalog &quot;wrapper&quot; is now quite confusing. Why should we need a catalog? For what purpose, precisely should the catalog be used?




What&#39;s the difference between a catalog and a schema in a relational database?

If I use a migration to update a database, and I add an integer field like this:

    t.integer :foo :default =&gt; 0, :null =&gt; false

What is the default state of existing and new records in the database?  I hoping the answer is:
- Both will read back foo as 0.

Is default =&gt; 0 necessary, if I have :null =&gt; false?

Just trying to understand the difference between the two...

How do :default =&gt; 0 and :null =&gt; false differ for integer fields in migrations?

I added a table that I thought I was going to need, but now no longer plan on using it. How should I remove that table?

I&#39;ve already run migrations, so the table is in my database. I figure `rails generate migration` should be able to handle this, but I haven&#39;t figured out how yet.

I&#39;ve tried:  

    rails generate migration drop_tablename

but that just generated an empty migration.

What is the &quot;official&quot; way to drop a table in Rails?

Rails DB Migration - How To Drop a Table?

I have a web application using sqlalchemy (within Pylons). I need to effiently change the schema to be able to change the production version at least on a daily basis, maybe more, without losing the data.

I have played a little bit with sqlalchemy-migrate over the week-end and I would say that it gave me a bad impression. First **I think it cannot help with migration between two databases engines**; that&#39;s something that could probably be done with sqlalchemy alone. 
Second the docs do not seem up to date. I had to change some command-line options, like giving the repository path at each command, this could be a bug of migrate. 

But the worst thing it the &quot;manage.py **test**&quot; command. Not only it actually **modifies the database** (this point is clearly indicated in the documentation so I can&#39;t blame migrate) but my first migration script just made plain stupid schema migration, leaving the upgraded-downgraded db with a **different schema than the original**. But the &quot;manage.py test&quot; just answered something like

     success !

That is, it did not even check if the schema was left in a coherent state. 
So **is it worth using migrate?** Is there any advantage compared to the Do It Yourself method associated with good practices [as proposed by S.Lott][1] ?
Are there alternatives to sqlalchemy-migrate actually simplifying the migration process or am I just trying to use migrate with a bad a *priori* (then please show me why is&#39;t clearly superior to creating CSV columns as proposed in the link above)?

Many Thanks!


  [1]: https://stackoverflow.com/questions/4165452/how-to-efficiently-manage-frequent-schema-changes-using-sqlalchemy/4165496#4165496

Is it worth using sqlalchemy-migrate ?

How do I describe an enumeration column in a Rails 3 migration?

How do I do a `script/generate migration` to create a join table for a `has_and_belongs_to_many` relationship?

The application runs on Rails 2.3.2, but I also have Rails 3.0.3 installed.

Rails migration for has_and_belongs_to_many join table

Why are some rake tasks not listed by `rake -T`? Like `db:migrate:reset`? I can execute it without a problem, but why is it not listed there? Is there a way to get a real full list of rake tasks?

&lt;pre&gt;
% rake -T
(in /home/zeus/projects/my_project)
rake about              # List versions of all Rails frameworks and the environment
rake db:create          # Create the database from config/database.yml for the current Rails.env (use db:create:all to create all dbs in the config)
rake db:drop            # Drops the database for the current Rails.env (use db:drop:all to drop all databases)
rake db:fixtures:load   # Load fixtures into the current environment&#39;s database.
rake db:migrate         # Migrate the database (options: VERSION=x, VERBOSE=false).
rake db:migrate:status  # Display status of migrations
rake db:rollback        # Rolls the schema back to the previous version (specify steps w/ STEP=n).
rake db:schema:dump     # Create a db/schema.rb file that can be portably used against any DB supported by AR
rake db:schema:load     # Load a schema.rb file into the database
rake db:seed            # Load the seed data from db/seeds.rb
rake db:setup           # Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the db first)
rake db:structure:dump  # Dump the database structure to an SQL file
rake db:version         # Retrieves the current schema version number
rake doc:app            # Generate docs for the app -- also availble doc:rails, doc:guides, doc:plugins (options: TEMPLATE=/rdoc-template.rb, TITLE=&quot;Custom Title&quot;)
rake erd                # Generate an Entity-Relationship Diagram based on your models
rake log:clear          # Truncates all *.log files in log/ to zero bytes
rake middleware         # Prints out your Rack middleware stack
rake notes              # Enumerate all annotations (use notes:optimize, :fixme, :todo for focus)
rake notes:custom       # Enumerate a custom annotation, specify with ANNOTATION=CUSTOM
rake rails:template     # Applies the template supplied by LOCATION=/path/to/template
rake rails:update       # Update both configs and public/javascripts from Rails (or use just update:javascripts or update:configs)
rake routes             # Print out all defined routes in match order, with names.
rake secret             # Generate a crytographically secure secret key (this is typically used to generate a secret for cookie sessions).
rake spec               # Run all specs in spec directory (excluding plugin specs)
rake spec:acceptance    # Run the code examples in spec/acceptance
rake spec:controllers   # Run the code examples in spec/controllers
rake spec:helpers       # Run the code examples in spec/helpers
rake spec:lib           # Run the code examples in spec/lib
rake spec:mailers       # Run the code examples in spec/mailers
rake spec:models        # Run the code examples in spec/models
rake spec:rcov          # Run all specs with rcov
rake spec:requests      # Run the code examples in spec/requests
rake spec:routing       # Run the code examples in spec/routing
rake spec:views         # Run the code examples in spec/views
rake stats              # Report code statistics (KLOCs, etc) from the application
rake test               # Runs test:units, test:functionals, test:integration together (also available: test:benchmark, test:profile, test:plugins)
rake test:recent        # Run tests for recenttest:prepare / Test recent changes
rake test:uncommitted   # Run tests for uncommittedtest:prepare / Test changes since last checkin (only Subversion and Git)
rake time:zones:all     # Displays all time zones, also available: time:zones:us, time:zones:local -- filter with OFFSET parameter, e.g., OFFSET=-6
rake tmp:clear          # Clear session, cache, and socket files from tmp/ (narrow w/ tmp:sessions:clear, tmp:cache:clear, tmp:sockets:clear)
rake tmp:create         # Creates tmp directories for sessions, cache, sockets, and pids
&lt;/pre&gt;


Why is rake db:migrate:reset not listed in rake -T?

I have a dev Ruby on Rails database full of data. I want to delete everything and rebuild the database. I&#39;m thinking of using something like:

    rake db:recreate

Is this possible?

Purge or recreate a Ruby on Rails database

After adding migration files in the `db/migrate` folder and running `rake db:migrate`, I want get back to the previous step, I think using `VERSION=n` is the right way to do that, but I don&#39;t know the correct value of n to use. Is there any command to check the current n value?

It would be great if anyone could provide full instructions on how to use `rake db:migrate`.

How to rollback just one step using rake db:migrate

I&#39;m using Rails 3.0.3 and have data for my &quot;categories&quot; table already in the database, but want to create a seed file from it. Is there any rake task that will generate the seeds.rb format for me from this table?

Create seed file from data already in the database

On a freshly created Rails project (generated by `rails someName`), one can run some &#39;default&#39; rake tasks like:

 - `rake test`
 - `rake db:migrate`
 - etc

Question is, where does these tasks get described? The default `Rakefile` doesn&#39;t have all these tasks.

Furthermore, I checked out some project that uses `rspec` and I am able to run `rake spec` to run all the tests. Where does the `spec` target defined?

Content Type	Original Author	Original Content on Stackoverflow
Question	pingu	View Question on Stackoverflow
Solution 1 - Ruby on-Rails	Radek Paviensky	View Answer on Stackoverflow

Does rake db:schema:dump recreate schema.rb from migrations or the database itself?

Ruby on-Rails Problem Overview

Ruby on-Rails Solutions

Solution 1 - Ruby on-Rails

Should LINQ be avoided because it's slow?

display image from URL retrieved from ALAsset in iPhone

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