    rake db:migrate:redo VERSION=my_version

Or you can go up or down from a specific version:

    db:migrate:up VERSION=my_version
    db:migrate:down VERSION=my_version


I have a thick client, java swing application with a schema of 25 tables and ~15 JInternalFrames (data entry forms for the tables).  I need to make a design choice of straight JDBC or ORM (hibernate with spring framework in this case) for DBMS interaction.  Build out of the application will occur in the future.

Would hibernate be overkill for a project of this size?  An explanation of either yes or no answer would be much appreciated (or even a different approach if warranted).

TIA.

Hibernate or JDBC

[An Updated List 21st Aug 09]

Help me Compile a  List of all the Advantages &amp; Disadvantages of Building an Application on the Google App Engine

 
**Pros:**

 1. No need to buy servers or server space (no maintenance).
 2. Makes solving the problem of scaling easier.
 3. Free up to a certain level of consumed resources.

**Cons:**

 1. Locked into Google App Engine ?
 2. Developers have read-only access to the filesystem on App Engine.
 3. App Engine can only execute code called from an HTTP request (except for scheduled background tasks).
 4. Users may upload arbitrary Python modules, but only if they are pure-Python; C and Pyrex modules are not supported.
 5. App Engine limits the maximum rows returned from an entity get to 1000 rows per Datastore call.  (**Update** - App Engine now supports cursors for accessing larger queries)
 6. Java applications may only use a subset (The JRE Class White List) of the classes from the JRE standard edition.
 7. Java applications cannot create new threads.

**Known Issues!!** : http://code.google.com/p/googleappengine/issues/list

**Hard limits**

Apps per developer -	10&lt;br&gt;
Time per request -	30 sec&lt;br&gt;
Files per app -	3,000&lt;br&gt;
HTTP response size -	10 MB&lt;br&gt;
Datastore item size -	1 MB&lt;br&gt;
Application code size -	150 MB&lt;br&gt;
&lt;b&gt;Update&lt;/b&gt; Blob store now allows storage of files up to 50MB



**Pro or Con?**&lt;br&gt;
App Engine&#39;s infrastructure removes many of the system administration and development challenges of building applications to scale to millions of hits. Google handles deploying code to a cluster, monitoring, failover, and launching application instances as necessary.

While other services let users install and configure nearly any *NIX compatible software, App Engine requires developers to use Python or Java as the programming language and a limited set of APIs. Current APIs allow storing and retrieving data from a BigTable non-relational database; making HTTP requests; sending e-mail; manipulating images; and caching. Most existing Web applications can&#39;t run on App Engine without modification, because they require a relational database.


Pros &amp; Cons of Google App Engine

I&#39;ve deleted a table in the database, call it X.  db:migrate no longer works.  I have a migration file called CreateX.  Is there a way to run just that specific migration?

rails run specific migration

<p>I've deleted a table in the database, call it X.  db:migrate no longer works.  I have a migration file called CreateX.  Is there a way to run just that specific migration?</p>


So let&#39;s say I have Posts and Comments and the url for show is `/posts/1/comments/1`. I want to create a link to delete that comment in the comments controller destroy method. How do I do that?


How to create a delete link for a related object in Ruby on Rails?

I have this in my test

    Project.should_receive(:find).with(@project).and_return(@project)

but when object receive that method call two times, I have to do

    Project.should_receive(:find).with(@project).and_return(@project)
    Project.should_receive(:find).with(@project).and_return(@project)

Is there any way how to say something like

    Project.should_receive(:find).with(@project).and_return(@project).times(2)

How to say &quot;should_receive&quot; more times in RSpec

I&#39;m trying to run just one migration out of a whole bunch in my rails app.  How can I do this? I don&#39;t want to run any of the migrations before or after it. Thanks.

Rake just one migration

How would get find an average from an array?

If I have the array:

    [0,4,8,2,5,0,2,6]

Averaging would give me 3.375.



How do I create an average from a Ruby array?

&gt; **Possible Duplicate:**  
&gt; [How can I avoid running ActiveRecord callbacks?](https://stackoverflow.com/questions/632742/how-can-i-avoid-running-activerecord-callbacks)  

&lt;!-- End of automatically inserted text --&gt;

I have model like this

    class Vote &lt; ActiveRecord::Base  
        after_save :add_points_to_user

        .....
    end

Is it possible to somehow force model to skip calling `add_points_to_user` when saved? Possibly something like `ActiveRecord#delete` vs `ActiveRecord#destroy`?

How to skip ActiveRecord callbacks?

I have a rails project running that defines the standard production:, :development and :test DB-connections in config/database.yml

In addition I have a quiz_development: and quiz_production: definition pointing to a differnet host/db/user/password

My goal now is to define a Migration that uses &quot;`quiz_#{RAILS_ENV`}`&quot; as its database configuration.

What I have tried (and failed):

- Setting ActiveRecord::Base.connection in the Migration file
- Changing the db:migrate task in rails to set ActiveRecord::Base.connection there

Question:

How can I make rake db:migrate use that other database definition?


Thanks,
Frank

Using Rails Migration on different database than standard &quot;production&quot; or &quot;development&quot;

I&#39;m converting a db from postgres to mysql. 

Since i cannot find a tool that does the trick itself, i&#39;m going to convert all postgres sequences to autoincrement ids in mysql with autoincrement value.

So, how can i list all sequences in a **Postgres** DB (**8.1** version) with information about the table in which it&#39;s used, the next value etc with a SQL query?

Be aware that i can&#39;t use the `information_schema.sequences` view in the 8.4 release.


List all sequences in a Postgres db 8.1 with SQL

I was doing this kind of thing in my migrations:

  	add_column :statuses, :hold_reason, :string rescue puts &quot;column already added&quot;

but it turns out that, **while this works for SQLite, it does not work for PostgreSQL**. It seems like if the add_column blows up, **even if the Exception is caught,** the transaction is dead and so the Migration can&#39;t do any additional work.

Is there any **non-DB sepecific** ways to check if a column or table already exist? Failing that, is there any way to get my rescue block to really work?

Rails Migrations: Check Existence and Keep Going?

I&#39;m maintaining library written for PHP 5.2 and I&#39;d like to create PHP 5.3-namespaced version of it. However, I&#39;d also keep non-namespaced version up to date until PHP 5.3 becomes so old, that even Debian stable ships it ;)

I&#39;ve got rather clean code, about 80 classes following `Project_Directory_Filename` naming scheme (I&#39;d change them to `\Project\Directory\Filename` of course) and only few functions and constants (also prefixed with project name).

Question is: what&#39;s the best way to develop namespaced and non-namespaced versions in parallel?

* Should I just create fork in repository and keep merging changes between branches? Are there cases where backslash-sprinkled code becomes hard to merge?

* Should I write script that converts 5.2 version to 5.3 or vice-versa? Should I use PHP tokenizer? `sed`? C preprocessor?

* Is there a better way to use namespaces where available and keep backwards compatibility with older PHP?

----

*Update: [Decided against use of namespaces after all](http://pornel.net/phpns).*

Content Type	Original Author	Original Content on Stackoverflow
Question	Daniel	View Question on Stackoverflow
Solution 1 - Ruby on-Rails	JP Silvashy	View Answer on Stackoverflow

rails run specific migration

Ruby on-Rails Problem Overview

Ruby on-Rails Solutions

Solution 1 - Ruby on-Rails

Pros & Cons of Google App Engine

Hibernate or JDBC

Attributions