RoR with Existing tables in database using Postgresql

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PalaniKannan K

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Sep 3, 2010, 6:16:26 AM9/3/10
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Hi,

I am new bee to Rais. I need to create a Rails application with existing database with several number of tables. When i came across web, I didn't find any fruitful ideas for developing application using existing tables. Everything i found was to create new database with Create, Edit, Insert feature. I need to create a application using existing postgresql database stuffed with tables where i have to provide view only permission to the user.  Kinldy help me in this regard. I have 15 tables in my database which developed in postgresql. Advance thanx to my friends of RoR-Talk.
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Palani Kannan. K

Kannan

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Sep 3, 2010, 8:40:53 AM9/3/10
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Ar Chron

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Sep 3, 2010, 10:08:35 AM9/3/10
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Start with googling 'rails legacy database' for ideas.

Providing only 'read access' simply means your rails application should
not accept any new/create/update requests, and there are numerous ways
to defend against this.
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Richard Henwood

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Sep 3, 2010, 10:21:43 AM9/3/10
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Hi Palani,

you might find this helpful:

http://www.theirishpenguin.com/2009/11/26/generate-rails-migrations-from-
your-postgresql-or-mysql-database/

richard,

PalaniKannan K

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Sep 3, 2010, 11:58:01 AM9/3/10
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On 3 September 2010 16:08, Ar Chron <li...@ruby-forum.com> wrote:
Start with googling 'rails legacy database' for ideas.

Yaa... I will use this hint. Thank You.

Providing only 'read access' simply means your rails application should
not accept any new/create/update requests, and there are numerous ways
to defend against this.

Can you please tell me the ways... It will be useful to me. Tanx advance.

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PalaniKannan K

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Sep 3, 2010, 11:59:41 AM9/3/10
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On 3 September 2010 16:21, Richard Henwood <rjhe...@yahoo.co.uk> wrote:
On Fri, 03 Sep 2010 12:16:26 +0200, PalaniKannan K wrote:

> Hi,
>
> I am new bee to Rais. I need to create a Rails application with existing
> database with several number of tables. When i came across web, I didn't
> find any fruitful ideas for developing application using existing
> tables. Everything i found was to create new database with Create, Edit,
> Insert feature. I need to create a application using existing postgresql
> database stuffed with tables where i have to provide view only
> permission to the user.  Kinldy help me in this regard. I have 15 tables
> in my database which developed in postgresql. Advance thanx to my
> friends of RoR-Talk. --

Hi Palani,

you might find this helpful:

I feel that, this is same kind of results I got in google search... Creating model using dumped schemas of existing table. but, its not working. 

http://www.theirishpenguin.com/2009/11/26/generate-rails-migrations-from-
your-postgresql-or-mysql-database/


richard,

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Hassan Schroeder

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Sep 3, 2010, 12:23:36 PM9/3/10
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On Fri, Sep 3, 2010 at 8:59 AM, PalaniKannan K <kpalan...@gmail.com> wrote:

> I feel that, this is same kind of results I got in google search... Creating
> model using dumped schemas of existing table. but, its not working.

"its not working" isn't particularly useful information.

So you have an existing table, say "things". You create a model for
it, e.g.

class Thing < ActiveRecord::Base
end

Done. Maybe you have to tell it there's a non-Rails-standard index
field, etc., but basically that's it. There's no reason to be fooling with
migrations if you have an existing table, unless you can and want to
do transformations on them to make them more Rails-like.

So what have you tried, and what's the actual problem?

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twitter: @hassan

PalaniKannan K

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Sep 3, 2010, 2:18:58 PM9/3/10
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On 3 September 2010 18:23, Hassan Schroeder <hassan.s...@gmail.com> wrote:
On Fri, Sep 3, 2010 at 8:59 AM, PalaniKannan K <kpalan...@gmail.com> wrote:

> I feel that, this is same kind of results I got in google search... Creating
> model using dumped schemas of existing table. but, its not working.

"its not working" isn't particularly useful information.

So you have an existing table, say "things".  You create a model for
it, e.g.

 class Thing < ActiveRecord::Base
 end

Done. Maybe you have to tell it there's a non-Rails-standard index
field, etc., but basically that's it. There's no reason to be fooling with
migrations if you have an existing table, unless you can and want to
do transformations on them to make them more Rails-like.

Realy Sorry... If my problem was not understandable. I am a new bee... there is no perfect tutorials available for already existing tables to develop web interface. In before cases I used cgi and perl. Now I started ruby and RoR. I feel its totally different from cgi. If you know any turorials with examples, kindly tell me. In previously mentioned link, I am unable to understand.

So what have you tried, and what's the actual problem?

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Hassan Schroeder ------------------------ hassan.s...@gmail.com
twitter: @hassan

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Hassan Schroeder

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Sep 3, 2010, 3:14:22 PM9/3/10
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On Fri, Sep 3, 2010 at 11:18 AM, PalaniKannan K <kpalan...@gmail.com> wrote

> Realy Sorry... If my problem was not understandable. I am a new bee... there
> is no perfect tutorials available for already existing tables to develop web
> interface. In before cases I used cgi and perl. Now I started ruby and RoR.
> I feel its totally different from cgi. If you know any turorials with
> examples, kindly tell me. In previously mentioned link, I am unable to
> understand.

The earlier link was irrelevant, ignore it. The advice to google "rails
legacy database" from Ar Chron should help, though.

In any case, make a copy of your existing DB and point your Rails
app at it.

Create a model based on an existing table e.g. "things", as in

class Thing < ActiveRecord::Base
end

Then start a console and type

thing = Thing.first

Look at the result. That should get you started :-)

And no, sorry, I don't know of any specific tutorials on doing this. It
would probably be easier if you'd already developed at least a trivial
green-field Rails app (gone through the basic tutorials, guides, etc.)

FWIW, and good luck,

E. Litwin

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Sep 3, 2010, 5:47:57 PM9/3/10
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On Sep 3, 12:14 pm, Hassan Schroeder <hassan.schroe...@gmail.com>
wrote:
> Create a model based on an existing table e.g. "things", as in
>
>  class Thing < ActiveRecord::Base
>  end
>

Odds are, you will need to tell Rails what the primary key of your
legacy table is, unless it happens to be "id"

class Thing < ActiveRecord::Base
set_primary_key "[PKFieldName]"
end

Hassan Schroeder

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Sep 3, 2010, 6:10:14 PM9/3/10
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On Fri, Sep 3, 2010 at 2:47 PM, E. Litwin <eli...@rocketmail.com> wrote:

> Odds are, you will need to tell Rails what the primary key of your
> legacy table is, unless it happens to be "id"

Absolutely, and odds are the OP will encounter other grief in the form
of naming conventions/pluralization yadda yadda. :-)

But creating a model and seeing what happens and where it breaks[*]
is the best way to start, IMO. And as a matter of fact I'm currently up
to my armpits in a similar project, though I do have the leeway to do
a few Railsizations to the db schema, thankfully.

[*] by writing tests, hopefully!

FWIW,

Cuz Ican

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Sep 3, 2010, 6:52:52 PM9/3/10
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Haven't used them but I would check them out..
http://magicmodels.rubyforge.org/magic_model_generator/
http://github.com/ahe/reverse_scaffold

Also, read this forum to consider some potential messy things.
http://www.ruby-forum.com/topic/149050

PalaniKannan K

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Sep 6, 2010, 8:51:14 AM9/6/10
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Hi,

The Problem got solved... Thank you for valuable comments from each one in this thread.

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