Ruby Postgresql Tutorials

Ruby PostgreSQL tutorials

You only need to require the pg gem and establish the connection to the DB:

require 'pg'
# require 'active_record'  # uncomment for not Rails environment

ActiveRecord::Base.establish_connection(:adapter => "postgresql",
                                        :username => "username",
                                        :password => "password",
                                        :database => "database")

When you define models to inherit from ActiveRecord::Base they will use this database connection. Everything else should work like it does in Rails.

Ruby tutorial for how to write stored procedures for PostgreSQL?

Check this website: http://moulon.inra.fr/ruby/plruby.html , it has some nice examples.

How to Connect the Ruby to the Postgresql?

PGConn is wrong, the postrges gem called pg is using PG now.

Example:

require 'pg' 
conn = PG.connect( dbname: 'sales' ) 
conn.exec( "SELECT * FROM pg_stat_activity" ) do |result| 
    result.each do |row| 
        puts row.values_at('procpid', 'usename', 'current_query')
    end
end

Installing Postgres on windows for use with Ruby-on-Rails

An approach to installing Postgres on windows 7 for use as PostgreSQL database for a rails 3 (3.0.7) project.

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Preamble (you can skip this bit)

So the first thing to point out is that Postgres is not just a different file extension from .sqlite3, it's a whole mechanism for managing your databases. As such it has a client/server model, of which you'll need to set up both to use Postgres as the database for your rails app.

Motivation for going through considerable pain of Postgres setup versus almost effortless sqlite setup: if you're deploying to Heroku, they're currently using Postgres so some of your SQL calls that are fine on sqlite3 will break when used with Postgres. It's much easier to debug postgres locally rather than when it's on Heroku's servers.

So I did the following things:
(Disclaimer: I may have forgotten to include some of the things I did... it took me over 48 hours of on and off pain to get it to work... if the following advice doesn't work for you then the huge (2300 pages!!) but very thorough Postgres documentation should help. I'd recommend downloading this anyway if you're serious about using Postgres as it has a lot of material that I've only just begun to understand the significance of.)
(Second disclaimer: I have almost certainly broken 20 sensible Postgres guidelines and exposed security holes in the Postgres database whilst doing so. If there any obvious things an experienced Postgres user disagrees with, please edit my post.)

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.Step 1. Download and install PostgreSQL v9.0.4-1 from here because here said only 9.0.x would be supported on windows 7. I kept all the default options and just used 'secret' as the password when prompted by the Postgres installer for one (again not entirely sure what the consequences of sharing that info on the internet is... will soon find out I'm sure). You'll need this password in step 3.

.Step 2. Change environment variables such that Path (for system, not user (I'm not sure if this is significant or not)) is: C:\Program Files\PostgreSQL\9.0\bin
(n.b. I'm on 64-bit windows hence it not being installed for 32-bit in 'C:\Program Files (x86)\PostgreS...')

Don't forget to change access rights to folder PostgreSQL\9.0 and remove any default readonly rights on the folder or content.
(You may also need to restart your computer for these to take effect - thanks @Gavin -although not likely).

.Step 3. Test Postgres installation by trying to create a new database:
From command line: createdb -U postgres mydb_as_postgres.
You should be prompted to enter the password now, if you're not it may be that you need to start the server first (I can't remember whether I needed to do this or not). The easiest way is through pgAdmin III, which should be 'pgAdmin3.exe' in a folder somewhere like C:\Program Files\PostgreSQL\9.0\bin. Once you've started pgAdmin III there should be a panel on the left called 'Object Browser'. In this there should be a tree with:

Server Groups > Servers > PostgreSQL 9.0 (localhost:5432)

Right click on 'PostgreSQL 9.0 (localhost:5432)' and select 'Connect'.

The createdb -U postgres mydb_as_postgres command should create a new databse called 'mydb_as_postgres' which you can check by firing up pgAdmin III and double clicking on 'PostgreSQL 9.0 (localhost:5432)'. Under this there should be:

Databases (2) which should list 2 databases called mydb_as_postgres and postgres

I called it _as_postgres because the -U postgres part of the command tells Postgres to create the database with the postgres user as it's owner, which you need to specify when you're not signed in as the postgres user. I have all of my files stored as 'AJames' user though so if you're the same and want to keep developing your app when signed in as a different user you need to create a Postgres 'role' for that user now (see step 4).

.Step 4. Through pgAdmin III. Right-click on Login Roles (which for me is in):

Object Browser > Server Groups > Servers > PostgreSQL 9.0 (localhost:5432) > Login Roles

Right-click on Login Roles and select 'New Login Role...'
in Role name, put in your operating system user name, which for me is AJames,
and fill in your password under the 'Role Privileges' tab, I checked all the boxes, but an experienced postgres user would likely strongly recommend to only check the 'inherits rights from parent roles' and the 'can create database objects' But I'm not an experienced user and just want to debug Rails SQL calls in Postgres so I also checked the 'Superuser' and 'Can create roles', just in case.

.Step 5. You should now be able to create a new database without being signed in as the postgres user. Try typing:

createdb mydb_as_user

Hopefully this should work for you.

.Step 6. Okay, so you've got a development.sqlite3 file in your rails 'db/' directory. Initially I was going to set the next test as converting this from sqlite3 to psql.

I couldn't get this to work though but I left my attempts here as the solution I used required having the data in a Rails app on Heroku.com (see instead the solution from step 7 onwards). For those who only have a local app and no data in Heroku, they can't use the same approach, so they might need to explore something like this:

x6.1 First, test 'psql' by trying a command from your command line like:

psql mydb_as_user

this should display something like below (after you've typed in your password):

C:>psql mydb_as_user
Password:
psql (9.0.4)
WARNING: Console code page (850) differs from Windows code page (1252)
         8-bit characters might not work correctly. See psql reference
         page "Notes for Windows users" for details.
Type "help" for help.

mydb5=# 

x6.2 try entering:

CREATE TABLE users_table (id integer, "name" text);

It should display:

CREATE TABLE
mydb5=#

If you check in pgAdmin III, you should see the table there under:

Object Browser > Server Groups > Servers > PostgreSQL 9.0 (localhost:5432) > Databases > mydb_as_user > Schemas > public > Tables > users_table >

x6.3 Okay, next to try the conversion. Downloaded sqlite-shell precompiled binary for windows.

x6.4 Create a new directory, I used 'C:\temp' and put the sqlite3.exe and your development.sqlite3 files in it.

x6.5 Use the following commands (which are from here) to dump the development.sqlite3 database into Postgres.

sqlite3 development .dump | psql development2

you might get an error like:

psql: FATAL: database "development2" does not exist

x6.6 so I went into pgAdmin III and made a development 2 database, tried the command again and got:

ERROR:  syntax error at or near "PRAGMA"
LINE 1: PRAGMA foreign_keys=OFF;
        ^
BEGIN
COMMIT

Like I said, I couldn't get it to work. I'm sure there's a way of getting round that error but I thought of a different way and so I instead used this solution (which requires a Heroku account to have your data and does the conversion from sqlite3 to psql using the Taps gem (I believe):

.Step 7. in pgAdmin III I created another database. Under the properties tab I set name: 'development', owner: 'AJames' (replace this with your own Windows user name). And under the privileges tab, set role: 'public' and checked the ALL option (thought this resets to unchecked so I'm not sure that's necessary).

.Step 8. add
gem 'pg', '0.11.0'
to your gem file. You'll probably also want to remove the:
gem 'sqlite3'
at this point too.

.Step 9. set database.yml as suggested here to:

development:
  adapter: postgresql
  database: db/development
  username: AJames # replace this with your own user name
  password: secret # replace this with your own password
  host: localhost
  encoding: UTF8
  pool: 5
  timeout: 5000

If you are working on an open source project and don't want your password to be made publicly available, have a look at some of the answers to Securely providing the database password in a Rails app.

.Step 10. from command line in your rails app's root directory run:
rake db:migrate
This will create the new schema and all the tables in the Postgres database.

.Step 11. run heroku db:pull from your command line (again from in the root directory of your rails app) to pull all your data down and into your new empty Postgres database. I think at this point your taps gem will be doing this work for you.

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.Step 12. Hopefully there is no step 12! ...and it should now be working for you. Happy RoR PostgreSQL debugging! Please edit, or let me know, if there are any errors in this.

Also, here's a list of additional stuff that might be interesting/useful:

• This is a blog post about Postgres passwords, what they're for,
  why you need them, how to change them etc.
• This, under 'Creating a spatial database', is useful for newbies to
  understand what pg_hba.conf is about and the second link that
  Reno gave above, under the 'Using pgAdmin III GUI' is useful to
  testing to see if postgres is actually working, before trying to fit
  it with Rails (i.e. try creating a database and putting a table and
  some data into it).
• In the huge but very comprehensive Postgres documentation, I'd
  start on page 58, 'I. tutorial'. Then on pdf page 431(!) there's
  'Chapter 17. Server setup and operation' that I also found useful.

Ruby on rails : Data base sqlite3 to PostgreSQL [RALS]

You should follow this guide on setting up Postgres and Rails:

This section of the tutorial shows how to set up a user for Postgres:

Setting Up Postgres
Create a Postgres user for the Rails app we'll
create in the next step. To do this, switch into the Postgres user:

su - postgres Then create a user (or a "role", as Postgres calls it):

create role myapp with createdb login password 'password1'

However, you should use ubuntu instead of myapp to create the necessary role.

tips for installing postgres for a rails project on a linux box

This article from the Rails wiki should contain the information you are looking for.

I suggest you to install the pg GEM:

gem install pg

Also, Slicehost published a really interesting collection of article about using and configuring PostgreSQL on Ubuntu: http://articles.slicehost.com/postgresql

Multiple Rails projects with different databases for each

You can specify adapter to the ActiveRecord in two ways.

1. Using ENV['DATABASE_URL'] environment variable
2. Using database.yml configuration file

If you have both config/database.yml and ENV['DATABASE_URL'] set then Rails will merge the configuration together. I think this is what causes your problem.

If it is so, you can remove your environmental variable or specify url explicitly in your database.yml

I encourage you to read the following article for more information: http://guides.rubyonrails.org/configuring.html#configuring-a-database

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