How to return a specific key value from an hstore?

Question

I have a psql database that contains an hstore as a column, as such: column: "a" => "1", "b" => "2", "c" => "3"

In a standalone ruby script, I am correctly accessing my database, but I would like to output a specific value for "a", so that it only returns "1". When I attempt to do this from a loop it outputs "a" => "1" instead.

require 'rubygems'
require 'pg'
require 'open-uri'
require'activerecord-postgres-hstore'

conn = PGconn.connect("hostname", 1234, '', '', "x", "y", "z")

array = conn.exec('SELECT * FROM database')

  array.each do |uri|
    puts uri['column']
  end

The documentation on this page http://www.postgresql.org/docs/9.1/static/hstore.html shows that you can use hstore -> text to obtain the value, but I am unsure how to do this in ruby.

I have also seen this question how to parse and display hstore key/value in rails , but as I said the output gives me both key and value when I only want the value.

I should also say that while the database was created using rails, I do not want to use it for this script. Any help would be appreciated.

Answer 1

If you only want to extract the values for the 'a' keys in column then say exactly that and let the database do the work:

conn.exec(%q{SELECT column -> 'a' FROM database}).each do |_, a|
  # The value will be in `a`, `_` will be the made up column name.
end

or, if you want to work with other things:

conn.exec(%q{SELECT other_column, column -> 'a' as col_at_a FROM database}).each do |row|
  # Look at `row['other_column']` and `row['col_at_a']` ...
end