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Re: ruby/postgres - getting assoc array of rows?

From: CSN <cool_screen_name90001(at)yahoo(dot)com>
To: Michael Fuhr <mike(at)fuhr(dot)org>
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: ruby/postgres - getting assoc array of rows?
Date: 2005-11-20 19:36:20
Message-ID: 20051120193620.68688.qmail@web52908.mail.yahoo.com (view raw or flat)
Thread:
Lists: pgsql-interfaces
--- Michael Fuhr <mike(at)fuhr(dot)org> wrote:

> On Sun, Nov 20, 2005 at 02:31:45AM -0800, CSN wrote:
> > I tried:
> > puts "by name:     #{row['id']} #{row['name']}"
> > 
> > but it exits with:
> > pg.rb:16:in `[]': can't convert String into Integer (TypeError)
> 
> What versions of Ruby and ruby-postgres are you using?  Did you use
> exactly the code I posted or did you do something different?  The
> only way to get a PGrow object (other than building it yourself)
> is from PGresult#each or some method that calls it, so this won't
> work:

I'm using Ruby 1.8 and postgres 0.7.1 (installed via gem). Doing 'gem list -r' I see there's also
this, which I don't have installed:

postgres-pr (0.4.0, 0.3.6, 0.3.5, 0.3.4, 0.3.3, 0.3.2, 0.3.1, 0.3.0, 0.2.2, 0.2.1, 0.2.0, 0.1.1,
0.1.0, 0.0.1)
    A pure Ruby interface to the PostgreSQL (>= 7.4) database

My code is nearly identical to what you posted, however PGconn.new('dbname=mydb') gives this
error:
pg.rb:6:in `new': could not translate host name "dbname=mydb" to address: Name or service not
known (PGError)

This in the only connection code I could get to work:
conn = PGconn.connect("localhost", 5432, '', '', "mydb", "user", "password")

My code also differs in that I need to put "require 'rubygems'" before "require 'postgres'",
otherwise I get this error:
`require': no such file to load -- postgres (LoadError)

> conn = PGconn.new('dbname=test')
> result = conn.exec('SELECT 1 AS x')
> row = result[0]  # returns an Array
> puts row['x']    # raises TypeError
> 
> but this does work:
> 
> row = result.to_a[0]  # returns a PGrow
> puts row['x']

With that, I get (I'm doing "select * from items order by id limit 10"):
nil
nil
nil
nil
nil
nil
nil
undefined method `[]' for nil:NilClass (NoMethodError)


Here's my complete code I'm using with various lines comments/uncommented. Using "result.to_a[0]"
vs. "result.each", etc. appears to give a different type of row and some of the "puts" lines give
errors where they worked before, or work when they previously gave errors.


require 'rubygems'
require 'postgres'

conn = PGconn.connect("localhost", 5432, '', '', "mydb", "user", "password")
#conn = PGconn.new("dbname=mydb")
#conn = PGconn.connect(:pghost=>"localhost", :dbname=> "mydb", :login=>"user",
:password=>"password")

res = conn.exec("select * from items order by id limit 10;")

#rows=res.collect
#for row in res.result
res.each do |row|
#for row in res.to_a[0]
  #puts row[0] + row[1]
  puts "#{row['title']}" # error: undefined method `[]' for nil:NilClass (NoMethodError)
  #puts "by name:     #{row['id']} #{row['title']}" # gives error
  #print row # works
  #print row.inspect # works

  #puts row[0] # works
  #puts row.getvalue(0,0) # error: undefined method `getvalue' for "7518":String (NoMethodError)
end



> I'm not sure if the PGrow behavior is version-specific.  I don't
> see it mentioned in the ruby-postgres ChangeLog, so I'd have to dig
> a little more to find out.


Thanks for your help!
csn


> 
> -- 
> Michael Fuhr
> 



		
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