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Christian Kerth

2008-May-29 12:17 UTC

Overwrite active_record find?

Hey!

i need to overwrite active record find to synchronize database access

i''ve tried the following:

def self.find(*args)
           begin
                @@semaphore.synchronize {


                        super(args)


                }
            rescue
                puts "error: "+$!
                @@semaphore.unlock
            end
        end

        def self.find_by_sql(sql)

           begin
                @@semaphore.synchronize {


                      super(sql)


                }
            rescue
                puts "error: "+$!
                @@semaphore.unlock
            end
        end

I always get an error:

c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1227:in
`find_initial'': undefined method `first'' for nil:NilClass
(NoMethodError)
        from
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:in
`send''
        from
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:in
`find_by_requesttype_and_requeststatus''



Obviously the dynamic finder methos like
find_by_equesttype_and_requeststatus doesn''t work.

Any clues to fix this?

Thx
-- 
Posted via http://www.ruby-forum.com/.

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Frederick Cheung

2008-May-29 12:26 UTC

head link

Re: Overwrite active_record find?

On 29 May 2008, at 13:17, Christian Kerth wrote:
>
> Hey!
>
> i need to overwrite active record find to synchronize database access
>You need to say super(*args). alias_method_chain is usually a more  
prudent choice for this sort of stuff (and i assume you know that this  
won''t accomplish anything if you''re using a pack of mongrels
or
whatever - I suppose it would work if you had a single multithreaded  
script, but I''m still not sure what the point would be)

Fred> i''ve tried the following:
>
> def self.find(*args)
>           begin
>                @@semaphore.synchronize {
>
>
>                        super(args)
>
>
>                }
>            rescue
>                puts "error: "+$!
>                @@semaphore.unlock
>            end
>        end
>
>        def self.find_by_sql(sql)
>
>           begin
>                @@semaphore.synchronize {
>
>
>                      super(sql)
>
>
>                }
>            rescue
>                puts "error: "+$!
>                @@semaphore.unlock
>            end
>        end
>
> I always get an error:
>
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/ 
> base.rb:1227:in
> `find_initial'': undefined method `first'' for nil:NilClass
> (NoMethodError)
>        from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/ 
> base.rb:1514:in
> `send''
>        from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/ 
> base.rb:1514:in
> `find_by_requesttype_and_requeststatus''
>
>
>
> Obviously the dynamic finder methos like
> find_by_equesttype_and_requeststatus doesn''t work.
>
> Any clues to fix this?
>
> Thx
> -- 
> Posted via http://www.ruby-forum.com/.
>
> >

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Christian Kerth

2008-May-29 12:34 UTC

head link

Re: Overwrite active_record find?

Frederick Cheung wrote:
> You need to say super(*args). alias_method_chain is usually a more
> prudent choice for this sort of stuff (and i assume you know that this
> won''t accomplish anything if you''re using a pack of
mongrels or
> whatever - I suppose it would work if you had a single multithreaded
> script, but I''m still not sure what the point would be)
> 
> Fred
Problem is I''m using active_record without rails on a application that 
includes a mini http server (built on top of webrick) and a background 
task. Both operate on the same sqlite db. Because of concurrency issues 
with sql I''m trying to synchronize access to the database.

Iven with super(*args) i still get the error:

c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1227:in
`find_initial'': undefined method `first'' for nil:NilClass 
(NoMethodError)
        from 
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:in
`send''
        from 
c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/base.rb:1514:in
`find_by_requesttype_and_requeststatus''

-- 
Posted via http://www.ruby-forum.com/.

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Frederick Cheung

2008-May-29 12:43 UTC

head link

Re: Overwrite active_record find?

On 29 May 2008, at 13:34, Christian Kerth wrote:
>
> Frederick Cheung wrote:
>
>> You need to say super(*args). alias_method_chain is usually a more
>> prudent choice for this sort of stuff (and i assume you know that  
>> this
>> won''t accomplish anything if you''re using a pack of
mongrels or
>> whatever - I suppose it would work if you had a single multithreaded
>> script, but I''m still not sure what the point would be)
>>
>> Fred
>
> Problem is I''m using active_record without rails on a application
that
> includes a mini http server (built on top of webrick) and a background
> task. Both operate on the same sqlite db. Because of concurrency  
> issues
> with sql I''m trying to synchronize access to the database.
>
> Iven with super(*args) i still get the error:
>Should have been obvious - it looks like you''re not returning the  
right value (ie the result) from find_by_sql. Also bear in mind that  
find will call find_by_sql in some cases, so make sure whatever  
locking mechanism you''re using will support that. I''ve got a
hint of a
doubt that by background task you mean a separate process, in which  
case you''re out of luck (because each process would have its own lock).

Fred> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/ 
> base.rb:1227:in
> `find_initial'': undefined method `first'' for nil:NilClass
> (NoMethodError)
>        from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/ 
> base.rb:1514:in
> `send''
>        from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/ 
> base.rb:1514:in
> `find_by_requesttype_and_requeststatus''
>
> -- 
> Posted via http://www.ruby-forum.com/.
>
> >

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Christian Kerth

2008-May-29 13:05 UTC

head link

Re: Overwrite active_record find?

Frederick Cheung wrote:
> Should have been obvious - it looks like you''re not returning the
> right value (ie the result) from find_by_sql. Also bear in mind that
> find will call find_by_sql in some cases, so make sure whatever
> locking mechanism you''re using will support that. I''ve
got a hint of a
> doubt that by background task you mean a separate process, in which
> case you''re out of luck (because each process would have its own
lock).
I switched the locking mechanism to thread.exclusive, because a mutex 
doesn''t work because find is calling find_by_sql. Added the returns.

def self.find(*args)
           begin
                #@@semaphore.synchronize {
                    Thread.exclusive {
                        #puts "find"
                        return super(args)

                    }
                #}
            rescue
                puts "error: "+$!
               # @@semaphore.unlock
            end
        end

        def self.find_by_sql(sql)
           begin
                #@@semaphore.synchronize {
                    Thread.exclusive {
                      #puts "find_by_sql"
                      return super(sql)
                    }
                #}
            rescue
                puts "error: "+$!
               # @@semaphore.unlock
            end
        end


By background task is a second thread, not a seperate process, so the 
locking mechanism should work.

Is every find call using find_by_sql to retrieve data? Would it be 
enough to syncronize just find_by_sql then?

thx
-- 
Posted via http://www.ruby-forum.com/.

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Frederick Cheung

2008-May-29 13:39 UTC

head link

Re: Overwrite active_record find?

On 29 May 2008, at 14:05, Christian Kerth wrote:
>
> Frederick Cheung wrote:
>
>> Should have been obvious - it looks like you''re not returning
the
>> right value (ie the result) from find_by_sql. Also bear in mind that
>> find will call find_by_sql in some cases, so make sure whatever
>> locking mechanism you''re using will support that.
I''ve got a hint
>> of a
>> doubt that by background task you mean a separate process, in which
>> case you''re out of luck (because each process would have its
own
>> lock).
>
> I switched the locking mechanism to thread.exclusive, because a mutex
> doesn''t work because find is calling find_by_sql. Added the
returns.
>
>
>
> By background task is a second thread, not a seperate process, so the
> locking mechanism should work.
>
> Is every find call using find_by_sql to retrieve data? Would it be
> enough to syncronize just find_by_sql then?
>Almost all. a find with an :include doesn''t in rails 2.0.2. This sort  
of thing could change in the future though.

Fred> thx
> -- 
> Posted via http://www.ruby-forum.com/.
>
> >

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Russell Norris

2008-May-30 12:52 UTC

head link

Re: Overwrite active_record find?

FWIW you can just use super [with no args] if it''s going to use the
same
arguments passed to the method. This works even if you modify the arguments
like:

  def label(object_name, method, text = nil, options = {})
    text ||= method.to_s[].titleize
    super
  end

RSL

On Thu, May 29, 2008 at 8:26 AM, Frederick Cheung <
frederick.cheung-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
> On 29 May 2008, at 13:17, Christian Kerth wrote:
>
> >
> > Hey!
> >
> > i need to overwrite active record find to synchronize database access
> >
> You need to say super(*args). alias_method_chain is usually a more
> prudent choice for this sort of stuff (and i assume you know that this
> won''t accomplish anything if you''re using a pack of
mongrels or
> whatever - I suppose it would work if you had a single multithreaded
> script, but I''m still not sure what the point would be)
>
> Fred
> > i''ve tried the following:
> >
> > def self.find(*args)
> >           begin
> >                @@semaphore.synchronize {
> >
> >
> >                        super(args)
> >
> >
> >                }
> >            rescue
> >                puts "error: "+$!
> >                @@semaphore.unlock
> >            end
> >        end
> >
> >        def self.find_by_sql(sql)
> >
> >           begin
> >                @@semaphore.synchronize {
> >
> >
> >                      super(sql)
> >
> >
> >                }
> >            rescue
> >                puts "error: "+$!
> >                @@semaphore.unlock
> >            end
> >        end
> >
> > I always get an error:
> >
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/
> > base.rb:1227:in
> > `find_initial'': undefined method `first'' for
nil:NilClass
> > (NoMethodError)
> >        from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/
> > base.rb:1514:in
> > `send''
> >        from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-2.0.2/lib/active_record/
> > base.rb:1514:in
> > `find_by_requesttype_and_requeststatus''
> >
> >
> >
> > Obviously the dynamic finder methos like
> > find_by_equesttype_and_requeststatus doesn''t work.
> >
> > Any clues to fix this?
> >
> > Thx
> > --
> > Posted via http://www.ruby-forum.com/.
> >
> > >
>
>
> >
>
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Rails - May 2008 - Overwrite active_record find?

Overwrite active_record find?

Re: Overwrite active_record find?

Re: Overwrite active_record find?

Re: Overwrite active_record find?

Re: Overwrite active_record find?

Re: Overwrite active_record find?

Re: Overwrite active_record find?