# Overwrite active\_record find? **URL:** \ **Category:** Rails\ **Created:** [May 29, 2008, 2:17pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962 "2008-05-29T14:17:51Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 29, 2008, 2:17pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/1 "2008-05-29T14:17:51Z")
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 ---
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 29, 2008, 2:26pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/2 "2008-05-29T14:26:44Z")
On 29 May 2008, at 13:17, Christian K. 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 ---
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 29, 2008, 2:34pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/3 "2008-05-29T14:34:59Z")
Frederick C. 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’ ---
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 29, 2008, 2:44pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/4 "2008-05-29T14:44:31Z")
On 29 May 2008, at 13:34, Christian K. wrote: > > 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 ---
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 29, 2008, 3:40pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/5 "2008-05-29T15:40:52Z")
On 29 May 2008, at 14:05, Christian K. wrote: > > lock). > > 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 ---
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 29, 2008, 3:05pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/6 "2008-05-29T15:05:08Z")
Frederick C. 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 ---
**Author:** ![sealedsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/e68b1a/32.png) [@sealedsun](https://www.ruby-forum.com/u/sealedsun)\ **Post date:** [May 30, 2008, 3:09pm UTC](https://www.ruby-forum.com/t/overwrite-active-record-find/138962/7 "2008-05-30T15:09:32Z")
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 C. \<