Rails Ruby on Rails → 2.x

Comments and changes to this ticket

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  Barry Robison August 21st, 2008 @ 10:45 AM

  I believe that should be

     def tables(name = nil) #:nodoc:
       tables = []
  

  •  execute("SHOW TABLES", name).each { |field| tables << field[0] }
    

  •  execute("SHOW TABLES", name).each { |field| tables << field[0] } unless @tables
    

  •  @tables ||= tables
    

  •  tables
    

  •  @tables
    

    end

  at least that works better for me =0

• 

  Pratik August 21st, 2008 @ 11:12 AM

  • State changed from “new” to “invalid”

  Can't reproduce. Could you please also attach a failing test case ?

  Thanks.

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  Barry Robison August 21st, 2008 @ 11:21 AM

  Sorry I don't really know Ruby, just trying to performance analyze an app. The last statement in the block is the return value right? In the original patch that would be "tables", which is initialized to an empty array. It's only populated if @tables is not yet cached, so after the first run, you'll be returning an empty list instead of the cached one.

  Unless I'm missing something about ruby, which I probably am. And my revised patch got de-formated by the comment system =(

  ta, Barry

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  Barry Robison August 21st, 2008 @ 11:28 AM

  here's a similar method for not calling SHOW FIELDS every time a table is accessed, also seem to help speed.

  
        def columns(table_name, name = nil)#:nodoc:
          sql = "SHOW FIELDS FROM #{table_name}"
          columns = []
          @columnCache ||= {}
          execute(sql, name).each { |field| columns << MysqlColumn.new(field[0], field[4], field[1], field[2] == "YES") } unless @columnCache[table_name]
          @columnCache[table_name] ||= columns
          @columnCache[table_name]
        end
  

  hth, Barry

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  Fris February 20th, 2011 @ 11:02 AM

  Steps to repro:

  1. Install will_paginate gem.
     
  2. Make some valid code that displays a index of records from some model.
     
  3. Include a call to <%= will_paginate %> in the ERB view.
     
  4. DO NOT call paginate in the controller.

  Result:
  You will get an error like:

  You have a nil object when you didn't expect it!
  You might have expected an instance of Array.
  The error occurred while evaluating nil.each
  

  and there will be many SHOW TABLES calls in the log file (each one taking about 4ms in my case).

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  Fris February 20th, 2011 @ 11:18 AM

  I could not edit my post to add more info, so here it is (the stack trace of where the SHOW TABLES is being called from, I believe):

      ...rails303/gems/activesupport-3.0.3/lib/active_support/log_subscriber.rb:93:in `send`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/log_subscriber.rb:93:in `call`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/fanout.rb:47:in `publish`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/fanout.rb:25:in `publish`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/fanout.rb:25:in `each`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/fanout.rb:25:in `publish`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/instrumenter.rb:26:in `instrument`
      ...rails303/gems/activerecord-3.0.3/lib/active_record/connection_adapters/abstract_adapter.rb:195:in `log`
      ...rails303/gems/mysql2-0.2.6/lib/active_record/connection_adapters/mysql2_adapter.rb:314:in `execute`
      ...rails303/gems/mysql2-0.2.6/lib/active_record/connection_adapters/mysql2_adapter.rb:432:in `tables`
      ...rails303/gems/activerecord-3.0.3/lib/active_record/connection_adapters/abstract/schema_statements.rb:21:in `table_exists?`
      ...rails303/gems/activerecord-3.0.3/lib/active_record/base.rb:673:in `table_exists?`
      ...rails303/gems/activerecord-3.0.3/lib/active_record/base.rb:795:in `inspect`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb:16:in `debug_hash`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb:16:in `map`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb:16:in `debug_hash`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb:27:in `__home_base__rvm_gems_ruby_______p____rails____gems_actionpack_______lib_action_dispatch_middleware_templates_rescues__request_and_response_erb__147464093__612719698_0`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/template.rb:135:in `send`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/template.rb:135:in `render`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications.rb:54:in `instrument`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/template.rb:127:in `render`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/render/rendering.rb:59:in `_render_template`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications.rb:52:in `instrument`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/instrumenter.rb:21:in `instrument`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications.rb:52:in `instrument`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/render/rendering.rb:56:in `_render_template`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/render/rendering.rb:26:in `render`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/template_error.erb:21:in `__home_base__rvm_gems_ruby_______p____rails____gems_actionpack_______lib_action_dispatch_middleware_templates_rescues_template_error_erb__42385148__612684748_0`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/template.rb:135:in `send`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/template.rb:135:in `render`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications.rb:54:in `instrument`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/template.rb:127:in `render`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/render/rendering.rb:59:in `_render_template`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications.rb:52:in `instrument`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications/instrumenter.rb:21:in `instrument`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/notifications.rb:52:in `instrument`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/render/rendering.rb:56:in `_render_template`
      ...rails303/gems/actionpack-3.0.3/lib/action_view/render/rendering.rb:26:in `render`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/show_exceptions.rb:88:in `rescue_action_locally`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/show_exceptions.rb:68:in `render_exception`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/show_exceptions.rb:59:in `call`
      ...rails303/gems/railties-3.0.3/lib/rails/rack/logger.rb:13:in `call`
      ...rails303/gems/rack-1.2.1/lib/rack/runtime.rb:17:in `call`
      ...rails303/gems/activesupport-3.0.3/lib/active_support/cache/strategy/local_cache.rb:72:in `call`
      ...rails303/gems/rack-1.2.1/lib/rack/lock.rb:11:in `call`
      ...rails303/gems/rack-1.2.1/lib/rack/lock.rb:11:in `synchronize`
      ...rails303/gems/rack-1.2.1/lib/rack/lock.rb:11:in `call`
      ...rails303/gems/actionpack-3.0.3/lib/action_dispatch/middleware/static.rb:30:in `call`
      ...rails303/gems/railties-3.0.3/lib/rails/application.rb:168:in `call`
      ...rails303/gems/railties-3.0.3/lib/rails/application.rb:77:in `send`
      ...rails303/gems/railties-3.0.3/lib/rails/application.rb:77:in `method_missing`
      ...rails303/gems/railties-3.0.3/lib/rails/rack/log_tailer.rb:14:in `call`
      ...rails303/gems/rack-1.2.1/lib/rack/content_length.rb:13:in `call`
      ...rails303/gems/rack-1.2.1/lib/rack/handler/webrick.rb:52:in `service`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/httpserver.rb:104:in `service`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/httpserver.rb:65:in `run`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:173:in `start_thread`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:162:in `start`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:162:in `start_thread`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:95:in `start`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:92:in `each`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:92:in `start`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:23:in `start`
      ...ruby-1.8.7-p330/lib/ruby/1.8/webrick/server.rb:82:in `start`
      ...rails303/gems/rack-1.2.1/lib/rack/handler/webrick.rb:13:in `run`
      ...rails303/gems/rack-1.2.1/lib/rack/server.rb:213:in `start`
      ...rails303/gems/railties-3.0.3/lib/rails/commands/server.rb:65:in `start`
      ...rails303/gems/railties-3.0.3/lib/rails/commands.rb:30
      ...rails303/gems/railties-3.0.3/lib/rails/commands.rb:27:in `tap`
      ...rails303/gems/railties-3.0.3/lib/rails/commands.rb:27", "script/rails:6:in `require`", "script/rails:6"
  

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  Fris February 20th, 2011 @ 11:30 AM

  Just a wild guess, but maybe it's something to do with the call to inspect from debug_hash and the inspect is getting called on ActiveRecord::Base (which then calls table_exists?).

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  Fris February 20th, 2011 @ 11:33 AM

  Ps.I am using Rails 3.0.3

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  bingbing March 26th, 2011 @ 02:07 AM

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