Thursday, July 16, 2015

How to discover what is generating an SQL statement in your Rails log

Just spreading a really cool tip I came across. Ryan Bigg has this blog post showing how you can find out what is creating an SQL statement in your log. I was having a devil of a time figuring out where a particular callback was coming from and discovered his great post. Essentially you hook into ActiveSupport::Notifications and then put in logic in the regex piece to describe the query you are looking for. In this case I did this in development.rb:
  ActiveSupport::Notifications.subscribe('sql.active_record') do |_, _, _, _, details|  
   if details[:sql] =~ /UPDATE "answers" SET position =/  
    puts '*' * 50  
    puts caller.join("\n")  
    puts '*' * 50  
And then looked at the call stack to see where it was coming from. I could have output to the logger too. And I would not recommend doing this on Production.

Sunday, July 12, 2015

A new gem to help monitor Postgres performance in standalone instances

I just released my own gem for querying Postgres Databases for performance issues. I had used Heroku PG Extras and the Go Boundless New Relic Postgres plugin previously. Each are excellent tools with a lot of overlap. The holes for each-- hosting on Heroku needed for PG Extras and the lack of visibility into the queries themselves on New Relic-- pushed me to write this gem. My aim is to build an engine on it that will display the stats in screens that can be plugged into an application. We'll see how that goes.