Log call site for all queries

This new ActiveRecord configuration option allows you to easily
pinpoint what line of application code is triggering SQL queries in the
development log by appending below each SQL statement log the line of
Ruby code that triggered it.

It’s useful with N+1 issues, and to locate stray queries.

By default this new option ignores Rails and Ruby code in order to
surface only callers from your application Ruby code or your gems.

It is enabled on newly generated Rails 5.2 applications and can be
enabled on existing Rails applications:

```ruby
Rails.application.configure do
  # ...
  config.active_record.verbose_query_logs = true
end
```

The `rails app:upgrade` task will also add it to
`config/development.rb`.

This feature purposely avoids coupling with
ActiveSupport::BacktraceCleaner since ActiveRecord can be used without
ActiveRecord. This decision can be reverted in the future to allow more
configurable backtraces (the exclusion of gem callers for example).

1 files changed, 7 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 481159e501..88810cb328 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -18,6 +18,13 @@ module ActiveRecord
       mattr_accessor :logger, instance_writer: false
 
       ##
+      # :singleton-method:
+      #
+      # Specifies if the methods calling database queries should be logged below
+      # their relevant queries. Defaults to false.
+      mattr_accessor :verbose_query_logs, instance_writer: false, default: false
+
+      ##
       # Contains the database configuration - as is typically stored in config/database.yml -
       # as a Hash.
       #