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, 19 insertions, 2 deletions

diff --git a/activerecord/test/cases/log_subscriber_test.rb b/activerecord/test/cases/log_subscriber_test.rb
index 208e54ed0b..e2742ed33e 100644
--- a/activerecord/test/cases/log_subscriber_test.rb
+++ b/activerecord/test/cases/log_subscriber_test.rb
@@ -33,8 +33,9 @@ class LogSubscriberTest < ActiveRecord::TestCase
       super
     end
 
-    def debug(message)
-      @debugs << message
+    def debug(progname = nil, &block)
+      @debugs << progname
+      super
     end
   end
 
@@ -171,6 +172,22 @@ class LogSubscriberTest < ActiveRecord::TestCase
     assert_match(/SELECT .*?FROM .?developers.?/i, @logger.logged(:debug).last)
   end
 
+  def test_vebose_query_logs
+    ActiveRecord::Base.verbose_query_logs = true
+
+    logger = TestDebugLogSubscriber.new
+    logger.sql(Event.new(0, sql: "hi mom!"))
+    assert_match(/↳/, @logger.logged(:debug).last)
+  ensure
+    ActiveRecord::Base.verbose_query_logs = false
+  end
+
+  def test_verbose_query_logs_disabled_by_default
+    logger = TestDebugLogSubscriber.new
+    logger.sql(Event.new(0, sql: "hi mom!"))
+    assert_no_match(/↳/, @logger.logged(:debug).last)
+  end
+
   def test_cached_queries
     ActiveRecord::Base.cache do
       Developer.all.load