1 files changed, 21 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/explain_subscriber.rb b/activerecord/lib/active_record/explain_subscriber.rb
new file mode 100644
index 0000000000..fc76410499
--- /dev/null
+++ b/activerecord/lib/active_record/explain_subscriber.rb
@@ -0,0 +1,21 @@
+require 'active_support/notifications'
+
+module ActiveRecord
+  class ExplainSubscriber # :nodoc:
+    def call(*args)
+      if queries = Thread.current[:available_queries_for_explain]
+        payload = args.last
+        queries << payload.values_at(:sql, :binds) unless ignore_payload?(payload)
+      end
+    end
+
+    # SCHEMA queries cannot be EXPLAINed, also we do not want to run EXPLAIN on
+    # our own EXPLAINs now matter how loopingly beautiful that would be.
+    IGNORED_PAYLOADS = %w(SCHEMA EXPLAIN)
+    def ignore_payload?(payload)
+      payload[:exception] || IGNORED_PAYLOADS.include?(payload[:name])
+    end
+
+    ActiveSupport::Notifications.subscribe("sql.active_record", new)
+  end
+end