1 files changed, 29 insertions, 9 deletions

diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb
index 4d013f0ef4..abe6fff5d5 100644
--- a/activerecord/lib/active_record/explain.rb
+++ b/activerecord/lib/active_record/explain.rb
@@ -1,5 +1,5 @@
 module ActiveRecord
-  module Explain # :nodoc:
+  module Explain
     # logging_query_plan calls could appear nested in the call stack. In
     # particular this happens when a relation fetches its records, since
     # that results in find_by_sql calls downwards.
@@ -13,33 +13,34 @@ module ActiveRecord
     # whole. That is, the threshold is not checked against each individual
     # query, but against the duration of the entire block. This approach is
     # convenient for relations.
-    def logging_query_plan(&block)
-      if (t = auto_explain_threshold_in_seconds) && !Thread.current[LOGGING_QUERY_PLAN]
+    def logging_query_plan(&block) # :nodoc:
+      threshold = auto_explain_threshold_in_seconds
+      if threshold && !Thread.current[LOGGING_QUERY_PLAN] && !Thread.current[SILENCED]
         begin
           Thread.current[LOGGING_QUERY_PLAN] = true
           start = Time.now
           result, sqls, binds = collecting_sqls_for_explain(&block)
-          logger.warn(exec_explain(sqls, binds)) if Time.now - start > t
+          logger.warn(exec_explain(sqls, binds)) if Time.now - start > threshold
           result
         ensure
           Thread.current[LOGGING_QUERY_PLAN] = false
         end
       else
-        block.call
+        yield
       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.
     SKIP_EXPLAIN_FOR = %w(SCHEMA EXPLAIN)
-    def ignore_explain_notification?(payload)
+    def ignore_explain_notification?(payload) # :nodoc:
       payload[:exception] || SKIP_EXPLAIN_FOR.include?(payload[:name])
     end
 
     # Collects all queries executed while the passed block runs. Returns an
     # array with three elements, the result of the block, the strings with the
     # queries, and their respective bindings.
-    def collecting_sqls_for_explain(&block)
+    def collecting_sqls_for_explain # :nodoc:
       sqls  = []
       binds = []
       callback = lambda do |*args|
@@ -52,7 +53,7 @@ module ActiveRecord
 
       result = nil
       ActiveSupport::Notifications.subscribed(callback, "sql.active_record") do
-        result = block.call
+        result = yield
       end
 
       [result, sqls, binds]
@@ -60,7 +61,7 @@ module ActiveRecord
 
     # Makes the adapter execute EXPLAIN for the given queries and bindings.
     # Returns a formatted string ready to be logged.
-    def exec_explain(sqls, binds)
+    def exec_explain(sqls, binds) # :nodoc:
       sqls.zip(binds).map do |sql, bind|
         [].tap do |msg|
           msg << "EXPLAIN for: #{sql}"
@@ -72,5 +73,24 @@ module ActiveRecord
         end.join("\n")
       end.join("\n")
     end
+
+    SILENCED = :silence_explain
+
+    # Silences automatic EXPLAIN logging for the duration of the block.
+    #
+    # This has high priority, no EXPLAINs will be run even if downwards
+    # the threshold is set to 0.
+    #
+    # As the name of the method suggests this only applies to automatic
+    # EXPLAINs, manual calls to +ActiveRecord::Relation#explain+ run.
+    def silence_auto_explain
+      # Implemented as a flag rather that setting the threshold to nil
+      # because we should not depend on a value that may be changed
+      # downwards.
+      Thread.current[SILENCED] = true
+      yield
+    ensure
+      Thread.current[SILENCED] = false
+    end
   end
 end