1 files changed, 25 insertions, 17 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
index 7414eba6c5..705e6063dc 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
@@ -7,18 +7,14 @@ module ActiveRecord
           PostgreSQL::ExplainPrettyPrinter.new.pp(exec_query(sql, "EXPLAIN", binds))
         end
 
-        def select_value(arel, name = nil, binds = [])
-          arel, binds = binds_from_relation arel, binds
-          sql = to_sql(arel, binds)
-          execute_and_clear(sql, name, binds) do |result|
+        def select_value(arel, name = nil, binds = []) # :nodoc:
+          select_result(arel, name, binds) do |result|
             result.getvalue(0, 0) if result.ntuples > 0 && result.nfields > 0
           end
         end
 
-        def select_values(arel, name = nil, binds = [])
-          arel, binds = binds_from_relation arel, binds
-          sql = to_sql(arel, binds)
-          execute_and_clear(sql, name, binds) do |result|
+        def select_values(arel, name = nil, binds = []) # :nodoc:
+          select_result(arel, name, binds) do |result|
             if result.nfields > 0
               result.column_values(0)
             else
@@ -29,8 +25,8 @@ module ActiveRecord
 
         # Executes a SELECT query and returns an array of rows. Each row is an
         # array of field values.
-        def select_rows(sql, name = nil, binds = [])
-          execute_and_clear(sql, name, binds) do |result|
+        def select_rows(arel, name = nil, binds = []) # :nodoc:
+          select_result(arel, name, binds) do |result|
             result.values
           end
         end
@@ -85,17 +81,21 @@ module ActiveRecord
         # Queries the database and returns the results in an Array-like object
         def query(sql, name = nil) #:nodoc:
           log(sql, name) do
-            result_as_array @connection.async_exec(sql)
+            ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
+              result_as_array @connection.async_exec(sql)
+            end
           end
         end
 
-        # Executes an SQL statement, returning a PGresult object on success
-        # or raising a PGError exception otherwise.
-        # Note: the PGresult object is manually memory managed; if you don't
-        # need it specifically, you many want consider the exec_query wrapper.
+        # Executes an SQL statement, returning a PG::Result object on success
+        # or raising a PG::Error exception otherwise.
+        # Note: the PG::Result object is manually memory managed; if you don't
+        # need it specifically, you may want consider the <tt>exec_query</tt> wrapper.
         def execute(sql, name = nil)
           log(sql, name) do
-            @connection.async_exec(sql)
+            ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
+              @connection.async_exec(sql)
+            end
           end
         end
 
@@ -130,7 +130,7 @@ module ActiveRecord
 
           super
         end
-        protected :sql_for_insert
+        private :sql_for_insert
 
         def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil)
           if use_insert_returning? || pk == false
@@ -175,6 +175,14 @@ module ActiveRecord
           def suppress_composite_primary_key(pk)
             pk unless pk.is_a?(Array)
           end
+
+          def select_result(arel, name, binds)
+            arel, binds = binds_from_relation(arel, binds)
+            sql = to_sql(arel, binds)
+            execute_and_clear(sql, name, binds) do |result|
+              yield result
+            end
+          end
       end
     end
   end