eliminate warnings about multiple primary keys on habtm join tables

habtm join tables commonly have two id columns and it's OK to make those
two id columns a primary key.  This commit eliminates the warnings for
join tables that have this setup.

  ManageIQ/manageiq#6713

2 files changed, 4 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index b888148841..5fbd79d118 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -76,6 +76,9 @@ module ActiveRecord::Associations::Builder # :nodoc:
           left_model.retrieve_connection
         end
 
+        def self.primary_key
+          false
+        end
       }
 
       join_model.name                = "HABTM_#{association_name.to_s.camelize}"
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 6aa264d766..6f2e03b370 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
@@ -118,7 +118,7 @@ module ActiveRecord
         alias :exec_update :exec_delete
 
         def sql_for_insert(sql, pk, id_value, sequence_name, binds) # :nodoc:
-          unless pk
+          if pk.nil?
             # Extract the table from the insert sql. Yuck.
             table_ref = extract_table_ref_from_insert_sql(sql)
             pk = primary_key(table_ref) if table_ref