Move the warning about composite primary key to `AttributeMethods::PrimaryKey`

Actually schema dumper/creation supports composite primary key (#21614).
Therefore it should not show the warning about composite primary key in
connection adapter.

This change moves the warning to `AttributeMethods::PrimaryKey` and
suppress the warning for habtm join table.

Fixes #25388.

1 files changed, 8 insertions, 0 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 6f2e03b370..f5232127c4 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb
@@ -124,6 +124,8 @@ module ActiveRecord
             pk = primary_key(table_ref) if table_ref
           end
 
+          pk = suppress_composite_primary_key(pk)
+
           if pk && use_insert_returning?
             sql = "#{sql} RETURNING #{quote_column_name(pk)}"
           end
@@ -164,6 +166,12 @@ module ActiveRecord
         def exec_rollback_db_transaction
           execute "ROLLBACK"
         end
+
+        private
+
+        def suppress_composite_primary_key(pk)
+          pk unless pk.is_a?(Array)
+        end
       end
     end
   end