Reduce number of queries for document metadata retrieval

mayan/apps/metadata/__init__.py

@@ -46,7 +46,13 @@ def post_post_document_type_change_metadata(sender, instance, **kwargs):
         instance.metadata.create(metadata_type=metadata_type, value=None)
 
 
+@property
+def document_metadata(document):
+    return document.document_metadata.select_related('metadata_type')
+
+
 DocumentType.add_to_class('metadata_type', DocumentTypeMetadataTypeManager.factory)
+Document.add_to_class('metadata', document_metadata)
 
 register_links(['metadata:metadata_add', 'metadata:metadata_edit', 'metadata:metadata_remove', 'metadata:metadata_view'], [metadata_add, metadata_edit, metadata_remove], menu_name='sidebar')
 register_links(Document, [metadata_view], menu_name='form_header')

mayan/apps/metadata/api.py

@@ -105,7 +105,7 @@ def get_metadata_string(document):
     """
     Return a formated representation of a document's metadata values
     """
-    return u', '.join([u'%s - %s' % (metadata.metadata_type, metadata.value) for metadata in DocumentMetadata.objects.filter(document=document).select_related('metadata_type')])
+    return u', '.join([u'%s - %s' % (document_metadata.metadata_type, document_metadata.value) for document_metadata in document.metadata.all()])
 
 
 def convert_dict_to_dict_list(dictionary):

mayan/apps/metadata/models.py

@@ -45,7 +45,7 @@ class DocumentMetadata(models.Model):
     Link a document to a specific instance of a metadata type with it's
     current value
     """
-    document = models.ForeignKey(Document, verbose_name=_(u'Document'), related_name='metadata')
+    document = models.ForeignKey(Document, verbose_name=_(u'Document'), related_name='document_metadata')
     metadata_type = models.ForeignKey(MetadataType, verbose_name=_(u'Type'))
     value = models.CharField(max_length=255, blank=True, null=True, verbose_name=_(u'Value'), db_index=True)