Is this iteration necessary?

Hi my usage of get_serving_url is serverside now I wonder if this can be done in template instead of iterating serverside?

class Ad(GeoModel,search.SearchableModel): 
    .......

class Image(db.Model):   #migrate to blobstore
    reference = db.ReferenceProperty(Ad, collection_name='matched_images', verbose_name="Title")
    primary_image = blobstore.BlobReferenceProperty() 
    .........

    class AdHandler(I18NHandler):
        def get(self, id):
            ad = Ad.get_by_id(long(id))
            image = ad.matched_images.get()
            url = ''
            if image:
                url = images.get_serving_url(str(image.primary_image.key()))
            if not ad:
                self.error(404)
                return
            imv = []
            L = {}
            table = ''
            for i in ad.matched_images:
                if i.primary_image:
                    i1 = images.get_serving_url(开发者_如何学运维str(i.primary_image.key()))
                    imv.append(i1)
            self.render_template("imageinfo.html",
                                 {'url':url, 'imv':imv, 'ad':ad, 'image': image,
                                  'logout_url': users.create_logout_url('/'),}
                                 )

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I´d suggest you store the image url in the database. This url´s are static, and whenever you do a get_serving_url theres a lot of CPU time involved. I saw a drastic improvement in my own app when I did this. Also, by doing so, your initial problem will be solved immediately.