Python jsonfield.JSONField() Examples

def optimize_queryset_for_list(queryset):
        """ Used by serializers to improve performance when listing assets """
        queryset = queryset.defer(
            # Avoid pulling these `JSONField`s from the database because:
            #   * they are stored as plain text, and just deserializing them
            #     to Python objects is CPU-intensive;
            #   * they are often huge;
            #   * we don't need them for list views.
            'content', 'report_styles'
        ).select_related(
            # We only need `username`, but `select_related('owner__username')`
            # actually pulled in the entire `auth_user` table under Django 1.8.
            # In Django 1.9+, "select_related() prohibits non-relational fields
            # for nested relations."
            'owner',
        ).prefetch_related(
            # We previously prefetched `permissions__content_object`, but that
            # actually pulled the entirety of each permission's linked asset
            # from the database! For now, the solution is to remove
            # `content_object` here *and* from
            # `ObjectPermissionNestedSerializer`.
            'permissions__permission',
            'permissions__user',
            # `Prefetch(..., to_attr='prefetched_list')` stores the prefetched
            # related objects in a list (`prefetched_list`) that we can use in
            # other methods to avoid additional queries; see:
            # https://docs.djangoproject.com/en/1.8/ref/models/querysets/#prefetch-objects
            Prefetch('tags', to_attr='prefetched_tags'),
            Prefetch(
                'asset_versions',
                queryset=AssetVersion.objects.order_by(
                    '-date_modified'
                ).only('uid', 'asset', 'date_modified', 'deployed'),
                to_attr='prefetched_latest_versions',
            ),
        )
        return queryset