Django pickle.dumps（model.query）hit db

Question

私はRedjisに保存するためにdjango Queryオブジェクトをpickleしようとしています。ここで

materials = Material.objects.prefetch_related('tags_applied').prefetch_related('materialdata_set').prefetch_related('source') 
materials_ids = MaterialData.objects.filter(tag_id__in=tags).values_list('material_id', flat=True) 
materials = materials.filter(pk__in=materials_ids) 
key_name = SAMPLES_UUID + ':' + str(redis_uuid) 
redis_cl.set_key(key_name, pickle.dumps(materials.query)) 
redis_cl.expire(key_name, SAMPLES_TIMEOUT) 

debug_panelからのトレースは（私は怠惰なページネーションを使用）です： ソースクエリは次のとおりです。

SELECT "san_material" "ID"、 "san_material" "のcreated_at"、 」。 "author"、 "san_material"、 "url"、 "san_material"。 "publication_datetime"、 "san_material"。 "text"、 "san_material"。 "サイズ"、 " san_material "、" san_material "、" san_material "。" source_id "、 " san_material "。" material_type "、" san_material "。" updated_at "、 " san_material " "elastic_sync」、 "san_material"。 "トークン"、 "san_material"。 "detection_datetime"、 "san_material"。 "article_title"、 "san_material"。 "publication_datetime_article"、 "san_material"。 "author_article"、" san_material "highlight_data" FROM "san_material" WHERE（ "san_material"。 "detect_datetime" BETWEEN '2016-07-01T00：00：00 + 03：00 ':: timestamptz AND ' 2016-07-27T10：39：00 +03：00 ':: timestamptz AND "san_material"。 "id" IN （SELECT U0。 "material_id" FROM "san_materialdata" U0 WHERE U0。 "tag_id" IN（660）））ORDER BY "san_material"検出日時 "DESC LIMIT 51

しかし、サブクエリヒットデシベルです。

/home/maxx/analize/san/utils.py in wrapper(82) 
    result = method_to_decorate(*args, **kwds) 
/home/maxx/analize/san/views/flux.py in flux(111) 
    redis_cl.set_key(key_name, pickle.dumps(materials.query)) 
/usr/lib/python2.7/pickle.py in dumps(1393) 
    Pickler(file, protocol).dump(obj) 
/usr/lib/python2.7/pickle.py in dump(225) 
    self.save(obj) 
/usr/lib/python2.7/pickle.py in save(333) 
    self.save_reduce(obj=obj, *rv) 
/usr/lib/python2.7/pickle.py in save_reduce(421) 
    save(state) 
/usr/lib/python2.7/pickle.py in save(288) 
    f(self, obj) # Call unbound method with explicit self 
/usr/lib/python2.7/pickle.py in save_dict(657) 
    self._batch_setitems(obj.iteritems()) 
/usr/lib/python2.7/pickle.py in _batch_setitems(675) 
    save(v) 
/usr/lib/python2.7/pickle.py in save(333) 
    self.save_reduce(obj=obj, *rv) 
/usr/lib/python2.7/pickle.py in save_reduce(421) 
    save(state) 
/usr/lib/python2.7/pickle.py in save(288) 
    f(self, obj) # Call unbound method with explicit self 
/usr/lib/python2.7/pickle.py in save_dict(657) 
    self._batch_setitems(obj.iteritems()) 
/usr/lib/python2.7/pickle.py in _batch_setitems(675) 
    save(v) 
/usr/lib/python2.7/pickle.py in save(288) 
    f(self, obj) # Call unbound method with explicit self 
/usr/lib/python2.7/pickle.py in save_list(604) 
    self._batch_appends(iter(obj)) 
/usr/lib/python2.7/pickle.py in _batch_appends(620) 
    save(x) 
/usr/lib/python2.7/pickle.py in save(333) 
    self.save_reduce(obj=obj, *rv) 
/usr/lib/python2.7/pickle.py in save_reduce(421) 
    save(state) 
/usr/lib/python2.7/pickle.py in save(288) 
    f(self, obj) # Call unbound method with explicit self 
/usr/lib/python2.7/pickle.py in save_dict(657) 
    self._batch_setitems(obj.iteritems()) 
/usr/lib/python2.7/pickle.py in _batch_setitems(675) 
    save(v) 
/usr/lib/python2.7/pickle.py in save(308) 
    rv = reduce(self.proto) 
/home/maxx/venv/analize/lib/python2.7/copy_reg.py in _reduce_ex(84) 
    dict = getstate() 

：U0 "TAG_ID" IN（660）ここで

"san_materialdata" U0 FROM

SELECT U0 "material_id"

どうすれば修正できますか？ 2.5秒で

('Save obj time:', 2.5215649604797363, 'arg:', 'rhs') 
('Save obj time:', 2.5219039916992188, 'arg:', 'children') 
('Save obj time:', 2.5219550132751465, 'arg:', 'where') 

その3回：

p.s iはデフ_batch_setitemsに引数を保存する時間を測定しました。どうして？

Answer 1

Djangoのクエリのは怠惰なクエリのですが、私はあなたが書かれているかを説明しましょう：

materials = Material.objects.prefetch_related('tags_applied' 
    ).prefetch_related('materialdata_set').prefetch_related('source') 


materials_ids = MaterialData.objects.filter(tag_id__in=tags).values_list('material_id', flat=True) 

# till now materials_id is queryset, means it will not hit DB. 
# as soon it execute next line of code it will hit db, because in next line you are using materials_ids. 

materials = materials.filter(pk__in=materials_ids) 

# So you can avoid hiting db if you are not required to use materials 
key_name = SAMPLES_UUID + ':' + str(redis_uuid) 
redis_cl.set_key(key_name, pickle.dumps(materials.query)) 
redis_cl.expire(key_name, SAMPLES_TIMEOUT) 

あなたが適切な使用してこれを修正することができますジャンゴに参加する：私はあなたがMaterialDataモデルがを持っていると思います

品目はに資材としてモデルです。

materials = MaterialData.objects.filter(tag_id__in=tags).prefetch_related(
'material__tags_applied' 
).prefetch_related('material__materialdata_set').prefetch_related('material__source').values(*all values realted to mateials you can put here by adding materials__ before each material field *) 

# to fetch foreign key attribue you use field followed by duble underscore 

key_name = SAMPLES_UUID + ':' + str(redis_uuid) 
redis_cl.set_key(key_name, pickle.dumps(materials.query))