python - Django haystack whoosh 超慢

Question

我有一个简单的 django-haystack 和 whoosh 引擎设置。搜索产生 19 个对象花了我 8 秒。我使用 django-debug-toolbar 来确定我有一堆重复的查询。

然后我将搜索 View 更新为预取关系，这样就不会发生重复查询:

class MySearchView(SearchView):
    template_name = 'search_results.html'
    form_class = SearchForm
    queryset = RelatedSearchQuerySet().load_all().load_all_queryset(
        models.Customer, models.Customer.objects.all().select_related('customer_number').prefetch_related(
            'keywords'
        )
    ).load_all_queryset(
        models.Contact, models.Contact.objects.all().select_related('customer')
    ).load_all_queryset(
        models.Account, models.Account.objects.all().select_related(
            'customer', 'account_number', 'main_contact', 'main_contact__customer'
        )
    ).load_all_queryset(
        models.Invoice, models.Invoice.objects.all().select_related(
            'customer', 'end_customer', 'customer__original', 'end_customer__original', 'quote_number', 'invoice_number'
        )
    ).load_all_queryset(
        models.File, models.File.objects.all().select_related('file_number', 'customer').prefetch_related(
            'keywords'
        )
    ).load_all_queryset(
        models.Import, models.Import.objects.all().select_related('import_number', 'customer').prefetch_related(
            'keywords'
        )
    ).load_all_queryset(
        models.Event, models.Event.objects.all().prefetch_related('customers', 'contracts', 'accounts', 'keywords')
    )

但即便如此，搜索仍然需要 5 秒。然后我使用了 django-debug-toolbar 中的探查器，它给了我以下信息:

据我所知，问题出在 haystack/query:779::__getitem__ 上，它被击中了两次，每次耗时 1.5 秒。我浏览了有问题的代码，但无法理解它。那么我从这里去哪里呢？

Answer 1

你在问题​​中说:

I then updated my search view to prefetch relations […]

不过，您提供的代码不使用 QuerySet.prefetch_related对于他们中的大多数人。相反，您的示例代码使用 QuerySet.select_related对他们中的大多数人来说；这不会预取对象。

每种方法的文档都非常丰富，可以帮助您确定哪种方法适合您的情况。

特别是，the QuerySet.prefetch_related documentation说:

select_related works by creating an SQL join and including the fields of the related object in the SELECT statement. For this reason, select_related gets the related objects in the same database query. However, to avoid the much larger result set that would result from joining across a ‘many’ relationship, select_related is limited to single-valued relationships - foreign key and one-to-one.

prefetch_related, on the other hand, does a separate lookup for each relationship, and does the ‘joining’ in Python. This allows it to prefetch many-to-many and many-to-one objects, which cannot be done using select_related, in addition to the foreign key and one-to-one relationships that are supported by select_related. It also supports prefetching of GenericRelation and GenericForeignKey, however, it must be restricted to a homogeneous set of results. For example, prefetching objects referenced by a GenericForeignKey is only supported if the query is restricted to one ContentType.